Pharmacology, Biochemistry and Behavior (v.99, #3)

Influences of activity wheel access on the body temperature response to MDMA and methamphetamine by N.W. Gilpin; M.J. Wright; G. Dickinson; S.A. Vandewater; J.U. Price; M.A. Taffe (295-300).
Recreational ingestion of the drug 3,4-methylenedioxymethamphetamine (MDMA, “Ecstasy”) can result in pathologically elevated body temperature and even death in humans. Such incidents are relatively rare which makes it difficult to identify the relative contributions of specific environmental and situational factors. Although animal models have been used to explore several aspects of MDMA-induced hyperthermia and it is regularly hypothesized that prolonged physical activity (e.g., dancing) in the nightclub environment increases risk, this has never been tested directly. In this study the rectal temperature of male Wistar rats was monitored after challenge with doses of MDMA and methamphetamine (MA), another drug frequently ingested in the rave/nightclub environment, either with or without access to an activity wheel. Results showed that wheel activity did not modify the hyperthermia produced by 10.0 mg/kg MDMA. However, individual correlations were observed in which wheel activity levels after a locomotor stimulant dose of MDMA were positively related to body temperature change and lethal outcome. A modest increase in the maximum body temperature observed after 5.6 mg/kg MA was caused by wheel access but this was mostly attributable to a drop in temperature relative to vehicle treatment in the absence of wheel activity. These results suggest that nightclub dancing in the human Ecstasy consumer may not be a significant factor in medical emergencies.► Determination of the role of repetitive exercise on MDMA/METH hyperthermia. ► Use of activity wheel to model rave dancing in rodents. ► Data show no mean effect of wheel running on hyperthermia. ► Rare individual mortality points to interaction with wheel running and MDMA.
Keywords: Thermoregulation; Ecstasy; Locomotor; Stimulant; Hyperthermia;

Rapid delivery of cocaine facilitates acquisition of self-administration in rats: An effect masked by paired stimuli by Charles W. Schindler; Elizabeth S. Cogan; Eric B. Thorndike; Leigh V. Panlilio (301-306).
In general, faster infusions of cocaine are more likely to support behavior related to abuse than are slower infusions. However, some studies of cocaine self-administration in rats have failed to support this finding, possibly because the effect was masked by other factors. One such factor may be the pairing of a stimulus with the infusion, a procedure that is known to facilitate acquisition of drug self-administration. We compared fast and slow infusions by allowing groups of rats to acquire cocaine self-administration at a dose of 1 mg/kg/infusion, delivered over different durations (1.8 or 100 s). Two groups were trained with either short or long infusions paired with a visual stimulus change (lights off), and two other groups were trained with short or long durations but with no stimulus change. Both groups trained with a paired stimulus acquired cocaine self-administration. With no stimulus change, the rats trained with the 1.8-s infusion acquired cocaine self-administration at a rate comparable to the two groups that were trained with a paired stimulus. However, most rats in the group trained with the 100-s infusion that was not accompanied by a stimulus change failed to acquire cocaine self-administration. The stimulus itself did not support responding. These results indicate that infusing a given dose of cocaine over a longer duration reduces its ability to support self-administration, but drug-paired stimuli can partially mask this effect by enhancing the effectiveness of slow infusions.► In this study we examined the effects of infusion duration on cocaine self-administration in rats. ► We found that when a stimulus was associated with the cocaine infusion, infusion duration had little effect on the acquisition of cocaine self-administration. ► When no stimulus was associated with the cocaine infusion, cocaine self-administration was acquired only with the faster cocaine infusion. ► These results indicate that infusing a given dose of cocaine more rapidly reduces its ability to support self-administration, but drug-paired stimuli can mask this effect by enhancing the effectiveness of slow infusions.
Keywords: Cocaine; Self-administration; Infusion duration; Acquisition; Rat;

Acetaminophen modulation of hydrocodone reward in rats by Arbi Nazarian; Deepthi Are; John M. Tenayuca (307-310).
Abuse of prescription opioid analgesics in non-medical context has been on the rise over the past decade. The most commonly abused analgesic in this drug class consists of a combined formulation of hydrocodone and acetaminophen. The present study was aimed to determine the rewarding effects of hydrocodone, acetaminophen, and their combination using the conditioned place preference (CPP) paradigm. Using a 6-day CPP paradigm, rats were paired with hydrocodone (0.5, 1.0 or 5.0 mg/kg) or acetaminophen (50, 100 or 300 mg/kg) to determine whether the drugs given alone would produce a CPP. Rats conditioned with the highest dose of hydrocodone exhibited place preference, whereas rats conditioned with acetaminophen did not demonstrate place preference. In a second experiment, varying doses of hydrocodone and acetaminophen were combined to determine whether acetaminophen would enhance hydrocodone reward. Acetaminophen (100 mg/kg) enhanced the rewarding effects of hydrocodone (1 mg/kg), although the effect was unique to this particular dose combination. Higher or lower doses of acetaminophen combined with hydrocodone did not alter hydrocodone CPP. The present findings suggest that acetaminophen has a limited potential of modulating the rewarding properties of hydrocodone in rats.► Illicit abuse of analgesics containing hydrocodone and acetaminophen is on the rise. ► Hydrocodone produced CPP in rats, whereas acetaminophen was devoid of such effect. ► When combined, acetaminophen enhanced hydrocodone CPP in a dose specific manner. ► Hydrocodone caused locomotor activity. ► When combined, acetaminophen did not enhance hydrocodone-induced locomotion.
Keywords: Hydrocodone; Acetaminophen; Reward; Conditioned place preference; Prescription opioid analgesics; Drug abuse;

Stimulus control by 5-methoxy-N,N-dimethyltryptamine in wild-type and CYP2D6-humanized mice by J.C. Winter; D.J. Amorosi; Kenner C. Rice; Kejun Cheng; Ai-Ming Yu (311-315).
In previous studies we have observed that, in comparison with wild type mice, Tg-CYP2D6 mice have increased serum levels of bufotenine [5-hydroxy-N,N-dimethyltryptamine] following the administration of 5-MeO-DMT. Furthermore, following the injection of 5-MeO-DMT, harmaline was observed to increase serum levels of bufotenine and 5-MeO-DMT in both wild-type and Tg-CYP2D6 mice. In the present investigation, 5-MeO-DMT-induced stimulus control was established in wild-type and Tg-CYP2D6 mice. The two groups did not differ in their rate of acquisition of stimulus control. When tested with bufotenine, no 5-MeO-DMT-appropriate responding was observed. In contrast, the more lipid soluble analog of bufotenine, acetylbufotenine, was followed by an intermediate level of responding. The combination of harmaline with 5-MeO-DMT yielded a statistically significant increase in 5-MeO-DMT-appropriate responding in Tg-CYP2D6 mice; a comparable increase occurred in wild-type mice. In addition, it was noted that harmaline alone was followed by a significant degree of 5-MeO-DMT-appropriate responding in Tg-CYP2D6 mice. It is concluded that wild-type and Tg-CYPD2D6 mice do not differ in terms of acquisition of stimulus control by 5-MeO-DMT or in their response to bufotenine and acetylbufotenine. In both groups of mice, harmaline was found to enhance the stimulus effects of 5-MeO-DMT.► 5-Methoxy-N,N-dimethyltryptamine is a naturally-occurring hallucinogen. ► CYP2D6-humanized mice have increased levels of bufotenine following 5-MeO-DMT. ► Wild type and Tg-CYP2D6 mice did not differ in rate of acquisition of stimulus control. ► 5-MeO-DMT did not generalize to bufotenine and only partially to acetylbufotenine. ► Harmaline, a mono amine oxidase inhibitor, enhanced the stimulus effects of 5-MeO-DMT.
Keywords: Drug-induced stimulus control; Harmaline; 5-methoxy-N,N-dimethyltryptamine; Drug interaction; CYP2D6; Humanized mice;

