Long-lasting effects on habituation and passive avoidance performance of a period of chronic ethanol administration in the rat

Abstract

Rats were fed a liquid diet to which an increasing concentration of ethanol was added over a period of 3 weeks; a concentration of 10% ethanol was then maintained for a further 4 weeks. The rats were then returned to a normal ad libitum diet of rat pellets. In order to assess the long-term effects of this ethanol diet, the performance of different groups of rats was assessed 3 and 5 months after the normal diet was resumed. At both times, the ex-ethanol-treated rats showed significantly impaired between-day habituation of exploratory head-dipping at holes that were empty, but normal between-day habituation of head-dipping at the hole with the same object underneath on all 3 days. The ex-ethanol-treated rats also showed a reduced response to the introduction of an object at a previously empty hole and, following this, a subsequent disruption of between-day habituation of head-dipping at this hole. Within-session habituation of head-dipping was unimpaired. There were no deficits in the acquisition or short-term retention of a passive avoidance response, but on retention testing 24 h after training the ex-ethanol-treated rats showed a decreased latency to enter the shocked compartment. On the trials 24 h and 48 h after training the rats tested 5 months after their ethanol treatment showed impaired extinction of the passive avoidance response.