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Introduction: It has been suggested that nicotinic acetylcholine receptors (nAchRs) expressed in the ventral tegmental area (VTA) and the nucleus accumbens (nAcc) modulate the effects of drug abuse. This research assessed the effects of intra-accumbal administration of the nAchR antagonist (mecamylamine) and agonist (cytisine) on the operant oral self-administration of ethanol (EtOH) in rats. Methods: Male Wistar rats were water-deprived for 24 h and then trained to lever-press for EtOH reinforcement on a fixed-ratio 1 (FR1) schedule for three sessions. After that, the number of responses in the FR schedule increased to 3 until the response rate remained stable at 80%. After this training, the rats received an intra-accumbal injection of the nAchR antagonist, mecamylamine (0.0, 1.25, 2.5, and 5.0 µg), then nAchR agonist, cytisine (0.0, 0.8, 1.6, and 3.2 µg) or the combination of mecamylamine (0.0, 1.25, 2.5, and 5.0 µg) and cytisine (3.2 µg) before being provided access to EtOH on a FR3 schedule. Results: The data showed that intra-accumbal administration of mecamylamine reduced operant oral self-administration of EtOH, whereas cytisine increased operant oral self-administration of EtOH. This effect was reversed by mecamylamine. Conclusion: These findings suggest that nAchRs in the nAcc may modulate the operant oral self-administration of EtOH in rats. [ABSTRACT FROM AUTHOR]

Female and male glial fibrillary acidic protein-thymidine kinase (GFAP-TK) transgenic rats were made ethanol dependent via a six-week chronic intermittent ethanol vapor (CIE) and ethanol drinking (ED) procedure. During the last week of CIE, a subset of male and female TK rats was fed valcyte to ablate dividing progenitor cells and continued the diet until the end of this study. Following week six, all CIE rats experienced two weeks of forced abstinence from CIE-ED, after which they experienced relapse to drinking, extinction, and reinstatement of ethanol seeking sessions. CIE increased ED in female and male rats, with females having higher ethanol consumption during CIE and relapse sessions compared with males. In both sexes, valcyte reduced the levels of Ki-67-labeled progenitor cells in the subgranular zone of the dentate gyrus and did not alter the levels in the medial prefrontal cortex (mPFC). Valcyte increased ED during relapse, increased lever responses during extinction and, interestingly, enhanced latency to extinguish ethanol-seeking behaviors in males. Valcyte reduced the reinstatement of ethanol-seeking behaviors triggered by ethanol cues in females and males. Reduced seeking by valcyte was associated with the normalization of cytokines and chemokines in plasma isolated from trunk blood, indicating a role for progenitor cells in peripheral inflammatory responses. Reduced seeking by valcyte was associated with increases in tight junction protein claudin-5 and oligodendrogenesis in the dentate gyrus and reduction in microglial activity in the dentate gyrus and mPFC in females and males, demonstrating a role for progenitor cells in the dentate gyrus in dependence-induced endothelial and microglial dysfunction. These data suggest that progenitor cells born during withdrawal and abstinence from CIE in the dentate gyrus are aberrant and could play a role in strengthening ethanol memories triggered by ethanol cues via central and peripheral immune responses.

Oxytocin (OXT), a pro-social peptide, is increasingly recognized as a potential protective substance against drug addiction. In the context of ethanol, previous research has shown OXT's properties in reducing self-administration, alleviating motor impairment in rodents, and reducing craving in humans. However, its role in behavioral sensitization, a neuroadaptive response resulting from repeated drug exposure linked to an increased drug incentive, remains unexplored. OXT is recognized for its role in regulating the hypothalamic–pituitary–adrenal (HPA) axis, in which corticosterone is acknowledged as a significant factor in the development of behavioral sensitization. This study aimed to investigate the effects of carbetocin (CBT), an analogue of OXT, on the expression of behavioral sensitization to ethanol and the concurrent alterations in plasma corticosterone levels in male and female Swiss mice. We also aimed to confirm previous studies on OXT's impact on ethanol consumption in male mice, but with a focus on CBT, using the two-bottle choice model and the drinking in the dark (DID) methodology. For the sensitization study, the mice received either ethanol (1.8 g/kg, i.p.) or saline treatments daily for 15 consecutive days, followed by treatment with carbetocin (0.64 mg/kg, i.p.) or a vehicle for 6 days. Subsequently, on day 22, all the animals underwent an ethanol challenge to assess the expression of behavioral sensitization. The plasma corticosterone levels were measured on days 21 and 22. The CBT effectively prevented the expression of ethanol-induced behavioral sensitization in both male and female subjects, with no alterations having been detected in their corticosterone levels. In the ethanol consumption study, following an initial phase of ethanol acquisition, the male mice underwent a 6-day treatment with CBT i.p. or saline before being re-exposed to ethanol. We also found a reduction in their ethanol consumption due to the CBT treatment. In conclusion, carbetocin emerges as a promising and effective intervention for mitigating ethanol-induced behavioral sensitization and reducing ethanol intake, highlighting its potential significance in alcohol addiction treatment. [ABSTRACT FROM AUTHOR]

Oxytocin (OXT), a pro-social peptide, is increasingly recognized as a potential protective substance against drug addiction. In the context of ethanol, previous research has shown OXT’s properties in reducing self-administration, alleviating motor impairment in rodents, and reducing craving in humans. However, its role in behavioral sensitization, a neuroadaptive response resulting from repeated drug exposure linked to an increased drug incentive, remains unexplored. OXT is recognized for its role in regulating the hypothalamic–pituitary–adrenal (HPA) axis, in which corticosterone is acknowledged as a significant factor in the development of behavioral sensitization. This study aimed to investigate the effects of carbetocin (CBT), an analogue of OXT, on the expression of behavioral sensitization to ethanol and the concurrent alterations in plasma corticosterone levels in male and female Swiss mice. We also aimed to confirm previous studies on OXT’s impact on ethanol consumption in male mice, but with a focus on CBT, using the two-bottle choice model and the drinking in the dark (DID) methodology. For the sensitization study, the mice received either ethanol (1.8 g/kg, i.p.) or saline treatments daily for 15 consecutive days, followed by treatment with carbetocin (0.64 mg/kg, i.p.) or a vehicle for 6 days. Subsequently, on day 22, all the animals underwent an ethanol challenge to assess the expression of behavioral sensitization. The plasma corticosterone levels were measured on days 21 and 22. The CBT effectively prevented the expression of ethanol-induced behavioral sensitization in both male and female subjects, with no alterations having been detected in their corticosterone levels. In the ethanol consumption study, following an initial phase of ethanol acquisition, the male mice underwent a 6-day treatment with CBT i.p. or saline before being re-exposed to ethanol. We also found a reduction in their ethanol consumption due to the CBT treatment. In conclusion, carbetocin emerges as a promising and effective intervention for mitigating ethanol-induced behavioral sensitization and reducing ethanol intake, highlighting its potential significance in alcohol addiction treatment.

Female and male glial fibrillary acidic protein-thymidine kinase (GFAP-TK) transgenic rats were made ethanol dependent via a six-week chronic intermittent ethanol vapor (CIE) and ethanol drinking (ED) procedure. During the last week of CIE, a subset of male and female TK rats was fed valcyte to ablate dividing progenitor cells and continued the diet until the end of this study. Following week six, all CIE rats experienced two weeks of forced abstinence from CIE-ED, after which they experienced relapse to drinking, extinction, and reinstatement of ethanol seeking sessions. CIE increased ED in female and male rats, with females having higher ethanol consumption during CIE and relapse sessions compared with males. In both sexes, valcyte reduced the levels of Ki-67-labeled progenitor cells in the subgranular zone of the dentate gyrus and did not alter the levels in the medial prefrontal cortex (mPFC). Valcyte increased ED during relapse, increased lever responses during extinction and, interestingly, enhanced latency to extinguish ethanol-seeking behaviors in males. Valcyte reduced the reinstatement of ethanol-seeking behaviors triggered by ethanol cues in females and males. Reduced seeking by valcyte was associated with the normalization of cytokines and chemokines in plasma isolated from trunk blood, indicating a role for progenitor cells in peripheral inflammatory responses. Reduced seeking by valcyte was associated with increases in tight junction protein claudin-5 and oligodendrogenesis in the dentate gyrus and reduction in microglial activity in the dentate gyrus and mPFC in females and males, demonstrating a role for progenitor cells in the dentate gyrus in dependence-induced endothelial and microglial dysfunction. These data suggest that progenitor cells born during withdrawal and abstinence from CIE in the dentate gyrus are aberrant and could play a role in strengthening ethanol memories triggered by ethanol cues via central and peripheral immune responses.

Enhanced dopamine (DA) neurotransmission from the ventral tegmental area (VTA) to the ventral striatum is thought to drive drug self-administration and mediate positive reinforcement. We examined neuronal firing rates in slices of mouse midbrain following adolescent binge-like alcohol drinking and find that prior alcohol experience greatly enhanced the sensitivity to excitation by ethanol itself (10-50 mM) in a subset of ventral midbrain DA neurons located in the medial VTA. This enhanced response after drinking was not associated with alterations of firing rate or other measures of intrinsic excitability. In addition, the phenomenon appears to be specific to adolescent drinking, as mice that established a drinking preference only after the onset of adulthood showed no change in alcohol sensitivity. Here we demonstrate not only that drinking during adolescence induces enhanced alcohol sensitivity, but also that this DA neuronal response occurs over a range of alcohol concentrations associated with social drinking in humans.

