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Schedule-controlled behavior in rats exposed perinatally to the PCB mixture Aroclor 1254
M M Taylor1, K M Crofton, R C MacPhail
1Neurotoxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
Insights
Perinatal exposure to Aroclor 1254 (A1254) did not affect learning and memory in rats. This study found no disruption in temporally organized behavior under fixed-interval schedules following PCB exposure.
Area of Science:
- Neuroscience
- Toxicology
- Behavioral Science
Background:
- Polychlorinated biphenyls (PCBs) exposure can negatively impact cognitive functions, including learning and memory in children and behavior in animals.
- Previous research indicates PCBs detrimentally affect schedule-controlled behavior.
Purpose of the Study:
- To investigate the effects of perinatal Aroclor 1254 (A1254) exposure on behavior maintained under fixed-interval (FI) schedules.
- To assess performance under FI 30-s, FI 5-min, and FI 3-min with reinforcement omission schedules.
Main Methods:
- Long-Evans rats were exposed to 0 or 6 mg/kg/day A1254 from gestation day 6 through postnatal day 21.
- Behavioral assessments were conducted around postnatal day 90 using FI schedules.
- Performance measures included index of curvature (IOC), response rate, and postreinforcement pause (PRP).
Main Results:
- No effects of A1254 on behavior acquisition under the FI 30-s schedule were observed.
- Transitioning to the FI 5-min schedule showed no treatment-related effects on response rate, IOC, or PRP.
- During reinforcement omission, response rate increased and IOC/PRP decreased, irrespective of A1254 treatment.
Conclusions:
- Perinatal A1254 exposure in rats does not appear to disrupt temporally organized behavior.
- These findings contradict previous studies suggesting negative impacts of PCBs on behavior.
Abstract:
Exposure to polychlorinated biphenyls (PCBs) has been shown to detrimentally affect learning and memory in children as well as schedule-controlled behavior in experimental animals. The objective of the present series of experiments was to extend research into the effects of PCBs on behavior maintained under both short (30 s) and long (5 min) fixed-interval (FI) schedules as well as an FI 3-min with reinforcement omission. Long-Evans rats were exposed to 0 or 6 mg/kg/day Aroclor 1254 (A1254) via oral gavage from Gestation Day 6 (GD 6) through Postnatal Day 21 (PND 21). At approximately PND 90, acquisition and steady-state performance were assessed under a series of FI reinforcement schedules consisting of FI 30-s, FI 5-min, and FI 3-min with 33% of the scheduled reinforcers omitted. Performance measures included index of curvature (IOC), response rate, and postreinforcement pause (PRP). There were no effects of A1254 on the acquisition of behavior under the FI 30-s schedule. Subsequently, there was an initial decrease in response rate and IOC and an increase in PRP following the transition from FI 30-s to the FI 5-min; there were, however, no treatment-related effects on any measure. During the reinforcement-omission procedure, there was an increase in the rate of responding and a decrease in IOC and PRP following omission intervals irrespective of treatment. These data are inconsistent with previous findings and suggest that perinatal A1254 exposure in the rat does not disrupt temporally organized behavior.