title: The characterization of cardiac histaminergic chronotropic receptors in the rabbit.
abstract: The effects of selective histamine receptor analogs were studied in spontaneously beating rabbit atria. Atrial rate was increased by histamine (an H1 and H2 agonist), 4-methylhistamine and impromidine (H2 agonists), and 2-pyridylethylamine (PEA, an H1 agonist). The responses to histamine, 4-methylhistamine, and impromidine were not affected by propranolol (1 x 10(-7) M) or reserpine pretreatment. However, the response to PEA was nearly abolished upon pretreatment with propranolol or reserpine. Cimetidine pretreatment (H2 receptor blockade) competitively antagonised the positive chronotropic effects of histamine, 4-methylhistamine, and impromidine. Promethazine pretreatment (H1 receptor blockade) competitively blocked the chronotropic effects of histamine but had no effect on the responses to 4-methylhistamine or impromidine. These results suggest that stimulation of H1 and H2 receptors will cause a positive chronotropic response.
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D011968:Receptors, Histamine / Q000187:drug effects / Q000502:physiology*; D011969:Receptors, Histamine H1 / Q000502:physiology; D011970:Receptors, Histamine H2 / Q000502:physiology; D012110:Reserpine / Q000494:pharmacology
chemical_list: D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D012110:Reserpine; D011433:Propranolol