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  • Title: Intrapericardial blocking agents have extracardiac effects in dogs.
    Author: Mittelstadt SW, O'Hagan KP, Bell LB, Clifford PS.
    Journal: Am J Physiol; 1994 Jun; 266(6 Pt 2):R1970-5. PubMed ID: 7912904.
    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.
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