Nonhuman primate models of alcohol use disorder (AUD) frequently utilize schedule-induced polydipsia to initiate ethanol drinking. Previous research has demonstrated that specific characteristics of drinking during the final phase of induction, in which monkeys consume 1.5 g/kg of ethanol per day, can predict whether monkeys become heavy or light drinkers when they subsequently have free access to ethanol (22 hours per day; Baker, Farro, Gonzales, Helms, & Grant, 2017; Grant et al., 2008). A monkey's position in the social dominance hierarchy is another factor associated with ethanol drinking in nonhuman primates; lower social status is associated with higher ethanol intakes. In the present study, characteristics of drinking during induction were measured in 12 male cynomolgus monkeys living in three established social groups (4 monkeys per group). All monkeys were induced to consume water, then increasing doses of ethanol (0.5, 1.0, and 1.5 g/kg) for 30 sessions per dose using a 300-s fixed-time schedule of food pellet delivery. Drinking sessions occurred five days per week and monkeys were group-housed on the other two days. Contrary to our hypothesis that subordinate monkeys would show characteristics of drinking during the last phase of induction that were predictive of later heavy drinking, no significant differences were observed between dominant and subordinate monkeys in any phase of induction. When ethanol availability was subsequently increased to 22 hours per day for 5 weeks, the intakes of subordinate- and dominant-ranked monkeys diverged, with higher intakes on average in subordinates. Several factors unique to the conditions of induction may have obscured any influence of social rank, including the limited duration of sessions and limited maximal ethanol intake. The data support the conclusion that the effects of social rank on ethanol consumption require unrestricted access to ethanol. [ABSTRACT FROM AUTHOR]

Early life stress is known to impact vulnerability to psychopathological disorders in adulthood, including anxiety and alcohol use disorder (AUD), but the mechanisms underlying susceptibility to these outcomes are not fully understood. In the current study, we used adolescent social isolation (ASI) to determine whether Heterogeneous Stock (HS) rats, an outbred model used for genetic fine-mapping, could be used to study the genetics contributing to ASI-induced anxiety- and AUD-like behavior. We isolated (ASI) or group-housed (adolescent group-housed; AGH) 64 male HS rats at 4 weeks of age. After 5 weeks in these housing conditions, multiple anxiety and coping/despair-like behaviors were measured. All rats were then individually housed and assessed for voluntary ethanol self-administration. At euthanasia, synaptoneurosomes were isolated from a subset of brains to examine the expression of two proteins associated with alcohol drinking-related behaviors, GluA1 and SK2, in the dorsal (dHC) and ventral hippocampus (vHC). We found that ASI increased hyperactivity in the open field test relative to AGH, with no changes in other anxiety-like behaviors. Surprisingly, ASI rats demonstrated decreased immobility and increased climbing in the forced swim test relative to AGH. In contrast to prior studies by us and others, we found no difference in self-administration of 20% ethanol, with decreased ethanol self-administration in ASI relative to AGH rats at higher ethanol concentrations. Furthermore, while ASI in Long-Evans rats resulted in decreased SK2 expression in vHC synaptosomes, no differences were seen in vHC synaptosomes for SK2 or GluA1 in HS rats. These results demonstrate that HS rats are protected against many of the negative effects previously seen in response to ASI, namely anxiety-like behavior and increased ethanol self-administration. The current work suggests that a lack of change in SK2 and GluA1 expression levels in the vHC may play a role in conferring this protection. [ABSTRACT FROM AUTHOR]

While ethanol-paired stimuli are frequently postulated to increase drinking motivation and thus increase ethanol responding and precipitate relapse, no study has demonstrated increases in ethanol-reinforced responding following presentation of an ethanol-paired stimulus that had not previously been part of a contingent relationship. Previous studies have shown that food-paired stimuli can increase food responding that is at low rates and increase food consumption in food-sated rats. In Experiment 1, we show that an ethanol-paired stimulus can increase ethanol responding that is at low levels late in the experimental session, presumably due to satiation. However, these increases may have resulted from either associative or non-associative mechanisms. In Experiment 2, we compared the effects of an ethanol-paired stimulus to those of the same stimulus in a Truly-Random-Control group. In a Truly-Random-Control, the stimulus and ethanol each are presented on independent random schedules, and thus any differences between the effects of the stimulus in the experimental and control groups is likely attributable to the association between the stimulus and ethanol. The stimulus increased ethanol-reinforced responding in both the experimental and control groups, but these increases were greater in the experimental than the control group. Thus, both stimulus-change and the pairing of the stimulus with ethanol may result in increases in ethanol-reinforced responding. [ABSTRACT FROM AUTHOR]

Ethanol-paired conditioned stimuli (CSs) are widely thought to invigorate ethanol responding, and thus, precipitate relapse to drinking. However, preclinical studies investigating this issue using Pavlovian-Instrumental-Transfer (PIT) procedures have had mixed results, with some studies finding PIT while others did not. The studies failing to show PIT used Lewis rats and induced ethanol drinking using a post-prandial drinking procedure. The present experiments examined whether either of these two variables influenced the magnitude of PIT observed. In the first experiment, ethanol drinking in Lewis rats was induced using either sucrose fading or post-prandial drinking. In the second experiment, ethanol drinking was induced using post-prandial drinking in either Long-Evans Hooded or Lewis rats. In both experiments, rats were trained to respond for ethanol under a random interval schedule. Subsequently with the lever removed, 2-min light presentations were paired with ethanol deliveries. Finally, with the lever returned, the effect of light presentations on responding was tested while responding was in extinction. Light presentations similarly affected responding in Lewis rats regardless of the method of drinking induction. Likewise, light presentations similarly affected responding in both Lewis and Long-Evans Hooded rats. Neither ethanol induction method nor rat strain affected the magnitude of PIT observed, and thus, neither likely explains previous failures to observe PIT with ethanol-maintained behavior. [ABSTRACT FROM AUTHOR]

Little is known about the influence of rearing environments concurrent with voluntary intermittent access to ethanol on subsequent adult ethanol-related behaviors. Previous research has shown that adult rats reared in post-weaning, social isolation conditions (IC) respond more for operant ethanol compared to laboratory standard conditions (SC). Ethanol-exposed adolescents tend to consume more ethanol in adulthood than rats exposed as adults. The current study examined voluntary ethanol consumption during adolescence between IC and SC rats, subsequent operant responding for ethanol, and extinction of responding in the same rats as adults. Differences in ethanol metabolism may alter the amount of reward value per unit of ethanol consumed. Therefore, the current study also examined blood ethanol concentrations (BEC) between IC rats and SC rats. Ethanol-naïve Long-Evans rats arrived in the lab at postnatal day (PND) 21 and were separated into either IC or SC where they remained for the duration of the experiments. On PND 27, rats received intermittent access to 20% ethanol (3 days/week) for 4 or 6 weeks. Rats in the 6-week cohort were then trained to lever press for 20% ethanol in 30-min sessions followed by extinction. A separate cohort was reared in IC or SC, injected with 1.5 or 3.0 g/kg of ethanol (intraperitoneally [i.p.]), followed by BEC measurement. Overall, IC rats had higher ethanol preference and consumption during adolescence/early adulthood. IC and SC rats did not differ in their rates of operant responding for ethanol, and SC rats responded more than IC rats during extinction. There were no differences in BEC between IC and SC rats. These findings highlight the importance of the environment during rat adolescent development with isolation conditions increasing binge-like drinking and ethanol preference after 3-4 weeks without differences in metabolism as a potential factor. Additionally, the findings indicate that intermittent adolescent access to ethanol may change typical differences in operant responding patterns between IC and SC rats in adulthood. [ABSTRACT FROM AUTHOR]

Abstract Many components of ethanol addiction such as reinforcement, withdrawal, extinction, and relapse are known to involve glutamate transmission. NAC could counteract glutamatergic dysregulation underlying ethanol addiction. We previously demonstrated the efficacy of N-acetylcysteine (NAC) treatment to reduce ethanol consumption, motivation, seeking, and relapse in rats displaying a binge drinking-like phenotype. The current study assessed whether acute NAC could reduce ethanol self-administration, ethanol-seeking behavior, motivation, and reacquisition of ethanol self-administration following abstinence in ethanol-dependent rats. Ethanol dependence was induced by chronic intermittent ethanol (CIE) vapor exposure for 10 weeks in male Wistar rats. Effects of NAC (0, 25, 50 or 100 mg/kg; i.p.) were evaluated during acute withdrawal, 8 h after inhalation chambers were turned off. We evaluated NAC effect on the expression of the xCT protein expression (the target of NAC) and glutamate transporters (GLT-1) in dependent rats. We showed that in dependent rats, the low dose of NAC (25 mg/kg) reduced ethanol self-administration and motivation to consume ethanol, evaluated in a progressive ratio paradigm. At 50 mg/kg, but not 25 mg/kg, NAC reduced extinction responding and reacquisition of self-administration after 1 month abstinence. The xCT protein expression was decreased in the nucleus accumbens in dependent compared with ethanol-naïve rats. Thus, NAC may be effective by decreasing glutamate transmission through presynaptic mechanisms (i.e. the stimulation of x c −-mediated increase in extrasynaptic glutamate levels). Our results demonstrate that NAC decreased ethanol self-administration, extinction responding, and relapse in ethanol-dependent animals, and thus strongly support clinical development of NAC for alcohol use disorders. Highlights • N-acetyl-cysteine (NAC) is a promising treatment for Substance Use Disorders. • Ethanol dependence was induced in rats by chronic intermittent ethanol vapor exposure. • NAC reduced ethanol self-administration, motivation, seeking and relapse in dependent rats. [ABSTRACT FROM AUTHOR]

