Re. Davies et al., A COMPARISON OF THE EFFECTS OF CAPSAICIN WITH INHIBITORY NERVE-STIMULATION IN THE RAT ANOCOCCYGEUS MUSCLE IN-VITRO, European journal of pharmacology, 355(2-3), 1998, pp. 195-202
Capsaicin was used to test whether centrifugal activation of sensory f
ibres in the rat anococcygeus muscle can contribute to non-adrenergic
non-cholinergic (NANC) relaxation of the muscle. In a solution contain
ing 0.5 mM Ca2+ and in the presence of carbachol (10 mu M) capsaicin e
voked a fast concentration-dependent relaxation of the muscle that was
usually followed by a smaller, slower, relaxant response. The fast re
laxant response was reduced when extracellular Ca2+ was raised to 2.5
mM, desensitized after a single application of capsaicin and was block
ed by tetrodotoxin (1 mu M) or ruthenium red (10 mu M) The fast respon
se was greatly reduced by haemoglobin, by cold storage of the muscles
or by N-monomethyl-L-arginine (100 mu M) in the absence but not in the
presence of L-arginine (100 mu M) It is concluded that centrifugal ac
tivation of sensory fibres evokes a nitric oxide-mediated relaxation o
f the anococcygeus muscles that probably contributes to electrically e
voked NANC relaxation. (C) 1998 Elsevier Science B.V. All rights reser
ved.