Experimental neuropathy induced by methyl mercury compounds: autoradiographic study of GABA uptake by dorsal root...

Methyl mercury chloride (MMC, 10 mg/kg body weight/day) was subcutaneously injected into rats for 1 week. Animals were killed at 5 or 14 days (at the onset of clinical symptoms) after injection of MMC. Morphologically, most of the myelinated fibers in peripheral nerves showed axonal degeneration. Ganglion cells showed histopathological changes similar to those in previous reports. The cytoplasm of satellite cells stained dark with toluidine blue and was narrow, and sometimes showed focal disappearance of rough endoplasmic reticula, ribosomes or filaments. Autoradiography in the control rats showed that 3H-GABA was exclusively localized within the satellite cells and Schwann cell cytoplasm of the myelinated fibers and was not revealed within the ganglion cells. The number of silver grains markedly decreased in the satellite cells of the MMC-treated rats. 14C-GABA uptake by dorsal root ganglia also decreased to 75.0% of the control on the 5th day and to 49.2% on the 14th day. Therefore, MMC was found to inhibit greatly the GABA uptake into the satellite cells in the earlier stage of poisoning, and was considered to affect primarily the satellite cells and Schwann cells as well as the ganglion cells.