Responsiveness of smooth muscle in the lower urinary tract of rabbits to various agonists.

1. We compared the responsiveness of smooth muscle in the lower urinary tract and prostate from rabbits to the agonists noradrenaline, phenylephrine, clonidine, acetylcholine, prostaglandin F2 alpha, and histamine. 2. These agonists contracted smooth muscle in the lower urinary tract and prostate. In terms of maximal developed tension, contractile responses to the agonists were produced in the following order of potency: acetylcholine > prostaglandin F2 alpha > histamine > or = phenylephrine > or = noradrenaline > clonidine in the urinary bladder body; acetylcholine = noradrenaline = phenylephrine > prostaglandin F2 alpha > histamine > or = clonidine in the urinary bladder base; noradrenaline > or = phenylephrine > or = clonidine > acetyl-choline > prostaglandin F2 alpha > or = histamine in the urethra; and noradrenaline > or = phenylephrine > histamine = acetylcholine = clonidine = prostaglandin F2 alpha in the prostate. 3. These results suggest that considerable responsiveness variation occurs in the lower urinary tract and prostate and support the idea that the urinary bladder body is primarily governed by cholinergic mechanisms (parasympathetic nerves), whereas the urethra and prostate are regulated by alpha 1-adrenergic mechanisms (sympathetic nerves) and the bladder base by both.