RT Journal Article SR Electronic T1 Absence of Tachykinin Involvement in Leukotriene D4and Antigen-Induced Contraction of Guinea Pig Isolated Bronchus JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 1102 OP 1109 VO 283 IS 3 A1 Cibulsky, Susan M. A1 Thompson, David C. YR 1997 UL http://jpet.aspetjournals.org/content/283/3/1102.abstract AB In guinea pig airways, contractions induced by leukotriene D4 or antigen are thought to be mediated primarily by an action of the agonist or of released mast cell-derived mediators directly on the airway smooth muscle cell. An indirect contractile action mediated by endogenous tachykinins also has been described for both of these stimuli. The present study evaluated the contribution of endogenous tachykinins to ovalbumin- and leukotriene D4-induced contractions in the guinea pig bronchus by modulating the concentrations of tachykinins within the tissues and by using neurokinin receptor antagonists. Acute depletion of tachykinins with capsaicin had no effect on responses elicited by either stimulus. Similarly, tetrodotoxin treatment failed to influence leukotriene D4-induced contractions. Inhibitors of neutral endopeptidase (thiorphan) and angiotensin-converting enzyme (lisinopril) enhanced neurally mediated tachykininergic responses and potentiated leukotriene D4. The latter effect persisted in the presence of tetrodotoxin or the neurokinin antagonists CP99994 and SR48968 and in tissues treated acutely with capsaicin. The potentiation was absent, however, from bronchi incubated withl-cysteine. Ovalbumin-induced contractions were unaltered by inhibition of neutral endopeptidase and angiotensin-converting enzyme. These observations suggest that tachykinins are not involved in mediation of leukotriene D4- or antigen-induced contractions of the guinea pig bronchus. The ability of protease inhibitors to potentiate leukotriene D4 but not antigen-induced responses is therefore ascribed to inhibition of bioinactivation of leukotriene D4 to leukotriene E4. The American Society for Pharmacology and Experimental Therapeutics