Electrophysiologic changes associated with chronic administration of organophosphates.

Changes in the electrophysiologic activity of the rat sciatic nerve were examined after repeated dosing with either of two organophosphate insecticides, parathion, and trichlorfon. Although the parathion treated animals showed overt signs of systemic toxicity, there were no significant changes in any of the measured parameters of sciatic nerve excitability. Trichlorfon, on the other hand, produced dose-dependent changes in the duration, rise time, relative area, and refractory period of the sciatic nerve compound action potential. The observed changes indicated an increased excitability of the nerve. During the early development of these electrophysiologic changes there were no accompanying histologic changes in the nerve. This suggests that changes in nerve excitability may be a sensitive indicator of neurotoxicity, and that continued trichlorfon exposure may lead to a cumulative alteration in nerve function.