Mercury Deposition and Its Relationship to Inner Ear Function in Methylmercury-Poisoned Rats: a Histological and Immunohistochemical Study

Abstract

Mercury deposition and its relationship to the inner ear function in methylmercury-poisoned rats were examined. Rats were poisoned with methylmercury chloride. After the appearance of signs of poisoning, the cerebellar and inner ear tissues were examined histochemically using an autoradiographic procedure. Mercury deposits were typically found in the cerebellum and appeared in parts of the vestibular nerves, cochlear nerves, spiral ganglion and stria vascularis. In the vestibule, a slight mercury deposition was observed in the acoustic maculae and in the cochlea; only one instance of mercury deposit in the organ of Corti was detected. The effect of mercury on the inner ear function was also assessed on the basis of immunohistochemical localization of substance P which is believed to be a neurotransmitter in the inner ear. However, no pathological changes were detected. These findings suggest that methylmercury deposition has little effect on the inner ear function.

Key Words:

• Minamata disease
• autoradiographic procedure
• immunohistochemistry
• substance P