Fenthion Treatment Produces Tissue-, Dose-, and Time-Dependent Decreases in Muscarinic Second Messenger Response in the Adult Rat CNS

Abstract

Fenthion (dimethyl 3-methyl-4-methylthiophenyl phosphorothionate) belongs to a class of organophosphate compounds used as insecticides throughout the world. It is commonly assumed that cholinesterase-inhibiting insecticides do not cause long-term toxic sequelae; however, some studies indicate that there may be persistent effects after the depressed cholinesterase activity has returned to normal (Karczmar, 1984). Exposure to fenthion has been reported to produce permanent ocular degeneration in laboratory animals and visual dysfunction in humans (Imai et al., 1983). We have reported that a single, moderate (100 mg/kg) dose of fenthion produces long-term changes in muscarinic receptor density and function in the rat retina in the absence of overt pathology (Tandon et al., 1994).