The effects of phenytoin on instrumental appetitive-to-aversive transfer in rats

Antiepileptic medications are the primary treatment for seizure conditions. Over the past several years, it has become clear that the medications them selves may contribute to the negative cognitive side effects that people wi th epilepsy often report. In the experiments reported here, the effects of phenytoin treatment have been evaluated in rats performing an instrumental appetitive-to-aversive transfer task. We find that rats treated with phenyt oin fail to acquire the avoidance response when transferred from an appetit ive to an aversive context. This deficit is not due to any sensory or motor slowing resulting from the drug, nor is it a deficit that is specific to l earning in an aversive context. Rather, we suggest that the deficits shown by phenytoin-treated rats in the appetitive-to-aversive transfer reflect a fundamental inability in altering the associations that were formed during the initial appetitive training. (C) 1999 Elsevier Science Inc.