Perinatal effects of two pyrethroid insecticides on brain neurotransmitter function in the neonatal rat.

The influence of 2 synthetic pyrethroid insecticide formulations, ie 10 mg fenvalerate/kg bw and 15 mg cypermethrin/kg bw, given during gestation and lactation periods to pregnant and nursing dams by gavage in corn oil on the morphological development and neurochemical indices was studied in neonatal rats. Exposed pups showed a significant increase in the levels of dopamine and muscarinic receptors of striatal membrane in both treatment groups. Alterations in these parameters were more marked in lactationally exposed pups. These pups also showed a significant decrease in the activity of brain monoamine oxidase and Na+, K(+)-ATPase and a significant increase in acetylcholinesterase from gestational exposure to fenvalerate. Significant decreases were observed during lactation in monoamine oxidase and acetylcholinesterase in fenvalerate-exposed pups and in acetylcholinesterase and Na+, K(+)-ATPase in cypermethrin-exposed pups. These results suggest disturbances in dopaminergic and cholinergic pathways which are more pronounced during the "growth spurt" period and may lead to a functional delay in brain maturation.