Premium
α 2 ‐Adrenoceptor‐mediated modulation of the nitrergic innervation of the canine isolated ileocolonic junction
Author(s) -
Boeckxstaens G.E.,
Man J.G.,
Pelckmans P.A.,
Herman A.G.,
Maercke Y.M.
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb13732.x
Subject(s) - yohimbine , prazosin , endocrinology , phenylephrine , medicine , guanethidine , stimulation , chemistry , agonist , carbachol , clonidine , muscle contraction , cholinergic , oxymetazoline , antagonist , atropine , receptor , blood pressure
1 The effects of specific α‐adrenoceptor agonists and antagonists on electrically‐evoked non‐adrenergic non‐cholinergic (NANC) relaxations, previously demonstrated as nitrergic, were investigated in isolated circular muscle strips of the canine ileocolonic junction. 2 During a substance P‐induced contraction and in the presence of atropine and guanethidine, the specific α 1 ‐adrenoceptor agonist, phenylephrine and antagonist, prazosin, as well as the specific α 2 ‐adrenoceptor antagonist, yohimbine, had no effect on the NANC relaxations evoked by electrical field stimulation. In contrast, clonidine and the more specific α 2 ‐adrenoceptor agonist, UK‐14,304, significantly reduced the electrically‐induced relaxations, preferentially those in response to low frequency stimulation. The inhibitory effect of UK‐14,304 on these relaxations was antagonized by yohimbine. 3 During a noradrenaline‐induced contraction, clonidine, but not UK‐14,304 significantly augmented the relaxations to electrical stimulation. 4 The adrenoceptor agonists and antagonists used had no effect on concentration‐response curves to NO or on the relaxation induced by nitroglycerin. 5 These results indicate that stimulation of prejunctional α 2 ‐adrenoceptors inhibits the nitrergic NANC relaxations induced by field stimulation and thus suggest prejunctional regulation of nitric oxide release via α 2 ‐adrenoceptors in the canine ileocolonic junction.