Carbonic anhydrase (CA) is abundant in glial cells in the brain and CA type II isoform (CA II) activity in the hippocampus plays an important role in buffering extracellular pH transients produced by neural activity. Chronic ethanol exposure results in respiratory and metabolic acidosis, producing shifts in extracellular pH in the brain and body. These neurophysiological changes by ethanol are hypothesized to contribute to the continued drinking behavior and physical withdrawal behavior in subjects consuming ethanol chronically. We explored whether chronic ethanol self-administration (ethanol drinking, 10% v/v; ED) without or under the influence of chronic intermittent ethanol vapor (CIE-ED) experience alters the expression of CA II in the hippocampus. Postmortem hippocampal tissue analyses demonstrated that CA II levels were enhanced in the hilus region of the hippocampus in ED and CIE-ED rats. We used a novel molecule—4-fluoro-N-(4-sulfamoylphenyl) benzenesulfonamide (4-FS)—a selective CA II inhibitor, to determine whether CA II plays a role in ethanol self-administration in ED and CIE-ED rats and physical withdrawal behavior in CIE-ED rats. 4-FS (20 mg/kg, i.p.) reduced ethanol self-administration in ED rats and physical withdrawal behavior in CIE-ED rats. Postmortem hippocampal tissue analyses demonstrated that 4-FS reduced CA II expression in ED and CIE-ED rats to control levels. In parallel, 4-FS enhanced GABAA receptor expression, reduced ratio of glutamatergic GluN2A/2B receptors and enhanced the expression of Fos, a marker of neuronal activation in the ventral hippocampus in ED rats. These findings suggest that 4-FS enhanced GABAergic transmission and increased activity of neurons of inhibitory phenotypes. Taken together, these findings support the role of CA II in assisting with negative affective behaviors associated with moderate to severe alcohol use disorders (AUD) and that CA II inhibitors are a potential therapeutic target to reduce continued drinking and somatic withdrawal symptoms associated with moderate to severe AUD.

Rationale: Recent preclinical research suggested that histone deacetylase inhibitors (HDACIs) and specifically class I HDAC selective inhibitors might be useful to treat alcohol use disorders (AUDs).Objective: The objective of this study was to find a new inhibitor of the HDAC-1 isoenzyme and to test its efficacy in an animal model of AUDs.Methods: In the present study, we prepared new derivatives bearing sulfonylhydrazide-type zinc-binding group (ZBG) and evaluated these compounds in vitro on HDAC-1 isoenzyme. The most promising compound was tested on ethanol operant self-administration and relapse in rats.Results: We showed that the alkylsulfonylhydrazide-type compound (ASH) reduced by more than 55% the total amount of ethanol consumed after one intracerebroventricular microinjection, while no effect was observed on motivation of the animals to consume ethanol. In addition, one ASH injection in the central amygdala reduced relapse.Conclusions: Our study demonstrated that a new compound designed to target HDAC-1 is effective in reducing ethanol intake and relapse in rats and further confirm the interest of pursuing research to study the exact mechanism by which such inhibitor may be useful to treat AUDs. [ABSTRACT FROM AUTHOR]

Alcohol use disorder is a chronic and highly relapsing disorder, characterized by a loss of control over alcohol consumption and craving. Several studies suggest a key role of glutamate in this disorder. In recent years, the modulation of cystine/glutamate exchange via the xc- system has emerged as a new therapeutic alternative for reducing the excitatory glutamatergic transmission observed after ethanol self-administration in both rats and humans. The objective of this study was to determine whether a treatment with N-acetylcysteine (NAC), a cystine prodrug, could reduce ethanol self-administration, ethanol-seeking behavior and reacquisition of ethanol self-administration. Male Long Evans rats were trained to self-administer 20 percent ethanol in operant cages for several weeks. Once the consumption surpassed 1 g of ethanol/kg body weight/15 minutes, the effect of an acute intraperitoneal injection of NAC (0, 25, 50 or 100 mg/kg) 1 hour before the beginning of each test was evaluated on different aspects of the operant self-administration behavior. We demonstrated antimotivational properties of NAC (100 mg/kg), as ethanol-reinforced responding was reduced in a fixed ratio (-35 percent) and in a progressive ratio schedule (-81 percent). NAC also reduced ethanol-seeking behavior (-77 percent) evaluated as extinction responding in a single extinction session. NAC was able to reduce reacquisition in rats that were abstinent for 17 days, while NAC had no effect on ethanol relapse in rats previously exposed to six extinction sessions. Overall, our results demonstrate that NAC limits motivation, seeking behavior and reacquisition in rats, making it a potential new treatment for the maintenance of abstinence. [ABSTRACT FROM AUTHOR]

Background Pavlovian-Instrumental-Transfer ( PIT) examines the effects of associative learning upon instrumental responding. Previous studies examining PIT with ethanol (EtOH)-maintained responding showed increases in responding following presentation of an EtOH-paired conditioned stimulus ( CS). Recently, we conducted 2 studies examining PIT with an EtOH-paired CS. One of these found increases in responding, while the other did not. This less robust demonstration of PIT may have resulted from the form of the CS used, as we used a 120-second light stimulus as a CS, while the previous studies used either a 120-second auditory stimulus or a 10-second light stimulus. This study examined whether using conditions similar to our earlier study, but with either a 120-second auditory or a 10-second light stimulus as a CS, resulted in more robust PIT. We also examined the reliability of our previous failure to observe PIT. Methods Three experiments were conducted examining whether PIT was obtained using (i) a 120-second light stimulus, (ii) a 10-second light stimulus, or (iii) a 120-second auditory stimulus as CSs. Results We found PIT was not obtained using (i) a 120-second light stimulus as a CS, (ii) a 10-second light stimulus as a CS, or (iii) a 120-second auditory stimulus as a CS. Conclusions These results suggest that CS form does not account for our earlier failure to see PIT. Rather, factors like rat strain or how EtOH drinking is induced may account for when PIT is or is not observed. [ABSTRACT FROM AUTHOR]

Acute ethanol activates the hypothalamic-pituitary-adrenal (HPA) axis, while long-term exposure results in a blunted neuroendocrine state, particularly with regards to the primary endpoint, cortisol, the primary glucocorticoid produced in the adrenal cortex. However, it is unknown if this dampened neuroendocrine status also influences other adrenocortical steroids. Plasma concentration of the mineralocorticoid and neuroactive steroid precursor deoxycorticosterone (DOC) is altered by pharmacological challenges of the HPA axis in cynomolgus monkeys. The present study investigated HPA axis regulation of circulating DOC concentration over the course of ethanol (4% w/v) induction and self-administration in non-human primates (Macaca fasciculata, n = 10). Plasma DOC, measured by radioimmunoassay, was compared at baseline (ethanol naïve), during schedule-induced polydipsia, and following 6-months of 22 h/day access to ethanol and water. The schedule induction of ethanol drinking did not alter basal DOC levels but selectively dampened the DOC response to pharmacological challenges aimed at the anterior pituitary (ovine corticotrophin-releasing hormone) and adrenal gland (post-dexamethasone adrenocorticotropin hormone), while pharmacological inhibition of central opioid receptors with naloxone greatly enhanced the DOC response during induction. Following 6 months of ethanol self-administration, basal DOC levels were increased more than twofold, while responses to each of the challenges normalized somewhat but remained significantly different than baseline. These data show that HPA axis modulation of the neuroactive steroid precursor DOC is markedly altered by the schedule induction of ethanol drinking and long-term voluntary ethanol self-administration. The consequences of chronic ethanol consumption on HPA axis regulation of DOC point toward allostatic modification of hypothalamic and adrenal function. [ABSTRACT FROM AUTHOR]

