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 microM) significantly reduced these contractions indicating a possible contribution of a peptidergic neurotransmitter to the contractions. The effect of capsaicin on electrically induced contractions was significantly inhibited by capsazepin indicating an action on vanilloid receptors. In both preparations, electrically induced contractions were not modified by tachykinin NK(1)- and NK(2)-receptor antagonists singly and in combination. It was therefore concluded that a component of the atropine-sensitive electrically induced contractions of ovine airways smooth muscles involved the release of a peptide neurotransmitter which is probably not a tachykinin. However, an action of capsaicin on prejunctional vanilloid receptors located on cholinergic nerves cannot be ruled out.
Mustafa
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Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, P.O. Box 24923, 13110 Safat, Kuwait.
Oriowo
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MA
D000109:Acetylcholine / Q000502:physiology*; D000818:Animals; D002211:Capsaicin / Q000031:analogs & derivatives / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects*; D064729:Neurokinin-1 Receptor Antagonists; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology; D010456:Peptides, Cyclic / Q000494:pharmacology; D011812:Quinuclidines / Q000494:pharmacology; D011955:Receptors, Drug / Q000037:antagonists & inhibitors; D018041:Receptors, Neurokinin-2 / Q000037:antagonists & inhibitors; D012701:Serotonin / Q000494:pharmacology; D012756:Sheep; D013373:Substance P / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects; D014132:Trachea / Q000187:drug effects* / Q000294:innervation / Q000502:physiology
D064729:Neurokinin-1 Receptor Antagonists; D010456:Peptides, Cyclic; D011812:Quinuclidines; D011955:Receptors, Drug; D018041:Receptors, Neurokinin-2; C073361:cyclo(Gln-Trp-Phe-Gly-Leu-Met); C076851:L 703606; D012701:Serotonin; D013373:Substance P; D002217:Carbachol; C071423:capsazepine; D000109:Acetylcholine; D002211:Capsaicin