Effects of inorganic ions on the detrusor contraction induced by electro field stimulation

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The effect of magnesium ions on detrusor contraction was investigated in vitro using the rat detrusor muscle strips. Detrusor contractility caused by intramural nerve stimulation increased in a magnesium-free solution but decreased in a high magnesium solution. Cumulative addition of MgCl(-)2(-) suppressed the electrically induced contractile response of the detrusor dose-dependently. Mg-ion also suppressed atropine resistant detrusor contraction in a dose-dependent manner. Mg ion suppressed the detrusor contraction induced by carbachol and potassium. The effect of Mg ion on detrusor contraction was enhanced by verapamil, but was inhibited by Bay-K8644. Procaine increased the inhibitory effect of Mg ion on detrusor contractility. However, caffeine did not modify the effect of Mg ion. These results suggest that Mg ion suppresses detrusor muscle contractility through an inhibitory mechanism acting on calcium channels in the smooth muscle cell membrane. We also investigated similary effec … More ts of Mg ion on rabbit whole bladder.The detrusor contraction induced by intramural nerve stimulation in human neurogenic bladders was investigated in comparison with control bladders. The response of neurogenic bladders induced by intramural stimulation was significantly stronger than that of control bladders. Tetrodotoxin almost completely inhibited the detrusor contraction in both groups. After application of atropine remaining contraction of neurogenic bladders was significantly greater than that of control bladders. The subthreshold KCL ehanced the detrusor contractility significantly more in control bladders compared to neurogenic bladders. The contraction of neurogenic bladders in Ca-free solution persisted longer than that of controls. In conclusion, though there was no intrinsic difference in detrusor contractility, contractile response to electrical field stimulation, atropine resistance, enhancement of response by pottasium, and contractility in Ca-free solution were significantly different between neurogenic and control bladders. Less