Cues associated with alcohol use can readily enhance self-reported cravings for alcohol, which increases the likelihood of reusing alcohol. Understanding the neuronal mechanisms involved in alcohol-seeking behavior is important for developing strategies to treat alcohol use disorder. In all experiments, adult female alcohol-preferring (P) rats were exposed to three conditioned odor cues; CS+ associated with EtOH self-administration, CS- associated with the absence of EtOH (extinction training), and a CS0, a neutral stimulus. The data indicated that presentation of an excitatory conditioned cue (CS+) can enhance EtOH- seeking while the CS- can inhibit EtOH-seeking under multiple test conditions. Presentation of the CS+ activates a subpopulation of dopamine neurons within the interfascicular nucleus of the posterior ventral tegmental area (posterior VTA) and basolateral amygdala (BLA). Pharmacological inactivation of the BLA with GABA agonists inhibits the ability of the CS+ to enhance EtOH-seeking but does not alter context-induced EtOH-seeking or the ability of the CS- to inhibit EtOH-seeking. Presentation of the conditioned odor cues in a non-drug-paired environment indicated that presentation of the CS+ increased dopamine levels in the BLA. In contrast, presentation of the CS- decreased both glutamate and dopamine levels in the BLA. Further analysis revealed that presentation of a CS+ EtOH-associated conditioned cue activates GABA interneurons but not glutamate projection neurons. Overall, the data indicate that excitatory and inhibitory conditioned cues can contrarily alter EtOH-seeking behaviors and that different neurocircuitries are mediating these distinct cues in critical brain regions. Pharmacotherapeutics for craving should inhibit the CS+ and enhance the CS- neurocircuits. • EtOH-seeking prolonged if EtOH cue exposure occurs in a non-drug-paired environment. • BLA mediates the actions of EtOH cue on EtOH-seeking, but not extinction cue actions. • EtOH cue stimulates DA release in the BLA, while extinction cues reduce DA. • EtOH cue disproportionately activates DA neurons in the posterior VTA. • Extinction cues reduce glutamate levels in the BLA. [ABSTRACT FROM AUTHOR]

Motivational increases due to exposure to alcohol-paired Conditioned Stimuli (CS) are central to some accounts of alcoholism. However, few studies isolate a stimulus's function as a CS from its other potential functions. Pavlovian-Instrumental-Transfer (PIT) procedures isolate a stimulus's function as a CS from its other functions. Though there are several relevant studies using PIT, knowledge gaps exist. Particularly, it is not clear that an alcohol-paired CS will increase alcohol seeking compared to the same stimulus in a Truly-Random-Control group, nor whether such increases are specific to alcohol seeking. To address these knowledge gaps in Experiment 1, rats responded for ethanol (0.1 ml 8% w/v) under an RI 30-sec schedule, then the lever was removed and half the rats had ethanol delivered during occasional 120-sec light presentations, while the remainder had ethanol and the light presented under independent RT schedules. Later the lever was returned and the light was presented during responding in extinction (PIT test). Following this test, levers were again removed and the light was presented without ethanol (light extinction), following again by a PIT test. Responding in the two groups during light presentations did not differ in either PIT test. Experiment 2 repeated Experiment 1 using food instead of ethanol. In Experiment 2, responding during light presentations increased in the paired group. In Experiment 3, rats were trained on a concurrent FR schedule of food and ethanol delivery. Ethanol was delivered following 5 responses and the response requirement for food adjusted so that similar numbers of food and ethanol deliveries were obtained. Subsequently, rats underwent conditioning, control and testing procedures identical to those in Experiment 1. In Experiment 3, the ethanol-paired CS increased ethanol-responding, but not food-responding. These results are most easily interpreted as changes in responding resulting from CS-elicited behavior rather than motivational changes. This interpretation is more compatible with some descriptions of the role of an alcohol-paired CS in alcoholism than others. [ABSTRACT FROM AUTHOR]

A bidirectional relationship between stress and alcohol exists whereby stressful events are comorbid with problematic alcohol use and prolonged alcohol exposure results in adaptations of the physiological stress response. Endocrine response to stress is initiated in the hypothalamic paraventricular nucleus (PVN) with the synthesis and release of corticotropin-releasing hormone (CRH) and arginine-vasopressin (AVP). Alterations in CRH and AVP following long-term alcohol exposure in rodents is well demonstrated, however little is known about the response to alcohol in primates or the mechanisms of adaptation. We hypothesized that long-term alcohol self-administration in nonhuman primates would lead to ultrastructural changes in the PVN underlying adaptation to chronic alcohol. Double-label immunogold electron microscopy was used to measure presynaptic GABA and glutamate density within synaptic terminals contacting CRH- and AVP-immunoreactive dendrites. Additionally, pituitary-adrenal hormones (ACTH, cortisol, DHEA-s and aldosterone) under two conditions (low and mild stress) were compared before and after self-administration. All hormones were elevated in response to the mild stressor independent of alcohol consumption. The presynaptic glutamate density in recurrent (i.e., intra-hypothalamic) CRH terminals was highly related to alcohol intake, and may be a permissive factor in increased drinking due to stress. Conversely, glutamate density within recurrent AVP terminals showed a trend-level increase following alcohol, but was not related to average daily consumption. Glutamate density in non-recurrent AVP terminals was related to aldosterone under the low stress condition while GABAergic density in this terminal population was related to water consumption. The results reveal distinct populations of presynaptic terminals whose glutamatergic or GABAergic density were uniquely related to water and alcohol consumption and circulating hormones.

Animal models have long been used to study the mechanisms underlying the complex association between alcohol and stress. Female mice prevented from running on a home-cage activity wheel increase voluntary ethanol consumption. β-endorphin is an endogenous opioid involved in negatively regulating the stress response and has also been implicated in the risk for excessive drinking. The present study investigates the role of β-endorphin in moderating free-choice consumption of ethanol in response to a blocked activity wheel. Female, transgenic mice with varying levels of the opioid peptide were given daily 2-h access to 20% ethanol with rotations on a running wheel blocked on alternate days. Subjects with low β-endorphin exhibited enhanced stress sensitivity by self-administering larger quantities of ethanol on days when wheel running was prevented. β-endorphin levels did not influence voluntary activity on the running wheel. There were genotypic differences in plasma corticosterone levels as well as corticotropin-releasing hormone mRNA content in multiple brain regions associated with the stress response in these free drinking and running subjects. Susceptibility to stress is enhanced in female mice with low levels of β-endorphin, and better understanding of the role for this opioid in mitigating the response to stressors may aid in the development of interventions and treatments for excessive use of alcohol in women. [ABSTRACT FROM AUTHOR]

It is well known that the glutamatergic system plays a crucial role in alcohol addiction and especially in relapse-like behaviour. However, results of clinical studies on compounds that influence the activity of the glutamatergic system have been disappointing so far. The aim of our study was to establish treatment conditions under which the N-methyl-Daspartate receptor (NMDAR) antagonist memantine may produce more reliable treatment effect with respect to alcohol relapse-like behaviour. For this purpose, male Wistar rats were trained to associate several discrete stimuli with ethanol delivery. Thereafter, half of the animals received a brief memory reactivation session followed by two administrations of 20 mg/kg of memantine, while the other half received the same treatment without memory reactivation. Afterwards, a cue-induced ethanol-seeking behaviour test was performed followed by repeated extinction sessions and a reacquisition test. Our data show that administration of memantine reduced responding on the ethanol-associated lever in a cue-induced ethanol-seeking test. This reduction did not depend on whether or not a memory reactivation session was introduced prior to memantine administration. Following extinction, however, reacquisition of ethanol self-administration was only impaired in the group where memantine was given after a short memory reactivation session, showing that this schedule of drug administration produced a long-lasting disruption of the association between the conditioned stimuli and the delivery of ethanol. In conclusion, we show that memantine disrupted the drug-cue association, which consequently interfered with relapse-like behaviour supporting the possibility that memantine is a treatment option for alcoholism. [ABSTRACT FROM AUTHOR]

A bidirectional relationship between stress and ethanol exists whereby stressful events are comorbid with problematic ethanol use and prolonged ethanol exposure results in adaptations of the physiological stress response. Endocrine response to stress is initiated in the hypothalamic paraventricular nucleus (PVN) with the synthesis and release of corticotropin-releasing hormone (CRH) and arginine-vasopressin (AVP). Alterations in CRH and AVP following long-term ethanol exposure in rodents is well demonstrated, however little is known about the response to ethanol in primates or the mechanisms of adaptation. We hypothesized that long-term ethanol self-administration in nonhuman primates would lead to ultrastructural changes in the PVN underlying adaptation to chronic ethanol. Double-label immunogold electron microscopy (EM) was used to measure presynaptic gamma-aminobutyric acid (GABA) and glutamate density within synaptic terminals contacting CRH- and AVP-immunoreactive dendrites. Additionally, pituitary-adrenal hormones (ACTH, cortisol, DHEA-s and aldosterone) under two conditions (low and mild stress) were compared before and after self-administration. All hormones were elevated in response to the mild stressor independent of ethanol consumption. The presynaptic glutamate density in recurrent (i.e., intra-hypothalamic) CRH terminals was highly related to ethanol intake, and may be a permissive factor in increased drinking due to stress. Conversely, glutamate density within recurrent AVP terminals showed a trend-level increase following ethanol, but was not related to average daily consumption. Glutamate density in non-recurrent AVP terminals was related to aldosterone under the low stress condition while GABAergic density in this terminal population was related to water consumption. The results reveal distinct populations of presynaptic terminals whose glutamatergic or GABAergic density were uniquely related to water and ethanol consumption and circulating hormones. [ABSTRACT FROM AUTHOR]

