title: Contractile properties of urethral smooth muscles of young and aged female dogs: morphological and pharmacological aspects.
abstract: BACKGROUND
  Alpha1-adrenoceptors are highly concentrated in the urethral smooth muscles and may play an important role in the contraction of this area. However, detailed examinations of age-related changes of the properties of urethral smooth muscle have rarely been undertaken.
  
  
  METHODS
  The contractile properties of urethras from young non-parous and old parous female beagles were determined with a urethral function study, macroscopic autoradiography for urethras using [3H]-labeled tamsulosin and morphometry of the urethral muscles.
  
  
  RESULTS
  The antagonistic effect (pA2) of prazosin for norepinephrine was 7.76+/-0.13 in young dogs and 7.62+/-0.06 in aged dogs. The specific binding of [3H]-tamsulosin (a relatively selective alpha1A-adrenoceptor antagonist) was recognized diffusely in proximal urethras with in vitro autoradiography. The density of binding in smooth muscles was approximately 60 and 40% in circular longitudinal layers, respectively, for both dogs.
  
  
  CONCLUSIONS
  The female canine urethra had alpha1A, and alpha1L-adrenoceptors. No age-related changes were seen in the function of the proximal urethra, distribution of alpha1-adrenoceptor binding sites and smooth muscle densities.
authors.affiliation: Department of Urology, Faculty of Medicine, The University of Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Ahmed
authors.forename: N
authors.initials: N
authors.lastname: Moriyama
authors.forename: R
authors.initials: R
authors.lastname: Fukasawa
authors.forename: H
authors.initials: H
authors.lastname: Nishimatsu
authors.forename: Y
authors.initials: Y
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Kitamura
authors.forename: S
authors.initials: S
authors.lastname: Tatemichi
authors.forename: K
authors.initials: K
authors.lastname: Akiyama
authors.forename: Y
authors.initials: Y
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Aisaka
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000378:metabolism / Q000494:pharmacology; D000375:Aging / Q000502:physiology*; D000818:Animals; D001345:Autoradiography; D004285:Dogs; D005260:Female; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D013449:Sulfonamides / Q000378:metabolism; D000077409:Tamsulosin; D014521:Urethra / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D013449:Sulfonamides; D010656:Phenylephrine; D000077409:Tamsulosin; D009638:Norepinephrine; D011224:Prazosin