PERINATAL MANGANESE EXPOSURE - BEHAVIORAL, NEUROCHEMICAL, AND HISTOPATHOLOGICAL EFFECTS IN THE RAT

Manganese chloride (Mn) was dissolved in the drinking water (0, 2, or 10 mg/ml) of dams and their litters from conception until postnatal da y (PND) 30. Parturition was uneventful in the Mn-exposed rats and no p hysical abnormalities were observed. The rats exposed to 10 mg/ml Mn s howed a 2.5-fold increase in cortical Mn levels. Their weight gain was attenuated from PND 9-24 and they were hyperactive at PND 17. Neither the 2 nor the 10 mg/ml Mn-exposed groups differed from the controls o n the elevated plus apparatus or on the Morris water maze and the radi al arm maze. Brain monoamine levels and choline acetyltransferase acti vity were unaffected. Tyrosine hydroxylase immunohistochemistry showed that dopamine cells of the substantia nigra were intact. Glial fibril lary acidic protein immunoreactivity was not increased in cortex, caud ate, and hippocampus. However, both the low- and high-dose Mn-exposed groups showing thinning of the cerebral cortex. This could have result ed from perinatal malnutrition or from a direct effect of Mn on cortic al development. (C) 1997 Elsevier Science Inc.