title: Orchiectomy or androgen receptor blockade attenuates baroreflex-mediated bradycardia in conscious rats.
abstract: BACKGROUND
  Previous studies have shown that testosterone enhances baroreflex bradycardia. Therefore, conscious unrestrained rats were used to investigate the role of the androgen receptor in the testosterone-mediated modulation of baroreflex bradycardia. Androgen depletion (3 weeks), and androgen receptor blockade (20-24 h), were implemented to test the hypothesis that testosterone influences baroreflex bradycardia via its activity at the androgen receptor in male rats. Phenylephrine (1-16 microg kg(-1)) was used to assess baroreflex bradycardia.
  
  
  RESULTS
  Androgen depletion attenuated baroreflex bradycardia (P < 0.01). The antiandrogen flutamide (5, 15, or 30 mg kg(-1), s.c.) caused dose-related attenuation of baroreflex bradycardia in spite of a significant (P < 0.05) increase in serum testosterone. The latter did not lead to increased serum 17beta-estradiol level.
  
  
  CONCLUSIONS
  The data suggest: 1) Androgen depletion or adequate androgen receptor blockade attenuates baroreflex bradycardia. 2) The reflex increase in serum testosterone may counterbalance the action of the lower doses (5 or 15 mg kg(-1)) of flutamide. 3) The absence of a change in serum 17beta-estradiol rules out its contribution to flutamide action on baroreflex bradycardia.
authors.affiliation: Department of Pharmacology, The Brody School of Medicine at East Carolina University, Greenville, NC, 27858, USA.
authors.forename: Gregg R
authors.initials: GR
authors.lastname: Ward
authors.affiliation: Department of Pharmacology, The Brody School of Medicine at East Carolina University, Greenville, NC, 27858, USA.
authors.forename: Abdel A
authors.initials: AA
authors.lastname: Abdel-Rahman
mesh_terms: D000726:Androgen Antagonists / Q000009:adverse effects / Q000494:pharmacology*; D059002:Androgen Receptor Antagonists; D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D001919:Bradycardia / Q000139:chemically induced / Q000503:physiopathology*; D003243:Consciousness / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009919:Orchiectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D011944:Receptors, Androgen / Q000502:physiology
chemical_list: D000726:Androgen Antagonists; D059002:Androgen Receptor Antagonists; D011944:Receptors, Androgen