[Effect of ethmozine on action potentials and myocardial contraction in guinea pigs].
Ethmozine decreased the maximum rate of action potential rise (Vmax) in a dose-dependent manner. Using the Scatchard plot the apparent dissociation constant was calculated to be 1.52 X 10(-5) g/ml. Ethmozine also decreased the force of contraction in the concentration range between 1 X 10(-6) and 1 X 10(-4) g/ml with the apparent dissociation constant obtained from the Scatchard plot being equal to 1.48 X 10(-5) g/ml. The linear correlation coefficient between the decrease in Vmax and the decrease in the force of contraction was found to be equal to 0.998. Negative inotropic action of ethmozine was less pronounced when the stimulation frequency had been switched from 0.8 to 0.1 Hz. The decrease in Vmax under the action of ethmozine (3 X 10(-5) g/ml) was diminished from 56 +/- 7% (0.8 Hz) to only 3 +/- 8% (0.1 Hz). This was accompanied by the decrease in the negative inotropic effect: from 58 +/- 9% (0.8 Hz) to 16 +/- 15% (0.1 Hz). It was assumed that the negative inotropic action of ethmozine was mediated by the Na--Ca exchange, which was inhibited by the decrease of the intracellular Na+ concentration due to the blockade of sodium channels by ethmozine.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002121:Calcium Channel Blockers; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D016293:Moricizine; D009200:Myocardial Contraction / Q000187:drug effects*; D010640:Phenothiazines / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D007473:Ion Channels; D010640:Phenothiazines; D016293:Moricizine
Vliianie étmozina na potentsial deĭstviia i silu sokrashcheniia miokarda morskoĭ svinki.