Acquisition of a fixed ratio schedule in adult male rats neonatally exposed to ethanol and/or cocaine

Acquisition of an operant learning task for sucrose reinforcement was exami ned in rats after neonatal exposure to ethanol and/or cocaine. Subjects wer e raised using an artificial rearing procedure from postnatal days 4 to 11 and were intragastrically fed a milk diet containing either ethanol (6 g/kg /day), cocaine (60 mg/kg/day), the combination (6 g/kg/day + 60 mg/kg/day), or an isocaloric control diet. There was also a suckled sham control. Adul t male offspring (postnatal day 65 to postnatal day 68) were shaped to leve r press for sucrose reinforcement and then began daily 15-min sessions of f ixed ratio (FR) training. The number of days to acquire an FR 20 was measur ed. Neonatal exposure to the ethanol/cocaine combination significantly incr eased the number of days to reach the FR 20. There was also a trend for few er of these subjects to reach the FR 20, although this difference was not s tatistically significant. These results suggest that subjects neonatally ex posed to the ethanol/cocaine combination have difficulty learning an operan t task. This impairment was unique to the ethanol/cocaine combination group and suggests that polydrug exposure during development may have a more adv erse outcome than exposure to ethanol or cocaine alone.