Journal of Smooth Muscle Research
Online ISSN : 1884-8796
Print ISSN : 0916-8737
ISSN-L : 0916-8737
Original
Mechanisms of the inhibitory effects of a phenoxazine compound, 2-amino-4,4α-dihydro-4 α-7-dimethyl-3H-phenoxazine-3-one, on the contraction of the smooth muscle of the guinea pig taenia cecum
Saifuding MushaMasaru WatanabeAkio TomodaMasato Konishi
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2007 Volume 43 Issue 1 Pages 15-24

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Abstract

To elucidate the mechanisms involved in the relaxing effect of 2-amino-4, 4α-dihydro-4α-7-dimethyl-3H-phenoxazine-3-one (Phx-1) on smooth muscle, we investigated its effects on the contraction of both intact and skinned (cell membrane permeabilized) preparations from the guinea pig taenia cecum. In intact preparations, Phx-1 concentration-dependently suppressed the contraction induced by either acetylcholine (ACh) or high-K+ with an IC50 value estimated at around 100 μM. Similar inhibitory actions of Phx-1 on force were observed in intracellular Ca store depleted preparations. In cell membrane depolarized preparations in the absence of extracellular Ca, however, Phx-1 had little effect on either caffeine- or ACh-induced contractions. In skinned preparations, Phx-1 suppressed Ca2+-induced contractions at concentrations higher than 100 μM. These results suggest that inhibition of smooth muscle contraction by Phx-1 is due mainly to inhibition of Ca2+-influx, although Phx-1 also seems to have direct inhibitory effects on the activities of the contractile apparatus.

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https://creativecommons.org/licenses/by-nc/4.0/deed.ja
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