title: Physiology of erectile function.
abstract: BACKGROUND
  There are numerous investigations concerning the balance and interactions between relaxant and contractile factors regulating penile smooth muscle (arterial and trabecular) tone, the determinant of penile flaccidity or erection. Enhanced knowledge of erectile physiology may improve management of men with erectile dysfunction. Aim. To provide state-of-the-art knowledge on the physiology of erectile function.
  
  
  METHODS
  An international consultation in collaboration with the major urology and sexual medicine associations assembled over 200 multidisciplinary experts from 60 countries into 17 committees. Committee members established specific objectives and scopes for various male and female sexual medicine topics. The recommendations concerning state-of-the-art knowledge in the respective sexual medicine topic represent the opinion of experts from five continents developed in a process over a two-year period. Concerning the physiology of erectile function and pathophysiology of erectile dysfunction committee, there were seven experts from five countries.
  
  
  METHODS
  Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.
  
  
  RESULTS
  Key roles in the mechanism determining the tone of penile smooth muscle are played by the rise of the intracellular concentration of free calcium and the sensitivity of the contractile machinery to calcium, endothelial health, endothelium-derived nitric oxide, endothelium-derived hyperpolarizing factor (EDHF), neuronal nitric oxide, cyclic guanosine monophosphate-dependent protein kinase and phosphodiesterase type 5.
  
  
  CONCLUSIONS
  A number of new mechanisms have been identified for the local regulation of penile smooth muscle contractility and therefore penile erection. Molecules participating in these pathways can be considered targets for the development of new treatments to treat erectile dysfunction.
authors.affiliation: Fundacion para la Investigacion y el Desarrollo en Andrologia, Madrid, Spain. isdtejada@terra.es
authors.forename: Iñigo
authors.initials: I
authors.lastname: Sáenz de Tejada
authors.forename: Javier
authors.initials: J
authors.lastname: Angulo
authors.forename: Selim
authors.initials: S
authors.lastname: Cellek
authors.forename: Nestor
authors.initials: N
authors.lastname: González-Cadavid
authors.forename: Jeremy
authors.initials: J
authors.lastname: Heaton
authors.forename: Robert
authors.initials: R
authors.lastname: Pickard
authors.forename: Ulf
authors.initials: U
authors.lastname: Simonsen
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D007172:Erectile Dysfunction / Q000503:physiopathology; D006801:Humans; D007391:International Cooperation; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology; D010100:Oxygen / Q000502:physiology; D010410:Penile Erection / Q000502:physiology*; D010727:Phosphoric Diester Hydrolases / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology; D014664:Vasodilation / Q000502:physiology
chemical_list: D017869:Cyclic GMP-Dependent Protein Kinases; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517381:PDE5A protein, human; D010100:Oxygen