Alteration of the voltage-dependence of the twitch tension in frog skeletal muscle fibres by a polyether, Bistramide A.

Bistramide A, a toxin isolated from Lissoclinum bistratum Sluiter, was applied to frog skeletal muscle fibres. Micromolar concentrations of toxin decreased the amplitude of the twitch tension. Bistramide A shifted the activation and the steady-state inactivation characteristics of the tension on the voltage axis towards more positive and negative membrane potentials respectively. The data suggest that Bistramide A binds to the activated and inactivated state of the dihydropyridine-receptor which senses the T-tubule membrane potential.