Imidazole inhibits a temperature-dependent component of mammalial skeletal muscle action potential

Temperature-dependent transition of conductance in ionic channels has been described in several membrane systems. We report here an abrupt change in the maximal rate of rise of the action potentials of the rat extensor digitorum longus (EDL) at 32 degrees C, indicating alteration in the functional characteristics of the sodium channels. Tetrodotoxin (TTX) and imidazole were used to investigate further the change in properties of the sodium channels with respect to temperature. TTX is known for its specificity in blocking sodium channels. It has been proposed that the guanidinium group of the TTX molecule is essential for its activity. Other guanidinium compounds have also been shown to be effective in blocking the sodium channels. In this study, imidazole, a compound structurally similar to guanidine, was also tested. We find that TTX and imidazole affect the maximal rate of rise of the action potential in a temperature-dependent manner.