0100488918

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ANTISPASMODIC MECHANISM OF NORADRENALINE IN THE ISOLATED RAT RECTUM, PARTICULARLY IN RELATION TO Ca

English (英語)

The Kobe journal of the medical sciences

23(1-4)

35-40

1977-12

Antispasmodic mechanism of noradrenaline (NA) was investigated in relation to the mobilization of Ca in the isolated rat rectum. The findings on the relaxing effects of NA on the contractions induced by increasing concentrations of K suggest that the antispasmodic mechanism of NA may be related to inhibition of the membrane activity concerning Ca mobilization, but not related to inhibition of the ability of contractile elements responding to Ca. The antispasmodic action of NA on the phasic contraction by acetylcholine in normal medium was similar to that in Ca-free medium. Thus, NA would inhibit the release of Ca from storage sites. Furthermore, analysis of the concentration-action curve of acetylcholine concerning phasic contraction affected by NA in normal and Ca-free media provides additional evidence for such an assumption. The antispasmodic action of NA was not significantly modified by treatment with the removal of external Na. However, the shift of concentration-action curve of acetylcholine concerning phasic contraction induced by NA was slightly attenuated by removal of external Na. From these findings, it appears that as a mechanism of its antispasmodic action, NA would inhibit the release of Ca from storage sites, and that the Ca release-inhibiting action of NA would be hard to be affected by removal of external Na.

concentration-action curve

紀要論文