Inhibitory effect of capsaicin on cholinergic transmission in ovine airways: evidence for non-cholinergic contractions

Electrical stimulation of ovine trachealis smooth muscle and bronchial ring segments induced neurogenic and monophasic atropine-sensitive contractions . Pretreatment of the tissues with capsaicin (100 mu M) significantly reduc ed these contractions indicating a possible contribution of a peptidergic n eurotransmitter to the contractions. The effect of capsaicin on electricall y induced contractions was significantly inhibited by capsazepin indicating an action on vanilloid receptors. In both preparations, electrically induc ed contractions were not modified by tachykinin NK1- and NK2-receptor antag onists singly and in combination. It was therefore concluded that a compone nt of the atropine-sensitive electrically induced contractions of ovine air ways smooth muscles involved the release of a peptide neurotransmitter whic h is probably not a tachykinin. However, an action of capsaicin on prejunct ional vanilloid receptors located on cholinergic nerves cannot be ruled out . (C) 1999 Elsevier Science B.V. All rights reserved.