Retrograde Axonal Transport of Mercury in Rat Sciatic Nerve

Mercuric chloride was injected into the triceps surae muscle of adult male Wistar rats. Following a survival period of 1, 2, 3, 6, or 100 days, the rats were euthanized by transcardial perfusion. Sections of lumbar spinal cord segments (L 4-L 6) with corresponding dorsal root ganglia were subjected to the autometallographical silver-enhancement technique in order to localize mercury at both light and electron microscopical levels. Intramuscular injections of mercury resulted in ipsilateral accumulations of mercury in ventral horn motoneurons and dorsal root ganglion cells after a survival period of 2 days. Mercury deposits were still present when animals were allowed to survive 100 days. The mercury staining was suppressed ipsilateral to the intramuscular mercury injection by a microinjection of colchicine into the sciatic nerve or by ligation of the sciatic nerve. At the ultrastructural level, mercury was detected within lysosomes of target cells. The findings indicate that mercury is transported retrogradely in axons of ventral horn motoneurons and dorsal root ganglion cells.