Intrapericardial blocking agents have extracardiac effects in dogs.
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.
Mittelstadt
S W
SW
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226.
O'Hagan
K P
KP
Bell
L B
LB
Clifford
P S
PS
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
D006584:Hexamethonium Compounds; D018738:Hexamethonium; D001285:Atropine; D011433:Propranolol