Beneficial effects of resveratrol on scopolamine but not mecamylamine induced memory impairment in the passive avoidance and Morris water maze tests in rats by Nejat Gacar; Oguz Mutlu; Tijen Utkan; Ipek Komsuoglu Celikyurt; Semil Selcen Gocmez; Güner Ulak (316-323).
Resveratrol (3,5,4-trihydroxy-trans-stilbene), which is found in grapes and red wine has been shown to protect neuronal cells with its antioxidant activity, improve memory function in dementia and reverse acetylcholine esterase (AChE) activity. The aim of this study was to investigate the effect of resveratrol on emotional and spatial memory in naive rats, as well as on scopolamine- and mecamylamine-induced memory impairment in the passive avoidance and Morris water maze (MWM) tests. Resveratrol (12.5, 25 and 50 mg/kg), scopolamine (0.6 mg/kg) and mecamylamine (10 mg/kg) were administered to male Wistar rats. In the passive avoidance test, there was no significant difference in the first day latency between all groups, whereas scopolamine and mecamylamine significantly shortened the second day latency compared to the control group. Resveratrol reversed the effect of scopolamine at all doses used, but it had no effect on mecamylamine-induced memory impairment in the passive avoidance test. Both scopolamine and mecamylamine significantly decreased the time spent in the escape platform quadrant during the probe trial of the MWM test compared to the control group. Resveratrol reversed the effect of scopolamine at all doses, but did not change the effect of mecamylamine in the MWM test. There were no significant differences in the locomotor activities of any of the groups. In conclusion, we suggested that resveratrol had improving effects on learning and memory by acting on muscarinic cholinergic receptors and at least in part, may reverse AChE activity.► Resveratrol improved learning and memory in naive animals and in drug-induced models of dementia. ► Centrally acting muscarinic and nicotinic antagonists have dissociable effects on memory processes in rats. ► Treatment with resveratrol might modulate cholinergic neurotransmission and may, consequently, improve cognition. ► Resveratrol could be used safely in healthy people and in patients with dementia.
Keywords: Resveratrol; Cognition; Morris water maze; Passive avoidance; Rat;

Aged monkeys as a partial model for Parkinson's disease by P.J. Hurley; J.D. Elsworth; M.C. Whittaker; R.H. Roth; D.E. Redmond (324-332).
Parkinson's Disease (PD) and the natural aging process share a number of biochemical mechanisms, including reduced function of dopaminergic systems. The present study aims to determine the extent that motor and behavioral changes in aged monkeys resemble parkinsonism induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. The behavioral and physiological changes in PD are believed to result largely from selective depletion of dopamine in the nigrostriatal system. In the present study, ten aged female monkeys were compared with three groups: 9 untreated young adult female monkeys, 10 young adult male monkeys and 13 older male monkeys that had been exposed to MPTP. Trained observers, blind as to age and drug condition and without knowledge of the hypotheses, scored the monkeys using the Parkinson's factor score (Parkscore), which has been validated by a high correlation with post mortem striatal dopamine (DA) concentrations. The aged animals had higher scores on the Parkscore compared with the young adults, with most of its component behavioral items showing significance (tremor, Eating Problems, Delayed initiation of movement, and Poverty of Movement). l-Dopa and DA-agonists did not clearly reverse the principal measure of parkinsonism. DA concentrations post mortem were 63% lower in 3 aged monkeys in the ventral putamen compared with 4 young adults, with greater reductions in putamen than in caudate (45%). We conclude that aged monkeys, unexposed to MPTP, show a similar profile of parkinsonism to that seen after the neurotoxin exposure to MPTP in young adult monkeys. The pattern of greater DA depletion in putamen than in caudate in aged monkeys is the same as in human Parkinson's disease and contrasts with the greater depletion in caudate seen after MPTP. Aged monkeys of this species reflect many facets of Parkinson's disease, but like older humans do not improve with standard dopamine replacement pharmacotherapies.► We examine aged African Green monkeys for signs of Parkinson's disease. ► We utilize a sensitive behavioral measure for correlating dopamine function with signs of parkinsonism. ► Aged monkeys had signs similar to MPTP-exposed adult monkeys. ► Treatment with dopamine agonists does not restore normal function in aged monkeys as it often fails to do in older patients with Parkinson's disease. ► We show a greater loss of dopamine in putamen than in caudate, a pattern that is more similar to human Parkinson's disease than the pattern seen after MPTP exposure.
Keywords: Aging; Parkinson's disease; African Green monkey; Dopaminergic decline; MPTP; Dopamine agonists; l-Dopa; Apomorphine; Dihydrexidine; Pergolide;

Hesperidin induces antinociceptive effect in mice and its aglicone, hesperetin, binds to μ-opioid receptor and inhibits GIRK1/2 currents by Leonardo M. Loscalzo; Tin T. Yow; Cristina Wasowski; Mary Chebib; Mariel Marder (333-341).
This paper extended the evaluation of the depressant and antinociceptive activities of hesperidin in order to determine its effectiveness by the intraperitoneal and oral routes, its pharmacological interaction with diverse pathways of neurotransmission and the role of its aglycone, hesperetin. The capacity of hesperidin and hesperetin to bind to μ-opioid receptor and their actions on μ-opioid receptor co-expressed with GIRK1/GIRK2 channels (G protein-activated inwardly rectifying K+ channels) in Xenopus laevis oocytes were also determined.Hesperidin exhibited a depressant activity in the hole board and locomotor activity tests, antinociceptive activities in the abdominal writhing and hot plate tests and no motor incoordination in the inverted screen and rotarod assays, only by the intraperitoneal route. Hesperetin did not show any effects in vivo in mice in these models, but in vitro it displaced the [3H]DAMGO binding with low-affinity and inhibited inward currents through the expressed GIRK1/2 channels. Although hesperidin actions in vivo demonstrated to be mediated by an opioid mechanism of action, it failed to directly bind to and activate the μ-opioid receptor or produce any change on inward GIRK1/2 currents in vitro. However, it should be considered that hesperidin may be metabolized, possibly resulting in crucial changes in its biological activity.► Hesperidin showed depressant and antinociceptive effects only by the i.p. route. ► Hesperidin actions in vivo are mediated by an opioid mechanism of action. ► Hesperetin did not show any central nervous system effects in vivo in mice. ► Hesperetin binds to mu-opioid receptor with low-affinity. ► Hesperetin inhibited inward GIRK1/2 currents expressed in Xenopus oocytes.
Keywords: Hesperidin; Hesperetin; Depressant; Antinociception; μ-opioid receptor; Xenopus oocytes;

The present study was taken up to see the effect of chicoric acid (CA) on behavioral and biochemical alterations induced by chronic restraint stress in experimental Swiss albino mice. CA at 1 mg/kg dose level exhibited considerable antidepressant activity as shown by significant decrease in immobility period in the Porsolt's swim stress-induced behavioral despair test and escape failures in Learned “helplessness test”. The antidepressant activity shown by CA can be attributed to its modulating effect on nor-adrenaline (NA), dopamine (DA) and 5- hydroxy tryptamine (5-HT) as shown by their quantification in CA treated chronically stressed mice. Further, a significant antioxidant effect was exhibited by CA as shown by estimation of lipid peroxidation, glutathione (GSH) and glycogen in liver of chronically stressed mice. It also normalized altered values of serum glucose, triglycerides, aspartate aminotransferase (AST) alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in a dose dependent manner. The stress busting potential of CA was further confirmed by its regulating effect on raised plasma corticosterone levels and significant attenuation of the depleted ascorbic acid, cholesterol and corticosterone levels in adrenal glands. Thus, our results suggest that CA possesses considerable stress busting potential, and that anti-oxidation may be one of the mechanisms underlying its antistress action.► CA exhibited considerable antidepressant activity by showing decrease in immobility period in the Porsolt's swim stress-induced behavioral despair test and escape failures in Learned “helplessness test”. ► The antidepressant activity was further confirmed by its modulating effect on nor-adrenaline (NA), dopamine (DA) and 5- hydroxy tryptamine (5-HT). ► A regulating effect on lipid per oxidation, glutathione (GSH) and glycogen in liver of chronically stressed mice was also shown. ► It also normalized the raised corticosterone levels, the main marker of stress response in rodents.
Keywords: Chronic stress; Chicoric acid; Antioxidant;

