Influence of divalent cations on rabbit atria and modification of catecholamine response on pacemaker cells.
Spontaneously beating isolated atria of rabbits responded to Mn++ and Co++ with a progressively increasing negative chronotropism and inotropism, which was reversible by washout and by elevating the bath concentration of Ca++. The cumulative dose response curve for adrenaline for chronotropic response was markedly shifted to the right in the presence of Mn++ or Co++. This effect was also reversible. Verapamil produced only a moderate decline in spontaneous rate and contractility and did not block the chronotropic response to adrenaline. It is concluded that Mn++ and Co++ block the action of catecholamine on the pacemaker cells and they differ at least in part from organic calcium channel antagonists in their mechanism of action.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D002413:Cations, Divalent / Q000494:pharmacology*; D003035:Cobalt / Q000494:pharmacology; D003864:Depression, Chemical; D004837:Epinephrine / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D006325:Heart Atria / Q000187:drug effects; D006329:Heart Conduction System / Q000166:cytology / Q000187:drug effects; D008345:Manganese / Q000494:pharmacology; D011817:Rabbits; D014700:Verapamil / Q000494:pharmacology
D002395:Catecholamines; D002413:Cations, Divalent; D003035:Cobalt; D008345:Manganese; D014700:Verapamil; D002118:Calcium; D004837:Epinephrine