Rats on the grog: novel pharmacotherapies for alcohol craving

Differential Influence of Pueraria lobata Root Extract and Its Main Isoflavones on Ghrelin Levels in Alcohol-Treated Rats

The study was carried out on alcohol-preferring male Wistar rats. The following drugs were repeatedly (28×) administered: acamprosate (500 mg/kg, p.o.), naltrexone (0.1 mg/kg, i.p), and Pueraria lobata (kudzu) root extract (KU) (500 mg/kg, p.o.) and its isoflavones: daidzin (40 mg/kg, p.o.) and puerarin (150 mg/kg, p.o.). Their effects on a voluntary alcohol intake were assessed. KU and alcohol were also given for 9 days in an experiment on alcohol tolerance development. Finally, total and active ghrelin levels in peripheral blood serum were measured by ELISA method. Acamprosate, naltrexone, daidzin, and puerarin, reducing the alcohol intake, caused an increase in both forms of ghrelin levels. On the contrary, though KU inhibited the alcohol intake and alcohol tolerance development, it reduced ghrelin levels in alcohol-preferring rats. The changes of ghrelin concentration could play a role as an indicator of the currently used drugs. The other effect on the KU-induced shift in ghrelin levels in the presence of alcohol requires further detailed study.

Ventral pallidum cellular and pathway specificity in drug seeking

The ventral pallidum (VP) is central to the reinforcing effects across a variety of drugs and relapse to drug seeking. Emerging studies from animal models of reinstatement reveal a complex neurobiology of the VP that contributes to different aspects of relapse to drug seeking. This review builds on classical understanding of the VP as part of the final common pathway of relapse but also discusses the properties of the VP as an independent structure. These include VP neural anatomical subregions, cellular heterogeneity, circuitry, neurotransmitters and peptides. Collectively, this review provides a current understanding of the VP from molecular to circuit level architecture that contributes to both the appetitive and aversive symptoms of drug addiction. We show the complex neurobiology of the VP in drug seeking, emphasizing its critical role in addiction, and review strategic approaches that target the VP to reduce relapse rates.

Contingent and non-contingent recreational-like exposure to ethanol alters BDNF expression and signaling in the cortico-accumbal network differently

RATIONALE

Although brain-derived neurotrophic factor (BDNF) is part of a homeostatic pathway involved in the development of alcohol dependence, it is not clear whether this is also true after recreational ethanol consumption.

OBJECTIVES

We examined BDNF expression and signaling in the cortico-striatal network immediately and 24 h after either a single intravenous (i.v.) ethanol operant self-administration session or the last of 14 sessions.

METHODS

To compare contingent and non-contingent ethanol exposure, we incorporated the "yoked control-operant paradigm" in which rats actively taking ethanol (S-Et) were paired with two yoked controls receiving passive infusions of ethanol (Y-Et) or saline.

RESULTS

A single ethanol exposure transiently reduced BDNF mRNA levels in the medial prefrontal cortex (mPFC) of Y-Et. Immediately after the last of 14 sessions, mRNA and mature BDNF protein levels (mBDNF) were reduced in the mPFC in both S-Et and Y-Et while mBDNF expression was raised in the nucleus accumbens (NAc), suggesting enhanced anterograde transport from the mPFC. Conversely, 24 h later mBDNF expression and signaling were raised in the mPFC and NAc of S-Et rats but reduced in the NAc of Y-Et rats, with concomitant reduction of downstream signaling pathways.

CONCLUSIONS

Our findings indicate that recreational-like i.v. doses of ethanol promote early changes in neurotrophin expression, depending on the length and modality of administration, the brain region investigated, and the presence of the drug. A rapid intervention targeting the BDNF system might be useful to prevent escalation to alcohol abuse.

