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CORRELATIONS OF PESTICIDE-INDUCED CHOLINESTERASE INHIBITION AND MOTOR ACTIVITY CHANGES IN ADULT RATS.
Citation:
MOSER, V. C., D. L. HUNTER, R. S. MARSHALL, K. MCDANIEL, P. PHILLIPS, AND S. J. PADILLA. CORRELATIONS OF PESTICIDE-INDUCED CHOLINESTERASE INHIBITION AND MOTOR ACTIVITY CHANGES IN ADULT RATS. Presented at Behavioral Toxicology Society, Little Rock, AR, September 15, 1006 - September 19, 2006.
Description:
The acute neurobehavioral effects of acetylcholinesterase-inhibiting pesticides are primarily due to overstimulation of the cholinergic system. Lowered motor activity levels represent a sensitive endpoint with which to monitor functional changes in laboratory animals exposed to organophosphorus (OP) or N-methyl carbamate (NMC) pesticides. While these pesticides have been widely used and studied for decades, there are few, if any, reports of systematic comparisons across these chemical classes or studies which examine functional outcomes as a direct consequence (in the same animal) of acetylcholinesterase (ChE) inhibition. Using a standard experimental procedure, acute dose-response data were collected for nine OPs (azinphos methyl, diazinon, methamidophos, fenamiphos, acephate, chlorpyrifos, dimethoate, malathion, and profenophos) and seven NMCs (carbofuran, formatanate, methiocarb, methomyl, oxamyl, carbaryl, and propoxur). All testing occurred at the approximate time of peak effect. Long-Evans adult male rats were dosed and placed in figure-eight motor activity chambers for 30 minutes. Three to five doses of each pesticide were used along with concurrent controls for each study. Immediately afterwards, brain and blood were taken for ChE activity assays. Using data for each individual rat, Pearson correlation coefficients were determined for ChE activity in each tissue and for each type of motor activity (horizontally and vertically directed, although the latter data were collected for fewer pesticides). Some pesticides showed high correlation between brain and blood ChE inhibition and changes in motor activity, indicating good predictability; this was more often the case with the NMCs. A few OPs showed low to no correlation, mostly with the OPs that produced differential ChE inhibition in either blood or brain. Analysis of all NMCs together indicated that brain ChE correlated well with horizontal and vertical activity, and blood ChE correlated less well. On the other hand, OPs overall showed less correlation between brain and blood inhibition, but brain ChE still correlated quite well with horizontal activity. Thus, motor activity is an excellent indicator of brain ChE inhibition produced by acute NMC toxicity, but its usefulness for OP pesticides is chemical-specific.
(This abstract does not necessarily reflect USEPA policy)