REPEATED MATERNAL SEPARATION OF PREWEANLING RATS ATTENUATES BEHAVIORAL-RESPONSES TO PRIMARY AND CONDITIONED INCENTIVES IN ADULTHOOD

Early social experience has profound effects on a wide spectrum of beh aviors and neurochemical correlates in the rat. Repeated separation of rat pups from their dam during the early neonatal period causes acute perturbation of neuroendocrine and physiological status. The chronic sequelae of repeated separations have not been studied as extensively as the acute responses. Altered social experience at a later developme ntal stage, postweaning isolation rearing, is known to induce enduring changes in the behavioral responses to reward and reward-related stim uli in maturity. We have evaluated the influence of repeated early mat ernal separation on the responses to both primary and conditioned ince ntives in mature rats. Separated animals showed enhanced weight gain, a blunted locomotor response to a novel environment and a blunting of the response to both negative and positive contrast effects. Female se parated animals, but not males, exhibited a profound attenuation of th e acquisition of a conditioned anticipatory locomotor response to the presentation of food. These data are discussed with respect to the put ative involvement of ventral striatal dopamine systems in reward mecha nisms and the potential utility of early maternal separation as an ani mal model of depression.