title: Increased dependency of cardiac pacemaker activity on extracellular Ca after adrenergic blockade in the frog heart.
abstract: The frog sinus venosus shows spontaneous regular pacemaker activity, even in the absence of extracellular Ca2+. When an alpha-adrenergic blocking agent (phentolamine) is applied, the rate of pacemaker activity, height of action potential, rate of slow diastolic depolarization, and the maximum diastolic potential become strongly dependent upon the extracellular Ca2+ concentration.
mesh_terms: D000320:Adrenergic Fibers / Q000187:drug effects; D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D004562:Electrocardiography; D005110:Extracellular Space / Q000187:drug effects*; D006321:Heart / Q000294:innervation; D006325:Heart Atria / Q000187:drug effects; D006329:Heart Conduction System / Q000187:drug effects*; D007473:Ion Channels / Q000187:drug effects*; D010477:Perfusion; D010646:Phentolamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology*; D011892:Rana catesbeiana
chemical_list: D007473:Ion Channels; D001285:Atropine; D011433:Propranolol; D002118:Calcium; D010646:Phentolamine