Mechanisms of the inhibitory effects of a phenoxazine compound, 2-amino-4,4 alpha-dihydro-4 alpha-7-dimethyl-3H-phenoxazine-3-one, on the contraction of the smooth muscle of the guinea pig taenia cecum.

To elucidate the mechanisms involved in the relaxing effect of 2-amino-4, 4alpha-dihydro-4alpha-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 IC(50) value estimated at around 100 muM. Similar inhibitory actions of Phx-1 on force were observed in intracellular Ca store depleted preparations.

A phenoxazine compound, 2-amino-4,4alpha-dihydro-4alpha-7-dimethyl-3H-phenoxazine-3-one reverses the phenylephrine or high-K+ induced contraction of smooth muscles in rat aorta and guinea pig tenia cecum.

2-Amino-4,4alpha-dihydro-4alpha-7-dimethyl-3H-phenoxazine-3-one (Phx-1) reversed concentration dependently the contraction of both rat aorta and guinea pig tenia cecum induced by phenylephrine or high-K(+). Since Phx-1 suppresses the responses of human mononuclear cells to phytohemagglutinin, (Akazawa et al. Tohoku J.