Sex-dependent effects of acute stress and alcohol exposure during adolescence on mRNA expression of brain signaling systems involved in reward and stress responses in young adult rats

Abstract

Background: Adolescent stress and alcohol exposure increase the risk of maladaptive behaviors and mental disorders in adulthood, with distinct sex-specific differences. Understanding the mechanisms underlying these early events is crucial for developing targeted prevention and treatment strategies.

Methods: Male and female Wistar rats were exposed to acute restraint stress and intermittent alcohol during adolescence. We assessed lasting effects on plasma corticosterone (CORT) and adrenocorticotropic hormone (ACTH) levels, and mRNA expression of genes related to corticotropin releasing hormone (CRH), neuropeptide Y (NPY), corticoid, opioid, and arginine vasopressin systems in the amygdala and hypothalamus.

Results: The main findings are as follows: (1) blood alcohol concentrations (BAC) increased after the final alcohol administration, but stressed males had lower BAC than non-stressed males; (2) Males gained significantly more weight than females; (3) Stressed females showed higher ACTH levels than non-stressed females, with no changes in males; (4) Stress increased CORT levels in males, while stressed, alcohol-treated females had lower CORT levels than non-stressed females; (5) CRH: Females had lower Crhr1 levels in the amygdala, while alcohol reduced Crhr2 levels in males but not females. Significant interactions among sex, stress, and alcohol were found in the hypothalamus, with distinct patterns between sexes; (6) NPY: In the amygdala, stress reduced Npy and Npy1r levels in males but increased them in females. Alcohol decreased Npy2r levels in males, with varied effects in females. Similar sex-specific patterns were observed in the hypothalamus; (7) Corticoid system: Stress and alcohol had complex, sex-dependent effects on Pomc, Nr3c1, and Nr3c2 in both brain regions; (8) Opioid receptors: Stress and alcohol blunted the elevated expression of Oprm1, Oprd1, and Oprk1 in the amygdala of males and the hypothalamus of females; (8) Vasopressin: Stress and alcohol interacted significantly to affect Avp and Avpr1a expression in the amygdala, with stronger effects in females. In the hypothalamus, alcohol increased Avp levels in females.

Conclusions: This study demonstrates that adolescent acute stress and alcohol exposure induce lasting, sex-specific alterations in systems involved in reward and stress responses. These findings emphasize the importance of considering sex differences in the prevention and management of HPA dysfunction and psychiatric disorders.

Keywords: Adolescence; Amygdala; Binge drinking; HPA axis; Hypothalamus; Restraint; Sexual dimorphism.

Fig. 1

Effects of acute stress, adolescent alcohol, and sex on BAC, body weight gain, and plasma ACTH and CORT levels. BAC at two different time-points of the intermittent alcohol exposure (A); total body weight gain (B); plasma ACTH levels (C); and plasma CORT levels (D) in male and female rats exposed to acute stress and alcohol exposure during adolescence. Bars represent the mean ± SEM (6 rats/subgroup). Data were analyzed using three-way ANOVA. Symbols are used to represent how significant interactions occur: (*) denotes p < 0.05, comparing stressed rats to non-stressed rats in males or females; (+) denotes p < 0.05, comparing rats to non-stressed, saline-treated rats in males or females

Fig. 2

Effects of acute stress, adolescent alcohol, and sex on CRH signaling-related genes in the amygdala and hypothalamus. Crh expression in the amygdala (A); Crhr1 expression in the amygdala (B); Crhr2 expression in the amygdala (C); Crh expression in the hypothalamus (D); Crhr1 expression in the hypothalamus (E); and Crhr2 expression in the hypothalamus (F) of male and female rats exposed to acute stress and alcohol exposure during adolescence. Bars represent the mean ± SEM (6 rats/subgroup). Data were analyzed using three-way ANOVA. Symbols are used to represent how significant interactions occur: (*) denotes p < 0.05, comparing stressed rats to non-stressed rats in males or females; (**) denotes p < 0.05, comparing alcohol-treated rats to saline-treated rats in males or females; (***) denotes p < 0.05, comparing alcohol-treated rats to saline-treated rats in the stress or non-stress subgroup; (+) denotes p < 0.05, comparing rats to non-stressed, saline-treated rats in males or females; (+++) denotes p < 0.05, comparing rats to non-stressed, alcohol-treated rats in males or females

