Prenatal cocaine dampened behavioral responses to methylphenidate in male and female adolescent rats.

Clinical and animal data point toward deficits in attention and arousal after prenatal cocaine exposure. Since methylphenidate (MPD) is widely used to treat attention disorders, we wanted to determine whether prenatal cocaine (PC) exposure affects the behavioral response to MPD in young rats of both sexes. Pregnant dams received 60 mg/kg of cocaine or vehicle from gestational days 8-22 by intragastric intubations. After delivery, litters were culled to 10 (5 males, 5 females) and fostered. On a single day between PND 41-44 locomotion was recorded in a Plexiglas box within an Accuscan activity monitor after receiving a single injection of 10 mg/kg intraperitoneally of MPD or saline. Rats were also videotaped for analysis of stereotyped behavior. Results showed that MPD administration enhanced locomotion compared to saline injected groups. PC exposure in male rats did not have any effect on the locomotor response to MPD compared to prenatal controls. However, PC-exposed males showed a lower amount of time spent in low intensity stereotypy compared to prenatal control males and both groups of females that received MPD. PC exposure in female rats that received MPD dampened the locomotor response compared to prenatal control females that also received MPD. In conclusion PC exposure dampens the behavioral response to MPD differentially in males and females with an apparent selectivity of locomotion in females and stereotyped behavior in males.