Effect of manganese chloride and Verapamil on automaticity of digitalized Purkinje fibers.
The effects of manganese chloride (MnCl2) and verapamil on automaticity of digitlazied Purkinje fibers were studied using conventional microelectrode techniques. The stduied wer made in isolated, spontaneously beating Purkinje prearations. Quabain alone consistently increased the automatic rate, whereas no such increase was observed when the preparations were superfused with a mixture of ouabain adn MnCl2. MnCl2 was also shown to be effective is suppressing the enhanced automaticity induced by ouabain. Mncl2 alone did not have a significant effect on the spontaneous rate of Purkinje fibers. The effect of verapamil was similar to that of MnCl2 in preventing and suppressing the ouabain-induced increase in automaticity. MnCl2 and verapamil have been shown to inhibt tha slow inward calcium current of cardiac fibers. The results therefore suggest that  an inward calcium ion current may play a role in the development of digitalis-induced increase in the stope of phase 4 depolarization in Purkinje fibers.
D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors; D004285:Dogs; D006329:Heart Conduction System / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects; D008345:Manganese / Q000494:pharmacology*; D008564:Membrane Potentials; D010042:Ouabain / Q000494:pharmacology* / Q000506:poisoning; D011690:Purkinje Fibers / Q000187:drug effects*; D014700:Verapamil / Q000494:pharmacology*
D008345:Manganese; D010042:Ouabain; D014700:Verapamil; D002118:Calcium