Hormonal regulation of rat seminal vesicle sensitivity to adrenaline, noradrenaline, acetylcholine and acetyl-beta-methylcholine.

1. The influence of the hormonal condition of rats on the responsiveness of their seminal vesicles to drugs was investigated by determining pD(2) and alpha values for adrenaline, for noradrenaline, for acetylcholine and for acetyl-beta-methylcholine on isolated vesicles of normal, of castrated, and of oestradiol-treated castrated rats.2. pD(2) values of adrenaline, of noradrenaline, of acetylcholine and of acetyl-beta-methylcholine acting on seminal vesicles of castrated or of oestradiol-treated castrated rats were greater than the corresponding values obtained on the organs of normal rats. The differences were significant at the level P<0.001.3. Similar results were obtained for the relative intrinsic activity of noradrenaline and acetyl-beta-methylcholine.4. Consequently affinity of adrenaline, noradrenaline, acetylcholine and of acetyl-beta-methylcholine for their corresponding receptors and the stimulus produced by each unit of the noradrenaline-receptor or acetyl-beta-methylcholine-receptor complex were enhanced.5. The data indicate that an increase in the sensitivity of the smooth musculature of seminal vesicles to adrenaline and noradrenaline as well as to acetylcholine and acetyl-beta-methylcholine is obtained by castration, or by treatment with oestradiol following castration.