ACUTE EFFECTS OF DIFFERENT TYPES OF ANTICHOLINESTERASE AGENTS ON THE IN-VIVO HIPPOCAMPAL POPULATION SPIKE IN RATS

Organophosphates are anticholinesterase agents and are among the most used neurotoxic pesticides. Released into the environment, they can re present a major ecotoxicological and hygienic-toxicological hazard. If humans or animals are exposed to organophosphates, their nervous syst em will always be affected more or less seriously, but the mechanisms of neurotoxicity are, in numerous cases, not yet well known. In the pr esent study, we investigated the effect of acute treatment with two or ganophosphates, dichlorvos and dimethoate, with physostigmine as refer ence anticholinesterase drug, and the influence of pretreatment with a tropine on the hippocampal Population spikes of rats in vivo under ure thane anesthesia. It was found that the organophosphates and physostig mine exerted very similar effects on the population spikes (a phenomen on with well-described cholinergic modulation): each drug induced a si gnificant amplitude increase. Atropine, a muscarinic antagonist, had t he opposite effect alone and abolished the existing effect of the orga nophosphates or of physostigmine. It was concluded that the effect of the tested anticholinesterase agents an the hippocampal population spi ke includes a cholinergic mechanism. (C) 1998 Academic Press