Accumulation of mercury in brainstem nuclei of mice after retrograde axonal transport.

Adult mice were injected intramuscularly in the region of the vibrissae muscles on the left side of the nose with a small volume of mercuric chloride dissolved in distilled water. The animals were killed after 1-6 weeks and fixed by whole-body perfusion. Frozen sections were taken from different levels of the brain stem and from the kidney. The sections were subjected to silver acetate autometallography for visualization of mercury. Mercury was found to accumulate in neurones of the facial nerve nuclei, of the motor trigeminal nuclei and of the trigeminal mesencephalic nuclei of the brain stem, after retrograde axonal transport. Mercury was also demonstrated in proximal tubular cells of the kidney. The mechanism for uptake of mercury at the neuromuscular junctions, and the fate of mercury within neurones are analysed. The possible significance of retrograde metal transport for the development of motor neurone disease is discussed.