A comparison of the effects of capsaicin with inhibitory nerve stimulation in the rat anococcygeus muscle in vitro.
Capsaicin was used to test whether centrifugal activation of sensory fibres in the rat anococcygeus muscle can contribute to non-adrenergic non-cholinergic (NANC) relaxation of the muscle. In a solution containing 0.5 mM Ca2+ and in the presence of carbachol (10 microM) capsaicin evoked a fast concentration-dependent relaxation of the muscle that was usually followed by a smaller, slower, relaxant response. The fast relaxant response was reduced when extracellular Ca2+ was raised to 2.5 mM, desensitized after a single application of capsaicin and was blocked by tetrodotoxin (1 microM) or ruthenium red (10 microM). The fast response was greatly reduced by haemoglobin, by cold storage of the muscles or by N-monomethyl-L-arginine (100 microM) in the absence but not in the presence of L-arginine (100 microM). It is concluded that centrifugal activation of sensory fibres evokes a nitric oxide-mediated relaxation of the anococcygeus muscles that probably contributes to electrically evoked NANC relaxation.
Department of Pharmacology, St.Thomas's Campus, United Dental and Medical Schools of Guy's and St. Thomas's, London, UK.
R E
RE
Davies
P M
PM
Bashforth
R J
RJ
Docherty
D000818:Animals; D002118:Calcium / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology*; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D009569:Nitric Oxide; D002211:Capsaicin; D002118:Calcium