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. ÂŠ 2004 Elsevier Inc. All rights reserved.