Rats selectively bred for ethanol preference or nonpreference have altered working memory

To examine whether the cognitive deficit observed in chronic alcoholics is because of the chronic exposure to alcohol or to a factor that contributes to the chronic alcohol use, working memory was evaluated under a delayed matching-to-position task in rats selectively bred for ethanol preference or nonpreference (iP/iNP, iHAD1/iLAD1, and iHAD2/iLAD2). Before the study on working memory, rats were studied under a progressive ratio schedule of food presentation to determine whether differences in motivation to respond for food existed between the alcohol-preferring and -nonpreferring strains. No such differences were observed. Under the delayed matching-to-position schedule, the length of the delay was titrated such that accuracy was maintained at approximately 80%, and the mean length of the delay for each experimental session provided a measure of working memory function. In two (iP/iNP and iHAD1/iLAD1) of the three pairs of selectively bred rats, nonpreference to ethanol was associated with better working memory performance. In the third pair of selectively bred rats (iHAD2/iLAD2), the relationship was reversed, with increased ethanol preference associated with better working memory function after saline administration. After ethanol administration, both the mean delay and the rate of responding were decreased in all six strains. Based upon an ED50 analysis, there was little evidence of strain difference in sensitivity to ethanol on either parameter. Additional studies are needed to better understand the relationship between working memory and ethanol preference in these rats.