Pharmacologic characterization of isolated canine bronchial smooth muscle

The response of isolated canine bronchial smooth muscle to several agonists was investigated. Carbachol, serotonin, histamine and acetylcholine, in that order of potency, elicited a concentration-related contraction of bronchial smooth muscle. The maximal contractions produced by histamine and serotonin were somewhat less than those obtained with carbachol. Prostaglandin F2alpha and bradykinin failed to cause contraction. Bronchial smooth muscle strips in which a tone was induced with submaximal concentrations of carbachol underwent a concentration-related relaxation when exposed to prostaglandin E2,(+/-)-isoprenaline and (--)-norepinephrine, in that order of potency. Bradykinin, in three of four experiments, failed to relax the tissue.