Behavioral and biochemical effects of postnatal parathion exposure in the rat.

Preweanling rat pups were exposed daily to parathion (1.3 mg/kg or 1.9 mg/kg) or vehicle (corn oil) on postnatal days 5-20, a time period critical to development of behavioral and biochemical parameters of the cholinergic nervous system. This exposure resulted in dose-dependent reductions in acetylcholinesterase activity and muscarinic receptor binding in the cortex. During the preweanling period, there were no differences among the groups in most reflex measures, eye opening or incisor eruption. Postweanling behavioral assessment revealed small deficits in tests of spatial memory in both the T-maze and the radial arm maze. There were no differences in neuromuscular abilities or spontaneous activity measures. Thus, biochemical and behavioral deficits in cholinergic nervous system functioning occurred in the absence of severe signs of toxicity and in the absence of generalized nonspecific behavioral disturbances.