Astaxanthin limits fish oil-related oxidative insult in the anterior forebrain of Wistar rats: Putative anxiolytic effects? by Rita Mattei; Tatiana G. Polotow; Cristina V. Vardaris; Beatriz A. Guerra; José Roberto Leite; Rosemari Otton; Marcelo P. Barros (349-355).
The habitual consumption of marine fish is largely associated to human mental health. Fish oil is particularly rich in n-3 polyunsaturated fatty acids that are known to play a role in several neuronal and cognitive functions. In parallel, the orange-pinkish carotenoid astaxanthin (ASTA) is found in salmon and displays important antioxidant and anti-inflammatory properties. Many neuronal dysfunctions and anomalous psychotic behavior (such as anxiety, depression, etc.) have been strongly related to the higher sensitivity of cathecolaminergic brain regions to oxidative stress. Thus, the aim of this work was to study the combined effect of ASTA and fish oil on the redox status in plasma and in the monoaminergic-rich anterior forebrain region of Wistar rats with possible correlations with the anxiolytic behavior. Upon fish oil supplementation, the downregulation of superoxide dismutase and catalase activities combined to increased “free” iron content resulted in higher levels of lipid and protein oxidation in the anterior forebrain of animals. Such harmful oxidative modifications were hindered by concomitant supplementation with ASTA despite ASTA-related antioxidant protection was mainly observed in plasma. Although it is clear that ASTA properly crosses the brain-blood barrier, our data also address a possible indirect role of ASTA in restoring basal oxidative conditions in anterior forebrain of animals: by improving GSH-based antioxidant capacity of plasma. Preliminary anxiolytic tests performed in the elevated plus maze are in alignment with our biochemical observations.► Fish oil has shown cognitive/mental benefits, but coadjutant antioxidants are apparently necessary based on a hormesis principle. ► Anxiety behavior has been related to highly oxidative-sensitive regions in mammal brains. ► Fish oil augmented oxidative injuries in the anterior forebrain of rats but apparently showed anxiolytic effects. ► Salmonid carotenoid astaxanthin increased antioxidant capacity in plasma and inhibited oxidative injury in rat brains. ► It is still unclear if astaxanthin exerts its antioxidant effects in situ or indirectly by preserving reduced glutathione in plasma.
Keywords: Astaxanthin; Omega-3; Anxiety; Fish oil; Antioxidant; Brain; Carotenoid; Elevated plus maze;

A high fructose diet does not affect amphetamine self-administration or spatial water maze learning and memory in female rats by Emily C. Bruggeman; Chen Li; Amy P. Ross; James M. Doherty; Bonnie F. Williams; Kyle J. Frantz; Marise B. Parent (356-364).
High energy diets can have a detrimental effect on brain plasticity. For example, a high fructose diet impairs spatial memory in male rats. The aim of the present study was to determine whether a high fructose diet impairs another form of learning and memory: drug reinforcement learning. Female Sprague–Dawley rats were fed a high fructose diet (60%) from weaning at postnatal day (PND) 21, then allowed to acquire lever-pressing maintained by intravenous (i.v.) amphetamine at PND 68, 109, or 165. Acquisition was tested on a fixed ratio one (FR1) schedule of reinforcement (0.025 mg/kg/infusion, 1 h daily sessions, 10 sessions over 14 days), followed by testing for reinforcing efficacy on a progressive ratio (PR) schedule (0.025, 0.01, and 0.1 mg/kg/infusion), 14 days of abstinence, and within-session extinction and reinstatement tests. Subsequently, water maze acquisition and retention were tested in these subjects as well as a separate cohort tested in the water maze only. The diet had no effect on acquisition, reinforcing efficacy, extinction, or reinstatement of amphetamine seeking. Nor did the diet alter any measures of spatial memory. The high fructose diet did decrease body mass and increase relative liver and spleen mass, but did not affect plasma triglyceride concentrations consistently. Together with prior research on males, these results suggest that the metabolism of fructose and the effects of a high fructose diet on learning and memory may be sex-dependent.► A high fructose diet increased relative liver and spleen mass in females. ► A high fructose diet did not impair amphetamine self-administration in females. ► This diet also did not impair spatial water maze memory in females.
Keywords: Estrogen; Memory; Fructose; Addiction; Amphetamine; Reinforcement;

Nicotine induces profound behavioral responses in the model organism Caenorhabditis elegans. We tested the effect of a broad range of concentrations of nicotine (from 0.001 mM to 30 mM in nematode growth medium) on C. elegans locomotor behavior. We also followed the time-course influence on the sensitivity of C. elegans to nicotine (from 0 min to 300 min). A low concentration (0.001 mM) of this alkaloid causes a reduction of the speed of movement. By contrast, moderate concentrations (0.01 and 0.1 mM) induced acceleration of the mean speed of locomotion of C. elegans. High doses of nicotine (above 1 mM) induced slowing down of the movements and, finally, paralysis. Time-dependent analysis revealed that the stimulating effect of nicotine abolished the slowing down of C. elegans in control experiments after 30 min in the presence of 0.001, 0.1 and 10 mM nicotine. In the presence of 0.1 mM nicotine, the stimulation phase lasted up to 70 min. The evidence indicates that nicotine can have dual effects on the speed of locomotion, which is dependent on differences in its dosage and treatment time.► Nicotine induces profound behavioral responses in Caenorhabditis elegans. ► A low nicotine concentration (0.001 mM) causes a reduction of the movement speed. ► Moderate concentrations (0.01 and 0.1 mM) induce acceleration of the mean speed. ► High doses of nicotine (≥ 1 mM) slow down of the movements or lead to paralysis.
Keywords: Nicotine; Locomotion rate; Behavior; Caenorhabditis elegans;

N-Methyl-d-aspartate receptor antagonist MK-801 suppresses glial pro-inflammatory cytokine expression in morphine-tolerant rats by Ching-Hang Liu; Chen-Hwen Cherng; Shinn-Long Lin; Chun-Chang Yeh; Ching-Tang Wu; Yueh-Hua Tai; Chih-Shung Wong (371-380).
Chronic opioid therapy induces tolerance and hyperalgesia, which hinders the efficacy of opioid treatment. Previous studies have shown that inhibition of neuroinflammation and glutamatergic receptor activation prevents the development of morphine tolerance. The aim of the present study was to examine whether N-Methyl-d-aspartate receptors are involved in the regulation of chronic morphine-induced neuroinflammation in morphine-tolerant rats.Morphine tolerance was induced in male Wistar rats by intrathecal infusion of morphine (15 μg/h) for 5 days. Tail-flick latency was measured to estimate the antinociceptive effect of morphine. Morphine challenge (15 μg, intrathecally) on day 5 at 3 h after discontinuation of morphine infusion produced a significant antinociceptive effect in saline-infused rats, but not in morphine-tolerant rats. Pretreatment with MK-801 (20 μg, intrathecally) 30 min before morphine challenge preserved its antinociceptive effect in morphine-tolerant rats. Morphine-tolerant rats expressed high levels of the pro-inflammatory cytokines interleukin-1β, interleukin-6, and tumor necrosis factor-α and the increase in interleukin-1β and interleukin-6, and tumor necrosis factor-α levels was prevented by MK-801 pre-treatment at both the protein and mRNA levels.The results show that a single dose of MK-801 reduces the increase in pro-inflammatory cytokines in the spinal cord, thus re-sensitizing neurons to the antinociceptive effect of morphine in morphine-tolerant rats. This study provides a piece of theoretical evidence that NMDA antagonist can be a therapeutic adjuvant in treating morphine tolerant patients for pain relief.► MK-801 preserves morphine's antinociceptive effect in the morphine-tolerant rats. ► MK-801 provides anti-inflammatory effect. ► NMDA receptor antagonist can be an adjuvant to treat morphine-tolerant patients.
Keywords: MK-801; Morphine tolerance; Glial cell activation; Pro-inflammatory cytokine;

