[Experimental studies on urinary incontinence. II. Function and distribution of alpha 1- and alpha 2-adrenoceptors in male and female rabbit urethral smooth muscle].
The effects of various alpha-adrenergic agonists and antagonists on the contractile properties of the isolated urethra of male and female rabbits were examined and the population of alpha 1- and alpha 2-adrenoceptors, using radioligand receptor binding techniques, was also quantified to define the functional role of postsynaptic alpha-adrenoceptors in urethral smooth muscle. Norepinephrine, epinephrine (non-specific alpha-adrenergic agonists) and phenylephrine (alpha 1-adrenergic agonists) induced increases in contractile force in both the male and female urethra. Clonidine (alpha 2-adrenergic agonist) caused a relatively large contractile response in the female urethra but only a small contractile response in the male urethra. Receptor binding studies indicated that the male urethra contains almost equal amounts of alpha 1- and alpha 2-adrenoceptors (32 vs. 34 fmol/mg protein, respectively) whereas the female urethra contains a significantly greater density of alpha 2- than alpha 1-adrenoceptors (122 vs. 34 fmol/mg protein, respectively). Our studies have indicated that: (1) both alpha 1-and alpha 2-adrenoceptors cause contractile responses in male and female rabbit urethra; (2) the greater response to alpha 2-agonist in female than male urethra is correlated with a higher density of alpha 2-adrenoceptors in this tissue.
Morita
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D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000032:analysis / Q000187:drug effects; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000032:analysis*; D012727:Sex Characteristics; D014521:Urethra / Q000032:analysis* / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha