EFFECTS OF POSTNATAL EXPOSURE OF MONKEYS TO A PCB MIXTURE ON SPATIAL DISCRIMINATION REVERSAL AND DRL PERFORMANCE

Behavioral impairment as a consequence of PCB exposure beginning in ut ero has been reported in both humans and animals. The present study as sessed the behavioral consequences of postnatal exposure to PCBs. Male monkeys (Macaca fascicularis) were dosed from birth to 20 weeks of ag e with 7.5 mu g/kg/day of a PCB mixture representative of the PCBs typ ically found in human breast milk (eight monkeys) or vehicle (four mon keys). Blood PCB levels at 20 weeks of age were 0.30-0.37 ppb for cont rol and 1.84-2.84 ppb for treated monkeys, and fat levels were 50-198 and 1694-3560 ppb for the two groups, respectively. At about 4.5-5.0 y ears of age, monkeys performed on a series of three spatial discrimina tion reversal tasks, followed by a differential reinforcement of low r ate (DRL) 30-s schedule of reinforcement. There were no differences be tween groups for the number of errors across reversals for any of the discrimination reversal tasks, whereas the PCB-treated group tended to have shorter median response latencies than the control group. On the DRL schedule, there were robust differences in performance between th e treated and control groups. Treated monkeys displayed shorter mean a nd median interresponse times (IRTs), obtained fewer reinforcements, a nd emitted more nonreinforced responses. The treated groups also had m ore short IRTs (less than or equal to 10 s) than control monkeys. Perf ormance of the treated group did not improve to control levels over th e 51 sessions of the DRL 30-s schedule; their performance remained muc h less efficient than that of controls. The results of this study exte nd previous research in this cohort of monkeys, and provide further ev idence that PCB exposure limited io the early postnatal period and res ulting in environmentally relevant body burdens produces long-term beh avioral effects. Published by Elsevier Science Inc.