The Japanese Suncus murinus, the house musk shrew, is a small insectivore commonly used in emetic research. The Guamanian S. murinus has not had extensive testing as an emetic model, but it is readily available for use in emetic experiments in the United States, unlike the Japanese Suncus. This study determined that Guamanian S. murinus is an acceptable model for emesis research and its differences from the Japanese strain were examined. Motion and nicotine were used as emetic stimuli and comparable doses of 8-OH-DPAT were used to compare emetic susceptibility to the Japanese strain. The Guamanian strain had decreased susceptibility to motion and increased susceptibility to nicotine as compared to the Japanese, as well as increased sensitivity to 8-OH-DPAT, with lower doses of the recovery drug eliminating retching episodes. The study also determined that Guamanian S. murinus are smaller and more aggressive than the Japanese strain, but just as effective as a model for emetic research.► Guamanian Suncus are less susceptible to motion compared to Japanese Suncus. ► Guamanian Suncus are more susceptible to nicotine compared to Japanese Suncus. ► Guamanian Suncus require less 8-OH-DPAT for emetic relief than Japanese Suncus. ► Guamanian Suncus are smaller and more aggressive than Japanese Suncus. ► Guamanian Suncus are an acceptable and effective model for emetic research.
Keywords: Suncus murinus; Emesis; 8-OH-DPAT; Nicotine; Motion;

The α2-adrenergic system is involved in pain processing and inflammation-induced sensitization. α2-adrenoceptor agonists induce analgesia, and this effect is greater when administered in combination with other analgesics. In the present study, we assessed a possible enhancement of antinociception combining the α2-adrenoceptor agonist medetomidine with subeffective doses of NCX701 (nitroparacetamol). The effects of the drugs were studied in spinal cord neuronal responses from adult male Wistar rats with carrageenan-induced inflammation, using the recording of single motor unit technique. The experiments showed that the i.v. administration of medetomidine and NCX701 induced a more potent and effective antinociceptive effect than medetomidine when given alone (ID50: 0.47 ± 0.1 vs. 1.1 ± 0.1 μg/kg) or in the presence of paracetamol, in naturally-evoked nociceptive responses. In addition, the duration of antinociception was significantly longer (P < 0.001, 100 min after administration). The use of low doses of NCX701 and α2-adrenoceptor agonists might open new perspectives in the treatment of inflammatory pain.► The α2-adrenoceptor agonist medetomidine induces analgesia in inflammation. ► The antinociception induced by medetomidine was enhanced by low doses of NCX701. ► The ID50 and inhibitory doses of medetomidine were significantly reduced by NCX701. ► The duration of medetomidine-induced antinociception was significantly enlarged by NCX701.
Keywords: Pain; Inflammation; Cyclooxygenase inhibitors; nitro-NSAIDs; Single motor unit;

Effects of pregnanolone and flunitrazepam on the retention of response sequences in rats by Russell J. Amato; Joseph M. Moerschbaecher; Peter J. Winsauer (391-398).
Neuroactive steroids produce effects similar to other GABAA modulators (e.g., benzodiazepines and barbiturates) and have a large therapeutic potential; however, a greater understanding of the effects of these substances on learning and memory is needed. To specifically assess the effects of a neurosteroid on memory, pregnanolone (1–18 mg/kg) was administered to male Long-Evans rats responding under a repeated acquisition and delayed-performance procedure in which different 4-response sequences were acquired and then retested after varying delays. Responding was maintained under a second-order fixed-ratio (FR) 2 schedule of food reinforcement, and incorrect responses (errors) produced a 5-sec timeout. For comparison purposes, both a high (flunitrazepam) and low efficacy agonist/antagonist (flumazenil) of the GABAA receptor complex were also administered both alone and in combination. Retention of each sequence was quantified as percent savings in errors-to-criterion and this dependent measure was shown to be sensitive to increases in delay. When administered 15 min prior to the end of either a 30- or 180-minute delay, pregnanolone produced both dose- and delay-dependent decreases in percent savings, response rate and accuracy; this effect was selective in that decreases in retention occurred at doses lower than those that disrupted response rate or accuracy. Flunitrazepam (0.056–1 mg/kg) produced similar disruptions in retention and these disruptions were antagonized by 5.6 mg/kg of flumazenil. Both an ineffective (0.056 mg/kg) and an effective (0.18 mg/kg) dose of flunitrazepam also potentiated the dose- and delay-dependent disruptions in retention produced by pregnanolone. These data indicate that the neurosteroid pregnanolone disrupts retention in a manner similar to the benzodiazepine flunitrazepam, and suggests that the interaction of flunitrazepam and pregnanolone on retention may be mediated by the GABAA receptor complex.► Pregnanolone disrupted retention on a repeated acquisition and performance task. ► The effects of pregnanolone on retention were similar to those of flunitrazepam. ► Flumazenil attenuated the disruptions produced by flunitrazepam on retention. ► Flunitrazepam potentiated the disruptions produced by pregnanolone. ► Disruptions in retention produced by pregnanolone may be GABAA mediated.
Keywords: Memory; Pregnanolone; Flunitrazepam; Flumazenil; GABAA receptor; Rats;

The present study investigates the interaction of curcumin with four antiepileptic drugs (AEDs) in male Wistar rats. In the first protocol, seizures were induced using pentylenetetrazole (PTZ) and valproate was injected intraperitoneally (i.p.) in therapeutic and sub-therapeutic doses 30 min before PTZ administration. Curcumin was co-administered with sub-therapeutic dose of valproate 60 min before PTZ injection. In the second protocol, seizures were induced by maximal-electroshock. Phenytoin, phenobarbitone and carbamazepine were injected in their therapeutic and sub-therapeutic doses 120, 60 and 30 min, respectively, before seizure induction. Curcumin was administered along with sub-therapeutic doses of phenytoin, phenobarbitone and carbamazepine, 60 min before induction of seizures. Behavioral parameters were assessed using elevated plus maze test and passive avoidance paradigm. Rat brain oxidative stress parameters were assessed and the serum levels of the AEDs were estimated. The AEDs in their therapeutic doses produced complete protection against seizures. However, sub-therapeutic doses of these AEDs failed to completely protect against seizures. Co-administration of curcumin with sub-therapeutic dose of valproate significantly increased the latency to myoclonic jerks. The percentage protection against seizures with sub-therapeutic doses of valproate, phenytoin, phenobarbitone and carbamazepine was also enhanced by concomitant curcumin administration. Both PTZ and MES induced seizures caused significant impairment of cognitive functions. Co-administration of curcumin with these AEDs in their sub-therapeutic doses prevented the impairment of learning and memory due to seizures whereas no such improvement was observed in the groups administered the sub-therapeutic doses of the AEDs alone. Additionally, curcumin reversed the oxidative stress due to seizures. However, curcumin co-administration did not cause any significant alteration in the serum levels of the AEDs. The results thus suggest the potential of curcumin as an adjunct to these AEDs in epilepsy with the advantage of increasing the efficacy, reducing the dose and side effects of the AEDs.► Curcumin interacts with valproate, phenytoin, phenobarbitone and carbamazepine. ► Curcumin with lower dose of antiepileptic drugs (AEDs) enhanced seizure protection. ► Curcumin with AEDs in their sub-therapeutic doses prevented cognitive impairment. ► Curcumin reversed the oxidative stress due to seizures. ► Curcumin can be used as an adjunct to these AEDs in epilepsy.
Keywords: Curcumin; Antiepileptic drugs; Interaction; Pentylenetetrazole (PTZ); Maximal-electroshock (MES); Oxidative stress; Cognitive impairment;

