title: A role for peripheral 5-HT2 receptors in serotonin-induced facilitation of the expulsion phase of ejaculation in male rats.
abstract: BACKGROUND
  The urethrogenital reflex (UGR) is used as a physiological animal model of the autonomic and somatic activity that accompanies ejaculatory-like reflexes (ELRs). Serotonin (5-HT) plays an important role in regulating ejaculation.
  
  
  OBJECTIVE
  To examine the effects of intraurethral 5-HT on ELRs and to examine the effects of various 5-HT receptor subtypes on the 5-HT-induced changes in the ELRs.
  
  
  METHODS
  The effects of intraurethral infusion of 5-HT on ELRs were examined by monitoring the urethrogenital reflex in male rats. The effects of various 5-HT receptor-specific antagonists on the 5-HT-induced responses were examined.
  
  
  METHODS
  Main outcome measures were urethral pressure threshold required to elicit the UGR and bulbospongiosus activity or ELRs.
  
  
  RESULTS
  Intraurethral infusion of 5-HT (10-1,000 μM) produced a dose-dependent facilitation of the UGR, i.e., decrease in threshold urethral perfusion pressure and an increase in number of ELRs. The 5-HT3 receptor antagonists tropisetron (1 and 3 mg/kg, i.v.) and ramosetron (0.1 and 1 mg/kg, i.v.), the 5-HT7 receptor antagonist SB269970 (3 mg/kg, i.v.), and the 5-HT1 A receptor antagonist WAY-100635 (1 mg/kg, i.v.) all failed to inhibit 5-HT-induced facilitation of the UGR. However, ritanserin (1 mg/kg, i.v.), a nonselective 5-HT2 receptor antagonist, and xylamidine (0.01-1 mg/kg, i.v.), a peripherally restricted nonselective 5-HT2 receptor antagonist, significantly inhibited both the decrease in urethral pressure threshold and the increase in number of ELRs induced by intraurethral infusion of 5-HT.
  
  
  CONCLUSIONS
  These results suggest that in the male rat urethra, peripheral 5-HT2 receptors are involved in the 5-HT-induced facilitation of the expulsion phase of ejaculation.
authors.affiliation: Astellas Pharma Inc., Tsukuba, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Ishigami
authors.forename: Katsuro
authors.initials: K
authors.lastname: Yoshioka
authors.forename: Venkateswarlu
authors.initials: V
authors.lastname: Karicheti
authors.forename: Lesley
authors.initials: L
authors.lastname: Marson
mesh_terms: D000818:Animals; D004542:Ejaculation / Q000187:drug effects* / Q000502:physiology*; D008297:Male; D010879:Piperazines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011985:Receptors, Serotonin; D044348:Receptors, Serotonin, 5-HT2 / Q000502:physiology*; D012018:Reflex / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D014521:Urethra / Q000187:drug effects / Q000502:physiology
chemical_list: D010879:Piperazines; D011725:Pyridines; D011985:Receptors, Serotonin; D044348:Receptors, Serotonin, 5-HT2; D012702:Serotonin Antagonists; C104425:serotonin 7 receptor; D012701:Serotonin; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide
keywords: 5-HT2; Ejaculation; Serotonin; Urethra; Urethrogenital Reflex