Sex differences in function and distribution of alpha 1- and alpha 2-adrenoceptors in rabbit urethra.
To define the functional role of postsynaptic alpha-adrenoceptors in urethral smooth muscle, we examined the effects of various alpha-adrenergic agonists and antagonists on the contractile properties of the isolated urethra of male and female rabbits and quantified the population of alpha 1-and alpha 2-adrenoceptors, using radioligand receptor binding techniques. Norepinephrine (NE), epinephrine, and phenylephrine, an alpha 1-adrenergic agonist, induced increases in contractile force in both the male and female urethra. Clonidine, an 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, respectively), whereas the female urethra contains a significantly greater density of alpha 2- than alpha 1-adrenoceptors (122 vs. 34 fmol/mg, respectively). Our studies indicate that both alpha 1- and alpha 2-adrenoceptors cause contractile responses in male and female rabbit urethra; and 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.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012727:Sex Characteristics; D014521:Urethra / Q000032:analysis*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D015016:Yohimbine; D009638:Norepinephrine; D004837:Epinephrine