Papp_2004_Pestic.Biochem.Physiol_79_94

Organophosphates are irreversible blockers of acetylcholinesterase and are widely used as insecticide agents. Their action is not limited to the target organisms so that occupational or food-borne exposure of humans usually leads to neurotoxicity in which several other mechanism, apart from cholinesterase inhibition, may play a role. In the present study, rats were treated with three different organophosphates (chlorfenvinphos, diisopropyl fluorophosphate, and dimethoate) for 4 weeks, and alterations in two forms of stimulus evoked activity--somatosensory and visual cortical sensory evoked potentials and peripheral nerve action potential--were compared. In the treated rats, there was significant increase in the somatosensory evoked response latency and non-significant increase in its duration. In the visual evoked potential, only duration was altered. The conduction velocity of the peripheral nerve was decreased. Comparison of the changes in the cortical- and peripheral evoked activity showed that the slowed peripheral impulse conduction only partly explains the increase in the cortical response latency. Hence, possible mechanisms of direct cortical action of the organophosphates are also discussed.