Chronological relationship between neurological signs and electrophysiological changes in rats with methylmercury poisoning - special reference to selenium protection.

In order to see chronological relationship between electrophysiological changes and "early" neurological sign (tail rotation) elicited in rats poisoned with methylmercury, we made serial measurements of amplitude of compound action potential and sensory nerve conduction velocity of the tail nerve in rats with five dose schedules [methylmercury vs selenium, (1)20 ppm:0.1 ppm, (2)20: 0.3, (3)20: 0.6, (4)10: 0.1, (5)10: 0.6]. We observed the following sequence in the onset of neuro-electro-physiolo-somatic signs: fall in compound action potential greater than decrease in sensory nerve conduction velocity greater than tail rotation greater than weight loss. Protective potency of dietary selenium against neurotoxicity of methylmercury was observed with regard to both electrophysiological changes and neurological signs.