CRF-1 antagonist and CRF-2 agonist decrease binge-like ethanol drinking in C57BL/6J mice independent of the HPA axis

Abstract

Recent evidence suggests that corticotropin-releasing factor (CRF) receptor (CRFR) signaling is involved in modulating binge-like ethanol consumption in C57BL/6J mice. In this report, a series of experiments were performed to further characterize the role of CRFR signaling in binge-like ethanol consumption. The role of central CRFR signaling was assessed with intracerebroventricular (i.c.v.) infusion of the nonselective CRFR antagonist, alpha-helical CRF(9-41) (0, 1, 5, 10 microg/1 microl). The contribution of central CRF type 2 receptor (CRF(2)R) signaling was assessed with i.c.v. infusion of the selective CRF(2)R agonist, urocortin (Ucn) 3 (0, 0.05, 0.1, or 0.5 microg/1 microl). The role of the hypothalamic-pituitary-adrenal (HPA) axis was assessed by pretreating mice with intraperitoneal (i.p.) injection of (1) the corticosterone synthesis inhibitor, metyrapone (0, 50, 100, 150 mg/kg) or (2) the glucocorticoid receptor antagonist, mifepristone (0, 25, 50 mg/kg), and (3) by using radioimmunoassay to determine whether binge-like ethanol intake influenced plasma corticosterone levels. Finally, we determined whether the ability of the CRF(1)R antagonist, CP-154,526 (CP; 0, 10, 15 mg/kg, i.p.), to blunt binge-like drinking required normal HPA axis signaling by comparing the effectiveness of CP in adrenalectomized (ADX) and normal mice. Results showed that i.c.v. infusion of a 1 microg dose of alpha-helical CRF(9-41) significantly attenuated binge-like ethanol consumption relative to vehicle treatment, and i.c.v. infusion of Ucn 3 dose-dependently blunted binge-like drinking. On the other hand, metyrapone nonselectively reduced both ethanol and sucrose consumption, mifepristone did not alter ethanol drinking, and binge-like drinking did not correlate with plasma corticosterone levels. Finally, i.p. injection of CP significantly attenuated binge-like ethanol intake in both ADX and normal mice. Together, these results suggest that binge-like ethanol intake in C57BL/6J mice is modulated by CRF(1)R and CRF(2)R signaling, such that blockade of CRF(1)R or activation of CRF(2)R effectively reduces excessive ethanol intake. Furthermore, normal HPA axis signaling is not necessary to achieve binge-like drinking behavior.

Figure 1

The effects of α-helical CRF on (a) mean 4-h 20% ethanol consumption and (b) blood–ethanol concentrations (n=5–10 per group). (c) Effects of α-helical CRF on mean 4-h 10% sucrose consumption in C57BL/6J animals (n=10 per group). Data represent mean±SEM, and are normalized for body weight. ^*p<0.05 vs vehicle-treated group determined by Bonferroni post hoc analyses.

Figure 2

The effects of Ucn3 on (a) mean 4-h 20% ethanol consumption (b) and blood–ethanol concentrations (n=6–8 per group). (c) Effects of Ucn3 on mean 4-h 10% sucrose consumption in C57BL/6J animals (n=10 per group). Data represent mean±SEM, and are normalized for body weight. ^*p<0.05 vs vehicle-treated group determined by Bonferroni post hoc analyses.

Figure 3

Effects of mifepristone on (a) mean 4-h 20% ethanol consumption (n=8–10 per group), and (b) mean hourly 20% ethanol consumption (n=10 per group). The effects of metyrapone on (c) mean 4-h 20% ethanol consumption (n=9 per group), and (d) mean 4-h 10% sucrose consumption (n=7–8 per group). (e) Effects of 4-h 20% ethanol consumption or water consumption on mean plasma corticosterone levels, and (f) correlations between plasma corticosterone levels and 4-h 20% ethanol consumption, in C57BL/6J animals (n=15 per group). Data represent mean±SEM, and are normalized for body weight. ^*p<0.05 vs vehicle-treated group determined by Bonferroni post hoc analyses.

Figure 4

(a) Effects of adrenalectomy on mean 2-h 20% ethanol consumption by C57BL/6J animals during the first 3 days of the DID procedure (n=24–40 per group). Effects of CP on (b) mean 4-h 20% ethanol consumption, and (c) blood–ethanol concentrations by ADX or SHAM C57BL/6J animals on day 4 (n=8–14 per group). (d) Effects of adrenalectomy on mean 2-h 3% sucrose consumption by C57BL/6J animals (n=23–40). Data represent mean±SEM, and are normalized for body weight. ^*p<0.05 vs vehicle-treated group, ⁺p<0.05 vs SHAM group, determined by Bonferroni post hoc analyses.