Effects of methylmercury on the brain of infant rats reared artificially.

Fetal Minamata Disease leads to cerebral palsy, blindness, and deafness accompanying microcephaly. Fetal Minamata Disease has been considered to be exposed to methylmercury during mid and late gestation periods. Brain development in the late gestation in human seems to be equivalent to that in the postnatal stage in rats and mice. Artificial rearing systems for infant rats exclude the maternal and nutrient factors. We administered methylmercury to the infant rats in the artificial rearing system attempting to produce an animal model for Fetal Minamata Disease. Brain weight and brain weight/body weight ratio decreased, and pyknotic degeneration of the nerve cells in the inner granular layer of the cerebellum increased in the groups treated with methylmercury. But, we could not observe drastic degeneration in their brains which mimicked Fetal Minamata Disease in human.