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KMID : 0365819830230010155
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Journal of Pusan Medical College
1983 Volume.23 No. 1 p.155 ~ p.165
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In Vitro Effects of Calcium on Serotonin-Induced Contraction of the Cat Carotid Arteries
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Abstract
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The influences of Ca" upon the contractility of the isolated carotid arterial smooth muscle induced´ by serotonin were studied. Segmented muscle strips were prepared from the cat carotid artery, and the mechanism of serotonin-induced contraction was investigated using variable extracellular Ca" and Ca" influx-blocking agents. All experiments were performed in Tris-buffered Tyrode solution which was aerated with 100% oxygen and kept at 37°.
The results obtained were follows:
1. Serotonin caused dose-dependent contraction of the carotid arterial segment. Maximal contraction was observed at 5 X l0´´ M serotonin concentration and KED~. was about 10´` M.
2. In the absence of external Ca´´, serotonin-induced contraction appeared a little, but this contraction was very little as compared with 2.5 mM external Ca=´. Serotonin was able to mobilize the intracellular Ca=´.
3. When arterial segments were bathed in a solution of 4.0 MM Ca", the response to serotonin was inhibited as compared with 2.5 mM Ca=´, indicating that extracellular Ca´ had an autoinhibitory effect of the influx of Cat´.
4. The contraction induced by serotonin was abolished by the treatment with lanthanum, verapamil and diltiazem, which are known to be a selective Cat´ influx-blocker.
5. Following the inhibition of contractile force by Cal´ influx-blocker, the vascular contraction wasreappeared by the addition of norepinephrine, and it was blocked by alpha-adrenergic receptor blocking agent, phenoxybenzamine.
These results suggest that serotonin-induced contraction of the cat carotid artery is the effect of both transmembrane Ca´° influx and the mobilization of intracellular Ca=´.
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