Actions of a calcium antagonist, the D-600, on electrical and mechanical properties of frog skeletal muscle

Abstract

1. 1. On the isolated frog sartorius muscle, D-600, a purported calcium antagonist, depressed action potential production by inhibiting ionic conductances. 2. 2. D-600 in low concentrations (< 3 × 10 −5 M) potentiated twitch tension while higher concentrations (> 3 × 10 −5 M) depressed twitch tension. 3. 3. It is proposed that D-600 inhibits the excitation-contraction coupling (ECC) via a variety of mechanisms and not merely by inhibition of calcium fluxes.