Two pesticides of the carbamate type, Carbaryl (1 naphthyl N methylcarbamate) and Arprocarb (2-isopropoxyphenyl-N-methylcarbamate) were tested for neurotoxicologic effects in subacute experiments using male white rats of the Wistar R strain. The authors examined the process of learning and performance of a previously learned task in a maze, and studied EEG patterns under resting conditions and under rhythmic light stimulation. The cholinesterase activity of the plasma, of erythrocytes and of various parts of the brain were recorded, body and organ weights were determined and histologic examinations were performed. In the neurotoxicologic examinations mild, but permanent and increasing, functional deviations of the nervous system were found, which could be readily demonstrated by the methods used. Carbaryl caused mild inhibition of the cholinesterase activity in various parts of the brain; the blood cholinesterase activity was practically unchanged. Protein content of the brain parts increased significantly after treatment with both compounds. No alterations were found in body and organ weights, respectively (except that of the adrenals), and no change was observed in the histologic examinations. Although the authors do not regard the agents as dangerous neurotoxic agents, they emphasize the necessity of observing all necessary precautions because subacute poisoning may occur. After exposure to these reversible cholinesterase inhibitors, the presence of a normal value for blood cholinesterase activity does not preclude the possibility of poisoning.
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