[The effect of Mn++ on the electrotropic and inotropic vagal effect].
An isolated rabbit atrium, innervated by vagal nerve, was tested. Increased Mn++ concentrations decrease the areas of the action potentials and the amplitudes of contractions. At 2 mM Mn++ the contraction disappears and an extremely sharp action potential is recorded. By variation of both Ca++ and Mn++ concentrations one can observe parallely shifted concentration-response curves for the amplitudes of the contractions. This result is described by the model of a competitive-antagonistic Mn++-Ca++ action. At 1 mM Mn++ the inotropic and electrotropic effects disappear. Small concentrations of Mn++ (0.15 mM) increase the electrotropic vagal effects. At 0.5 mM Mn++ both vagal effects are diminished. The discussion of the results is based on the action of acetylcholine on the slow inward current of calcium and sodium ions.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006321:Heart / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D008345:Manganese / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects*; D009200:Myocardial Contraction / Q000187:drug effects*; D011817:Rabbits; D014630:Vagus Nerve / Q000502:physiology*
D008345:Manganese; D002118:Calcium
Der Einfluss von Mn++ auf elektro- und inotrope Vaguswirkungen