Prenatal ethanol weakens the efficacy of reinforcers for adult mice

Pregnant C57BL/6cr mice were fed a liquid diet containing 20% of the total calories from either ethanol (E) or sucrose (S) for gestation days 5-17. Adult male and female (six of each from both prenatal-treatment groups) offspring were tested under various schedules of food reinforcement. The first phase was a test of fixed-ratio (FR) acquisition in which the required number of responses per unit of reinforcement was increased from 1 to 20 to 100. Prenatal ethanol exposure interacted with other factors to produce an acquisition deficit. The second phase involved responding under extinction (Ext). Under standard Ext procedures there were no prenatal-ethanol effects; however, when a conditioned reinforcer was superimposed on an FR 5, the E males did not increase their rates as much as the S males. Finally, under a multiple FR 5 DRO 15-sec (differential-reinforcement-of-other-behavior) arrangement, prenatal-ethanol effects were found in each component. For the FR 5 component, prenatal ethanol eliminated the sex differences found in the S subjects. For the DRO 15-sec component, prenatal ethanol elevated response rates. The results indicate a general decreased efficacy of positive reinforcement in adult mice following prenatal ethanol exposure.