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Potassium induces relaxation and hyperpolarization of circular muscles but contraction of longitudinal muscles of pig duodenum
Author(s) -
Kimura I.,
Kimura M.,
Kimura M.
Publication year - 1984
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.1476-5381.1984.tb10134.x
Subject(s) - hyperpolarization (physics) , tetrodotoxin , phentolamine , chemistry , ouabain , contraction (grammar) , inhibitory postsynaptic potential , muscle contraction , biophysics , anatomy , membrane potential , endocrinology , medicine , biology , biochemistry , stereochemistry , sodium , receptor , nuclear magnetic resonance spectroscopy , organic chemistry
1 The mechanisms by which K + relaxes circular muscles of pig duodenum were investigated, and compared with the response of the longitudinal muscles to K + . 2 Circular muscles were concentration‐dependently relaxed by 8.3–23.6 m m K + , but contracted by 47.2–143.4 m m K + . 3 Longitudinal muscles were contracted by 11.8–94.4 m m .K + . 4 The relaxation of circular muscles was correlated with hyperpolarization (4 mV), but evoked Ca 2+ spikes were not suppressed. 5 Neither ouabain (0.14 μ m ) nor phentolamine (10 μ m ) blocked the relaxation, but tetrodotoxin (TTX, 0.63 μ m ) blocked both the relaxation and hyperpolarization. Mesaconitine (0.16 μ m ) increased the relaxation. Inhibitory junction potentials and concomitant relaxations were also blocked by TTX. 6 The results suggest that K + ‐induced relaxation is caused by the release of a non‐adrenergic inhibitory transmitter.