Stress is a well-known risk factor in relapse to drug abuse. Several forms of stress in animals have been used with varied degrees of success to elicit reinstatement of drug-seeking after chronic drug self-administration. Here, we tested the ability of the benzodiazepine (BZ) inverse agonist, FG 7142, to elicit anxiety-like behavior and potentiate stress responses in rats as measured by standard behavioral and hormonal indices and for its ability to affect reinstatement of cocaine-seeking in rats with a prior history of cocaine self-administration. FG 7142 elicited anxiety-like behavior on the elevated plus maze (EPM) in cocaine-naïve rats, and cocaine-naïve rats injected with FG 7142 exhibited increased plasma corticosterone levels following EPM exposure. However, in animals with a history of cocaine self-administration, FG 7142 failed to affect elevated plus maze performance and did not affect plasma corticosterone response to the EPM. Furthermore, FG 7142 failed to reinstate cocaine-seeking, nor did it alter conditioned cue-induced reinstatement. These data indicate that the anxiety-related and stress potentiating qualities of BZ inverse agonism are attenuated in cocaine-experienced animals and do not lead to reinstatement of cocaine-seeking.► Relapse to cocaine abuse can be elicited by stress. ► Pharmacological stressors can serve as probes in understanding this phenomenon. ► FG 7142 potentiates the stress response of rats to the EPM. ► These effects are absent in cocaine trained rats. ► FG 7142 does not influence extinguished cocaine seeking behavior.
Keywords: Benzodiazepine; Cocaine; FG 7142; Reinstatement; Relapse; Self-administration;

Oral tremor induced by galantamine in rats: A model of the parkinsonian side effects of cholinomimetics used to treat Alzheimer's disease by Lyndsey E. Collins; Nicholas E. Paul; Shams F. Abbas; Chelsea E. Leser; Samantha J. Podurgiel; Daniel J. Galtieri; James J. Chrobak; Younis Baqi; Christa E. Müller; John D. Salamone (414-422).
Anticholinesterases are the most common treatment for Alzheimer's disease, and, in recent years, a new group of cholinesterase inhibitors (i.e. rivastigmine, galantamine, and donepezil) has become available. Although these drugs improve cognitive symptoms, they also can induce or exacerbate parkinsonian symptoms, including tremor. The present studies were conducted to determine if galantamine induces tremulous jaw movements, a rodent model of parkinsonian tremor, and to investigate whether these oral motor impairments can be reversed by co-administration of adenosine A2A antagonists. The first experiment demonstrated that systemic injections of galantamine (0.75–6.0 mg/kg I.P.) induced a dose-related increase in tremulous jaw movements in rats. In a second study, co-administration of the muscarinic antagonist scopolamine (0.0156–0.25 mg/kg I.P.) produced a dose dependent suppression of tremulous jaw movements induced by a 3.0 mg/kg dose of galantamine, indicating that galantamine induces these tremulous oral movements through actions on muscarinic acetylcholine receptors. In two additional studies, analyses of freeze-frame video and electromyographic activity recorded from the lateral temporalis muscle indicated that the local frequency of these galantamine-induced jaw movements occurs in the 3–7 Hz frequency range that is characteristic of parkinsonian tremor. In the final experiment, the adenosine A2A antagonist MSX-3 significantly attenuated the tremulous jaw movements induced by the 3.0 mg/kg dose of galantamine, which is consistent with the hypothesis that co-administration of adenosine A2A antagonists may be beneficial in reducing parkinsonian motor impairments induced by anticholinesterase treatment.► Galantamine is a common dementia treatment, but also induces parkinsonian tremor. ► Galantamine induced tremulous jaw movements in rats. ► These tremulous jaw movements occurred largely in the 3–7 Hz frequency range. ► These oral tremors were blocked by adenosine A2A antagonism. ► Adenosine A2A antagonists may be useful for treating galantamine-induced tremor.
Keywords: Acetylcholine; Muscarinic; Adenosine A2A; Basal ganglia; Parkinsonism; Tremulous jaw movements;

Low dose, short-term rivastigmine administration does not affect neurocognition in methamphetamine dependent individuals by Ari D. Kalechstein; Jin H. Yoon; Daniel E. Croft; Susanne Jaeggi; James J. Mahoney; Richard De La Garza (423-427).
Neurocognitive impairment is a well-documented consequence of methamphetamine addiction. Not surprising, methamphetamine-associated neurocognitive impairment has been identified as an important target of treatment. Thus, this study sought to determine whether rivastigmine, an acetylcholinesterase inhibitor and cognition enhancing agent, could improve neurocognitive performance in a sample of long-term, high-dose methamphetamine addicts who were not seeking treatment at the time of enrollment in the study. This double-blind, placebo-controlled study evaluated whether a daily dose 0, 3, or 6 mg of rivastigmine, administered over six consecutive days, would enhance performance on measures of attention/information processing speed, episodic memory, and executive/frontal lobe functioning relative to test performance at baseline. The results revealed that rivastigmine did not alter neurocognition in this cohort. There are a number of factors that may have mitigated the effects of rivastigmine in this particular study, including especially the short-term, low-dose treatment regimen utilized. The negative findings notwithstanding, the study serves as a springboard for future investigations that will examine whether other medications can alter neurocognition in methamphetamine dependent study participants.► This is the first study, to our knowledge, to examine whether a cholinesterase inhibitor can improve neurocognitive functioning in methamphetamine dependent individuals. ► Short-term, low-dose rivastigmine administration does not improve neurocognition in methamphetamine dependent individuals. ► The methodology was sufficiently rigorous to detect such effects, i.e., within-subjects, double-blind, placebo control. ► Given the results of studies in other populations, higher dosing over a longer period of time would be most likely to yield a positive effect. ► This study further demonstrates that rivastigmine can be safely administered to methamphetamine dependent individuals without adverse effects.
Keywords: Methamphetamine; Cognition; Neurocognition; Neuropsychological impairment; Rivastigmine; Acetylcholine;

