• Journal of Yeungnam Medical Science
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• v.11 no.2
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• pp.363-374
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• 1994

The purpose of this study was to investigate the characteristics or the potassium channels existing in the rat urinary bladders. Smooth muscle strips of rat detrusor urinae were examined by isometric myography. Relaxation responses of detrusor muscle strips to the three potassium channel openers pinacidil, a cyanoguanidine derivative, BRL 38227, a benzopyran derivative and RP 52891, a tertrahydrothiopyran derivative were examined. The potassium channel openers reduced the basal tone, and the rank order of potency was RP 52891>pincidil>BRL 38227. Procaine, an inhibitor of the voltage-sensitive potassium channel tended to increase the basal tone, but it did not affect the relaxant effects of the calcium-activated potassium channel opener did not antagonize the relaxant effects, but it reduced the Emax of RP 52891 and BRL 38227. Glibenclamide, an inhibitor of the ATP-sensitive potassium channel, antagonized the relaxant effects of pinacidil, RP 52891 and BRL 38227 reducing the Emax of RP 52891 and BRl 38227. Galanin which inhibits secretion of insulin through opening the ATP-sensitive potassium channels in pancreatic ${\beta}$-cells rather increased the basal tone of the isolated detrusor strips. These results suggest that the urinary bladder of the rat has mainly the ATP-sensitive, glibenclamide sensitive potassium channel, which is a different type from that in the pancreatic ${\beta}$-islet cells..

• The Korean Journal of Pharmacology
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• v.31 no.2
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• pp.195-206
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• 1995

The study was undertaken to examine the possibility of the involvement of $K^+$ channels in the mechanism of relaxant-action of imipramine on the isolated canine detrusor muscle strips. Canine urinary bladder were isolated, and smooth muscle strips of 15 mm long and 2 mm wide from the mid-portion of anterior wall were made in the Tyrode solution of $0{\sim}4^{\circ}C$. The strips were prepared for isometric myography in Biancani's isolated muscle chamber containing 1 ml of Tyrode solution, which was maintained with pH 7.4 by aeration with $95%\;O_2/5%CO_2\;at\;37^{\circ}C$. RP 52891, a non-specific $K^+$ channel opener, concentration-dependently suppressed the spontaneous phasic contractions of the detrusor strips. Imipramine, a tricyclic antidepressant, also reduced the spontaneous contractions in a concentration-dependent manner. RP 52891 was more potent than imipramine(p<0.05), and Imipramine was more efficient than RP 52891(p<0.05).Procaine, a voltage-dependent $K^+$ channel blocker, glibenclamide, an ATP-dependent $K^+$ channel blocker, and apamin, a calcium-dependent $K^+$ channel blocker antagonized the relaxant effect of RP 52891, but not of imipramine. Imipramine reduced the electric field stimulation (EFS) -induced contractions concentration-dependently. None of the $K^+$ channel blockers employed for this study, procaine, glibenclamide or apamin antagonized the inhibitory action of imipramine on the EFS-induced contraction. These results suggest that in canine detrusor, the $K^+$ channels of the characteristics of voltage-dependent, ATP-dependent and/or calcium-dependent are exist, and the inhibitory action of imipramine on the contractility of the detrusor is independent from the $K^+$ channels.