Effects of treadmill running exercise during the adolescent period of life on behavioral deficits in juvenile rats induced by prenatal morphine exposure.

Prenatal exposure to morphine throughout pregnancy results in an array of prolonged or permanent neurochemical and behavioral deficits, including deficits in learning and memory in children of addicted mothers. This study investigated the effects of forced exercise on behavioral deficits of pups born to mothers addicted to morphine in rats. After mating and ensuring of pregnancy of female Wistar rats, they were divided into morphine or saline groups and in the second half of pregnancy (on days 11-18 of gestation) were injected subcutaneously with morphine or saline, respectively. Pups were weaned at postnatal day (PND) 21 and trained at mild intensity on a treadmill 20 days. On PND 41-47, the behavioral responses were studied. Light/dark (L/D) box and elevated plus maze (EPM) apparatus were used for investigation of anxiety, shuttle box and forced swimming tests were used to assess passive avoidance learning and memory and depression behavior, respectively. The results showed that prenatal morphine exposure caused reductions in time spent in light compartment of L/D box and EPM open arm, while postnatal exercise reversed these effects. We also found that prenatal morphine exposure caused a reduction in step through latency in passive avoidance memory test and exercise counteracted with this effect. Performance in the forced swimming test did not affected by prenatal morphine exposure or postnatal exercise. Exercise seems to be one of the strategies in reduction of behavioral deficits of children born to addicted mothers to morphine.