가토 질 평활근의 이완에 있어 칼륨통로의 역할과 칼륨통로개방제의 효과

초록

Purpose: The female vagina and clitoris undergo physiologic changes during the arousal or excitement phase following sexual stimulation. Engorgement and elongation of the vagina and clitoris depend on increased blood flow. This study was performed to investigate the role of K⁺ channels and to assess the effect of pinacidil, a K_ATP-channel opener, on the relaxation of vaginal smooth muscle. It is anticipated that future management strategies for women with vasculogenic female sexual dysfunction, similar to treatments for men with vasculogenic erectile dysfunction, may include the clinical application of vasodilators. Materials and Methods: Seventeen New Zealand white female rabbits were euthanized, and the entire vagina was excised. Strips of the vaginal wall were prepared for isometric tension measurement in an organ bath. Electrical field stimulation (EFS) was applied using a Grass SD9 stimulator. Magnitude of contraction was measured at baseline tension, while relaxation was assessed in tissues pre-contracted with 5 μM phenylephrine. Results: EFS induced a biphasic contraction/relaxation response. Atropine did not abolish the EFS-induced contraction, whereas bretylium did. Acetylcholine, minoxidil, and pinacidil induced dose-dependent relaxation, with potency in the order of pinacidil > minoxidil > acetylcholine. L-arginine, PGE₁, and acetylcholine induced relaxation of pre-contracted strips by approximately 10%, 10%, and 50–60%, respectively. Kv and K_ATP channel blockers partially suppressed relaxation induced by acetylcholine, minoxidil, and pinacidil. The maxi-K channel blocker suppressed acetylcholine-induced relaxation but did not inhibit the effects of the K_ATP-channel openers. Conclusions: These results suggest that relaxation of vaginal smooth muscle is mediated largely by cholinergic mechanisms and partly by the nitric oxide pathway. Activation of K_ATP and maxi-K channels independently induces vaginal smooth muscle relaxation. Additionally, the K_ATP-channel opener pinacidil may be an effective relaxing agent for vaginal smooth muscle.

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