title: Effects of Silodosin and Tamsulosin on the Seminal Vesicle Contractile Response.
abstract: OBJECTIVE
  To understand the mechanisms underlying ejaculation dysfunction caused by α1A-adrenocetor (AR) antagonists, the effects of α1A-AR antagonists on the contractile responses of the seminal vesicle were investigated.
  
  
  METHODS
  Isolated seminal vesicles from guinea pigs were cannulated and pressurized, and the changes in the intraluminal pressure were recorded. Periodic applications of electrical stimulation (ES) caused biphasic increase in the intraluminal pressure, that is, initial and subsequent contractions. The effects of silodosin and tamsulosin, α1A-AR antagonists, on the contractile responses were examined.
  
  
  RESULTS
  The ES-induced biphasic contractions were blocked by tetrodotoxin (TTX). Silodosin and tamsulosin suppressed the initial contractions in a dose-dependent manner, while also exerting various inhibitory effects on the subsequent contractions. Increases in the intraluminal pressure facilitated spontaneous phasic contractions. The spontaneous contractions were not affected by TTX or α1A-AR antagonists, but were abolished by nifedipine.
  
  
  CONCLUSIONS
  The initial contractions triggered by neuronal excitations were suppressed by silodosin and tamsulosin, suggesting that the ejaculation dysfunction may be attributed to the α1A-AR antagonist-mediated suppression of nerve-evoked contractions in the seminal vesicle. The subsequent contractions may be induced by mechanical stimulation associated with the initial, nerve-evoked contractions. Alternatively, other transmitters may be involved to various degrees in the neuromuscular transmission of the seminal vesicle.
authors.affiliation: Department of Urology, Kurume University School of Medicine, Kurume, Japan.
authors.forename: Tokumasa
authors.initials: T
authors.lastname: Hayashi
authors.affiliation: Division of Integrated Autonomic Function, Department of Physiology, Kurume University School of Medicine, Kurume, Japan.
authors.forename: Mitsue
authors.initials: M
authors.lastname: Takeya
authors.affiliation: Division of Microscopic and Developmental Anatomy, Department of Anatomy, Kurume University School of Medicine, Kurume, Japan.
authors.forename: Kei-ichiro
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Department of Urology, Kurume University School of Medicine, Kurume, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Matsuoka
mesh_terms: D058668:Adrenergic alpha-1 Receptor Antagonists / Q000494:pharmacology*; D000818:Animals; D006168:Guinea Pigs; D007211:Indoles / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D012669:Seminal Vesicles / Q000187:drug effects*; D013449:Sulfonamides / Q000494:pharmacology*; D000077409:Tamsulosin
chemical_list: D058668:Adrenergic alpha-1 Receptor Antagonists; D007211:Indoles; D013449:Sulfonamides; C095285:silodosin; D000077409:Tamsulosin
keywords: ejaculation; seminal vesicle; silodosin; tamsulosin; α1-adrenoceptor antagonist