Abstract

In this study, we have characterized the response of five sequential segments of urinary bladder to cholinergic, adrenergic, and purinergic agonists. The results indicate that an abrupt alteration in pharmacological response between bladder body and base occurs at the level of the ureteral orifices. The bladder body responds preferentially to urecholine (muscarinic cholinergic), isoproterenol (beta adrenergic) and ATP (purinergic), whereas the bladder base responds perferentially to methoxamine alpha adrenergic). In parallel studies, the density of both muscarinic cholinergic receptors ([3H]quinuclidinyl benzilate binding sites) and beta adrenergic receptors were significantly higher in the body than in the base, whereas the concentration of alpha adrenergic receptors was greater in the bladder base than in the body. From these studies, we conclude that the differences in the response of the bladder base and body to cholinergic and adrenergic agents are primarily due to differences in the densities of the specific autonomic receptors. In addition, the response of the bladder to ATP (which is a putative neurotransmitter in the urinary bladder) can also be separated between body and base. The distribution is similar to that observed for urecholine.