Central cholinergic activation by chlorfenvinphos, and organophosphate, in the rat

Effects of 2-chloro-1-(2, 4-dichlorophenyl) vinyl diethyl phosphate, chlorfenvinphos, on spontaneous EEG, EMG and ChE activity in the brain and red blood cells were investigated in male Wistar rats. Chlorfenvinphos up to 1 mg/kg p.o. did not affect the ChE activity and the awake-sleep cycle. In doses over over 2 mg/kg, the ChE activity in the brain and red blood cells significantly decreased. The spontaneous EEG showed a prominent arousal pattern and appearance of slow wave sleep and parasleep was markedly depressed. Maximum inhibition of brain ChE activity was obtained 3 hr after the treatment and lasted for more than 72 hr. The duration of arousal pattern was proportional to the doses, however, the awake-sleep cycle returned to control on the 2nd day and a rebound increase in parasleep occurred on the 3rd day. Atropine depressed the EEG arousal pattern induced by chlorfenvinphos, without affecting ChE activity in the brain. The brain noradrenaline level was not altered with chlorfenvinphos. These results indicate that the appearance of EEG arousal pattern after chlorfenvinphos may be derived from central cholinergic activation.