Perinatal lead exposure alters the expression of neuronal nitric oxide synthase in rat brain

Environmental exposure to lead (Pb) is known to affect the de-veloping nervous system causing cognitive de cits in children. The diffusible nitric oxide (NO) is a biological messenger known to be involved in brain development. We examined the developmental changes of neuronalnitric oxide synthase (nNOS) in cerebellumand hippocampus of developing rat brain by radiometric assay, West-ern blot analysis and immunohistochemistry. Pb-exposure (0.2% Pb acetate) was initiated on gestation day 6 through the drink-ing water of the dam and continued through birth and postnatal days (PNDs) 1 to 21. The pups were never exposed to Pb directly. Pb exposure was stopped on weaning of pups from mothers on PND 21. The changes in nNOS were measured in the offspring on PNDs 7, 14, 21, and 35. The nNOS activity was increased gradu-ally from PNDs 7 to 35 in both cerebellum and hippocampus of control rats when the enzyme activity was determined in the pres