The neurotoxic effects of organophosphorous compounds had been amply investigated. There are, however, only a limited number of relevant data concerning neurotoxic effects of these substances exerted on central electrophysiological processes. The aim of the present study was to find out whether the effects of acute and subchronic administration of three organophosphorous compounds (dimethoate, parathion-methyl and dichlorvos) on the spontaneous and evoked cortical activity are comparable.
In the acute experiments, male Wistar rats were treated with 1/1 or 1/5 LD50 per os (parathion-methyl: 22.5 and 4.5 mg/kg; dimethoate: 700 and 140 mg/kg; dichlorvos: 98 and 19.6 mg/kg) and the changes of the cortical activity were recorded for at least 2.5 or 4.0 hours. In the subchronic administration, the animals were given 1/25 or 1/100 LD50 (parathion-methyl 0.9 and 0.225 mg/kg; dimethoate 28.0 and 7.0 mg/kg; dichlorvos 3.92 and 0.98 mg/kg) for 4, 8 or 12 weeks after which the animals were prepared and recording was done.
In acute experiments, dimethoate was the substance causing the strongest decrease of the ECoG whereas parathion-methyl induced the least changes. The duration of the evoked potentials was the most affected by dimethoate.
After 12 weeks of administration, parathion-methyl caused the largest alteration in the spontaneous and stimulus-evoked activity of the somatosensory and auditory focus while in the visual focus dichlorvos was the most effective.
The results of the study showed that the changes caused by the subchronic administration of the substances were sometimes equal to or larger than those caused by the acute large doses