Fig. 3

Effects of acute stress, adolescent alcohol, and sex on NPY signaling-related genes in the amygdala and hypothalamus. Npy expression in the amygdala (A); Npy1r expression in the amygdala (B); Npy2r expression in the amygdala (C); Npy expression in the hypothalamus (D); Npy1r expression in the hypothalamus (E); and Npy2r expression in the hypothalamus (F) of male and female rats exposed to acute stress and alcohol exposure during adolescence. Bars represent the mean ± SEM (6 rats/subgroup). Data were analyzed using three-way ANOVA. Symbols are used to represent how significant interactions occur: (*) denotes p < 0.05, comparing stressed rats to non-stressed rats in males or females; (**) denotes p < 0.05, comparing alcohol-treated rats to saline-treated rats in males or females; (***) denotes p < 0.05, comparing alcohol-treated rats to saline-treated rats in the stress or non-stress subgroup; (+) denotes p < 0.05, comparing rats to non-stressed, saline-treated rats in males or females; (++) denotes p < 0.05, comparing rats to stressed, saline-treated rats in males or females; (+++) denotes p < 0.05, comparing rats to non-stressed, alcohol-treated rats in males or females

Fig. 4

Effects of acute stress, adolescent alcohol, and sex on corticoid signaling-related genes in the amygdala and hypothalamus. Pomc expression in the amygdala (A); Nr3c1 expression in the amygdala (B); Nr3c2 expression in the amygdala (C); Pomc expression in the hypothalamus (D); Nr3c1 expression in the hypothalamus (E); and Nr3c2 expression in the hypothalamus (F) of male and female rats exposed to acute stress and alcohol exposure during adolescence. Bars represent the mean ± SEM (6 rats/subgroup). Data were analyzed using three-way ANOVA. Symbols are used to represent how significant interactions occur: (*) denotes p < 0.05, comparing stressed rats to non-stressed rats in males or females; (**) denotes p < 0.05, comparing alcohol-treated rats to saline-treated rats in males or females; (***) denotes p < 0.05, comparing alcohol-treated rats to saline-treated rats in the stress or non-stress subgroup; (+) denotes p < 0.05, comparing rats to non-stressed, saline-treated rats in males or females

Fig. 5

Effects of acute stress, adolescent alcohol, and sex on opioid receptor genes in the amygdala and hypothalamus. Oprm1 expression in the amygdala (A); Oprk1 expression in the amygdala (B); Oprd1 expression in the amygdala (C); Oprm1 expression in the hypothalamus (D); Oprk1 expression in the hypothalamus (E); and Oprd1 expression in the hypothalamus (F) of male and female rats exposed to acute stress and alcohol exposure during adolescence. Bars represent the mean ± SEM (6 rats/subgroup). Data were analyzed using three-way ANOVA. Symbols are used to represent how significant interactions occur: (*) denotes p < 0.05, comparing stressed rats to non-stressed rats in males or females; (**) denotes p < 0.05, comparing alcohol-treated rats to saline-treated rats in males or females; (***) denotes p < 0.05, comparing alcohol-treated rats to saline-treated rats in the stress or non-stress subgroup; (+) denotes p < 0.05, comparing rats to non-stressed, saline-treated rats in males or females

Fig. 6

Effects of acute stress, adolescent alcohol, and sex on opioid signaling-related genes and vasopressin system genes in the amygdala and hypothalamus. Oprs1 expression in the amygdala (A); Oprl1 expression in the amygdala (B); Oprs1 expression in the hypothalamus (C); Oprl1 expression in the hypothalamus (D); Avp expression in the amygdala (E); Avpr1 expression in the amygdala (F); Avp expression in the hypothalamus (G); and Avpr1 expression in the hypothalamus (F) of male and female rats exposed to acute stress and alcohol exposure during adolescence. Bars represent the mean ± SEM (6 rats/subgroup). Data were analyzed using three-way ANOVA. Symbols are used to represent how significant interactions occur: (*) denotes p < 0.05, comparing stressed rats to non-stressed rats in males or females; (**) denotes p < 0.05, comparing alcohol-treated rats to saline-treated rats in males or females; (+) denotes p < 0.05, comparing rats to non-stressed, saline-treated rats in males or females; (++) denotes p < 0.05, comparing rats to stressed, saline-treated rats in males or females; (+++) denotes p < 0.05, comparing rats to non-stressed, alcohol-treated rats in males or females