Evidence for predominant mediation of alpha1-adrenoceptor in the tonus of entire urethra of women.
OBJECTIVE
We separated the entire length of the isolated human female urethra into seven parts from external urethral meatus to bladder neck and examined regional differences in contractile responses to noradrenaline, clonidine, acetylcholine and KCl.


METHODS
The entire urethra was obtained from 9 female patients with a mean age of 72.2 +/- 1.8 years. The entire urethra (35 to 42 mm. in length) was transversely cut into seven parts, and the contractile responses to noradrenaline, clonidine, acetylcholine and KCl of these parts were examined.


RESULTS
Noradrenaline but not clonidine produced concentration-dependent contraction in all parts, with a peak amplitude in middle to proximal urethra. In contrast, acetylcholine produced contraction only in proximal urethra and bladder neck. The amplitudes of noradrenaline-induced contraction were normalized against those induced by KCl, revealing similarity in patterns between noradrenaline-induced contractions and urethral pressure profile in human female urethra. These contractions to noradrenaline and acetylcholine were competitively inhibited by prazosin (pK(B): 8.38 +/- 0.10) and atropine (pK(B): 8.52 +/- 0.43), respectively.


CONCLUSIONS
These findings suggest that sympathetic innervation helps maintain resting urethral tonus, mainly through alpha1-adrenoceptors.
Taki
N
N
Department of Pharmacology, School of Medicine, Fukui Medical University, Matsuoka, Japan.
Taniguchi
T
T
Okada
K
K
Moriyama
N
N
Muramatsu
I
I
D000109:Acetylcholine / Q000494:pharmacology; D000368:Aged; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D009129:Muscle Tonus / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D014521:Urethra / Q000187:drug effects / Q000502:physiology*
D018340:Receptors, Adrenergic, alpha-1; D011189:Potassium Chloride; D000109:Acetylcholine; D009638:Norepinephrine