The influence of sulfide and cyanide on axonal function.

The absorption of hydrogen sulfide (H2S) gas by sciatic nerve bundles from Rana pipiens produces an anaesthetic effect of short duration. Subsequent compound action potential (CAP) levels are higher than before exposure while the conduction velocity (CV) shows only small variation. Exposure to hydrogen cyanide (HCN) gas produces declining CAP and CV levels. The effect of H2S on the CAP is faster than that of HCN and the recovery time is shorter, although there is evidence of permanent change. Unlike HCN there is no indication that H2S inhibits the energy metabolism of the nerve cells, except possibly when the nerves are exposed to extremely high sulfide concentrations. A mode of action for H2S is proposed.