The glucocorticoid receptor antagonist mifepristone reduces ethanol intake in rats under limited access conditions.

There is a substantial amount of evidence indicating control over ethanol intake by steroid hormones, particularly adrenal glucocorticoids. Thus far, however, studies employing pharmacological methods have failed to find effects of glucocorticoid receptor blockade on voluntary ethanol consumption. Since length of ethanol access period can influence ethanol consumption levels as well as potential pharmacological effects in such studies, the present study was conducted to determine the effects of acute administration of the glucocorticoid receptor (GR) antagonist mifepristone on voluntary ethanol intake under limited access conditions. Rats were fluid restricted and given concurrent access to 10% ethanol and water in a two-bottle choice paradigm for 1 h/day, 5 days a week. Both fluids were available ad libitum during the remaining 2 days per week. Administration of mifepristone (1, 5 and 20 mg/kg i.p.) immediately prior to the limited access two-bottle access period dose-dependently suppressed ethanol intake (maximum 40% at 20 mg/kg). The mineralcorticoid receptor (MR) antagonist spironolactone (10, 25 and 50 mg/kg i.p.) was without effect on ethanol intake, and neither compound had an effect on water intake. These data confirm an active role of GRs in modulating voluntary ethanol consumption, particularly under conditions of limited access.

A role for corticotropin releasing factor (CRF) in ethanol consumption, sensitivity, and reward as revealed by CRF-deficient mice.

RATIONALE: Corticotropin-releasing factor (CRF) plays an integral role in mediating stress responses and anxiety. However, little is known regarding the role of CRF in ethanol consumption, a behavior often associated with stress and anxiety in humans. OBJECTIVE: The present study sought to determine the role of CRF in ethanol consumption, locomotor sensitivity and reward by examining these behaviors in C57BL/6J x 129S mice with a targeted disruption in the gene encoding the CRF prohormone. METHODS: Male wild-type and CRF-deficient mice were given concurrent access to ethanol and water in both limited and unlimited-access two-bottle choice paradigms. Taste reactivity (saccharin or quinine vs water) was examined in a similar manner under continuous-access conditions. Blood ethanol levels and clearance were measured following limited ethanol access as well as a 4-g/kg i.p. injection of ethanol. Locomotor stimulant effects of ethanol were measured in an open-field testing chamber, and the rewarding effects of ethanol were examined using the conditioned place preference paradigm. RESULTS: CRF-deficient mice displayed normal body weight, total fluid intake, taste reactivity and blood ethanol clearance, but consumed approximately twice as much ethanol as wild types in both continuous- and limited-access paradigms. CRF-deficient mice failed to demonstrate a locomotor stimulant effect following acute administration of ethanol (2 g/kg i.p.), and also failed to demonstrate a conditioned place preference to ethanol at 2 g/kg i.p., but did display such a preference at 3 g/kg i.p. CONCLUSIONS: CRF deficiency may lead to excessive ethanol consumption by reducing sensitivity to the locomotor stimulant and rewarding effects of ethanol.

Ethanol consumption patterns and conditioned place preference in mice lacking preproenkephalin.

There is a great deal of evidence suggesting that endogenous opioid systems are involved in the control of ethanol-seeking behavior and reward. To ascertain the role of the enkephalinergic opioid peptide system in these processes, we examined voluntary ethanol consumption patterns in mice lacking the preproenkephalin (Penk) gene using a two-bottle choice paradigm with free access to water and increasing concentrations of ethanol (2, 4, 8, and 10% v/v). We also examined the ability of ethanol (2 g/kg i.p.) to establish a conditioned place preference in these mice. No differences in ethanol consumption or preference were observed between wildtypes and Penk null mutant mice. In addition, both genotypes displayed a similar conditioned place preference to ethanol. These data suggest that the preproenkephalin system is not involved in voluntary ethanol consumption patterns or ethanol reward.

The corticotropin-releasing factor/urocortin system and alcohol.

This article represents the proceedings of a symposium at the RSA meeting in Montreal, Canada. The organizer was Andrey E. Ryabinin, and the chair was George F. Koob. The presentations were (1) Introduction, by Stephen C. Heinrichs; (2) Role of CRF and its receptors in the hypothalamic-pituitary-adrenal response to alcohol, by Soon Lee and Catherine Rivier; (3) A role for CRF in the allostasis of alcohol dependence, by George F. Koob and Amanda J. Roberts; (4) CRF and alcohol: Lessons from knockouts, microinjections, and microdialysis, by M. Foster Olive, Kristin K. Mehmert, R. Camarini, Joseph A. Kim, Heather N. Koenig, Michelle A. Nannini, and Clyde W. Hodge; and (5) Selective sensitivity of urocortin-containing neurons to alcohol self-administration, by Andrey E. Ryabinin and Ryan K. Bachtell.

Elevated extracellular CRF levels in the bed nucleus of the stria terminalis during ethanol withdrawal and reduction by subsequent ethanol intake.

Corticotropin-releasing factor (CRF) is widely distributed throughout the brain and has been shown to mediate numerous endocrine and behavioral responses to stressors. During acute ethanol withdrawal, CRF release is increased in the central nucleus of the amygdala (CeA), and there is evidence to suggest that this activation of amygdala CRF systems may mediate the anxiogenic properties of the ethanol withdrawal syndrome. The present study was conducted to determine if another CRF-containing limbic structure, the bed nucleus of the stria terminalis (BNST), we would exhibit similar increases in CRF neurotransmission during ethanol withdrawal. Rats were administered an ethanol-containing (6.7% v/v) or control liquid diet for 2 weeks and subsequently implanted with microdialysis probes into the lateral BNST. A 50-75% increase in dialysate CRF levels was observed following removal of the ethanol-containing diet, while no changes were observed in control animals. When ethanol-withdrawn animals were given subsequent access to the ethanol-containing diet, dialysate CRF levels returned to basal levels. However, when ethanol-withdrawn animals were given subsequent access to the control diet, dialysate CRF levels increased further to 101% above basal levels. These data demonstrate that extracellular CRF levels are increased in the BNST during ethanol withdrawal, and that these increases are reduced by subsequent ethanol intake.

Effects of acute acamprosate and homotaurine on ethanol intake and ethanol-stimulated mesolimbic dopamine release.

The purpose of the present study was to determine the acute effects of the anticraving compound acamprosate (calcium acetylhomotaurinate) and the closely related compound homotaurine on ethanol intake and ethanol-stimulated dopamine release in the nucleus accumbens. Male rats were treated with acamprosate (200 or 400 mg/kg intraperitoneally, i.p.) or homotaurine (10, 50, or 100 mg/kg i.p.) 15 min prior to access to 10% ethanol and water for 1 h in a two-bottle choice restricted access paradigm. A separate group of rats was implanted with microdialysis probes in the nucleus accumbens and given an acute injection of ethanol (1.5 g/kg i.p.) that was preceded by saline, acamprosate, or homotaurine. Acamprosate and homotaurine dose-dependently reduced ethanol intake and preference. These compounds also delayed or suppressed ethanol-stimulated increases in nucleus accumbens dopamine release, suggesting that acamprosate and homotaurine may reduce ethanol intake by interfering with the ability of ethanol to activate the mesolimbic dopamine reward system.