Age-independent and dose-response effects of ethanol on spatial memory in rats

Results of previous studies have shown that ethanol impairs the acquisition of spatial memory in adolescent rats at doses below those required to impa ir the acquisition in adults. However, the previous work did not identify d oses of ethanol that failed to impair acquisition in adolescents or that im paired acquisition in both adolescent and adult animals. This was our aim i n the present study. Male, Long-Evans hooded rats (adolescent and adult) we re treated intraperitoneally with 0.0, 0.5, or 2.5 g/kg of ethanol 30 min b efore daily training on a spatial or nonspatial version of the Morris water maze task. Twenty-four hours after training on the spatial task the animal s were given a 1-min probe trial. The low dose of ethanol (0.5 g/kg) failed to impair the performance of animals from either age group on any tasks. I t did, however, enhance the initial rate of acquisition on the spatial task . The 2.5-g/kg dose eliminated acquisition of spatial learning in animals o f both ages and significantly attenuated performance on a nonspatial task i n both age groups. However, the treatment effect in the nonspatial task was eliminated with controlling for baseline performance. These results establ ish a low dose of ethanol (0.5 g/kg) that does not impair acquisition of sp atial memory in adolescent or adult rats. Moreover, the study findings show that 2.5 g/kg of ethanol markedly impairs acquisition of spatial memory in both adolescent and adult animals. (C) 2001 Elsevier Science Inc. All righ ts reserved.