Origin of Ca2+ Necessary for Carbachol-Induced Contraction in Longitudinal Muscle of the Proximal Colon of Rats

The origin of Ca2+ necessary for carbachol (CCh)-induced contraction of longitudinal muscle of the proximal colon of rats was studied. CCh induced contraction of the muscle consisting of two phases, phasic and tonic phases, with a concomitant biphasic increase in [Ca2+]i. After removal of Ca2+ from...

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Bibliographic Details
Published in:Japanese journal of pharmacology 2001, Vol.87(4), pp.309-317
Main Authors: Takeuchi, Tadayoshi, Sumiyoshi, Masahiro, Kitayama, Munenori, Hirayama, Nobue, Fujita, Akikazu, Hata, Fumiaki
Format: Article
Language:English
Subjects:
Aminobenzoates - pharmacology
Animals
Caffeine - pharmacology
Calcium - metabolism
Calcium Channel Blockers - pharmacology
Carbachol - pharmacology
Chlorobenzoates
Cinnamates - pharmacology
Colon - drug effects
Enzyme Inhibitors - pharmacology
Gastrointestinal Motility - drug effects
Male
Muscle Contraction - drug effects
Muscle, Smooth - drug effects
Nicardipine - pharmacology
Origin of calcium
ortho-Aminobenzoates
Parasympathomimetics - pharmacology
Phosphodiesterase Inhibitors - pharmacology
Rat proximal colon
Rats
Rats, Wistar
Sarcoplasmic reticulum
Sarcoplasmic Reticulum - drug effects
Sarcoplasmic Reticulum - metabolism
Thapsigargin - pharmacology
Voltage-dependent calcium channel
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Summary:The origin of Ca2+ necessary for carbachol (CCh)-induced contraction of longitudinal muscle of the proximal colon of rats was studied. CCh induced contraction of the muscle consisting of two phases, phasic and tonic phases, with a concomitant biphasic increase in [Ca2+]i. After removal of Ca2+ from the bathing solution of the colonic segments, CCh-induced contraction was rapidly inhibited; there was almost complete inhibition 1 min after the removal. Nicardipine, a blocker of voltage-dependent calcium channel, also significantly inhibited CCh-induced contraction. On the other hand, treatment of the colonic segments with thapsigargin, an inhibitor of sarcoplasmic reticulum (SR) Ca2+-ATPase, did not significantly affect the contraction except causing a slight decrease in the rate of contraction. These results suggest that Ca2+ entering through voltage-dependent calcium channels, but not released from SR, is essential for CCh-induced contraction of longitudinal muscle of the proximal colon of rats. This strict dependency of the CCh-induced contraction on extracellular Ca2+ was discussed in relation to the results obtained in the fundus of rats.
ISSN:0021-5198
1347-3506
DOI:10.1254/jjp.87.309