[Potential- and stimulus-dependence of the effect of dihydropyridine Ca-agonists on calcium channels in heart fibers].

It has been shown on the frog auricle fibres by the method of double sucrose bridge that the dependence of the effect of dihydropyridine Ca agonists BAYK 8644, CGP 28 392 and (-S)202 = 791 on calcium channels on the membrane potential is to a large extent due to the activation and following inactivation of Ca channels "silent" in the control. This effect takes place due to a shift by Ca agonists of the stationary curve of channel activation to hyperpolarization. The absence of stimulus-dependence of the agonist effect and constant time of Ca current reactivation suggest that the agonists bind with resting channels.