Influence of age at drinking onset on the alcohol deprivation effect and stress-induced drinking in female rats.

We have recently observed increased stress responsiveness with regard to alcohol consumption in male rats that consumed alcohol since their adolescent period. Thus, early age at drinking onset can induce enhanced stress-induced alcohol drinking in male rats. However, it is not known whether female rats respond in a similar way. Therefore, we compared the drinking behavior of two female Wistar rat groups--one that acquired alcohol consumption during adolescence (adolescent group) and the other that acquired their drinking during adulthood (adult group) in a model of long-term voluntary alcohol drinking with repeated deprivation and stress phases. Furthermore, we studied the influence of age at drinking onset on the efficacy of acamprosate treatment. Thirty-nine female Wistar rats aged 31 days (adolescents) and 71 days (adults) were given ad libitum access to water, as well as to 5% and 20% ethanol solutions during an observation period of 29 weeks. A deprivation phase of 14 days was introduced following 8 weeks of access to alcohol in order to measure the alcohol deprivation effect (ADE). After 15 and 25 weeks of alcohol access, all animals were subjected for 3 consecutive days of forced swim and electric foot-shock stress, respectively. After 29 weeks of access to alcohol all animals underwent a second deprivation phase and the subsequent ADE was measured either under acamprosate (200 mg/kg) or vehicle treatment. Drinking before the first deprivation phase was not different between animal groups. However, the expression of the first ADE was more pronounced in adult female rats and alcohol intake stayed increased for the remainder of the experiment in the adult group. Both repeated swim stress and foot-shock stress produced a more pronounced increase in ethanol consumption in the adolescent group compared to the adult group. Acamprosate reduced relapse-like drinking in the adult female rat group. However, it had no effect on the ADE in the adolescent group. In conclusion, female rats that initiate alcohol consumption during adolescence might be more susceptible to stress-induced alcohol consumption. Adolescent alcohol drinking might also result in a reduced response to acamprosate.