Changes in physiological and electrophysiological parameters in rabbits after single exposure to chlorphenvinphos

In order to evaluate some of the central effects of an organophosphorus pesticide--chlorphenvinphos (CVP), the time course of changes in the activity of blood cholinesterase (ChE), body temperature and hippocampal EEG were compared in rabbits after acute i.p. exposure. The pesticide was administered twice at an interval of 80-90 days. The Deichmann-LeBlanc scheme of dosing (one animal/one dose) was adopted starting with 22 mg/kg. CVP resulted in a dose-dependent decrease in plasma and erythrocyte ChE activity, a decrease in body temperature ranging from 0.7 degrees to 3.5 degrees C, and in an increase in content of the immobility-related, rhythmic slow activity (I-RSA) in the hippocampal EEG. Changes in body temperature appeared at lower doses than those in the hippocampal EEG. Contrary to the changes in ChE activity, which lasted 4-30 days, those in body temperature and in hippocampal EEG disappeared within 24 hours after the injection. CVP administered at the same dose 80-90 days after the first injection, resulted again in an inhibition of ChE activity, but the effect on the hippocampal EEG was less clear, and that on body temperature was variable; no effect, an increase or a decrease appeared. The data suggest that: i) body temperature is a more sensitive index of a central action of CVP administered for the first time than the hippocampal EEG; ii) the brain cholinergic mechanisms are relatively resistant to the acute action of the OP and undergo fast adaptive changes; iii) even single exposure to CVP may produce some long-lasting functional changes in the brain of some subjects, which has been proven by the changed response to the second exposure.