Ethanol-induced changes in the expression of proteins related to neurotransmission and metabolism in different regions of the rat brain by Natalie M. Zahr; Richard L. Bell; Heather N. Ringham; Edith V. Sullivan; Frank A. Witzmann; Adolf Pfefferbaum (428-436).
Despite extensive description of the damaging effects of chronic alcohol exposure on brain structure, mechanistic explanations for the observed changes are just emerging. To investigate regional brain changes in protein expression levels following chronic ethanol treatment, one rat per sibling pair of male Wistar rats was exposed to intermittent (14 h/day) vaporized ethanol, the other to air for 26 weeks. At the end of 24 weeks of vapor exposure, the ethanol group had blood ethanol levels averaging 450 mg%, had not experienced a protracted (> 16 h) withdrawal from ethanol, and revealed only mild evidence of hepatic steatosis. Extracted brains were micro-dissected to isolate the prefrontal cortex (PFC), dorsal striatum (STR), corpus callosum genu (CCg), CC body (CCb), anterior vermis (AV), and anterior dorsal lateral cerebellum (ADLC) for protein analysis with two-dimensional gel electrophoresis. Expression levels for 54 protein spots were significantly different between the ethanol- and air-treated groups. Of these 54 proteins, tandem mass spectroscopy successfully identified 39 unique proteins, the levels of which were modified by ethanol treatment: 13 in the PFC, 7 in the STR, 2 in the CCg, 7 in the CCb, 7 in the AV, and 5 in the ADLC. The functions of the proteins altered by chronic ethanol exposure were predominately associated with neurotransmitter systems in the PFC and cell metabolism in the STR. Stress response proteins were elevated only in the PFC, AV, and ADLC perhaps supporting a role for frontocerebellar circuitry disruption in alcoholism. Of the remaining proteins, some had functions associated with cytoskeletal physiology (e.g., in the CCb) and others with transcription/translation (e.g., in the ADLC). Considered collectively, all but 4 of the 39 proteins identified in the present study have been previously identified in ethanol gene- and/or protein-expression studies lending support for their role in ethanol-related brain alterations.► Rats exposed to vaporized ethanol for 26 weeks attained blood levels of 450 mg%. ► Six brain regions were micro-dissected and submitted to proteomic investigation. ► Findings support a disrupted frontocerebellar circuitry following ethanol exposure. ► Findings also support regionally non-selective metabolic compromise.
Keywords: Vapor chambers; Proteomics; Frontocerebellar circuitry;

Evidence that PGE2 in the dorsal and median raphe nuclei is involved in LPS-induced anorexia in rats by Brigitte S. Kopf; Wolfgang Langhans; Nori Geary; Brian Hrupka; Lori Asarian (437-443).
Anorexia is an element of the acute-phase immune response. Its mechanisms remain poorly understood. Activation of inducible cyclooxygenase-2 (COX-2) in blood–brain-barrier endothelial cells and subsequent release of prostaglandins (e.g., prostaglandin E2, PGE2) may be involved. Therefore, we sought to relate the effects of prostaglandins on the anorexia following gram-negative bacterial lipopolysaccharide treatment (LPS) to neural activity in the dorsal and median raphe nuclei (DRN and MnR) in rats. COX-2 antagonist (NS-398, 10 mg/kg; IP) administration prior to LPS (100 μg/kg; IP) prevented anorexia and reduced c-Fos expression the DRN, MnR, nucleus tractus solitarii and several related forebrain areas. These data indicate that COX-2-mediated prostaglandin synthesis is necessary for LPS anorexia and much of the initial LPS-induced neural activation. Injection of NS-398 into the DRN and MnR (1 ng/site) attenuated LPS-induced anorexia to nearly the same extent as IP NS-398, suggesting that prostaglandin signaling in these areas is necessary for LPS anorexia. Because the DRN and MnR are sources of major serotonergic projections to the forebrain, these data suggest that serotonergic neurons originating in the midbrain raphe play an important role in acute-phase response anorexia.► NS-398 administered 1 h before LPS completely eliminated LPS anorexia. ► NS-398 eliminated LPS‐induced c‐Fos expression after LPS in several brain areas. ► Injection of PGE2 into the dorsal/median raphe reduced food intake by 35%. ► Central injection of NS-398 into the dorsal/median raphe attenuated LPS anorexia.
Keywords: Prostaglandin; Serotonin; Eating; Infection;

Attenuation of apomorphine-induced sensitization by buspirone by Huma Ikram; Darakhshan Jabeen Haleem (444-450).
Apomorphine, a dopamine D1/D2 agonist is effective in the treatment of parkinson's disease; but its long term use is often associated with the dependence and addiction. The development of locomotor sensitization to psychostimulants including apomorphine is considered to be an important contributor to psychostimulant drug abuse. Previous studies have shown that long term administration of drugs of abuse increases the effectiveness of somatodendritic 5-hydroxytryptamine (5-HT)-1A receptors. Repeated administration of buspirone attenuates the effectiveness of somatodendritic 5-HT1A receptors. The present study was designed to test the hypothesis that coadministration of buspirone may attenuate apomorphine induced sensitization. Administration of apomorphine at a dose of 1.0, 2.0 & 4.0 mg/kg increased motor activity in an activity box in a dose dependent manner. Locomotor enhancing effects of a low dose of apomorphine were augmented upon repeated administration suggesting drug-induced sensitization. The sensitization effects were significant in an activity box as well as in an open field. Coadministration of buspirone at a dose of 1.0 mg/kg reversed apomorphine-induced sensitization. Repeated administration of buspirone at a dose of 2.0 mg/kg but not 1.0 mg/kg also elicited sensitization in motor behavior. It is suggested that buspirone may oppose the development of sensitization to apomorphine by decreasing the sensitivity of somatodendritic 5-HT1A receptors. Findings may help in extending therapeutics in parkinson's disease.► Buspirone coadministration at the dose of 1.0 mg/kg could attenuate apomorphine-induced motor sensitization. ► An increase in the inhibitory serotonergic influence on dopaminergic neurons may be the mechanisms by which buspirone could attenuate apomorphine-induced motor sensitization. ► Increase in the sensitivity of somatodendritic 5-HT1A receptors may have an important role in apomorphine-induced sensitization. ► Findings may have important consequences in the use of apomorphine for the treatment of Parkinson’s disease.
Keywords: Behavioral sensitization; Apomorphine; Buspirone; Serotonin; 5-HT1A receptors;

Powerful behavioral interactions between methamphetamine and morphine by Keith A. Trujillo; Monique L. Smith; Melissa M. Guaderrama (451-458).
Use of drugs of abuse in combination is common among recreational users and addicts. The combination of a psychomotor stimulant with an opiate, known as a ‘speedball,’ reportedly produces greater effects than either drug alone and has been responsible for numerous deaths. Historically, the most popular speedball combination is that of cocaine and heroin. However, with the growing popularity of methamphetamine in recent years, there has been increased use of this drug in combination with other drugs of abuse, including opiates. Despite this, relatively little research has examined interactions between methamphetamine and opiates. In the current research, behavioral interactions between methamphetamine and the prototypical opiate, morphine, were examined across a variety of dose combinations in Sprague–Dawley rats. The combination of methamphetamine and morphine produced stimulation of behavior that was dramatically higher than either drug alone; however, the magnitude of the interaction was dependent on the dose of the drugs and the specific behaviors examined. The results demonstrate complex behavioral interactions between these drugs, but are consistent with the idea that this combination is used because it produces a greater effect than either drug alone.► Interactions between methamphetamine (MA) and morphine (MOR) were examined in rats. ► MA caused a stimulant effect while MOR produced an inverted U-shaped dose response. ► The combination of MA and MOR produced effects greater than either drug alone. ► The greater than additive effect was dependent on the doses and behaviors examined. ► The results demonstrate complex behavioral interactions between MA and MOR.
Keywords: Speedball; Methamphetamine; Morphine; Locomotor behavior; Polydrug abuse; Synergism;

