Functional neurotoxic effects in rats acutely exposed to insecticide combinations

The aim of the present study was to analyse the alterations in the cortical and peripheral electrophysiological activity of rats acutely treated with combinations of insecticides. Young adult male Wistar rats were treated with 1/5 and 1/25 LD50 of the insecticides dimethoate, propoxur, cypermethrin and amitraz, given alone or in triple or quadruple combinations. After 24 h, spontaneous cortical activity, and stimulus-evoked cortical and peripheral responses, was recorded and analysed. All treatments changed the cortical activity spectrum. The effect of the 1/5 LD50 combinations indicated non-additive interactions. In the cortical-evoked responses, dimethoate and its combinations gave the strongest change in the latency, while amitraz and its combinations, in the response duration. In the tail nerve, relative refractory period was the most sensitive parameter. The frequency dependence of the cortical responses was the most strongly altered by propoxur, and the least, by amitraz. Our results indicate that simultaneous exposure by various pesticide agents, which happens possibly also in humans, deserves further investigation in, among others, neurotoxicological points of view.