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Effects of cromakalim on the contraction and the membrane potential of the circular smooth muscle of guinea‐pig stomach
Author(s) -
Ito Katsuaki,
Kanno Tomohiro,
Suzuki Keiko,
MasuzawaIto Kaoru,
Takewaki Tadashi,
Ohashi Hidenori,
Asano Masahisa,
Suzuki Hikaru
Publication year - 1992
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.1476-5381.1992.tb14255.x
Subject(s) - cromakalim , contraction (grammar) , guinea pig , muscle contraction , stomach , smooth muscle , anatomy , circular muscle , membrane potential , chemistry , biophysics , biology , medicine , biochemistry , receptor , agonist
Summary1 . The effects of cromakalim on mechanical and electrical activities of the circular smooth muscles of guinea‐pig stomach antrum were observed. 2 . Cromakalim (> 1 × 10 −7 m ) decreased the amplitude of spontaneous rhythmic contractions and also the acetylcholine‐enhanced spontaneous contractions. Cromakalim was less effective against the 25.9 m m and 35.9 m m K + ‐induced tonic contractions. 3 . Glibenclamide (1 × 10 −6 m ) itself caused no detectable change in the spontaneous contractions, those potentiated by acetylcholine or tonic contractions induced by high K + solutions, but attenuated the actions of cromakalim. On the other hand, charybdotoxin (3 × 10 −8 m ) increased the amplitude of spontaneous contractions but failed to affect the actions of cromakalim. 4 . Cromakalim (> 1 × 10 −6 m ) decreased the amplitude and duration of slow waves, and hyperpolarized the membrane. These actions of cromakalim were completely antagonized by 1 × 10 −6 m glibenclamide, whereas part of the effects of cromakalim on mechanical activity was resistant to glibenclamide. 5 . The results suggest that the inhibition by cromakalim of the electrical activity and the hyperpolarization, which may be associated with the opening of glibenclamide‐sensitive K + channel, are responsible for its inhibitory action on circular smooth muscle of guinea‐pig stomach. Further, some effects independent of glibenclamide‐sensitive K + channel may also be responsible for the mechanical effect.