Physiologic and Pharmacologic Response Characteristics of Porcine Airways in Situ

Abstract

These data indicate that the swine is a suitable model for in situ study of airway smooth muscle response. The degree of histamine reactivity in porcine trachea appears to be similar to that of the dog (approximately 30% of the cholinergic contractile response). Swine have relatively sparse parasympathetic innervation to peripheral lung units (alveolar ducts) as measured by the minimal change in Cdyn during maximal stimulation of the vagus nerves. A major difference between porcine and canine airway smooth muscle is the relatively weak degree of β-adrenergic contraction observed in porcine species. Significant β-adrenergic contraction of the trachea was not observed in the swine. In contrast, the β-adrenergic response in the dog trachea after β-adrenergic blockade is substantial.58 Swine also have very weak inhibitory innervation to respiratory airways. There is no evidence of nonadrenergic inhibition as is seen in human airways. The direct sympathetic innervation of porcine airways also is substantially less than the dog and in this respect more closely approximates the human state, where adrenergic inhibition is thought to be minimal or absent.1