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Adrenoceptors mediating relaxation to catecholamines in rat isolated jejunum
Author(s) -
MacDonald A.,
Forbes I.J.,
Gallacher D.,
Heeps G.,
McLaughlin D.P.
Publication year - 1994
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.1476-5381.1994.tb13113.x
Subject(s) - jejunum , norepinephrine , adrenergic receptor , endocrinology , epinephrine , adrenergic , medicine , neuroscience , chemistry , biology , dopamine , receptor
1 The characteristics of adrenoceptors mediating relaxation to catecholamines in rat isolated jejunum were investigated. 2 Catecholamines and BRL 37344 produced relaxation of the KCl‐contracted strips with an order of potency of isoprenaline (1.0) > BRL 37344 (0.63) > noradrenaline (0.1) > adrenaline (0.04). 3 In the presence of both prazosin (1 μ m ) and propranolol (1 μ m ) only small dextral shifts of the concentration‐response curves to agonists were observed and an order of potency of BRL 37344 (2.5) > isoprenaline (1.0) > noradrenaline (0.2) > adrenaline (0.1) was obtained. 4 In the presence of prazosin (1 μ m ) and propranolol (1 μ m ), cyanopindolol (0.1 − 10 μ m ) produced a concentration‐dependent rightward shift of the concentration‐response curve to adrenaline with a Schild slope not significantly different from unity and a mean pA 2 value of 7.01. 5 The resistance of relaxant responses to propranolol, the relatively high potency of BRL 37344 compared to catecholamines and the competitive antagonism of relaxant responses to adrenaline by cyanopindolol suggest that β‐adrenoceptors in rat small intestine are mainly atypical in nature.