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LONG-TERM NEUROCHEMICAL AND BEHAVIORAL EFFECTS INDUCED BY ACUTE CHLORPYRIFOS TREATMENT
Citation:
Pope, C., T. Chakraborti, M. Chapman, AND J. Farrar. LONG-TERM NEUROCHEMICAL AND BEHAVIORAL EFFECTS INDUCED BY ACUTE CHLORPYRIFOS TREATMENT. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-92/256.
Description:
A single, maximal tolerated dose of the organophosphate insecticide chlorpyrifos (CPF, 279 mg/kg, sc) caused extensive inhibition of striatal and cortical cholinesterase (ChE) activity in adult rats at two (94-96%), four (64-74%) and six (36-38%) weeks after treatment. These persistent changes in ChE activity were concomitant with significant reductions in striatal muscarinic receptor ([3H] quinuclidinyl benzilate) binding sites (50, 31 and 18% reduction in Bmax at 2,4 and 6 weeks after exposure) and a slight but significant alteration in the apparent affinity constant (KD) at 2 and 4 weeks after treatment. either ChE activity nor muscarinic receptor binding were different from control levels at 12 weeks after exposure. PF treatment caused a significant reduction in motor activity for the first two days after treatment, after which basal activity levels were not different from controls. PF-treated rats showed significantly higher activity relative to controls, however, following challenge with the antimuscarinic agent scopolamine (1 mg/kg, ip) at 2,4,6,8,12 and 16 weeks after treatment. hese data indicate that a single, acute exposure to CPF in adult rats can cause long-term neurobehavioral/neuropharmacological changes which may persist following the recovery of neurochemical parameters generally associated with OP exposure and/or tolerance.