Deficits in fixed-interval performance following prenatal and postnatal lead exposure

Female rats were exposed daily to 750 mg/kg of lead acetate via a restricted watering schedule for 70-80 days prior to mating and then throughout pregnancy and nursing. At weaning, litters from half of the lead dams were placed directly on treatment for the duration of the experiment. These manipulations yielded 3 groups: Group Pb/Pb, offspring exposed during pre- and postweaning periods; Group Pb/C, offspring exposed only during preweaning periods: and Group C/C, control offspring. Beginning at 42-49 days of age, postnatal, offspring were shaped to bar press under a fixed-interval, 1-min schedule (FI1) and then given 20 sessions, each 45 min in length. Analyses revealed that Group Pb/Pb received fewere reinforcements across sessions than the other 2 groups, which did not differ. However, when the Pb/Pb offspring did receive reinforcement, they exhibited the scalloped pattern of responding characteristic of fixed-interval schedules.