This study examines the role of the cannabinoid CB2 receptor ( CB2r) on the vulnerability to ethanol consumption. The time-related and dose-response effects of ethanol on rectal temperature, handling-induced convulsions ( HIC) and blood ethanol concentrations were evaluated in CB2KO and wild-type ( WT) mice. The reinforcing properties of ethanol were evaluated in conditioned place preference ( CPP), preference and voluntary ethanol consumption and oral ethanol self-administration. Water-maintained behavior schedule was performed to evaluate the degree of motivation induced by a natural stimulus. Preference for non-alcohol tastants assay was performed to evaluate the differences in taste sensitivity. Tyrosine hydroxylase ( TH) and μ-opioid receptor gene expressions were also measured in the ventral tegmental area and nucleus accumbens ( NAcc), respectively. CB2KO mice presented increased HIC score, ethanol- CPP, voluntary ethanol consumption and preference, acquisition of ethanol self-administration, and increased motivation to drink ethanol compared with WT mice. No differences were found between genotypes in the water-maintained behavior schedule or preference for non-alcohol tastants. Naïve CB2KO mice presented increased μ-opioid receptor gene expression in NAcc. Acute ethanol administration (1-2 g/kg) increased TH and μ-opioid receptor gene expressions in CB2KO mice, whereas the lower dose of ethanol decreased TH gene expression in WT mice. These results suggest that deletion of the CB2r gene increased preference for and vulnerability to ethanol consumption, at least in part, by increased ethanol-induced sensitivity of the TH and μ-opioid receptor gene expressions in mesolimbic neurons. Future studies will determine the role of CB2r as a target for the treatment of problems related with alcohol consumption. [ABSTRACT FROM AUTHOR]

There is compelling evidence that acute ethanol exposure stimulates ventral tegmental area (VTA) dopamine cell activity and that VTA-dependent dopamine release in terminal fields within the nucleus accumbens plays an integral role in the regulation of ethanol drinking behaviors. Unfortunately, due to technical limitations, the specific temporal dynamics linking VTA dopamine cell activation and ethanol self-administration are not known. In fact, establishing a causal link between specific patterns of dopamine transmission and ethanol drinking behaviors has proven elusive. Here, we sought to address these gaps in our knowledge using a newly developed viral-mediated gene delivery strategy to selectively express Channelrhodopsin-2 (ChR2) on dopamine cells in the VTA of wild-type rats. We then used this approach to precisely control VTA dopamine transmission during voluntary ethanol drinking sessions. The results confirmed that ChR2 was selectively expressed on VTA dopamine cells and delivery of blue light pulses to the VTA induced dopamine release in accumbal terminal fields with very high temporal and spatial precision. Brief high frequency VTA stimulation induced phasic patterns of dopamine release in the nucleus accumbens. Lower frequency stimulation, applied for longer periods mimicked tonic increases in accumbal dopamine. Notably, using this optogenetic approach in rats engaged in an intermittent ethanol drinking procedure, we found that tonic, but not phasic, stimulation of VTA dopamine cells selectively attenuated ethanol drinking behaviors. Collectively, these data demonstrate the effectiveness of a novel viral targeting strategy that can be used to restrict opsin expression to dopamine cells in standard outbred animals and provide the first causal evidence demonstrating that tonic activation of VTA dopamine neurons selectively decreases ethanol self-administration behaviors.

Studies in animal models have shown that repeated episodes of alcohol dependence and withdrawal promote escalation of drinking that is presumably associated with alterations in the addiction neurocircuitry. Using a lithium chloride-ethanol pairing procedure to devalue the reinforcing properties of ethanol, the present study determined whether multiple cycles of chronic intermittent ethanol (CIE) exposure by vapor inhalation also alters the sensitivity of drinking behavior to the devaluation of ethanol's reinforcing effects. The effect of devaluation on operant ethanol self-administration and extinction was examined in mice prior to initiation of CIE (short drinking history) and after repeated cycles of CIE or air control exposure (long drinking history). Devaluation significantly attenuated the recovery of baseline ethanol self-administration when tested either prior to CIE or in the air-exposed controls that had experienced repeated bouts of drinking but no CIE. In contrast, in mice that had undergone repeated cycles of CIE exposure that promoted escalation of ethanol drinking, self-administration was completely resistant to the effect of devaluation. Devaluation had no effect on the time course of extinction training in either pre-CIE or post-CIE mice. Taken together, these results are consistent with the suggestion that repeated cycles of ethanol dependence and withdrawal produce escalation of ethanol self-administration that is associated with a change in sensitivity to devaluation of the reinforcing properties of ethanol. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effects of naltrexone (0.7 mg/kg) and/or topiramate (25 mg/kg) on ethanol consumption and the motivation to drink in an oral-operant conditioning paradigm in C57 BL/6 mice. Subsequent real-time polymerase chain reaction ( PCR) experiments were performed to analyze gene expression changes in tyrosine hydroxylase ( TH) in the ventral tegmental area ( VTA). The administration of naltrexone significantly reduced ethanol consumption and the motivation to drink during the different stages of the experiment, whereas the treatment with topiramate resulted in a much lower effect. Interestingly, the administration of naltrexone plus topiramate reduced ethanol consumption markedly compared with single-drug treatment. The water self-administration paradigm was also performed using the same drugs and no differences were found between treatment groups. Real-time PCR analyses revealed that naltrexone significantly normalized the increase of TH gene expression in the VTA induced by ethanol, whereas the administration of topiramate did not produce any significant effect. In the ethanol self-administration procedure, the combination of both drugs further reduced TH gene expression, reaching statistical significance compared with the vehicle, naltrexone or topiramate groups. Taken together, these findings indicate that the administration of naltrexone plus topiramate further reduced ethanol consumption and the motivation to drink in comparison with single-drug treatment. This action may be due, at least in part, to a greater decrease in TH gene expression in the VTA. These results suggest that the combination of both drugs deserves further exploration for the treatment of problems related to alcohol consumption. [ABSTRACT FROM AUTHOR]

While rats have been predominantly used to study operant ethanol self-administration behavior in the context of dependence, several studies have employed operant conditioning procedures to examine changes in ethanol self-administration behavior as a function of chronic ethanol exposure and withdrawal experience in mice. This review highlights some of the advantages of using operant conditioning procedures for examining the motivational effects of ethanol in animals with a history of dependence. As reported in rats, studies using various operant conditioning procedures in mice have demonstrated significant escalation of ethanol self-administration behavior in mice rendered dependent via forced chronic ethanol exposure in comparison to nondependent mice. This paper also presents a summary of these findings, as well as suggestions for future studies. [ABSTRACT FROM AUTHOR]

Rationale: Consumption of alcohol begins during late adolescence in a majority of humans, and the greatest drinking occurs at 18-25 years then decreases with age. Objectives: The present study measured the differences in ethanol intake in relation to age at the onset of ethanol access among nonhuman primates to control for self-selection in humans and isolate age effects on heavy drinking. Methods: Male rhesus macaques were assigned first access to ethanol during late adolescence ( n = 8), young adulthood ( n = 8), or early middle age ( n = 11). The monkeys were induced to drink ethanol (4 % w/ v in water) in increasing doses (water then 0.5, 1.0, 1.5 g/kg ethanol) using a fixed-time (FT) 300-s schedule of food delivery, followed by 22 h/day concurrent access to ethanol and water for 12 months. Age-matched controls consumed isocaloric maltose-dextrin solution yoked to the late adolescents expected to be rapidly maturing ( n = 4). Results: Young adult monkeys had the greatest daily ethanol intake and blood-ethanol concentration (BEC). Only late adolescents escalated their intake (ethanol, not water) during the second compared to the first 6 months of access. On average, plasma testosterone level was consistent with age differences in maturation and tended to increase throughout the experiment more for control than ethanol-drinking adolescent monkeys. Conclusions: Young adulthood in nonhuman primates strongly disposes toward heavy drinking, which is independent of sociocultural factors present in humans. Ethanol drinking to intoxication during the critical period of late adolescence is associated with escalation to heavy drinking. [ABSTRACT FROM AUTHOR]

There is compelling evidence that acute ethanol exposure stimulates ventral tegmental area (VTA) dopamine cell activity and that VTA-dependent dopamine release in terminal fields within the nucleus accumbens plays an integral role in the regulation of ethanol drinking behaviors. Unfortunately, due to technical limitations, the specific temporal dynamics linking VTA dopamine cell activation and ethanol self-administration are not known. In fact, establishing a causal link between specific patterns of dopamine transmission and ethanol drinking behaviors has proven elusive. Here, we sought to address these gaps in our knowledge using a newly developed viral-mediated gene delivery strategy to selectively express Channelrhodopsin-2 (ChR2) on dopamine cells in the VTA of wild-type rats. We then used this approach to precisely control VTA dopamine transmission during voluntary ethanol drinking sessions. The results confirmed that ChR2 was selectively expressed on VTA dopamine cells and delivery of blue light pulses to the VTA induced dopamine release in accumbal terminal fields with very high temporal and spatial precision. Brief high frequency VTA stimulation induced phasic patterns of dopamine release in the nucleus accumbens. Lower frequency stimulation, applied for longer periods mimicked tonic increases in accumbal dopamine. Notably, using this optogenetic approach in rats engaged in an intermittent ethanol drinking procedure, we found that tonic, but not phasic, stimulation of VTA dopamine cells selectively attenuated ethanol drinking behaviors. Collectively, these data demonstrate the effectiveness of a novel viral targeting strategy that can be used to restrict opsin expression to dopamine cells in standard outbred animals and provide the first causal evidence demonstrating that tonic activation of VTA dopamine neurons selectively decreases ethanol self-administration behaviors. [ABSTRACT FROM AUTHOR]

