Summary
The effects of the potassium channel opener cromakalim on smooth muscle contraction and 3H-acetylcholine release were studied simultaneously in guinea-pig longitudinal muscle myenteric plexus preparations which had been preincubated with 3H-choline. Cromakalim (10 μmol/1) inhibited more markedly the smooth muscle contractions caused by the release of endogenous acetylcholine (via electrical stimulation or via activation of nicotine- and 5-HT3-receptors) than contractions induced by pilocarpine. Cromakalim (10 ~mol/1) did not affect the release of 3Hacetylcholine evoked by electrical stimulation or by stimulation of nicotine- and 5-HT3-receptors. In contrast, the release of 3H-acetylcholine caused by stimulation of M1-receptors was concentration-dependently reduced by cromakalim (1–100 gmol/1). The results suggest that the relaxant effect of cromakalim on smooth muscle contraction is not caused by a reduction of acetylcholine release from myenteric neurones. An opening of cromakalim-sensitive potassium channels may be involved in the inhibition of the M1-receptor mediated acetylcholine release.
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This work was supported by the Deutsche Forschungsgemeinschaft (Ki 210/6-3).
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Schwörer, H., Kilhinger, H. Effects of cromakalim on acetylcholine release and smooth muscle contraction in guinea-pig small intestine. Naunyn-Schmiedeberg's Arch Pharmacol 339, 706–708 (1989). https://doi.org/10.1007/BF00168666
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DOI: https://doi.org/10.1007/BF00168666