Pre- and postnatal exposure to moderate levels of ethanol can have long-lasting effects on hippocampal glutamate uptake in adolescent offspring

The developing brain is vulnerable to the effects of ethanol. Glutamate is the main mediator of excitatory signals in the brain and is probably involved in most aspects of normal brain function during development. The aim of this study was to investigate vulnerability to and the impact of ethanol toxicity on glutamate uptake signaling in adolescent rats after moderate pre and postnatal ethanol exposure. Pregnant female rats were divided into three groups and treated only with water (control), non-alcoholic beer (vehicle) or 10% (v/v) beer solution (moderate prenatal alcohol exposure—MPAE). Thirty days after birth, adolescent male offspring were submitted to hippocampal acute slice procedure. We assayed glutamate uptake and measured glutathione content and also quantified glial glutamate transporters (EAAT 1 and EAAT 2). The glutamate system vulnerability was tested with different acute ethanol doses in naïve rats and compared with the MPAE group. We also performed a (lipopolysaccharide-challenge (LPS-challenge) with all groups to test the glutamate uptake response after an insult. The MPAE group presented a decrease in glutamate uptake corroborating a decrease in glutathione (GSH) content. The reduction in GSH content suggests oxidative damage after acute ethanol exposure. The glial glutamate transporters were also altered after prenatal ethanol treatment, suggesting a disturbance in glutamate signaling. This study indicates that impairment of glutamate uptake can be dose-dependent and the glutamate system has a higher vulnerability to ethanol toxicity after moderate ethanol exposure In utero. The effects of pre- and postnatal ethanol exposure can have long-lasting impacts on the glutamate system in adolescence and potentially into adulthood.

Alcohol, stress hormones, and the prefrontal cortex: a proposed pathway to the dark side of addiction

Chronic exposure to alcohol produces changes in the prefrontal cortex that are thought to contribute to the development and maintenance of alcoholism. A large body of literature suggests that stress hormones play a critical role in this process. Here we review the bi-directional relationship between alcohol and stress hormones, and discuss how alcohol acutely stimulates the release of glucocorticoids and induces enduring modifications to neuroendocrine stress circuits during the transition from non-dependent drinking to alcohol dependence. We propose a pathway by which alcohol and stress hormones elicit neuroadaptive changes in prefrontal circuitry that could contribute functionally to a dampened neuroendocrine state and the increased propensity to relapse-a spiraling trajectory that could eventually lead to dependence.

The serotonin-2 receptor modulator, (-)-trans-PAT, decreases voluntary ethanol consumption in rats

Serotonin (5-HT) 5-HT2C receptor agonists have shown promise as novel alcoholism pharmacotherapies, but developing selective agonists has been problematic. Female Sprague Dawley rats were given ethanol in a palatable gel vehicle during operant sessions. 5-HT2C receptor modulators (Ro60-0175, SB242,084, and (-)-trans-PAT) were administered before operant sessions. As a control for the effects of 5-HT2C receptor agonism on caloric intake, drugs were also tested using non-ethanol containing gelatin. Ro60-0175, a 5-HT2 family receptor agonist, decreased both ethanol and vehicle responding while (-)-trans-PAT, a 5-HT2C receptor agonist with 5-HT2A-2B receptor inverse agonist activity, selectively reduced only ethanol responding. The effect of 5-HT2C receptor agonists on self-administration after reinstatement of ethanol after a three week deprivation was also determined. (-)-trans-PAT eliminated increases in ethanol intake following ethanol deprivation whereas Ro60-0175 had no effect. These results emphasize the need for caloric controls and further support the idea that selective modulation of 5-HT2 family receptors is a potential pharmacotherapeutic approach in the treatment of alcoholism.

Ethanol affects acylated and total ghrelin levels in peripheral blood of alcohol-dependent rats

There is a hypothesis that ghrelin could take part in the central effects of alcohol as well as function as a peripheral indicator of the changes which occur during long-term alcohol consumption. The aim of this study was to determine a correlation between alcohol concentration and acylated and total form of ghrelin after a single administration of alcohol (intraperitoneal, i.p.) (experiment 1) and prolonged ethanol consumption (experiment 2). The study was performed using Wistar alcohol preferring (PR) and non-preferring (NP) rats and rats from inbred line (Warsaw High Preferring, WHP; Warsaw Low Preferring, WLP). It was found that ghrelin in ethanol-naive WHP animals showed a significantly lower level when compared with the ethanol-naive WLP or Wistar rats. After acute ethanol administration in doses of 1.0; 2.0 and 4.0 g/kg, i.p., the simple (WHP) or inverse (WLP and Wistar) relationship between alcohol concentration and both form of ghrelin levels in plasma were found. Chronic alcohol intake in all groups of rats led to decrease of acylated ghrelin concentration. PR and WHP rats, after chronic alcohol drinking, had lower levels of both form of ghrelin in comparison with NP and WLP rats, respectively, and the observed differences in ghrelin levels were in inverse relationship with their alcohol intake. In conclusion, it is suggested that there is a strong relationship between alcohol administration or intake, ethanol concentration in blood and both active and total ghrelin level in the experimental animals, and that ghrelin plasma concentration can be a marker of alcohol drinking predisposition.

