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The action of acetylcholine and other drugs on the efflux of potassium and rubidium from smooth muscle of the guinea‐pig intestine
Author(s) -
BURGEN A. S. V.,
SPERO L.
Publication year - 1997
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.1476-5381.1997.tb06813.x
Subject(s) - efflux , acetylcholine , atropine , contraction (grammar) , chemistry , muscarinic acetylcholine receptor , rubidium , guinea pig , muscle contraction , endocrinology , medicine , depolarization , potassium , pharmacology , receptor , biophysics , biology , biochemistry , organic chemistry
1 . A method is described for measuring continuously the efflux of potassium or rubidium from smooth muscle of the guinea‐pig. 2 . Muscarinic drugs cause at maximum a 100‐fold increase in the efflux rate, due to a direct increase in permeability and only to a minor extent secondary to depolarization. With acetylcholine the dose response curve for producing efflux is displaced to 1,000 times higher concentrations than that for contraction. 3 . The shift varies with different agonists. The efflux and contractile responses to agonists are antagonized to an equivalent extent by atropine and several other reversible antagonists but benzhexol has a relatively greater effect on efflux. An estimate of spare receptors was obtained with benzilylcholine mustard and was similar for both responses. Dibenamine and local anaesthetics led to a parallel shift of the contraction dose response curve but a depression without shift in the efflux response. 4 . The most satisfactory explanation of these results is that there are two types of the muscarinic receptor in the smooth muscle of the guinea‐pig intestine.