title: Intrapericardial blocking agents have extracardiac effects in dogs.
abstract: The purpose of this study was to determine if intrapericardial infusion of hexamethonium, propranolol, or atropine affected extracardiac receptors in anesthetized dogs. Intrapericardial hexamethonium (> or = 25 mg) decreased renal sympathetic nerve activity (RSNA) in a dose-dependent fashion. After 250 mg, RSNA began to decrease in 65 +/- 7 s. Whereas vagal stimulation caused a muscarinic receptor-mediated increase in tracheal smooth muscle tone (as indicated by a 9.6 +/- 1.1 mmHg increase in endotracheal cuff pressure), the increase in cuff pressure (1.8 +/- 0.4 mmHg) was attenuated after intrapericardial tropine (4 mg). When the ansa and vagus were stimulated simultaneously, beta-adrenergic receptor-mediated smooth muscle relaxation opposed the muscarinic receptor-mediated constriction resulting in an increase in cuff pressure of only 3.6 +/- 0.9 mmHg. After intrapericardial propranolol (8 mg), simultaneous ansa and vagal stimulation caused a 7.0 +/- 1.6 mmHg increase in cuff pressure, demonstrating that intrapericardial propranolol blocked beta-adrenergic receptor-mediated relaxation of tracheal smooth muscle. These results show that hexamethonium, atropine, and propranolol infused intrapericardially have extracardiac effects.
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226.
authors.forename: S W
authors.initials: SW
authors.lastname: Mittelstadt
authors.forename: K P
authors.initials: KP
authors.lastname: O'Hagan
authors.forename: L B
authors.initials: LB
authors.lastname: Bell
authors.forename: P S
authors.initials: PS
authors.lastname: Clifford
mesh_terms: D000818:Animals; D001285:Atropine / Q000008:administration & dosage* / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000008:administration & dosage* / Q000494:pharmacology; D007267:Injections; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D010496:Pericardium; D011433:Propranolol / Q000008:administration & dosage* / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects*; D014630:Vagus Nerve / Q000502:physiology
chemical_list: D006584:Hexamethonium Compounds; D018738:Hexamethonium; D001285:Atropine; D011433:Propranolol