The role of thiamine on excitable membrane of crayfish giant axon.

Electrophysiological and biochemical studies were performed to determine the role of thiamine in the excitable membrane of the crayfish giant axons, as it has been suggested that thiamine plays a role in the excitability of the membrane which is unrelated to the metabolic process. Thiamine (5mM) significantly increased the rising rate of the action potential without affecting the resting membrane potential and threshold potential. A recovery of the enhancement was evidenced by a wash of the axon with physiological solution. Pyrithiamine (10 mM) reduced the rising rate of the action potential without affecting the membrane and threshold potential. The reduction of dV/dt by pyrithiamine remained unchanged after a wash of the axon with physiological solution, while dV/dt increased after thiamine treatment. The amount of thiamine found in the crayfish axons was comparable to that observed in the rat sciatic nerve. In addition, pyrithiamine reduced the thiamine content in axons and protein binding thiamine of the axons. It is thus concluded that thiamine in the excitable membrane of crayfish axons plays a significant role in production of the action potential and is essential for maintaining the membrane excitability of crayfish axons.