Organophosphate Pesticides on Oxidase Activity in Rat Brain

The organophosphate pesticides have been used extensively for plant protection; however these chemicals may be toxic to mammals (1,2). Insecticidal action and toxic effect are due to their being potent cholinesterase inhibitors (3,4). Acetylcholine is believed to be the primary transmitter affected by organophosphate insecticides. Although the pesticidal action of organophosphate insecticides has been well studied (5-8), little information (3,9,10) is available about other neurochemical changes. Since in toxicity studies organophosphate pesticides have been found to alter catecholamine levels of the various brain regions (9,10), it is probable that this group of pesticides may affect the catecholamine or other neurotransmitter levels either by a change in the reuptake process or in the catabolism of these amines. In this study we report the effect of lebaycid (O,O-dimethyt-O-(4-methylmercapto-3-methylphenyl)-thiophosphate), metacid (O,O-dimethyl O-(p-nitrophenyl) phosphorothioate), and metasystox ((O,Odimethyl-S-2-ethylsulphinyl)-ethylthiophosphate) on monoamine oxidase which is inw~lved in the breakdown of catecholamines and other biologically active amines.