NEONATAL COCAINE EXPOSURE AND ACTIVITY RHYTHMS IN RATS

This study looked at the effects of neonatal cocaine exposure on activ ity rhythms over a 48-h period in rats. Subjects were artificially-rea red from postnatal days (PN) 4-10 via intragastric cannulas. The four treatment groups included two cocaine doses (20 and 40 mg/kg per day), an artificially-reared control and a normally reared suckled control. Subjects were tested at PN 38-40 in an automated running wheel. Neona tal cocaine exposure did not alter activity rhythms over the 48-h test period. However, there was a gender-specific effect of neonatal cocai ne exposure on response to the novel test chamber and to the experimen ter. The 20 mg/kg cocaine-exposed females showed increased running whe el activity relative to all other groups after placement in the runnin g wheel. During the second 24-h period, cocaine-exposed females from b oth cocaine groups showed increased activity relative to controls foll owing the entry of an experimenter to the test room. These findings su ggest that female rats exposed to cocaine neonatally show an increased response to novel environments and stimuli.