Long-term daily access to alcohol alters dopamine-related synthesis and signaling proteins in the rat striatum

Chronic alcohol exposure can adversely affect neuronal morphology, synaptic architecture and associated neuroplasticity. However, the effects of moderate levels of long-term alcohol intake on the brain are a matter of debate. The current study used 2-DE (two-dimensional gel electrophoresis) proteomics to examine proteomic changes in the striatum of male Wistar rats after 8 months of continuous access to a standard off-the-shelf beer in their home cages. Alcohol intake under group-housed conditions during this time was around 3-4 g/kg/day, a level below that known to induce physical dependence in rats. After 8 months of access rats were euthanased and 2-DE proteomic analysis of the striatum was conducted. A total of 28 striatal proteins were significantly altered in the beer drinking rats relative to controls. Strikingly, many of these were dopamine (DA)-related proteins, including tyrosine hydroxylase (an enzyme of DA biosynthesis), pyridoxal phosphate phosphatase (a co-enzyme in DA biosynthesis), DA and cAMP regulating phosphoprotein (a regulator of DA receptors and transporters), protein phosphatase 1 (a signaling protein) and nitric oxide synthase (which modulates DA uptake). Selected protein expression changes were verified using Western blotting. We conclude that long-term moderate alcohol consumption is associated with substantial alterations in the rat striatal proteome, particularly with regard to dopaminergic signaling pathways. This provides potentially important evidence of major neuroadaptations in dopamine systems with daily alcohol consumption at relatively modest levels.

Operant, oral alcoholic beer self-administration by C57BL/6J mice: effect of BHF177, a positive allosteric modulator of GABA(B) receptors

RATIONALE

With its high palatability, near-beer has been successfully used in rats as a vehicle to induce ethanol oral self-administration.

OBJECTIVES

The study aimed to develop an operant model of oral alcoholic beer self-administration promoting a stable intake of pharmacologically relevant amounts of ethanol in free-feeding C57BL/6J mice. It also aimed to assess the model's predictive validity by evaluating the influence of baclofen, a GABA(B) agonist, and BHF177, a GABA(B) positive allosteric modulator, on alcoholic beer self-administration.

METHODS

Mice were trained to self-administer, under a fixed ratio three schedule of reinforcement, 10 μl of beer containing increasing ethanol concentrations (0-18% v/v) in daily 30-min sessions. The effects on motor coordination (rotarod), locomotor activity (open field, automated cages) and anxiety-like behavior (elevated plus maze, EPM) were examined. Baclofen (1.25-5 mg/kg, intraperitoneal, i.p.) and BHF177 (3.75-30 mg/kg, i.p.) were used to see the effects on 9% alcoholic beer and near-beer self-administration.

RESULTS

Near-beer stably maintained operant oral self-administration in mice. Adding ethanol to near-beer reduced the number of active lever presses, while the corresponding amount of ethanol self-administration increased (0.8-1.0 g/kg/session). Motor impairment was observed when more than 1.3 g/kg/session of ethanol was self-administered with beer and slight but consistent hyperlocomotion with more than 0.9-1.0 g/kg/session. BHF177 (15 mg/kg) preferentially reduced 9% alcoholic beer self-administration, while the higher dose (30 mg/kg)-like baclofen 5 mg/kg-also reduced near-beer self-administration.

CONCLUSIONS

The operant model of oral alcoholic beer self-administration in C57BL/6J mice should prove useful for studying ethanol-reinforced behaviors and to identify candidate compounds for the pharmacological management of alcohol addiction.