Alcohol activates reward systems through an unknown mechanism, in some cases leading to alcohol abuse and dependence. Herein, we utilized a two-choice Capillary Feeder assay to address the neural and molecular basis for ethanol self-administration in Drosophila melanogaster. Wild-type Drosophila shows a significant preference for food containing between 5% and 15% ethanol. Preferred ethanol self-administration does not appear to be due to caloric advantage, nor due to perceptual biases, suggesting a hedonic bias for ethanol exists in Drosophila. Interestingly, rutabaga adenylyl cyclase expression within intrinsic mushroom body neurons is necessary for robust ethanol self-administration. The expression of rutabaga in mushroom bodies is also required for both appetitive and aversive olfactory associative memories, suggesting that reinforced behavior has an important role in the ethanol self-administration in Drosophila. However, rutabaga expression is required more broadly within the mushroom bodies for the preference for ethanol-containing food than for olfactory memories reinforced by sugar reward. Together these data implicate cAMP signaling and behavioral reinforcement for preferred ethanol self-administration in D. melanogaster. [ABSTRACT FROM AUTHOR]

Abstract: The current study assessed the effects of the selective kappa opioid antagonist JDTic on alcohol (EtOH) -seeking behavior, EtOH relapse, and maintenance responding for EtOH. Adult alcohol-preferring (P) rats were trained in 2-lever operant chambers to self-administer 15% EtOH (v/v) on a fixed-ratio 5 (FR-5) and water on a FR-1 schedule of reinforcement during 1-hr sessions. After 10weeks, rats underwent extinction training for seven sessions. Rats were then maintained in their home cages for 3weeks without EtOH access. All rats received an injection (s.c.) of 0, 1, 3, or 10mg/kg JDTic (n=11–14/group) after the first week of the home cage period. Rats were then tested using the Pavlovian Spontaneous Recovery paradigm (PSR; an animal model of alcohol-seeking) for four sessions during which, responses on the EtOH and water levers were recorded but did not produce their respective reinforcer. Following PSR testing rats were returned to their home cages without access to EtOH for one week prior to the start of EtOH relapse testing. To examine EtOH relapse responding, rats were returned to the operant chambers and the EtOH (FR5) and water (FR1) levers were active. Finally, rats were then tested over 17 operant sessions to assess the effects of JDTic on maintenance responding for EtOH. Rats received 0, 1, 3, or 10mg/kg JDTic (counterbalanced from the initial experiment) 30 minutes prior to the initial maintenance session. JDTic administered 14 and 25days prior to testing dose-dependently reduced the expression of an EtOH PSR and relapse responding. In contrast, JDTic did not alter EtOH responding under maintenance conditions. Overall, the results of this study indicate that different mechanisms mediate EtOH self-administration under relapse and maintenance conditions and kappa opioid receptors are involved in mediating EtOH-seeking behavior and relapse responding but not on-going EtOH self-administration. [Copyright &y& Elsevier]

Abstract: Rationale: The endogenous cannabinoid (CB) system mediates a number of behaviors associated with drug-seeking and drug self-administration. In this study the effects of CB1 receptor manipulations on operant ethanol (EtOH) responding during EtOH-seeking, EtOH-relapse as well as on-going EtOH self-administration were determined. Methods: Alcohol-preferring (P) rats were trained in 2-lever operant chambers to self-administer 15% EtOH (v/v) and water on a concurrent fixed-ratio 5–fixed-ratio 1 (FR5–FR1) schedule of reinforcement in daily 1-h sessions. After 10weeks, rats underwent 7 extinction sessions, followed by 2weeks in their home cages without access to EtOH or operant chambers. Rats were then returned to the operant chambers for testing of EtOH-seeking behavior (no EtOH present) for 4 sessions. After a week in their home cages following the EtOH-seeking test, rats were returned to the operant chambers with access to EtOH and water (relapse). Rats were then maintained in the operant chambers for daily 1-h sessions with access to 15% EtOH and water for several weeks. Results: The CB1 receptor antagonist (SR141716A), at doses of 1 and 2mg/kg, i.p. reduced EtOH-seeking and transiently reduced EtOH self-administration during relapse and maintenance. Conversely, treatment with the CB1 receptor agonist CP 55, 940, at doses of 1 and 10μg/kgi.p., increased EtOH-seeking and EtOH self-administration during relapse. Conclusions: The results of this study demonstrate that activation of CB1 receptors are involved in regulating EtOH-seeking as well as the reinforcing effects of EtOH under relapse and on-going self-administration conditions. [ABSTRACT FROM AUTHOR]

Abstract: The pubertal surge in gonadal hormones that occurs during adolescence may impact the long-term effects of early alcohol exposure and sex differences in drinking behavior in adulthood. We investigated this hypothesis by performing sham or gonadectomy surgeries in Long-Evans rats around post-natal day (P) 20. From P35–45, males and females were given saline or 3.0g/kg ethanol using a binge-like model of exposure (8 injections total). As adults (P100), they were trained to self-administer ethanol via a sucrose-fading procedure and then given access to different unsweetened concentrations (5–20%, w/v) for 5 days/concentration. We found that during adolescence, ethanol-induced intoxication was similar in males and females that underwent sham surgery. In gonadectomized males and females, however, the level of intoxication was greater following the last injection compared to the first. During adulthood, females drank more sucrose per body weight than males and binge-like exposure to ethanol reduced sucrose consumption in both sexes. These effects were not seen in gonadectomized rats. Ethanol consumption was higher in saline-exposed females compared to males, with gonadectomy reversing this sex difference by increasing consumption in males and decreasing it in females. Exposure to ethanol during adolescence augmented ethanol consumption in both sexes, but this effect was statistically significant only in gonadectomized females. Together, these results support a role for gonadal hormones during puberty in the short- and long-term effects of ethanol on behavior and in the development of sex differences in consummatory behavior during adulthood. [Copyright &y& Elsevier]

Ibogaine is a naturally occurring alkaloid that has been reported to decrease various adverse phenotypes associated with exposure to drugs of abuse and alcohol in human and rodent models. Unfortunately, ibogaine cannot be used as a medication to treat addiction because of severe side effects. Previously, we reported that the desirable actions of ibogaine to reduce self-administration of, and relapse to, alcohol consumption are mediated via the upregulation of the expression of the glial cell line-derived neurotrophic factor (GDNF) in the midbrain ventral tegmental area (VTA), and the consequent activation of the GDNF pathway. The ibogaine metabolite, noribogaine, and a synthetic derivative of ibogaine, 18-Methoxycoronaridine (18-MC), possess a similar anti-addictive profile as ibogaine in rodent models, but without some of its adverse side effects. Here, we determined whether noribogaine and/or 18-MC, like ibogaine, increase GDNF expression, and whether their site of action to reduce alcohol consumption is the VTA. We used SH-SY5Y cells as a cell culture model and found that noribogaine, like ibogaine, but not 18-MC, induces a robust increase in GDNF mRNA levels. Next, we tested the effect of intra-VTA infusion of noribogaine and 18-MC on rat operant alcohol self-administration and found that noribogaine, but not 18-MC, in the VTA decreases responding for alcohol. Together, our results suggest that noribogaine and 18-MC have different mechanisms and sites of action. [ABSTRACT FROM AUTHOR]

Abstract: Several studies indicated the involvement of serotonin-3 ([5-hydroxy tryptamine] 5-HT3) receptors in regulating alcohol-drinking behavior. The objective of this study was to determine the involvement of 5-HT3 receptors within the ventral tegmental area (VTA) in regulating ethanol self-administration by alcohol-preferring (P) rats. Standard two-lever operant chambers (Coulbourn Instruments, Allentown, PA) were used to examine the effects of seven consecutive bilateral microinfusions of ICS 205-930 (ICS), a 5-HT3 receptor antagonist, directly into the posterior VTA on the acquisition and maintenance of 15% (vol/vol) ethanol self-administration. P rats readily acquired ethanol self-administration by the fourth session. The three highest doses (0.125, 0.25, and 1.25μg) of ICS prevented acquisition of ethanol self-administration. During the acquisition postinjection period, all rats treated with ICS demonstrated higher responding on the ethanol lever, with the highest dose producing the greatest effect. In contrast, during the maintenance phase, the three highest doses (0.75, 1.0, and 1.25μg) of ICS significantly increased responding on the ethanol lever; after the 7-day dosing regimen, responding on the ethanol lever returned to control levels. Microinfusion of ICS into the posterior VTA did not alter the low responding on the water lever and did not alter saccharin (0.0125% wt/v) self-administration. Microinfusion of ICS into the anterior VTA did not alter ethanol self-administration. Overall, the results of this study suggest that 5-HT3 receptors in the posterior VTA of the P rat may be involved in regulating ethanol self-administration. In addition, chronic operant ethanol self-administration and/or repeated treatments with a 5-HT3 receptor antagonist may alter neuronal circuitry within the posterior VTA. [Copyright &y& Elsevier]

