Drug effects on receptors that relax the rat bladder in the lab

Isoproterenol relaxed KCl-precontracted rat bladder strips with a pD2 of 7.21, resulting in a residual contractile response of 3.2% after 30 microM.

• The beta1-agonist T-0509 and beta2-agonist terbutaline also relaxed bladder strips but with lower pD2 values and higher residual contractions.
• The relaxant effect of isoproterenol was significantly reduced by propranolol, metoprolol, and butoxamine, indicating involvement of beta-adrenoceptors.
• A combination of metoprolol and butoxamine caused a 15-fold shift in the concentration-response curve for isoproterenol.
• The partial agonist CGP 12177A produced weak relaxation and was resistant to blockade by propranolol.
• The study indicates the presence of beta1, beta2, and beta3-adrenoceptors in the rat urinary bladder body, all contributing to relaxation.

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