Adolescent oxytocin exposure causes persistent reductions in anxiety and alcohol consumption and enhances sociability in rats

Previous studies have suggested that administration of oxytocin (OT) can have modulatory effects on social and anxiety-like behavior in mammals that may endure beyond the time of acute OT administration. The current study examined whether repeated administration of OT to male Wistar rats (n = 48) during a key developmental epoch (early adolescence) altered their physiology and behavior in later-life. Group housed rats were given intraperitoneal injections of either 1 mg/kg OT or vehicle during early adolescence (post natal-days [PND] 33–42). OT treatment caused a transient inhibition of body weight gain that recovered quickly after the cessation of treatment. At PND 50, the rats pre-treated with OT displayed less anxiety-like behavior on the emergence test, while at PND 55 they showed greater levels of social interaction. A subgroup of OT pre-treated rats examined at PND 63 showed a strong trend towards increased plasma OT levels, and also displayed significantly increased OT receptor mRNA in the hypothalamus. Rats pre-treated with OT and their controls showed similar induction of beer intake in daily 70 min test sessions (PND 63 onwards) in which the alcohol concentration of beer was gradually increased across days from 0.44% to 4.44%. However, when given ad libitum access to beer in their home cages from PND 72 onwards (early adulthood), consumption of beer but not water was significantly less in the OT pre-treated rats. A “booster” shot of OT (1 mg/kg) given after 25 days of ad libitum access to beer had a strong acute inhibitory effect on beer intake without affecting water intake. Overall these results suggest that exogenous OT administered during adolescence can have subtle yet enduring effects on anxiety, sociability and the motivation to consume alcohol. Such effects may reflect the inherent neuroplasticity of brain OT systems and a feed-forward effect whereby exogenous OT upregulates endogenous OT systems.

Effects of oral loperamide on efficacy of naltrexone, baclofen and AM-251 in blocking ethanol self-administration in rats

Naltrexone is a μ-opioid receptor antagonist that has been extensively studied for its ability to block the rewarding effects of ethanol. Opioid receptors are widely distributed within the gastrointestinal tract (GIT). Typically, naltrexone is administered by parenteral routes in nonclinical studies. We initially tested if opioid receptors within the GIT would influence the ability of oral naltrexone to inhibit ethanol oral self-administration in rats using the co-administration of oral loperamide, a peripherally restricted opioid agonist. As expected, oral naltrexone only had modest effects on ethanol intake, and the response was not dose-dependent. However in rats, treatment with loperamide prior to the administration of naltrexone resulted in a suppression of ethanol intake which approached that observed with naltrexone given by the subcutaneous (SC) route. Importantly, administration of loperamide prior to administration of naltrexone did not alter blood concentrations of naltrexone. We then evaluated if oral loperamide would enhance effects of baclofen (a GABA(B) receptor agonist) and AM-251 (a CB-1 receptor antagonist) and found that pre-treatment with loperamide did potentiate the action of both drugs to reduce ethanol self-administration. Finally, the specific opioid receptor type involved was investigated using selective μ- and κ-receptor antagonists to determine if these would affect the ability of the AM-251 and loperamide combination to block ethanol drinking behavior. The effect of loperamide was blocked by ALKS 37, a peripherally restricted μ-receptor antagonist. These data suggest an important role for opioid receptors within the GIT in modulating central reward pathways and may provide new insights into strategies for treating reward disorders, including drug dependency.

Beer promotes high levels of alcohol intake in adolescent and adult alcohol-preferring rats

Previous studies suggest that high levels of alcohol consumption can be obtained in laboratory rats by using beer as a test solution. The present study extended these observations to examine the intake of beer and equivalent dilute ethanol solutions with an inbred line of alcohol-preferring P rats. In Experiment 1, male adolescent P rats and age-matched Wistar rats had access to either beer or equivalent ethanol solutions for 1h daily in a custom-built lickometer apparatus. In subsequent experiments, adolescent (Experiment 2) and adult (Experiment 3) male P rats were given continuous 24-h home cage access to beer or dilute ethanol solutions, with concomitant access to lab chow and water. In each experiment, the alcohol content of the beer and dilute ethanol solutions was gradually increased from 0.4, 1.4, 2.4, 3.4, 4.4, 5 to 10% EtOH (vol/vol). All three experiments showed a major augmentation of alcohol intake when rats were given beer compared with equivalent ethanol solutions. In Experiment 1, the overall intake of beer was higher in P rats compared with Wistar rats, but no strain difference was found during the 1-h sessions with plain ethanol consumption. Experiment 1 also showed that an alcohol deprivation effect was more readily obtained in rats with a history of consuming beer rather than plain ethanol solutions. In Experiments 2 and 3, voluntary beer intake in P rats represented ethanol intake of 10-15 g/kg/day, among the highest reported in any study with rats. This excessive consumption was most apparent in adolescent rats. Beer consumption markedly exceeded plain ethanol intake in these experiments except at the highest alcohol concentration (10%) tested. The advantage of using beer rather than dilute ethanol solutions in both selected and nonselected rat strains is therefore confirmed. Our findings encourage the use of beer with alcohol-preferring rats in future research that seeks to obtain high levels of alcohol self-administration.

