Abstract
Three compounds, benzimidazole, 2-aminobenzimidazole, and 2-anmino-4,4,6-trimethyl-3,4-dihydropyrimidine, possessing a guanidimum or amidine moiety in five-membered or six-membered cyclic structures, were studied for their actions on excitation in the frog sciatic nerve and time frog sartorius muscle. In both preparations, these compounds blocked the action potential; the minimum effective concentration used was 0.1 mM 2-aminobenzimidazole in the muscle. Microelectrode studies in the muscle showed that all three compounds significantly raised the voltage threshold at which a regenerative spike occurred, but did not produce any other significant effect. Thus, the resting potential, the resting membrane resistance, the inward (anomalous) and the outward (delayed) rectifications were the same in treated and untreated muscle fibers, as was the spike amplitude. These observations are interpreted to mean that these compounds have a selectivity for the sodium channel in the muscle membrane qualitatively similar to that possessed by tetrodotoxin and saxitoxin.
Footnotes
- Received January 31, 1972.
- Accepted May 29, 1973.
- © 1973 by The Williams & Wilkins Co.
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