Interaction between sympathetic and sensory nerves in rat small
arteries: involvement of endothelium-derived no..
Ahluwalia, Amrita, & Patrick Vallance.
Department of Pharmacology and Clinical Pharmacology St GeorgeOs
Hospital Medical School, Cranmer Terrace, Tooting, SW17 0RE
APStracts 3:0139H, 1996.
The aim of this study was to determine the effects of C-fibre
activation on the reactivity of resistance arteries. Rat small
mesenteric arteries were mounted in a tension myograph. Electrical
field stimulation (EFS) of vessels produced brief contractions which
were abolished by tetrodotoxin (1[mu]M, n=4) or guanethidine (5[mu]M,
n=4). Capsaicin caused concentration-related attenuation of the EFS
contraction (giving EFS responses of 61.7 +/- 4.3%, 39.8 +/- 5.9% and
14.0 +/- 3.9% (n=13-16) of control EFS contraction in the presence of
1,3 and 10[mu]M capsaicin respectively). This effect was attenuated
by the CGRP receptor antagonist, CGRP8-37 (1[mu]M, n=4, p<0.05),
L-NMMA (100 [mu]M, n=4, p<0.01) or endothelial denudation (n=5,
p<0.001). CGRP concentration-dependently inhibited (n=5) EFS
contraction but this was unaffected by L-NMMA (100[mu]M, n=4).
Capsaicin also relaxed preconconstricted vessels (U-46619). This
response was attenuated by ruthenium red (30[mu]M, n=5, concentration
ratio of 3.5 +/- 1.0) and CGRP8-37 (1[mu]M, n=5, p<0.05), whilst
L-NMMA (100[mu]M, n=6) showed variable effects and denudation had no
effect. These results show directly for the first time responses to
activation of capsaicin-sensitive C-fibres which modulate reactivity
and the responses to sympathetic stimulation of isolated rat small
mesenteric arteries, with the latter being an endothelial NO
dependent effect.
Received 29 November 1995; accepted in final form 13 March 1996.
APS Manuscript Number H1112-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 16 April 96