Self-administered and yoked nicotine produce robust increases in blood pressure and changes in heart rate with modest effects of behavioral contingency in rats by Eric C. Donny; Anthony R. Caggiula; Maggie Sweitzer; Nadia Chaudhri; Maysa Gharib; Alan F. Sved (459-467).
Experimenter-administered nicotine produces reliable increases in blood pressure and changes in heart rate. However, an extensive literature demonstrates that the effects of psychoactive drugs are dependent on whether administration is contingent on behavior. The present study assessed the cardiovascular effects of nicotine and whether those effects vary as a function of whether nicotine was self-administered or response-independent. Rats were divided into three groups according to a yoked design. The pattern of infusions for each triad was determined by the animal self-administering nicotine; the other two animals received either yoked nicotine or saline. Heart rate and blood pressure were measured during eighteen daily, 1 h drug sessions by radiotelemetry. Each session was preceded and followed by a 20 minute period during which cardiovascular function was monitored in the operant chambers, but drug was not available. Acute exposure to yoked nicotine produced a rapid rise in blood pressure that was larger than the increase observed with self-administered nicotine. Additional infusions during the first session resulted in a similar sustained elevation in blood pressure in the nicotine groups. Over subsequent sessions, self-administered nicotine produced a larger effect on systolic blood pressure particularly early in each session, although for both self-administered and yoked nicotine the hypertensive effects waned partially with repeated test sessions. This decrease was fully accounted for by a pre-session decrease in pressure; relative to pre-session levels the strong hypertensive effects of nicotine persisted. Initial exposure to nicotine produced a short-lived bradycardia that in subsequent sessions was replaced with a longer-lasting nicotine-induced tachycardia; neither effect was related to the behavioral contingency of nicotine delivery. Together, these data provide a rich picture of the cardiovascular effects of nicotine. Effects of behavioral contingency were observed, but differences were limited. Other non-pharmacological factors such as baseline shifts potentially related to nicotine-associated cues deserve further attention.► The cardiovascular effects of nicotine were characterized using a yoked design. ► Acute nicotine elevated blood pressure and decreased heart rate. ► Repeated exposure reduced the hypertensive effects of nicotine relative to saline. ► Baseline blood pressure decreased with days of nicotine exposure. ► Small, but significant, differences were seen as a function of response contingency.
Keywords: Nicotine; Self-administration; Contingency; Yoking; Blood pressure; Heart rate; Tolerance; Conditioning; Rats;

Anti-inflammatory drug ibuprofen decreases the β-amyloid (Aβ) deposition and associated inflammation in transgenic Alzheimer disease mice. Based on this, we studied whether ibuprofen could modulate the secondary pathology described in the thalamus of middle cerebral artery occlusion (MCAO) rats. Our hypothesis was that ibuprofen could decrease inflammatory reaction and Aβ load in the thalamus of MCAO rats, which in turn is reflected in improved behavioral outcome. Forty male Wistar rats (250–340 g) were subjected to sham-operation or transient occlusion of the right middle cerebral artery (120 min). Ibuprofen (40 mg/kg/day, per os) was administrated for 27 days beginning the treatment on post-operative day 2. MCAO controls were given vehicle. Sensorimotor impairment was assessed using the limb-placing, tapered ledged beam-walking and cylinder tests during the follow-up. The rats were perfused for histology on postoperative day 29. Histological data showed that ibuprofen did not affect Aβ or calcium load in the thalamus of MCAO rats. In addition, behavioral tests did not show significant difference between vehicle- and ibuprofen-treated MCAO rats. The present data do not support the idea that ibuprofen reduces the secondary Aβ/calcium pathology in the thalamus or associated sensorimotor impairment following cerebral ischemia.► Focal cerebral ischemia in the cortex leads to secondary pathology in the thalamus. ► Thalamic pathology includes inflammatory reaction, impaired calcium homeostasis and atypical β-amyloid processing. ► Anti-inflammatory drug ibuprofen did not alter thalamic pathology following cerebral ischemia.
Keywords: β-amyloid; Calcium; Ibuprofen; Inflammation; Middle cerebral artery occlusion; Thalamus;

In a previous study we showed that chronic intermittent heroin in rats enhanced responding with conditioned reinforcement and reversal learning of a conditioned magazine approach task when tested three days after the heroin treatment. Whether or not this enhanced appetitive learning persists after a protracted withdrawal period remains unknown and constitutes the aim of the present study. Forty-eight male Long Evans rats were each exposed to positive pairings of a light stimulus and food for 4 consecutive daily sessions. Then, two groups of rats received saline and two groups received heroin (2 mg/kg) injections before placement in activity monitors for 9 consecutive daily sessions. This was followed by testing in operant conditioning chambers where one lever produced the light stimulus previously paired with food and another no stimulus. For one saline and one heroin group this testing occurred after 2 days of withdrawal while for the other saline and heroin groups it occurred after 30 days of withdrawal. The results indicate that animals treated with heroin displayed progressively and significantly greater locomotor activity across sessions while animals treated with saline displayed locomotor activity that remained low and stable across sessions. In addition, the heroin groups in each withdrawal condition displayed significantly enhanced responding with conditioned reinforcement compared to their respective saline control groups. These results demonstrate that chronic intermittent heroin enhances appetitive learning for natural reinforcers and motivational processes and that this effect persists even after 30-days of withdrawal.► Repeated injections of heroin in rats produces sensitization to its locomotor-stimulant effects. ► Repeated injections of heroin in rats enhances responding reinforced by a food-associated conditioned stimulus. ► The enhancement of appetitive learning and motivational processes observed with chronic heroin lasts into a protracted withdrawal period, indicating that it is relatively long-lasting.
Keywords: Protracted withdrawal; Heroin; Locomotor sensitization; Conditioned reinforcement; Rats; Drug addiction;

Effects of anxiolytics in zebrafish: Similarities and differences between benzodiazepines, buspirone and ethanol by Daiane L. Gebauer; Natália Pagnussat; Ângelo L. Piato; Isabel C. Schaefer; Carla D. Bonan; Diogo R. Lara (480-486).
There is growing interest in zebrafish as a model organism in behavioral pharmacology research. Several anxiety behaviors have been characterized in zebrafish, but the effect of anxiolytic drugs on these parameters has been scarcely studied. The purpose of this work was to assess the predictive validity of acute treatment with anxiolytic drugs on behavioral parameters of anxiety. In the first task we simultaneously observed behavior of adult zebrafish on four parameters: height in the tank, locomotion, color, and shoal cohesion. The second task was the assessment of light/dark preference for 5 min. The benzodiazepines clonazepam, bromazepam, diazepam, and a moderate dose of ethanol significantly reduced shoal cohesion. Buspirone specifically increased zebrafish exploration of higher portions of the tank. In the light/dark task, all benzodiazepines, buspirone, and ethanol increased time spent in the light compartment. After treatment with anxiolytics, fish typically spent more than 60 s and rarely less than 40 s in the light compartment whereas controls (n = 45) spent 33.3 ± 14.4 s and always less than 60 s in the light compartment. Propranolol had no clear effects in these tasks. These results suggest that light/dark preference in zebrafish is a practical, low-cost, and sensitive screening task for anxiolytic drugs. Height in the tank and shoal cohesion seem to be useful behavioral parameters in discriminating different classes of these drugs.► The benzodiazepines and a moderate dose of ethanol reduced shoal cohesion. ► Buspirone increased zebrafish exploration of higher portions of the tank. ► Height in the tank and shoal cohesion are useful to discriminate anxiolytics.
Keywords: Zebrafish; Anxiety; Benzodiazepines; Shoal cohesion; Light/dark task;

