Deleterious effects of prenatal exposure to morphine on the spatial learning and hippocampal BDNF and long-term potentiation in juvenile rats: Beneficial influences of postnatal treadmill exercise and enriched environment.

Prenatal morphine exposure causes a variety of neurobehavioral alterations observed in later life. The present study investigated the effects of postnatal exercise and enriched environment (EE) on alterations in water maze learning and hippocampal long-term potentiation (LTP) and brain derived neurotrophic factor (BDNF) levels induced by exposure to morphine during prenatal period in rats. On gestation days 11-18, pregnant rats were injected twice daily with saline or morphine. Offspring were subjected to postnatal exercise and EE for 30 days and afterward, spatial learning and hippocampal LTP and BDNF levels were investigated. Prenatal morphine-exposure impaired the spatial learning and hippocampal LTP in both male and female offspring. Interestingly, postnatal exercise and EE increased performance in the water maze and improved LTP in both prenatally saline and morphine-exposed male and female rats. Prenatal morphine exposure also caused a reduction in the hippocampal BDNF levels in the female, but not male rats, and postnatal exercise and EE alleviated this deficit. Our results demonstrate that postnatal exercise and EE can improve deficits in water maze learning and hippocampal LTP and BDNF levels caused by prenatal morphine exposure.