Long-term effects of acute exposure to chlorphenvinphos on behavioural responsiveness to amphetamine and scopolamine in rats.

We investigated the effect of acute exposure to chlorphenvinphos (CVP) (2-chloro-1 (2,4-dichlorophenyl)-vinyl-diethyl-phosphate), an organophosphate anticholinesterase, on the amphetamine- and scopolamine-induced open-field locomotion in Wistar rats. CVP was administered at a single i.p. dose of 1.0 mg/kg (1/10 of LD50). In part of the rats cholinesterase (ChE) was determined. Three hours after CVP injection, the ChE activity decreased by about 27%. It returned to the preinjection level within 14 days after the exposure. In the behavioural part of the experiment, the animals were challenged with 1.0 mg/kg amphetamine or 0.75 mg/kg scopolamine three weeks after CVP exposure, i.e. after a period of time sufficient for cholinesterase recovery. It has been found that in the CVP-exposed rats, the behavioural responses to amphetamine or scopolamine challenge (the increase in locomotor activity) was significantly reduced compared to the controls. This suggests that acute exposure to CVP produced an increase in cholinergic activity which persisted long after ChE activity had returned to normal.