Chambers_1989_Pestic.Biochem.Physiol_33_125

Male rats were given a high sublethal dose of the organophosphate paraoxon (the potent anticholinesterase metabolite of the insecticide parathion) or a lethal dose of paraoxon antidoted with atropine to assure survival. These doses yielded a high level persistent inhibition of brain acetylcholinesterase, with 83-94% inhibition in the cerebral cortex, corpus striatum, and medulla oblongata within 2 hr of treatment, and still 25-45% inhibition 4 days after treatment. Recovery was faster in the medulla oblongata than the other two brain parts. Aging, as estimated by the amount of inhibition remaining after in vitro exposure to an oxime reactivator, gradually increased from no aging on the day of treatment to virtually complete aging at 4 days after treatment. Although a change in choline acetyltransferase activity could have helped compensate for the paraoxon-induced hypercholinergic activity to reduce overt symptomology and return other behaviors to normal levels, no paraoxon- or atropine-induced changes were observed in choline acetyltransferase specific activity in the cerebral cortex or corpus striatum at any time after treatment.