Characterization of the ethanol-deprivation effect in substrains of C57BL/6 mice

Abstract

Ethanol craving plays a major role in relapse drinking behavior. Relapse and ethanol craving are an important focus for the treatment of alcoholism. The ethanol-deprivation effect (EDE) is a widely used animal model of alcohol craving. While the EDE is widely studied in rats, the molecular mechanisms underlying EDE are not clearly understood. The C57BL/6 inbred mouse strain is widely used for behavioral and molecular analyses of ethanol drinking but studies on the EDE have not been reported in this strain. In the present study, we characterized a simple behavioral protocol that rapidly and reliably induced EDE in C57BL/6 mice. Briefly, single-housed adult male C57BL/6NCrl and C57BL/6J mice were presented at the beginning of dark phase with two-bottle choice drinking containing either 10% wt/vol ethanol or tap water for 18 h/day, as well as food ad libitum. Following ethanol drinking for 4 days or 14 days, mice were deprived of ethanol for a period of 4 days. To study EDE, mice were reinstated with two bottles containing either ethanol (10% wt/vol) or water. Mice were exposed to single or multiple ethanol-deprivation cycles. Ethanol consumption (g/kg/18 h) and percent ethanol preference (% preference/18 hrs) was recorded for individual mice. C57BL/6NCrl mice consumed moderate amounts (4.78 ± 0.63 g/kg) of ethanol but showed robust EDE after ethanol-drinking episodes (4 days or 14 days) as evidenced by increased ethanol consumption and ethanol preference following reinstatement of ethanol. While repeated ethanol deprivation in C57BL/6NCrl mice transiently increased ethanol consumption and ethanol preference, the magnitude of these behaviors was reduced as compared to the first deprivation cycle. In contrast, the C57BL/6J substrain consumed substantially higher levels (9.65 ± 0.90 g/kg) of ethanol but did not show a clear EDE after single or multiple ethanol-deprivation cycles. In conclusion, we established a simple and reliable behavioral model to study EDE in C57BL/6NCrl mice. A reliable behavioral model to study EDE in inbred C57BL/6NCrl mice could greatly facilitate further studies on molecular mechanisms of ethanol craving behavior.