Citation:

Tandon, P., S. Padilla, C. Pope, S. Barone, AND H. Tilson. FENTHION PRODUCES PERSISTENT DECREASES IN MUSCARINIC RECEPTOR FUNCTION IN THE ADULT RAT RETINA. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-94/518 (NTIS PB95148805), 1994.

Description:

reports have suggested that exposure to organophosphate pesticides damages the visual system. he Prolonged effects of an acute dose of fenthion (dimethyl 3-methyl-4-methylthiophenyl phosphorothionate) were studied on the cholinergic system in the rat retina. enthion was administered in a single dose of 0 or 100 mg/kg (s.c., in corn oil) to adult, male Long-Evans rats. he animals were killed 4,14 or 56 days after treatment and muscarinic receptor (mChR) function as well as cholinesterase-(ChE) activity measured in the retina and frontal cortex. enthion produced a long-lasting decrease in carbachol-stimulated inositolphosphate (IP) release in the retina: IP release was depressed at 4 days and this depression persisted up to 56 days after dosing The density of retinal mChR was decreased by 20% at 4 days and returned to control levels by 14 days. lthough fenthion produced 89% inhibition of retinal ChE activity at 4 days, by 56 days ChE activity had returned to normal. enthion had no effect on the metabolism of phospholipids in the retina as observed following intraocular injections of labelled precursors, [3H]myo-Inositol,[methyl-14c]choline or [2-3H]glycerol) 4 days after fenthion treatment. hese prolonged effects of fenthion on mChR function (signal, transduction) appear to be specific to the retina as the cortex showed no change in receptor-stimulated IP release even in the presence of significant mChR down-regulation. ortical ChE activity was inhibited to the same degree but the inhibition lasted longer than the retina. his dose of fenthion did not,produce overt morphological changes in the retina, as observed with light microscopy, although an increase in glial fibrillary

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