Ethanol and phencyclidine interact with respect to nucleus accumbens dopamine release: differential effects of administration order and pretreatment protocol

Executive dysfunction is a common symptom among alcohol-dependent individuals. Phencyclidine (PCP) injection induces dysfunction in the prefrontal cortex of animals but little is known about how PCP affects the response to ethanol. Using the in vivo microdialysis technique in male Wistar rats, we investigated how systemic injection of 5 mg/kg PCP would affect the dopamine release induced by local infusion of 300 mM ethanol into the nucleus accumbens. PCP given 60 min before ethanol entirely blocked ethanol-induced dopamine release. However, when ethanol was administered 60 min before PCP, both drugs induced dopamine release and PCP's effect was potentiated by ethanol (180% increase vs 150%). To test the role of prefrontal cortex dysfunction in ethanol reinforcement, animals were pretreated for 5 days with 2.58 mg/kg PCP according to previously used 'PFC hypofunction protocols'. This, however, did not change the relative response to PCP or ethanol compared to saline-treated controls. qPCR illustrated that this low PCP dose did not significantly change expression of glucose transporters Glut1 (SLC2A1) or Glut3 (SLC2A3), monocarboxylate transporter MCT2 (SLC16A7), glutamate transporters GLT-1 (SLC1A2) or GLAST (SLC1A3), the immediate early gene Arc (Arg3.1) or GABAergic neuron markers GAT-1 (SLC6A1) and parvalbumin. Therefore, we concluded that PCP at a dose of 2.58 mg/kg for 5 days did not induce hypofunction in Wistar rats. However, PCP and ethanol do have overlapping mechanisms of action and these drugs differentially affect mesolimbic dopaminergic transmission depending on the order of administration.

Intermittent access to beer promotes binge-like drinking in adolescent but not adult Wistar rats

Teenagers are more likely than adults to engage in binge drinking and could be more vulnerable to long-term brain changes following alcohol abuse. We investigated the possibility of excessive adolescent drinking in a rodent model in which beer (4.44% ethanol vol/vol) is presented to adult and adolescent male Wistar rats. Experiment 1 tracked ad libitum beer and water consumption in group-housed rats from postnatal day (PND) 28-96. Rats consumed an average of 7.8 g/kg/day of ethanol during adolescence (PND 34-55) and this gradually declined to a lower level of intake in adulthood (PND 56-93) of 3.9 g/kg/day. In Experiment 2, beer was made available to both adolescent (PND 29+) and adult (PND 57+) rats for 2h each day in a custom-built "lickometer" apparatus over 75 days. Access to beer was provided either 1 day out of every 3 ("intermittent" groups) or every day ("daily" groups). Relative to body weight, adolescent rats consumed more beer than adult rats in these limited access sessions. Adolescents with intermittent access consumed more than adolescents with daily access, a "binge"-like effect that was not observed in adult groups and that disappeared in adulthood. After 3 months of daily or intermittent alcohol consumption, the preference for beer versus sucrose was assessed. Rats previously kept under an intermittent schedule displayed a higher preference for beer relative to 3% sucrose, but only when testing occurred after 2 days of abstinence. In Experiment 3, adolescent (PND 30-37) and adult (PND 58-65) rats were given 20-min access to beer and their blood alcohol concentrations (BACs) were assessed. Adolescent groups consumed more alcohol than adults and showed higher BACS that were typical of human "binge" drinking (>80 mg/dL). Despite this, the correlation between BAC and beer intake was similar in both age groups. Together these results show that the intermittent presentation of alcohol itself appears to have subtle long-lasting effects on the motivation to consume alcohol. The findings support the use of beer solutions in modeling binge-like patterns of human alcohol consumption in adolescent rats.

