PRENATAL EXPOSURE TO MORPHINE AFFECTS JUVENILE PLAY-BEHAVIOR AND ADULT SOCIAL-BEHAVIOR IN RATS

The effects of morphine exposure in utero on play behavior and social behavior were investigated in a longitudinal study. Wistar rat dams we re SC injected daily with saline (control) or 10mg/kg morphine from da y 8 to day 21 of gestation. Play behavior of the offspring was measure d at 3 and 4 weeks of age and social behavior at 3 months of age. Pinn ing, a measure for play behavior and social grooming of the morphine-t reated offspring were significantly elevated compared to saline contro ls, especially on day 21. The onset-latency of pinning behavior was no t changed. Furthermore, prenatal morphine treatment resulted in more s ocial approach and less social avoidance behavior in adulthood, wherea s changes in general locomotor activity were not observed. The results are discussed in relation to the effects of in utero exposure of morp hine on the development of incentive aspects of play and social behavi or.