Sex-dependent effects of ethanol withdrawal from a single- and repeated binge episode exposures on social anxiety-like behavior and neuropeptide gene expression in adolescent rats

Abstract

Ethanol withdrawal sensitivity is a risk factor for the development of alcohol use disorder. Heavy episodic drinking during adolescence often encompasses repeated periods of withdrawal. Adolescent intermittent ethanol exposure of laboratory rodents produces several neurobiological deficits that differ between sexes, but the sensitivity to withdrawal as a contributor to the observed sex differences is not clear. The current study assessed the impact of acute withdrawal from a single- and repeated binge ethanol episodes during adolescence as well as protracted abstinence from repeated binge episodes on social anxiety-like behavior (indexed via significant decreases of social investigation) as well as oxytocin (OXT) and vasopressin (AVP) system gene expression in the hypothalamus (HYP) and central amygdala (CeA) in male and female Sprague Dawley rats. Females displayed social anxiety-like behavior during withdrawal from a single binge episode, whereas both sexes showed social anxiety-like changes following acute withdrawal from repeated binge episodes. After a period of protracted abstinence, only males still displayed ethanol-associated social alterations. Analysis of gene expression in separate, non-socially tested subjects revealed that withdrawal from repeated binge episodes during adolescence increased AVP gene expression in the HYP of males and decreased it in females. Males also displayed increased AVP and OXTR gene expression during acute withdrawal from repeated binge episodes in the CeA, with these changes persisting into adulthood. Together, these findings suggest that adolescent females are sensitive to withdrawal from both acute and repeated ethanol exposures, whereas males are sensitive to withdrawal from repeated ethanol exposures, with affective and transcriptional changes persisting into adulthood.

Keywords: AIE; adolescence; binge ethanol exposure; central amygdala; hypothalamus; oxytocin; sex differences; social behavior; vasopressin.

Figure 1.

Effects of withdrawal from a single or repeated binge episode(s) on social investigation (A-C) and the coefficient of preference/avoidance (D-F) in male and female Sprague Dawley rats. A. Withdrawal from a single binge episode significantly decreased social investigation on P30 in ethanol-exposed females relative to water-exposed controls. B. Withdrawal from repeated binge episodes significantly decreased social investigation on P54 in ethanol-exposed males and females relative to their water-exposed counterparts. C. Social investigation was significantly decreased on P75 following a 3-week period of abstinence from repeated binge episodes in ethanol-exposed males relative to water-exposed controls. D-F. Social preference was not affected by ethanol exposure. * p < 0.05 and ** p < 0.005 indicate significant differences between water and ethanol exposure conditions.

Figure 2.

Effects of withdrawal from a single or repeated binge episode(s) on OXT and AVP system gene expression in the HYP. A. OXT gene expression in males was higher on P75 than P30. B. OXT gene expression in females was higher on P75 than P54 and P30. C-D. No differences were found in OXTR gene expression between water and ethanol-exposed males (C) and females (D). E. AVP gene expression in males was higher on P75 than P30, and ethanol exposure increased AVP gene expression. F. In water-exposed females, AVP gene expression was higher on P75 than P54, and on P54 than P30, and in ethanol-exposed females, AVP gene expression was higher on P75 than P54. On P54, ethanol exposure decreased AVP gene expression relative to water-exposed females. G. AVPR1a gene expression in males was lower on P75 than P30, and ethanol exposure increased AVPR1a gene expression. H. AVPR1a gene expression in females was lower on P75 than P30. * p < 0.05 and ** p < 0.005 indicate significant differences between water and ethanol exposure conditions. # p < 0.05, ## p < 0.005, and ### p < 0.0005 indicate significant differences between postnatal days.

Figure 3.

Effects of withdrawal from a single or repeated binge episode(s) on OXT and AVP system gene expression in the CeA. A. OXT gene expression in males was reduced on P75 following a period of abstinence from repeated binge-like adolescent ethanol exposure relative to water-exposed controls. B. OXT gene expression in females was higher on P75 than P30. C. OXTR gene expression in males was higher on P75 and P54 than P30, and ethanol exposure increased OXTR gene expression relative to water exposure. D. OXTR gene expression in females was higher on P75 and P54 than P30. E. AVP gene expression in males was higher on P75 than P54 and P30, and higher on P54 than P30. AVP gene expression was higher in ethanol-exposed males than in water-exposed controls. F. AVP gene expression in females was higher on P75 than P54 and P30, and higher on P54 than P30. G. AVPR1a gene expression in males was higher on P54 and P75 than on P30, and ethanol exposure decreased AVPR1a gene expression relative to water exposure. H. AVPR1a gene expression in females was higher on P54 and P75 than on P30, and ethanol exposure decreased AVPR1a gene expression relative to water exposure. * p < 0.05, ** p < 0.005, and *** p < 0.0005 indicate significant differences between water and ethanol exposure conditions. # p < 0.05, ## p < 0.005, ### p < 0.0005, and #### p < 0.0001 indicate significant differences between postnatal days.