Abstract: The present study investigated the consequences of environmental enrichment on the impact of novelty and motivational properties of ethanol in spontaneously hypertensive rats (SHR), a validated model of attention deficit hyperactivity disorder (ADHD). This rat strain displays increased sensitivity to distinct classes of abused drugs, which makes it an interesting model for the study of the association between ADHD and drug abuse. Female SHR reared from weaning to adulthood in standard (SE) or enriched (EE) environment were tested on novelty-induced locomotion, saccharin consumption, ethanol consumption (forced and free-choice schedules) and ethanol-induced conditioned place preference (CPP). SHR reared in an EE showed reduced novelty-induced locomotion, consumed less saccharin and ethanol in a forced schedule and showed less ethanol preference in a free-choice schedule compared to SE rats. Moreover, EE rats did not develop CPP, whereas SE rats developed preference for ethanol (1.2g/kg). These results show that exposure to stimuli mimicking positive life experiences (environmental enrichment) induces persistent changes in the reward/motivational system of female SHR, suggesting an important role of the familiar environment during early stages of the neurodevelopment on the co-morbidity of ADHD and drug abuse. [Copyright &y& Elsevier]

Abstract: Alcohol and nicotine are frequently co-used and co-abused, and use of both drugs alone can affect hepatic drug metabolism. We investigated the influences of chronic nicotine treatment and voluntary ethanol intake on the induction of rat hepatic cytochrome P450 (CYP) enzymes that metabolize ethanol and nicotine. Rats were trained to voluntarily drink ethanol (6% v/v, 1 h) with nicotine pretreatment for 10 days. Another group of rats were treated with the same nicotine doses alone. Hepatic CYP2E1, CYP2B1/2 and CYP2D1 proteins were assessed by immunoblotting. Nicotine pretreatment (0.4, 0.8 and 1.2 mg/kg) increased voluntary ethanol intake on day 10 by 1.8, 2.0, and 1.4 fold respectively compared to saline pretreatment (P <0.01–0.3). CYP2E1 was increased 1.7, 1.8, and 1.4 fold by the three doses of nicotine alone (P <0.02–0.21); CYP2E1 levels were increased by voluntary ethanol intake alone and a further 2.4, 2.2, and 1.8 fold by 0.4, 0.8, and 1.2 mg/kg nicotine respectively versus saline pretreatment (P <0.002–0.06). CYP2B1/2 proteins were not induced by nicotine alone, but were increased by 2.2–2.5 fold by ethanol drinking (P <0.05). CYP2E1 (r =0.67, P <0.001) and CYP2B1/2 levels (r =0.49, P =0.007) correlated with alcohol consumption on day 10. There was no change in CYP2D1. Chronic nicotine increased voluntary ethanol intake thereby enhancing CYP2E1 and CYP2B1/2 levels. Thus CYPs are regulated not only directly by nicotine and ethanol, but also indirectly via an increase in the ethanol consumption in the presence of nicotine pretreatment. Together this may contribute to the co-abuse of these drugs and alter the metabolism of clinical drugs and endogenous substrates. [Copyright &y& Elsevier]

The sensitivity to ethanol central effects is partially determined by the subunit composition of brain nicotinic acetylcholine receptors (nAChRs). Thus, the effects of intraventral tegmental area (VTA) administration of the nicotinic subunit-specific antagonist, α-conotoxin MII (αCtxMII, α3β2*, β3*, α6*), were compared to those of systemic mecamylamine (MEC, an allosteric negative modulator of the nAChR), dihydro-β-erythroidine (DHβE, α4β2*), and methyllycaconitine (MLA, α7*) to elucidate involvement of different subunits of nAChRs in operant ethanol self-administration and relapse-like activation of ethanol consumption after ethanol deprivation in rats. The effects of drugs were studied in rats trained for operant oral self-administration of ethanol (FR = 1). For ethanol deprivation, trained animals were subjected to a period of alcohol deprivation for 10 days. αCtxMII was given directly into the VTA through implanted permanent intracranial cannulae, whereas MEC, DHβE, and MLA were administered systemically. αCtxMII reduced operant ethanol self-administration and blocked the deprivation-induced relapse-like ethanol consumption. MEC reduced operant ethanol self-administration and inhibited the deprivation-induced increase in alcohol consumption. DHβE did not alter ethanol self-administration in the lower-dose range but inhibited ethanol intake at a higher dose (4 mg/kg), although this effect might have been nonspecific. MLA failed to block self-administration of ethanol and relapse-like drinking after deprivation. Our results indicate that nAChRs are involved in the modulation of operant alcohol self-administration and relapse-like alcohol drinking behavior in rats. Our observations support the working hypothesis that systemically active selective ligands for nAChR α3β2*, β3, and/or α6* receptor subunits might be of therapeutic value for the treatment of alcoholism. [ABSTRACT FROM AUTHOR]

Background: Endogenous cannabinoids and their receptors, CB1 receptors in particular, have been implicated in mediation of ethanol reinforcement. Previously, suppression of ethanol drinking by CB1 antagonists has been demonstrated in many experimental paradigms. However, the exact mechanism by which CB1 antagonists modulate ethanol drinking remains elusive. In the present study, we assessed the role of CB1 receptors within the key regions of the mesolimbic dopamine pathway, the nucleus accumbens (NAcc) and ventral tegmental area (VTA), in regulation of ethanol self-administration. Methods: Adult male alcohol-prefer AA rats were trained to self-administer either 10% (w/v) ethanol or 0.1% (w/v) saccharin under an FR1 schedule during daily 30-minute sessions. Following stable baseline responding, rats were tested after systemic administration of the CB1 antagonist SR141716A (0 to 10 mg/kg) and the agonist WIN55,212-2 (0 to 2 mg/kg). Separate groups of rats were implanted with bilateral cannulas aimed at the NAcc or VTA, and tested after microinjections of SR141716A (0 to 3 μg) and WIN55,212-2 (0 to 5 μg) into the NAcc or VTA. The highest intracerebral doses were tested also in rats responding for a 0.1% saccharin solution. Results: SR141617A dose-dependently suppressed ethanol responding after systemic administration. Microinjections of SR141617A both into NAcc and VTA attenuated ethanol responding. In addition, intra-NAcc injections of SR141617A suppressed saccharin intake. Although low doses of systemically given WIN55,212-2 increased ethanol responding, no effects were seen after WIN55,212-2 microinjections into NAcc or VTA. Conclusions: Bidirectional changes in ethanol self-administration by the systematically administered CB1 agonist and antagonist show that ethanol reinforcement is controlled by CB1 receptors in alcohol-preferring AA rats. Replication of the suppressive effects by CB1 antagonism in the NAcc and VTA suggests that endocannabinoids and their receptors mediate ethanol reinforcement through interaction with the mesolimbic dopamine pathway. [ABSTRACT FROM AUTHOR]

Abstract: Stress is an often-reported cause for alcohol consumption in humans. Acute intermittent footshock is a frequently used paradigm to produce stress in laboratory animals including mice. The effect produced by intermittent footshock stress on ethanol self-administration has been inconsistent: both increases and decreases in ethanol consumption have been reported. The current set of studies further investigates, in three commonly studied mouse strains, the effect of footshock stress on ethanol self-administration. Furthermore, the effect of footshock on plasma corticosterone levels was determined to investigate potential biochemical correlates. Adult male C57BL/6J, DBA/2J, and A/J mice were allowed to self-administer 10% (wt/vol) ethanol for 12 days in a standard 23-h two-bottle paradigm before receiving either 15 min of mild inescapable footshock or no footshock. Shock intensity was equal to the mean intensity at which each strain vocalized as previously determined. Following footshock, animals had the opportunity to self-administer ethanol for an additional 23 h. Separate animals were subjected to either footshock or no shock prior to collection of plasma for corticosterone. Mild footshock stress altered ethanol self-administration and increased plasma corticosterone levels in C57BL/6J mice. Footshock stress did not alter ethanol self-administration or plasma corticosterone levels in DBA/2J or A/J mice. These data demonstrate that mild footshock stress is a suboptimal method of modeling the stress-induced increases in ethanol consumption often reported by humans. [Copyright &y& Elsevier]

Background: Alcohol abuse is a major public health burden that can lead to many adverse health effects such as impaired hepatic, gastrointestinal, central nervous system and immune system function. Preclinical animal models of alcohol abuse allow for experimental control over variables often difficult to control in human clinical studies (e.g., ethanol exposure before or during the study, history of other drug use, access to medical care, nutritional status, etc). Nonhuman primate models in particular provide increased genetic, anatomic and physiologic similarity to humans, relative to rodent models. A small percentage of macaques will spontaneously consume large quantities of ethanol; however, most nonhuman primate models of “voluntary” ethanol intake produce relatively low daily ethanol intake in the majority of monkeys. Methods: To facilitate study of chronic exposure to high levels of ethanol intake, a macaque model has been developed that induces consistent, daily high-level ethanol consumption. This multiple-session procedure employed 4 drinking sessions per day, with sessions occurring once every 6 hours. Results: The group average alcohol consumption was 4.6 g/kg/d (SEM 0.4), roughly twice the group average consumption of previous reports. Ethanol drinking sessions produced group mean blood ethanol levels of 95 mg/dl after 60 minutes, and fine motor control was impaired up to 90 minutes after a drinking session. Conclusion: This model of multiple-session, limited access, oral ethanol self-dosing produced consistent, high-level ethanol consumption with each session qualifying as a “binge” drinking session using the definition of “binge” provided by the NIAAA (>80 mg/dl/session). This model of ethanol drinking in macaques will be of great utility in the study of immunological, physiological and behavioral effects of ethanol in nonhuman primates. [ABSTRACT FROM AUTHOR]

