Related Experiment Videos
Effects of postnatal exposure of monkeys to a PCB mixture on concurrent random interval-random interval and
1Toxicology Research Division, Bureau of Chemical Safety, Food Directorate Health Protection Branch, Health Canada, Ottawa, Ontario. ricekrwc@midcoast.com
Insights
Postnatal exposure to polychlorinated biphenyls (PCBs) did not significantly alter complex behavioral task performance in monkeys. However, treated monkeys showed slower learning on a progressive ratio schedule, suggesting subtle behavioral deficits from PCB exposure.
Area of Science:
- Neuroscience
- Toxicology
- Primatology
Background:
- Polychlorinated biphenyls (PCBs) are environmental contaminants known to cause behavioral impairment following in utero exposure.
- The effects of postnatal PCB exposure on behavior, particularly in primates, require further investigation.
Purpose of the Study:
- To assess the behavioral consequences of postnatal exposure to a PCB mixture representative of human breast milk in male macaques.
- To evaluate the sensitivity of complex behavioral tasks to postnatal PCB exposure.
Main Methods:
- Male macaques were dosed with a PCB mixture or vehicle from birth to 20 weeks of age.
- Following a maturation period, monkeys performed concurrent schedules of reinforcement and later a progressive ratio schedule.
- Behavioral performance was analyzed during schedule transitions and steady states.
Main Results:
- No significant treatment-related differences were observed in performance on concurrent schedules of reinforcement.
- Monkeys exposed to PCBs exhibited more responses during initial progressive ratio schedule sessions, suggesting slower acquisition of steady-state performance.
- These findings indicate subtle, rather than overt, behavioral deficits from postnatal PCB exposure.
Conclusions:
- Postnatal PCB exposure did not impair performance on complex concurrent schedules in macaques.
- Evidence suggests that postnatal PCB exposure may lead to subtle deficits in behavioral learning and adaptation.
- Further research is needed to fully characterize the long-term behavioral impacts of early-life PCB exposure.
Abstract:
Behavioral impairment as a consequence of PCB exposure beginning in utero has been reported in both humans and animals. The present study assessed the behavioral consequences of postnatal exposure to PCBs. Male monkeys (Macaca fascicularis) were dosed from birth to 20 weeks of age with 7.5 microg/kg/day of a PCB mixture representative of the PCBs typically found in human breast milk (eight monkeys) or vehicle (four monkeys). Blood PCB levels at 20 weeks of age were 0.30-0.37 ppb for control and 1.84-2.84 ppb for treated monkeys, and fat levels were 50-198 and 1694-3560 ppb for the two groups, respectively. Beginning at about 5.0 years of age, monkeys performed under concurrent schedules of reinforcement in which separate random intervals were in effect on two buttons independently. After steady-state performance was reached, the relative reinforcement ratio on the buttons was changed a total of four times, and performance both during transition and steady state was examined. There was no evidence for treatment-related differences in performance across the series of changes in schedule contingencies. The negative results failed to support the hypothesis that performance on an intermittent schedule, combined with the requirement for shifting response strategy, would prove particularly sensitive to postnatal PCB exposure. Following the concurrent schedules, monkeys were tested under a progressive ratio (PR) schedule preceded by a training procedure consisting of a within-session series of increasing fixed ratios. PCB-treated monkeys emitted more responses than controls over the first few sessions of the PR, which may be indicative of retarded acquisition of their steady-state PR performance. These results extend previous studies in these monkeys on the characterization of PCB-induced behavioral deficits.