Effects of prenatal maternal ethanol on male offspring progressive-ratio performance and response to amphetamine

This study was designed to further explore the nature of our previously reported reduction in the efficacy of food reinforcers for prenatal ethanol-exposed mice. We determined the effect of prenatal ethanol exposure on responding for food delivered on a progressive-ratio (PR) reinforcement schedule, which has been shown to be sensitive to changes in motivation and/or value of reinforcers, and we assessed the effects of amphetamine on responding maintained by the PR schedule. Subjects were adult (12 months old) male offspring of C57BL/6J mice fed liquid diets containing either ethanol (25% ethanol-derived calories, N = 12) or sucrose (25% sucrose-derived calories, N = 9) during gestation days 5–17. Prenatal ethanol-exposed mice differed from controls by having lower response rates and a greater disruption of responding following amphetamine injections. The reduced responding for food reward on the PR schedule supports our previously advanced hypothesis that prenatal ethanol reduces the efficacy of food reinforcers. The enhanced effects of amphetamine found in these adult mice is in agreement with previous reports on young rats. Although either of the effects of prenatal ethanol exposure observed in the present study are suggestive of altered DA systems, current neurochemical studies on either rats or mice provide no support for the hypothesis.