title: Mechanism of the histamine-induced positive inotropic action in cardiac muscle.
abstract: Histamine, a positive inotropic agent which elevates cyclic AMP, was tested for ability to induce Ca2+ channels in 3 preparations of embryonic (16-day-old) chick ventricular myocardial cells whose fast Na+ channels were blocked by tetrodotoxin or voltage inactivated in 25 mM K+. In such inexcitable cells, histamine (10(-6)M) rapidly (1-3 min) induced slowly rising, overshooting, plateau-like responses accompanied by contractions. Mn2+, D600, or H2-receptor blocking agents abolished the slow responses. These results suggest that the positive inotropic action of histamine, like that of catecholamines, is mediated by an increased availability of slow Ca2+ channels.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000502:physiology; D002449:Cell Aggregation; D002642:Chick Embryo; D004558:Electric Stimulation; D006321:Heart / Q000196:embryology*; D006632:Histamine / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects*; D009924:Organ Culture Techniques; D013268:Stimulation, Chemical; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D013779:Tetrodotoxin; D006632:Histamine; D002118:Calcium