Drug addiction

Many drugs of abuse, including cannabinoids, opioids, alcohol and nicotine, can alter the levels of endocannabinoids in the brain. Recent studies show that release of endocannabinoids in the ventral tegmental area can modulate the reward-related effects of dopamine and might therefore be an important neurobiological mechanism underlying drug addiction. There is strong evidence that the endocannabinoid system is involved in drug-seeking behavior (especially behavior that is reinforced by drug-related cues), as well as in the mechanisms that underlie relapse to drug use. The cannabinoid CB(1) antagonist/inverse agonist rimonabant has been shown to reduce the behavioral effects of stimuli associated with drugs of abuse, including nicotine, alcohol, cocaine, and marijuana. Thus, the endocannabinoid system represents a promising target for development of new treatments for drug addiction.

Polymorphisms in the µ-opioid receptor gene (OPRM1) and the implications for alcohol dependence in humans

Twin and adoption studies have shown that alcohol dependence contains a substantial genetic component. In attempts to identify the genetic factors involved, association studies have linked the opioid system to alcohol dependence, with a main focus on the OPRM1 gene encoding the μ-opioid receptor. Our aim was to conduct a systematic review of the literature on the associations between polymorphisms in OPRM1 and alcohol dependence. We addressed findings of 12 studies that met our inclusion criteria. All studies employed a case–control design and included alcohol dependence as a dependent outcome measure. Our review showed that clinical studies do not unequivocally support an association between polymorphisms in OPRM1 and alcohol dependence. Factors that complicate genetic research on alcohol dependence, such as gene–environment interaction, and genetic and clinical heterogeneity, are discussed.

Topiramate moderately reduces the motivation to consume alcohol and has a marked antidepressant effect in rats

BACKGROUND

In recent human studies, the anticonvulsant drug topiramate (TPM) has shown efficacy in treating alcohol craving and mood disorders. However, preclinical evidence supporting such effects is surprisingly sparse. Three experiments were conducted here to assess possible anticraving and antidepressant effects of TPM using animal models.

METHODS

In Experiment 1, rats were given 23 weeks ad libitum access to food, water, and either beer (4.44% ethanol v/v) or "near-beer" (a calorie-matched nonalcoholic beer, 0.44% ethanol) in their home cages. They were then restricted to daily 1 hour operant sessions in which they licked for water and either beer or near-beer under a progressive ratio schedule of reinforcement in a lickometer apparatus. The acute effects of TPM on the motivation to consume beer or near-beer were then assessed. The effects of naloxone were also assessed (as a positive control) after TPM testing. In Experiment 2, rats were given 11 weeks of ad libitum home-cage access to food, water, and beer. They then received repeated daily injections of TPM and effects on beer consumption under ad libitum home cage access conditions were monitored. In Experiment 3, the effects of TPM were assessed in the modified Porsolt forced swim test, emergence test, and elevated plus-maze (EPM) using alcohol naïve rats.

RESULTS

Topiramate (10, 20, and 40 mg/kg) significantly reduced the motivation to lick for beer, although the maximal effect was moderate in comparison with naloxone (10 mg/kg). However, naloxone, unlike TPM, also reduced responding for near-beer suggesting an alcohol-specific effect of TPM. In Experiment 2, TPM (40 and 80 mg/kg) tended to transiently reduce alcohol consumption in the home cage under ad libitum access but this effect disappeared with repeated administration of the drug. TPM (10 to 80 mg/kg, given twice over 4 hours before test) produced a robust dose-dependent decrease in immobility and increase in active coping strategies in the forced swim test similar to that seen with desipramine (2 x 20 mg/kg). There were modest anxiolytic effects of TPM on the EPM and emergence tests.

CONCLUSIONS

With acute administration, TPM is moderately effective and relatively selective in reducing the drive to consume alcohol in Wistar rats. This anti-alcohol effect is modest in comparison with naloxone and appears to dissipate under conditions of chronic treatment and ad libitum alcohol access. A marked antidepressant-like effect in the forced swim test and partial anxiolytic effects in other animal models suggests that TPM may be a beneficial treatment for affective disorders. These preliminary results suggest further research is warranted to resolve the mechanisms involved in TPM modulation of both mood and alcohol consumption.

