title: Impact of systemically active neurohumoral factors on the erectile response of the rat.
abstract: BACKGROUND
  Mean arterial pressure (MAP) and specific regulation of penile blood flow are the primary determinants of an erection. While this concept is well recognized, the differential relationship between systemically acting vasoactive factors on arterial pressure and erectile responses is not well described.
  
  
  OBJECTIVE
  The aim of this study was to determine how the modification of systemic levels of neurohumoral factors impacts on the magnitude and efficiency of the erectile response.
  
  
  METHODS
  The main outcome measures for this study are changes in MAP and intracavernosal pressure (ICP) following electrostimulation of the cavernous nerve.
  
  
  METHODS
  Anesthetized adult, male Sprague-Dawley rats were catheterized for measuring MAP (carotid), ICP, and drug administration (vena cava). Erections were induced via cavernous nerve electrostimulation. Vasoactive drug infusions were used to produce changes in MAP levels including: hexamethonium, angiotensin II (ANGII)±hexamethonium, methoxamine±hexamethonium, losartan, MAHMA NONOate, and terbutaline.
  
  
  RESULTS
  In general, ICP and MAP were linearly correlated regardless of treatment. Hexamethonium markedly dropped MAP and proportionately decreased the magnitude of the erectile response. ANGII or methoxamine given to hexamethonium-pretreated or untreated rats increased MAP similarly, but produced contrasting effects on erectile responses. ANGII-induced pressor responses were associated with increased erectile responses whereas all methoxamine treatments markedly decreased erectile responses. Depressor changes with losartan or terbutaline, but not MAHMA NONOate, also impacted negatively on the efficiency of the erectile responses at lower arterial pressures.
  
  
  CONCLUSIONS
  In general, the magnitude of the erectile responses was found to be dependent upon the level of MAP, although the mechanism by which arterial pressure was changed impacted substantially on the characteristics of the relationship. The major finding was that circulation-wide α-adrenoceptor stimulation was extremely deleterious to erectile responses whereas global stimulation of ANG II receptors was actually proerectile. Overall, the results indicate that neurohumoral specificity in systemic hemodynamic control is also critical in establishing the optimal erectile environment in rats.
authors.affiliation: Department of Pharmacology & Toxicology, Queen's University, Kingston, ON, Canada.
authors.forename: Lindsay D
authors.initials: LD
authors.lastname: MacKenzie
authors.forename: Jeremy P W
authors.initials: JP
authors.lastname: Heaton
authors.forename: Michael A
authors.initials: MA
authors.lastname: Adams
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D018738:Hexamethonium / Q000494:pharmacology; D019808:Losartan / Q000494:pharmacology; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000502:physiology*; D010410:Penile Erection / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013726:Terbutaline / Q000494:pharmacology
chemical_list: D018377:Neurotransmitter Agents; D000804:Angiotensin II; D018738:Hexamethonium; D008729:Methoxamine; D019808:Losartan; D013726:Terbutaline