Effect of hormones on urethral sensitivity to phenylephrine in normal and incontinent dogs.

The effects of stilboestrol and progesterone on pressure responses of the urethra to the alpha-adrenergic agonist, phenylephrine, were investigated in normal and incontinent ovariectomised dogs. It was found that progesterone had no significant effect on normal dogs but after pretreatment with stilboestrol the dose response curve was shifted to the left so that one third to one eighth of the original dose of phenylephrine produced the same response. In incontinent animals the sensitivity to phenylephrine was reduced compared with normal animals and stilboestrol either had no effect or only partially restored normal sensitivity. These results suggest that incontinence may result in part from decreased effectiveness of adrenergic innervation to the urethra.