Delayed access to alcohol accelerates self-administration of alcohol on a progressive ratio schedule

In a previous report, we found that a 5-min. delay in alcohol access increases ethanol intake in rats trained to self-administer 5% ethanol. To assess the effects of this delay on the motivation to self-administer ethanol, Wistar rats were trained on a progressive ratio schedule of reinforcement and presented with the 5-min. delay. There was no change in break point (6 presses/delivery), active (125 presses/30 min.) or inactive (10 presses/30 min.) lever presses after the 5-min. delay compared to baseline. However, response cessation occurred 10 min. earlier in this delay session compared to baseline indicating that consumption was accelerated by delayed access to alcohol.

The neural correlates and role of D1 dopamine receptors in renewal of extinguished alcohol-seeking

We used an ABA renewal design to study the neural correlates, and role of D1 dopamine receptors, in contextual control over extinguished alcohol-seeking. Rats were trained to respond for 4% beer in one context (A), extinguished in a different (B) context, and then tested for responding in the original training context (A) or the extinction context (B). ABA renewal was mediated by D1 dopamine receptors because it was prevented by SCH23390. ABA renewal of alcohol-seeking was associated with selective increases in c-Fos protein induction in basolateral amygdala, ventral accumbens shell, and lateral hypothalamus (renewal-associated Fos). By contrast, being tested was associated with increased c-Fos induction in anterior cingulate, prelimbic and infralimbic cortex, rostral agranular insula, dorsomedial accumbens shell, and accumbens core (test-associated Fos). Renewal-associated Fos in ventral accumbens shell and lateral hypothalamus, but not basolateral amygdala, was D1 dopamine receptor dependent. Double immunofluorescence showed that renewal-associated Fos was expressed in orexin-negative lateral hypothalamic neurons. However, c-Fos induction in either lateral hypothalamic orexin-negative or orexin-positive neurons was positively and significantly correlated with alcohol-seeking. Test-associated c-Fos induction was observed in orexin-positive perifornical neurons. In both regions, c-Fos expression was dependent on D1 dopamine receptors. These results suggest that renewal of extinguished alcohol-seeking depends on a distributed neural circuit involving basolateral amygdala, ventral accumbens shell, and lateral hypothalamus that involves D1 dopamine receptors. Comparison with our previous results [Hamlin AS, Blatchford KE, McNally GP (2006) Renewal of an extinguished instrumental response: Neural correlates and the role of D1 dopamine receptors. Neuroscience 143:25-38] permits identification of similarities and differences in the correlates of renewal of extinguished drug- and natural-reward seeking.

Identification of neurotransmitter receptor genes involved in alcohol self-administration in the rat prefrontal cortex, hippocampus and amygdala

About half of the risk to develop alcoholism is related to genetic background and it is well known that alcohol consumption is highly individualized. In this study, we investigated how individual alcohol consumption behaviour in Wistar rats correlated with mRNA expression of 20 genes in the prefrontal cortex, hippocampus and amygdala. We found that the long-term alcohol consumption of an individual could be estimated by the mean of its consumption on Day 2 and 3. This short exposure minimized changes in gene expression induced by alcohol itself. We found a positive correlation in the prefrontal cortex of GABA(A) alpha5 (r=0.96), GABA(B1) (r=0.96), AMPA GluR1 (r=0.93), 5-HT(3A) (r=0.93) and the alpha adrenoceptors (alpha(1A)r=1.00, alpha(1B)r=0.93, alpha(2A)r=0.93) with consumption. In the hippocampus, we found negative correlations with the NMDA NR2A subunit (r=-0.86), the alpha(1A) adrenoceptor (r=-0.89) and the glucocorticoid receptor (r=-0.86). Finally, in the amygdala there was a negative correlation to NMDA NR2A (r= -0.79) and a positive correlation with serotonin 5-HT(2C) (r=0.79). In conclusion, we have used qPCR to identify specific genes in the brain that correlated to alcohol self-administration of an individual animal. This study suggests that alcohol consumption in the early stages of acquisition depends on the genetic background of the individual and that the prefrontal cortex is particularly important in this behaviour.

