Neonatal cocaine and/or ethanol exposure: effects on a runway task with suckling reward

This experiment employed a rodent model to examine the effects of neonatal exposure to cocaine, ethanol, or both drugs in combination on acquisition and extinction of an appetitive runway task. After implantation with an intragastric cannula, subjects were artificially reared (AR) from postnatal days (PND) 4-10. There were five treatment groups, including: cocaine (20 mg/kg/day), ethanol (4 g/kg/ day), cocaine/ethanol (20 mg/kg/day cocaine and 4 g/kg/day ethanol), stock (an AR control), and sham (a suckled control). Subjects were tested on PND 13-14. The runway task consisted of traversing a runway for nonnutritive suckling on an anesthetized dam and a subsequent milk reward, given manually by the experimenter. Pups from all treatment groups acquired and extinguished the runway task; however, pups exposed to cocaine had longer latencies to leave the start box than controls. Pups exposed to cocaine or ethanol, but not cocaine/ethanol, were impaired on the nipple attachment measures compared to sham controls. These results provide further support that the "third trimester" is a sensitive period for developmental drug exposure.