Supplementary Material for: β-Adrenoceptor-Mediated Relaxation of Carbachol-Pre-Contracted Mouse Detrusor

<b><i>Aims:</i></b> To study the β-adrenoceptor subtypes involved in the relaxation responses to (-)-isoprenaline in carbachol-pre-contracted (CCh) mouse detrusor muscle with intact and denuded mucosa. <b><i>Methods:</i></b> Isolated muscle strips from the urinary bladder of male C57BL6 mice or β<sub>2</sub>-adrenoceptor knockout mice were pre-contracted with CCh, 1 µM and relaxed with increasing concentrations of the β-adrenoceptor (β-AR) agonist (-)-isoprenaline and forskolin. For estimating the β-AR subtypes involved, subtype-selective receptor blockers were used, that is, CGP 20712A (β<sub>1</sub>-ARs), ICI 118,551 (β<sub>2</sub>-ARs), and L748,337 (β<sub>3</sub>-ARs). <b><i>Results:</i></b> Unlike in KCl-pre-contracted muscle, the mucosa did not affect the sensitivity of the relaxation response to (-)-isoprenaline in CCh-pre-contracted murine detrusor strips. Increasing concentrations of (-)-isoprenaline produced a biphasic concentration-relaxation response without any difference both during the presence and absence of mucosa. The relaxation fraction produced by low (-)-isoprenaline concentrations was mediated by β<sub>2</sub>-AR as evidenced by a shift of the concentration-response curve to higher concentrations with ICI 118,551, but not with CGP 20712A and L748,337, and by the absence of this fraction in β<sub>2</sub>-AR-KO mice. The relaxation response with low sensitivity to (-)-isoprenaline was not affected by any of the β-AR subtype-selective blockers and was the only response detected in detrusor strips from β<sub>2</sub>-AR-KO mice. <b><i>Conclusions: </i></b>In CCh-pre-contracted mouse detrusor, β<sub>2</sub>-ARs are responsible for the relaxation component with high sensitivity to (-)-isoprenaline as indicated by the conversion of a biphasic into a monophasic CRC with ICI 118,551 or by its absence in β<sub>2</sub>-AR KO mice. The mucosa does not impair relaxation under these conditions.