Sex differences in reinstatement of alcohol seeking in response to cues and yohimbine in rats with and without a history of adolescent corticosterone exposure

Abstract

Rationale: Women represent a vulnerable and growing population with respect to alcohol abuse. Elevated glucocorticoid exposure in adolescence increases addiction risk and stress sensitivity in adulthood. However, little is known about sex differences in ethanol craving-like behavior.

Objective: This study characterized sex differences in ethanol-motivated behavior following ethanol-paired cues and/or acute stimulation of the HPA axis in male and female rats with or without exposure to chronically elevated glucocorticoids in adolescence.

Methods: Adolescent corticosterone-treated (Experiment 1) or naïve (Experiment 2) male and female rats were trained as adults to self-administer ethanol paired with a cue, and tested for the effects of this cue, alone or in combination with yohimbine, on the reinstatement of ethanol seeking.

Results: Females showed elevated ethanol self-administration and seeking compared to males. In Experiment 1, corticosterone exposure in adolescence augmented cue-induced reinstatement of ethanol seeking in females only, and females were more sensitive to yohimbine in promoting reinstatement. Experiment 2 replicated these findings and showed that exposure to both yohimbine and alcohol-related cues enhanced the reinstatement of alcohol seeking, producing additive effects in females. Corticosterone levels were higher in females and in yohimbine-treated rats, and corticosterone and estradiol correlated with responding during reinstatement.

Conclusions: Chronic manipulations in adolescence and acute manipulations in adulthood of the HPA axis increase cue-induced reinstatement of ethanol seeking to a greater degree in females than in males. Elucidating the mechanisms that underlie these effects may lead to the development of sex-specific interventions aimed at mitigating alcohol relapse risk in females.

Keywords: Adolescence; Craving; Ethanol; Female; Relapse; Self-administration; Stress.

Fig. 1

Timeline of experimental procedures for Experiment 1 (A) and Experiment 2 (B). The number of days of testing and the age of the rat are indicated below each timeline, and the concentration of CORT (µg/ml) is indicated above timeline A. Thick bars represent CORT and ethanol drinking periods. Arrows represent reinstatement (REIN) days. Low YOH=0.625 mg/kg YOH; High YOH=1.25 mg/kg YOH

Fig. 2

Outcome measures in female (circles) and male (triangles) rats during adolescent CORT (closed symbols) or H2O treatment (open symbols); n=15 female H2O, n=16 female CORT, n=14 male H2O, n=14 male CORT. (A) Fluid Intake (ml/kg), #p<0.05=main effect of day; (B) CORT Intake (mg/kg), #p<0.05=main effect of day, *p<0.05 vs. female; (C) Body Weight (g), #p<0.05=main effect of day, *p<0.05=male vs. female, ^@p<0.05=H2O vs. CORT.

Fig. 3

Outcome measures during acquisition and extinction of ethanol self-administration in female (circles) and male (triangles) H2O (open symbols) or CORT (closed symbols)-treated rats. (A) Reinforcers earned; (B) Active (large symbols) vs. Inactive (small symbols) Lever Presses; (C) Ethanol Intake (g/kg); (D) Body Weight (g); #p<0.05=main effect of day, *p<0.05=male vs. female, for all panels.

Fig. 4

Responding during reinstatement testing in female (left panels) and male (right panels) H2O (solid bars) and CORT (hashed bars)-treated rats; n=15 female H2O, n=16 female CORT, n=13 male H2O; n=13 male CORT. (A) Active and (D) inactive lever presses during extinction (EXT; white bars) and reinstatement (REIN; black bars) of cue-induced reinstatement; *p<0.05=male vs. female, #p<0.05 EXT vs. REIN, ^$p<0.05 vs. H2O (REIN day only; p=0.06 H2O vs. CORT overall). (B) Active and (E) inactive lever presses following vehicle (VEH; white bars) or 0.625mg/kg yohimbine (YOH; black bars) injection; *p<0.05=male vs. female, #p<0.05 VEH vs. YOH. (C) Active and (F) inactive lever presses following vehicle (VEH; white bars) or 1.25mg/kg yohimbine (YOH; black bars) injection; *p<0.05=male vs. female, #p<0.05 VEH vs. YOH.

Fig. 5

Reinforcers earned during acquisition of saccharin self-administration in female (circles) and male (triangles; *p<0.05=male vs. female) rats treated with H2O (open symbols) or CORT (closed circles; ^$p<0.05=H2O vs. CORT, females only); n=9 female H2O, n=8 female CORT; n=6 male H2O and CORT.

Fig. 6

Outcome measures in female (circles) and male (triangles) rats (n=24 for each sex) during acquisition and extinction of ethanol self-administration. Main effects of sex (*p<0.05=male vs. female) and day (#p<0.05) were found for (A) Reinforcers Earned, (B) Active (closed symbols) and Inactive (open symbols) Lever Presses, (C) Ethanol Intake (g/kg), and (D) Body Weight (g).

Fig. 7

Responding and corticosterone levels during reinstatement; n=11 females in each condition; n=8 male NO CUE/VEH (vehicle), CUE/YOH (yohimbine); n=13 male NO CUE/YOH, CUE/VEH. (A) Active and (B) Inactive Lever Presses in female (left panels) and male (right panels) rats on the last day of extinction (solid bars) vs. the reinstatement day (hashed bars); *p<0.05=male vs. female, #p<0.05=extinction vs. reinstatement, ^p<0.05 vs. no cue, ^$p<0.05 vs. VEH. (C) Plasma CORT concentrations (pg/ml) immediately following the final reinstatement test in female (solid bars) and male (checked bars) rats, *p<0.05=male vs. female, ^p<0.05 vs. no cue, ^$p<0.05=YOH vs. VEH. (D) An overall significant (p<0.05) positive correlation was found between active lever presses and CORT (pg/ml), an effect evident in female (circles) but not male (triangles) rats.

Fig. 8

Estrogen-related outcomes. (A) Number of reinforcers earned on the last day of EtOH self-administration as a function of low (Non-Proestrus) or high (Proestrus) estradiol phases of the estrous cycle. (B) An overall significant (p<0.05) positive correlation was found between active lever presses and estradiol (pg/ml) during the final reinstatement test.