Memory deficits subsequent to chronic consumption of alcohol in mice: an analysis based on spontaneous alternation behavior.

Male mice of the BALB/c strain were given a solution of 15% ethanol as their only source of fluid for periods varying from 5 weeks to 8 months. For behavioral testing, they were compared with control groups which had received either an isocaloric solution of sucrose or tap water. Memory was tested by using spontaneous alternation behavior in a T maze. Each test consisted of two forced trials (acquisition) followed by a free trial (test) given at different acquisition--test intervals (from 30 s to 24 h). Results from two independent experiments showed that after 25 weeks of ethanol administration there was an accelerated rate of decay of spontaneous alternation as a function of the acquisition--test interval. Such a phenomenon persisted after ethanol was omitted from the diet. A third experiment showed that when tested on two successive sessions separated by a 5 h interval, experimental subjects exhibited a decreased ability to perform normally on the second test. Our data are interpreted as showing that long-term ethanol administration results in accelerated forgetting and increased vulnerability to proactive interference and, as such, they are compared to the memory dysfunctions observed in amnesic patients.