Effects of Methylmercuric chloride on sympathetic preganglionic nerves.

The effect of methylmercuric chloride was investigated on the isolated cervical sympathetic nerve of the rabbit. All concentrations of methylmercury tested decreased both major spikes, S1 and S2, of the electrically evoked compound action potential. The blocking effect is temperature-dependent and not reversible on washing. Despite severe inhibition of the spike, conduction velocities of the fiber groups involved were not changed. Threefold increases in the Ca2+ concentration in the Locke's bathing solution before exposure to methylmercury markedly slowed the progress of inhibition of both major spikes of the fiber groups in the cervical sympathetic nerve. The results suggest that methylmercury may act by interfering with the normal function of Ca2+ in the nerve.