Prenatal ethanol effects on reward efficacy for adult mice are gestation stage specific

We previously reported that adult mice exposed to ethanol throughout gestation (G5-17) responded slower than controls on reinforcement schedules which required large numbers of responses per unit of food, i.e., high fixed ratio (FR) schedules. The primary finding of the present study was that ethanol exposure during the last 5 days of gestation (G12-17) is sufficient to produce this effect whereas a similar exposure early in gestation (G5-10) is not. Both male and female mice exposed to ethanol late in gestation responded slower than either lab chow or pair-fed controls, and the effect was similar to that of mice exposed to ethanol throughout gestation (G5-17) in our earlier study. Thus, developmental events occurring late in gestation are important for the reduced reinforcing efficacy of food for prenatal-ethanol-exposed mice. In addition, the present experiment established the comparability of the sucrose and lab chow controls on this task. The results of the present study and our previous report are compatible with the hypothesis that the reduced responding on high FR schedules exhibited by prenatal-ethanol-exposed mice reflects a reduction in the efficacy of food reward. It is possible that the reduction in reward efficacy is due to altered development of neuronal systems functionally related to reward which develop late in gestation.