Problem solving following neonatal exposure to cocaine, ethanol, or cocaine/ethanol in combination in rats

This study examined the effects of neonatal drug exposure on performance in a digging maze. Subjects were Sprague-Dawley rats, artificially reared (AR) and fed through a gastrostomy tube from postnatal days (PND) 4–10. The AR groups included a cocaine group (20 mg/kg/day cocaine hydrochloride), an ethanol group (4 g/kg/day ethanol), a cocaine/ethanol group (20 mg/kg/day cocaine and 4 g/kg/day ethanol), and an AR control group. A suckled control raised by its dam was also included. At approximately PND 55, subjects were tested in a digging maze paradigm. The digging maze required subjects to use a species typical behavior (digging) to solve a novel problem (gaining access to water). While neonatal treatment had no effect on acquisition of a simple runway task for water reward, neonatal exposure to cocaine and ethanol in combination resulted in impaired performance on the digging maze task. None of the other neonatal treatment groups showed impairments on this task. These findings suggest that exposure to these doses of cocaine and ethanol during neonatal development may have more serious effects on problem solving tasks in rats than exposure to either drug alone.