Involvement of the endocannabinoid system in drug addiction

Recent studies have shown that the endocannabinoid system is involved in the common neurobiological mechanism underlying drug addiction. This system participates in the primary rewarding effects of cannabinoids, nicotine, alcohol and opioids, through the release of endocannabinoids in the ventral tegmental area. Endocannabinoids are also involved in the motivation to seek drugs by a dopamine-independent mechanism, demonstrated for psychostimulants and opioids. The endocannabinoid system also participates in the common mechanisms underlying relapse to drug-seeking behaviour by mediating the motivational effects of drug-related environmental stimuli and drug re-exposure. In agreement, clinical trials have suggested that the CB(1) cannabinoid antagonist rimonabant can cause smoking cessation. Thus, CB(1) cannabinoid antagonists could represent a new generation of compounds to treat drug addiction.

Challenges and opportunities for medications development in alcoholism: an international perspective on collaborations between academia and industry

This article represents the proceedings of a symposium presented at the 12th Congress of the International Society for Biomedical Research on Alcoholism held in Heidelberg/Mannheim, Germany, on September 30, 2004. The organizers and cochairs were Bankole A. Johnson, DSc, MD, PhD, and Karl Mann, MD. The presentations included the following: (1) A Perspective from Academia, by Bankole A. Johnson, DSc, MD, PhD; (2) A Perspective from NIAAA, by Mark L. Willenbring, MD; (3) A Perspective from US Clinical Practice, by Robert M. Swift, MD, PhD; (4) A European Perspective on Medications Development, by Otto M. Lesch, MD, PhD, and (5) A Scandinavian Perspective on Evidence-Based Addiction Treatment, by Mats Berglund, MD.

Cannabinoid CB1 receptors control conditioned drug seeking

Recent developments have implicated cannabinoid CB1 receptors as a novel target for a new class of therapeutic agents used to treat drug addiction. CB1 receptors are expressed in the motivational circuitry of the brain and modulate drug seeking. Blockade of the CB1 receptor is particularly effective in reducing cue-induced reinstatement of drug seeking, an animal analogue of cue-induced relapse in human addicts. These relapse-preventing properties are observed with different classes of abused drug (i.e. psychostimulants, opiates, nicotine and alcohol). In addition, recent evidence indicates a more general role of CB1 receptors in reward-related memories, which is consistent with the proposed role of endocannabinoids in memory-related plasticity. Relapse-preventing actions and inhibitory effects on weight gain were confirmed recently in clinical trials with the CB1 antagonist rimonabant. Collectively, these clinical and preclinical studies suggest that antagonists of CB1 receptors offer a novel approach in the treatment of addictive behaviours.

Development of medications for alcohol use disorders: recent advances and ongoing challenges

During the past decade, efforts to develop medications for alcoholism have burgeoned. Three agents, disulfiram, naltrexone and acamprosate, are now approved in a large number of countries. Although many patients have benefited from existing medications, their effects are moderate, and some alcoholics fail to respond to them. A host of new agents are currently under active investigation. Critical barriers must be overcome to ensure that future efforts in the development of medications for alcohol use disorders reach full fruition. These challenges include: establishing key targets for drug discovery; validating animal and human screening models; and developing biomarkers to help predict treatment success. In addition, it is important to formulate methodological and statistical strategies to efficiently conduct alcohol pharmacotherapy trials; to specify genetic and phenotypic patient characteristics associated with efficacy and safety for lead compounds; to forge productive alliances among governmental agencies, the pharmaceutical industry and academic researchers to further drug development; and, ultimately and perhaps most difficult, to engage the practitioner community to incorporate medications into the alcohol treatment process.

Imaginary Relish and Exquisite Torture: The Elaborated Intrusion Theory of Desire

The authors argue that human desire involves conscious cognition that has strong affective connotation and is potentially involved in the determination of appetitive behavior rather than being epiphenomenal to it. Intrusive thoughts about appetitive targets are triggered automatically by external or physiological cues and by cognitive associates. When intrusions elicit significant pleasure or relief, cognitive elaboration usually ensues. Elaboration competes with concurrent cognitive tasks through retrieval of target-related information and its retention in working memory. Sensory images are especially important products of intrusion and elaboration because they simulate the sensory and emotional qualities of target acquisition. Desire images are momentarily rewarding but amplify awareness of somatic and emotional deficits. Effects of desires on behavior are moderated by competing incentives, target availability, and skills. The theory provides a coherent account of existing data and suggests new directions for research and treatment.