In rats, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes anorexia that may lead to fatal wasting but has hitherto been poorly characterized. Therefore, we studied in-depth feeding and drinking behaviors of TCDD-sensitive L–E rats for 5 (100 μg/kg; lethal dose) or 10 (10 μg/kg; sublethal) days and of TCDD-resistant H/W rats for 14 (100 or 1000 μg/kg; both sublethal) days postexposure to TCDD. The 1000-fold higher resistance of H/W rats to acute lethality of TCDD results from a mutation in their AH receptor (AHR). We split days into four (morning, daytime, evening, and night) or two (light/dark) circadian periods and took the repeated nature of the data into account. In L–E rats at 100 μg/kg, the feed intake dropped precipitously, due to reduced meal sizes. In H/W rats, the hypophagia remained moderate and stemmed from a reduced meal frequency. While the suppression in L–E rats peaked during the morning (at 100 μg/kg), the main effects in H/W rats were seen during the constant light or dark phases. Furthermore, chronologic data analysis revealed alterations in consecutive feeding and drinking patterns. Thus, striking differences were found between these strains in the timing and structure of consummatory behaviors, suggesting involvement of the AHR in these behaviors.Display Omitted► TCDD suppressed feeding at different times of day in differently TCDD-sensitive rats. ► In sensitive rats decreased feeding chiefly resulted from reduced meal size. ► In resistant rats decreased feeding chiefly resulted from reduced meal frequency. ► Differences among rat strains suggest different TCDD effects on feeding regulation. ► AHR may have a modulating role in the circadian rhythms of consummatory behaviors.
Keywords: 2,3,7,8-Tetrachlorodibenzo-p-dioxin, TCDD; Feeding; Drinking; Rat strain differences; Automated monitoring; Wasting syndrome;

The purpose of this study was to investigate the effects of acute and chronic administration of anabolic–androgenic steroids (AAS) on nociception and morphine antinociception in acute pain models, as well as on chronic inflammatory nociception. In Experiment 1, adult, gonadally intact male rats were injected s.c. for 28 days with either 5 mg/kg testosterone (T), dihydrotestosterone (DHT), stanozolol (STAN), or safflower oil vehicle (N = 12–25/group). On day 28, rats in each group were tested on acute thermal and mechanical nociceptive assays, before and after morphine treatment. In Experiment 2, rats in each group (N = 8–10/group) were injected with mineral oil or complete Freund's adjuvant (CFA) into one hindpaw after 28 days of AAS treatment, and then tested for thermal hyperalgesia, mechanical allodynia, inflammation and locomotor suppression intermittently for 28 days. Experiment 3 replicated nociceptive measurements in Experiments 1 and 2, but with a single AAS or vehicle injection occurring 3 h prior to testing (N = 10–12/group). While chronic AAS administration tended to decrease body weight gain and alter reproductive organ weights in the expected manner, it did not significantly alter acute nociception nor attenuate the development of various chronic pain indices after CFA administration. Morphine antinociceptive potency was significantly decreased by chronic DHT on the hotplate test only. Acute AAS administration also did not significantly alter acute or chronic nociception, or morphine antinociceptive potency. Comparisons between acute and chronic AAS administration suggest that steroid tolerance did not occur in rats treated with AAS chronically. Taken together, these data do not support the hypothesis that AAS exposure alters nociception or morphine antinociception in gonadally intact males.► AAS decreases body weight gain. ► AAS altered reproductive organ weights. ► AAS did not significantly alter acute nociception. ► AAS did not attenuate development of chronic pain indices after CFA administration. ► Morphine antinociceptive potency was decreased by DHT on the hotplate test only.
Keywords: Androgen; Anabolic steroid; Testosterone; Dihydrotestosterone; Stanozolol; Pain;

Prepulse inhibition (PPI) of acoustic startle response is impaired in patients with schizophrenia and in animals acutely treated with dopamine agonists and NMDA antagonists. In this study, we investigated the time course of PPI disruption induced by repeated amphetamine, quinpirole, phencyclidine (PCP), and dizocilpine (MK-801) treatment. We focused on how PPI disruption development was influenced by drug administration regimens, comparing a constant versus an escalating dosing regimen. Male Sprague–Dawley rats were repeatedly treated with amphetamine (1.25–5.0 mg/kg, or constant 5.0 mg/kg, sc), PCP (0.50–2.0 mg/kg, or constant 0.5, 1.0 or 2.0 mg/kg, sc), quinpirole (0.03–0.12 mg/kg, or constant 0.12 mg/kg, sc), MK-801 (0.025–0.10 mg/kg, or constant 0.10 mg/kg, sc) or vehicle (saline) and tested for PPI once daily for 6 consecutive days. When amphetamine 5.0 mg/kg or quinpirole 0.12 mg/kg was administrated on a constant dosing schedule, both drugs disrupted PPI upon acute administration, but had no effect after repeated treatment and testing (days 2–5). However, when amphetamine 5.0 mg/kg or quinpirole 0.12 mg/kg was preceded by two lower doses in an escalating dosing regimen, both drugs still disrupted PPI on days 5 and 6 when the constant amphetamine and quinpirole had no effect. For PCP and MK-801, repeated treatment under both regimens produced a stable and persistent disruption of PPI. Startle magnitude increased progressively and dose-dependently under both regimens for all drugs except for quinpirole, which caused a decrease. These results suggest that the drug dosing schedule, rather than the absolute amount of drug that an animal receives, has a greater impact on the development of PPI-disruptive effect of dopamine agonists than NMDA antagonists. Thus, in order to mimic the emerging process of PPI deficit with dopamine agonists, an escalating dosing regimen should be used.► Acute administration of amphetamine (5.0 mg/kg) or quinpirole (0.12 mg/kg) disrupted prepulse inhibition of acoustic startle response. ► Repeated administration of amphetamine (5.0 mg/kg) or quinpirole (0.12 mg/kg) lost its disruption. ► An escalating dosing regimen with amphetamine (1.0–5.0 mg/kg) produced a persistent disruption over time. ► Acute and repeated treatment of phencyclidine (0.50–2.0 mg/kg) or MK-801 (0.025–0.10 mg/kg) produced a stable and persistent disruption of PPI.
Keywords: Prepulse inhibition of acoustic startle; Repeated amphetamine treatment; Repeated phencyclidine treatment; Quinpirole; Dizocilpine (MK-801); Sensitization effect; Tolerance effect;

Nicotine-induced conditioned place preference in adolescent rats by Reka Natarajan; John W. Wright; Joseph W. Harding (519-523).
A number of clinical reports have noted that women are more vulnerable to tobacco abuse than men, and adolescent females are especially vulnerable to nicotine addiction. Conditioned place preference (CPP) is a widely used technique for determining the rewarding effects of drugs with abuse potential in animal models. Several studies have reported that nicotine was ineffective in eliciting CPP in rats; while others have observed conditioned place aversion (CPA) rather than preference for nicotine. One recent investigation established CPP in adolescent female rats, however at a reasonably high dose; while a second reported dose dependence of nicotine-induced CPP in male but not female rats. The present study was designed to determine the lowest dose necessary to induce CPP to nicotine in adolescent female rats. Nicotine-induced CPP was obtained at a subcutaneous dose of 0.03 mg/kg (salt content) using a biased conditioning paradigm. Higher doses produced aversion and lower doses provided no rewarding or aversive effects. CPP persisted for at least 3 weeks following conditioning in the absence of further nicotine treatment. In contrast with results from adolescent human females and males, age-matched male rats also evidenced CPP at this very low dose of nicotine. These results indicate that even a low dose of nicotine is reinforcing and addicting in both adolescent male and female rats and brings into question the suggestion that nicotine induces greater addicting capacity in adolescent girls than boys.► Adolescent female rats revealed nicotine-induced CPP at a low dose of 0.03 mg/kg s.c. ► Same age adolescent male rats also showed nicotine-induced CPP at this same low dose. ► Nicotine-induced CPP lasted for three weeks with no further nicotine treatment. ► Results suggest that adolescent girls may be vulnerable to low levels of nicotine. ► In contrast with reports from human studies adolescent boys may share this sensitivity.
Keywords: Nicotine; Conditioned place preference; Conditioned place aversion; Adolescent rats;