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Similarity of relaxations evoked by BRL 34915, pinacidil and field‐stimulation in rat oesophageal tunica muscularis mucosae
Author(s) -
Akbarali H.I.,
Bieger D.,
Ohia S.E.,
Triggle C.R.
Publication year - 1988
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.1476-5381.1988.tb11672.x
Subject(s) - pinacidil , cromakalim , nifedipine , tetraethylammonium , tetrodotoxin , muscularis mucosae , stimulation , chemistry , potassium channel , muscle contraction , trachealis muscle , endocrinology , medicine , anatomy , biophysics , calcium , potassium , biology , agonist , receptor , biochemistry , glibenclamide , organic chemistry , charybdotoxin , diabetes mellitus
1 In the rat oesophageal tunica muscularis mucosae (TMM) the potassium channel openers, BRL 34915 and pinacidil, raised the threshold for concentration‐dependent K + contractions, suppressed contractions evoked by field stimulation of the TMM in the presence of tetrodotoxin (TTX) and tetraethylammonium (TEA), and relaxed tonic contractions resulting from muscarinic cholinoceptor stimulation. 2 BRL 34915 and both (+)− and (−)‐pinacidil increased 86 Rb efflux from tracer‐loaded tissues; nifedipine abolished this effect. 3 Relaxations produced by potassium channel openers were inhibited by a temperature drop from 37°C to 26.5°C, an increase in extracellular K + concentration to 64 m m , and treatment with the calcium channel antagonist, nifedipine. The same treatments also blocked field stimulation‐evoked TTX‐insensitive relaxations. 4 It is concluded that field stimulation of rat oesophageal smooth muscle in the presence of cholinoceptor‐induced tone results in an increase in K + permeability that is directly or indirectly coupled to Ca 2+ influx through potential‐operated channels.