Receptor function studies in specimens from the proximal human urethra obtained by transurethral resection.

During transurethral resection (TUR) for prostatic hyperplasia, specimens were taken from the proximal urethra. Muscle strips thus obtained were mounted in an organ bath and muscle contraction was induced by adding increasing concentrations of noradrenaline (NA), methoxamine (alpha 1-agonist) and clonidine (alpha 2-agonist). NA and methoxamine induced a dose-dependent muscle contraction, but clonidine had no effect. The influence of prazosin (alpha 1-antagonist) and yohimbine (alpha 2-antagonist) on the NA-induced muscle contraction was also evaluated. Both antagonists had an inhibitory effect, which was much more potent with prazosin. The specimens taken during TUR were found to be suitable for in vitro receptor function studies. The alpha-adrenergic receptor function in the proximal human urethra was found to be mainly of the alpha-type.