Operant performance of rats selectively bred for strong or weak acquisition of conditioned taste aversions

An ongoing program of selective breeding is successfully developing strains of Sprague-Dawley-derived rats that are strong or weak acquirers of a cyclophosphamide-induced taste aversion (TA). Although strain separation has been based exclusively upon the TA criterion, all subjects have also been studied with respect to the acquisition of shock-motivated environmental avoidance (SME A) responses. The separation of strains of strong and weak TA learners has not resulted in similar changes in SMEA learning efficiency. The present study was undertaken to extend this analysis by comparing the two strains on appetitively motivated operant behaviors. Both fixed-ratio (FR) and differential-reinforcement-of-low-rates (DRL) schedules were studied because of their respective contrast with and similarity to the TA paradigm. No strain differences in food-reinforced barpressing were detected under either the FR or the DRL schedule. These results indicate that strain separation on the basis of TA performance is not selecting for generalized learning or performance variables that are common to these tasks. However, in a finding that merits additional study, strong TA conditioners were found to satisfy a criterion for initial barpress acquisition under a continuous schedule of reinforcement in significantly fewer sessions than were required by the weak TA strain.