Effect of Nebivolol on the Isolated Rat Bladder Strips Precontracted with Carbachol or Potassium Chloride

Abstract

Objective: One of the proposed mechanism mediating the vasorelaxant effect of nebivolol is based on its agonistic activity on beta-2 and/or beta-3 adrenergic receptors. These receptors are also involved in the relaxation of urinary bladder. The aim of this study was to explore the ability of nebivolol to induce relaxation of the isolated rat bladder strip precontracted with cholinergic stimuli using carbachol or non-cholinergic stimuli using potassium chloride (KCl). Methods: The isolated bladder strips were mounted in organ bath and contracted by KCl (40 μM) or carbachol (1mM) before the cumulative addition of nebivolol (0.0001-100 μM). To investigate the role of beta-adrenergic receptors in the nebivolol-induced relaxant response, some bladder strips were incubated with propranolol (1 μM) for 30 min. Statistical significance was tested by Student's t-test. p<0.05 was considered to be statistically significant. Results: Nebivolol elicited concentration-dependent relaxant response in the bladder strips precontracted with KCl or carbachol. Although the relaxant response to nebivolol in the bladder strips precontracted with carbachol was significantly inhibited by propranolol (p<0.05), the nebivolol-induced relaxation failed to be inhibited by propranolol in the bladder strips precontracted with KCl. The maximum relaxation in response to nebivolol was found to be significantly higher in the bladder strips precontracted with carbachol compared to that of KCl (p<0.05). Conclusion: The findings of the present study indicate that beta-adrenergic receptors play role in the relaxant response of nebivolol in the isolated rat bladder strip precontracted with carbachol.