Pharmacological characterisation of capsaicin-induced relaxations in human and porcine isolated arteries

• Published in: Naunyn-Schmiedeberg's archives of pharmacology 2007-03, Vol.375 (1), p.29-38
• Main Authors: Gupta, Saurabh, Lozano-Cuenca, Jair, Villalón, Carlos M, de Vries, René, Garrelds, Ingrid M, Avezaat, Cees J J, van Kats, Jorge P, Saxena, Pramod R, MaassenVanDenBrink, Antoinette
• Format: Article
• Language: English
• Subjects: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid - pharmacology; Adolescent; Adult; Aged; Analgesics, Non-Narcotic - pharmacology; Animals; Arteries - drug effects; Arteries - physiology; Calcitonin Gene-Related Peptide - metabolism; Capsaicin - analogs & derivatives; Capsaicin - pharmacology; Coronary Vessels - drug effects; Coronary Vessels - physiology; Cyclic AMP - metabolism; Dipeptides - pharmacology; Dose-Response Relationship, Drug; Female; Humans; In Vitro Techniques; Male; Middle Aged; NG-Nitroarginine Methyl Ester - pharmacology; Original; Piperidines - pharmacology; Potassium Channel Blockers - pharmacology; Potassium Chloride - pharmacology; Protein Kinase Inhibitors - pharmacology; Quinazolines - pharmacology; Swine; Vasodilation - drug effects
• ISSN: 0028-1298; 1432-1912
• DOI: 10.1007/s00210-007-0137-y

Capsaicin, a pungent constituent from red chilli peppers, activates sensory nerve fibres via transient receptor potential vanilloid receptors type 1 (TRPV1) to release neuropeptides like calcitonin gene-related peptide (CGRP) and substance P. Capsaicin-sensitive nerves are widely distributed in human and porcine vasculature. In this study, we examined the mechanism of capsaicin-induced relaxations, with special emphasis on the role of CGRP, using various pharmacological tools. Segments of human and porcine proximal and distal coronary arteries, as well as cranial arteries, were mounted in organ baths. Concentration response curves to capsaicin were constructed in the absence or presence of the CGRP receptor antagonist olcegepant (BIBN4096BS, 1 microM), the neurokinin NK1 receptor antagonist L-733060 (0.5 microM), the voltage-sensitive calcium channel blocker ruthenium red (100 microM), the TRPV1 receptor antagonist capsazepine (5 microM), the nitric oxide synthetase inhibitor Nomega-nitro-L-arginine methyl ester HCl (L-NAME; 100 microM), the gap junction blocker 18alpha-glycyrrhetinic acid (10 microM), as well as the RhoA kinase inhibitor Y-27632 (1 microM). Further, we also used the K+ channel inhibitors 4-aminopyridine (1 mM), charybdotoxin (0.5 microM) + apamin (0.1 microM) and iberiotoxin (0.5 microM) + apamin (0.1 microM). The role of the endothelium was assessed by endothelial denudation in distal coronary artery segments. In distal coronary artery segments, we also measured levels of cyclic adenosine monophosphate (cAMP) after exposure to capsaicin, and in human segments, we also assessed the amount of CGRP released in the organ bath fluid after exposure to capsaicin. Capsaicin evoked concentration-dependent relaxant responses in precontracted arteries, but none of the above-mentioned inhibitors did affect these relaxations. There was no increase in the cAMP levels after exposure to capsaicin, unlike after (exogenously administered) alpha-CGRP. Interestingly, there were significant increases in CGRP levels after exposure to vehicle (ethanol) as well as capsaicin, although this did not induce relaxant responses. In conclusion, the capsaicin-induced relaxations of the human and porcine distal coronary arteries are not mediated by CGRP, NK1, NO, vanilloid receptors, voltage-sensitive calcium channels, K+ channels or cAMP-mediated mechanisms. Therefore, these relaxant responses to capsaicin are likely to be attributed to a non-specific, CGRP-independent