Abstract: The current study examined the effects of operant ethanol (EtOH) self-administration on gene expression kin the nucleus accumbens (ACB) and amygdala (AMYG) of inbred alcohol-preferring (iP) rats. Rats self-trained on a standard two-lever operant paradigm to administer either water–water, EtOH (15% v/v)–water, or saccharin (SAC; 0.0125% g/v)–water. Animals were killed 24 h after the last operant session, and the ACB and AMYG dissected; RNA was extracted and purified for microarray analysis. For the ACB, there were 513 significant differences at the p <0.01 level in named genes: 55 between SAC and water; 215 between EtOH and water, and 243 between EtOH and SAC. In the case of the AMYG (p <0.01), there were 48 between SAC and water, 23 between EtOH and water, and 63 between EtOH and SAC group. Gene Ontology (GO) analysis indicated that differences in the ACB between the EtOH and SAC groups could be grouped into 15 significant (p <0.05) categories, which included major categories such as synaptic transmission, cell and ion homeostasis, and neurogenesis, whereas differences between the EtOH and water groups had only 4 categories, which also included homeostasis and synaptic transmission. Several genes were in common between the EtOH and both the SAC and water groups in the synaptic transmission (e.g., Cav2, Nrxn3, Gabrb2, Gad1, Homer1) and homeostasis (S100b, Prkca, Ftl1) categories. Overall, the results suggest that changes in gene expression in the ACB of iP rats are associated with the reinforcing effects of EtOH. [Copyright &y& Elsevier]

Background: Emerging evidence indicates that Group I metabotropic glutamate receptors (mGluR1 and mGluR5) differentially regulates ethanol self-administration in several rodent behavioral models. The purpose of this work was to further characterize involvement of Group I mGluRs in the reinforcing effects of ethanol using a progressive ratio schedule of reinforcement. Methods: Alcohol-preferring (P) rats were trained to self-administer ethanol (15% v/v) versus water on a concurrent schedule of reinforcement, and the effects of the Group I mGluR antagonists were evaluated on progressive ratio performance. The rats were then trained to self-administer sucrose (0.4% w/v) versus water, and the effects of the antagonists were tested on progressive ratio performance. Results: The mGluR1 antagonist, 3,4-dihydro-2H-pyrano[2,3]b quinolin-7-yl ( cis-4-methoxycyclohexyl) methanone (JNJ 16259685; 0 to 1 mg/kg) and the mGluR5 antagonist, 6-methyl-2-(phenylethynyl) pyridine (MPEP; 0 to 10 mg/kg) dose-dependently reduced ethanol break point. In separate locomotor activity assessments, the lowest effective dose of JNJ 16259685 (0.3 mg/kg) produced a motor impairment, whereas the lowest effective dose of MPEP (3 mg/kg) did not. Thus, the reduction in ethanol break point by mGluR1 antagonism was probably a result of a motor impairment. JNJ 16259685 (0.3 mg/kg) and MPEP (10 mg/kg) reduced sucrose break point and produced motor impairments. Thus, the reductions in sucrose break point produced by both Group I antagonists were probably because of nonspecific effects on motor activity. Conclusions: Together, these results suggest that glutamate activity at mGluR5 regulates motivation to self-administer ethanol. [ABSTRACT FROM AUTHOR]

Abstract: The Group I family of metabotropic glutamate receptors includes subtype 1 (mGlu1) and subtype 5 (mGlu5) receptors. This family of receptors has generated interest as potential targets for different areas of therapeutic development, including intervention for alcohol and drug abuse. Most of this interest is driven by findings showing involvement of mGlu5 receptors in the regulation of drug self-administration; however, studies examining the role of mGlu1 receptors in drug self-administration are limited. The purpose of this work was to examine the role of mGlu1-receptor antagonism in the maintenance of ethanol self-administration and the self-administration of an alternate nondrug reward, sucrose. Male alcohol-preferring inbred rats were trained to self-administer ethanol (15% vol/vol) versus water on a concurrent schedule of reinforcement, and the effect of the mGlu1-receptor antagonist JNJ16259685 (0.1–1.0mg/kg intraperitoneal [IP]) was evaluated on self-administration. The rats were then trained to self-administer sucrose (0.4% wt/vol) versus water, and the same dose range of JNJ16259685 was tested. Locomotor activity was tested in a separate assessment to evaluate potential nonspecific motor effects of the antagonist. Ethanol self-administration was dose dependently reduced by JNJ16259685. This reduction was likely due to a motor impairment as the lowest effective dose (0.1mg/kg) significantly reduced locomotor behavior. Sucrose self-administration was reduced by the highest JNJ16259685 dose (1.0mg/kg), and this reduction was also likely due to a motor impairment. Interestingly, ethanol self-administration was more sensitive to mGlu1-receptor antagonism than sucrose self-administration as lower JNJ16259685 doses reduced ethanol-reinforced responding and motor behavior. Together, these results suggest that mGlu1 receptors do not play a specific role in modulating ethanol self-administration or the self-administration of an alternate nondrug reward (i.e., sucrose). [Copyright &y& Elsevier]

Abstract: Models of dependence-induced increases in ethanol self-administration will be critical in increasing our understanding of the processes of addiction and relapse, underlying mechanisms, and potential therapeutics. One system that has received considerable attention recently is the CRF1 system that may mediate the link between anxiety states and relapse drinking. C57BL/6J mice were trained to lever press for ethanol, were made dependent and then were allowed to self-administer ethanol following a period of abstinence. The effect of the CRF1 antagonist, antalarmin, was examined on this abstinence-induced self-administration in a separate group of mice. Finally, dependence-induced changes in ethanol self-administration were examined in CRF1 knockout and wild type mice. The results indicated that ethanol self-administration was increased following the induction of dependence, but only after a period of abstinence. This increase in ethanol self-administration was blocked by antalarmin. Furthermore, CRF1 knockout mice did not display this increased ethanol self-administration following dependence and abstinence. These studies, using both a pharmacological and genetic approach, support a critical role for the CRF1 system in ethanol self-administration following dependence. In addition, a model is presented that may be useful for studies examining underlying mechanisms of the ethanol addiction process as well as for testing potential therapeutics. [Copyright &y& Elsevier]

Abstract: The purpose of the present study was to characterize cue-induced reinstatement of ethanol seeking in selectively bred Sardinian alcohol-preferring (sP) rats trained to lever press for ethanol in 30-min self-administration sessions. Four responses on an “active” lever led to presentation of 0.1ml of 15% (vol/vol) ethanol by a liquid dipper and concurrent activation of a set of discrete light and auditory cues. In a 70-min extinction/reinstatement session, responding was first extinguished for 60min. Subsequently, different stimuli were delivered in a noncontingent manner and reinstatement of nonreinforced responding was assessed. Fifteen presentations of the ethanol-predictive stimulus complex, including the dipper cup containing 5 or 15% ethanol, potently reinstated responding on the previously active lever. The magnitude of reinstatement increased with the number of stimulus presentations and concentration of ethanol presented by the dipper cup. Fifteen presentations of the ethanol-predictive stimulus complex, including the dipper cup filled with water (0% ethanol), did not produce any reinstatement. These results indicate that (1) noncontingent presentations of the ethanol-predictive stimulus complex may reinstate ethanol seeking in sP rats and (2) the orosensory properties of ethanol may play an important role in reinstatement of ethanol seeking in sP rats. The latter finding concurs with clinical observations that odor and taste of alcoholic beverages elicit immediate craving responses in abstinent alcoholics. [Copyright &y& Elsevier]

The development of mouse models of ethanol consumption and ethanol-seeking behavior is of particular importance in understanding the underlying mechanisms of drug abuse because these models can enable an analysis of an effect of specific genotype on drug-seeking behavior and the interaction of potential therapeutics with genotype. However, there are some limitations with present models, notably the inability to examine appetitive and consummatory behavior separately. In the present study, C57BL/6 mice were trained to self-administer 10% ethanol in a modified operant protocol that allowed a clear delineation of consummatory and appetitive phases. The utility of this procedure was confirmed with the use of the metabotropic glutamate 5 (mGlu5) receptor antagonist 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]-pyridine (MTEP). Limited-access consumption during the dark phase of the light–dark cycle with intermittent access (every second or third day) led to a high level of consumption by the mice. MTEP caused a dose-dependent decrease in both the consumption of ethanol and the appetitive response for ethanol. Furthermore, this effect was unrelated to any effect of MTEP on locomotor activity. The model provides a useful paradigm for examining both the appetitive and consummatory phases of ethanol consumption in mice; furthermore, the data indicate mGlu5 receptors are involved in both phases. [ABSTRACT FROM AUTHOR]