title: Chronotropic response to acetylcholine injected into the sinus node artery of the isolated atrium of the dog.
abstract: Injection of a single bolus of acetylcholine into the sinus node artery of the isolated atrium of the dog produces a triphasic response similar to that previously observed after a single stimulus to the  vagus nerves. There is an initial, brief but pronounced, cardiac deceleration followed by a brief, slight acceleration, which is then followed by a more prolonged deceleration which is of lesser magnitude than the initial deceleration. The most likely cause of the intermediate phase of cardiac acceleration is a direct effect of acetylcholine on the pacemaker cells, as it is also with the primary and tertiary phases of cardiac deceleration.
mesh_terms: D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure; D003331:Coronary Vessels; D004285:Dogs; D004562:Electrocardiography; D004566:Electrodes; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D007269:Injections, Intra-Arterial; D008026:Ligation; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010138:Pacemaker, Artificial; D010477:Perfusion; D010643:Phenoxybenzamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D012849:Sinoatrial Node / Q000187:drug effects*; D013268:Stimulation, Chemical
chemical_list: D010643:Phenoxybenzamine; D001285:Atropine; D011433:Propranolol; D000109:Acetylcholine; D009638:Norepinephrine