TY - JOUR T1 - POTENTIATION OF BRONCHOMOTOR RESPONSES BY <em>BETA</em> ADRENERGIC ANTAGONISTS JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 434 LP - 445 VL - 181 IS - 3 AU - L. DIAMOND Y1 - 1972/06/01 UR - http://jpet.aspetjournals.org/content/181/3/434.abstract N2 - Pharmacological deprivation of normal beta adrenergic function potentiated histamine-induced bronchoconstriction in dogs and guinea pigs. At dosage levels producing equivalent degrees of negative chronotropism, oxprenolol, propranolol and sotalol were approximately equipotent in their ability to enhance the bronchomotor response to histamine, whereas D-(—)-N-isopropyl-p-nitrophenylethanolamine and practolol showed considerably less activity. Experiments were performed to elucidate the mechanism underlying the potentiation phenomenon. The bronchomotor response to histamine was enhanced by adrenalectomy or by interruption of efferent sympathetic activity with guanethidine on by spinal cord lesioning. Disruption of the pulmonary affenent autonomic pathways by means of bilateral cervical vagotomy and thonacic posterior rhizotomy failed to potentiate the bronchomotor response to histamine. A beta adnenolytically induced hyper-reactive state persisted after pharmacological inactivation of alpha adrenoceptive sites. Based on these findings it appears unlikely that a specialized adrenergic homeostatic reflex with sensory receptors located in the lungs normally functions to counteract episodes of bronchospasm. The results also indicate that the enhanced airway responsiveness which attends beta adrenergic blockade is not dependent upon the existence of excitatory alpha adrenergic receptors subserving bronchoconstriction in the respiratory tract. It is suggested that circulating catecholamines, baroreceptormediated changes in autonomic outflow and tonic sympathetic activity may play a more important role in the regulation of airway caliber than heretofore has been recognized. © 1972, by The Williams &amp; Wilkins Co. ER -