title: New concepts of regulation of retinal vessel tone.
abstract: OBJECTIVE
  To review the mechanisms of local regulation of the vascular tone of the retinal and choroidal circulations.
  
  
  METHODS
  Literature review.
  
  
  RESULTS
  The vascular endothelial cell may produce nitric oxide, endothelins, prostaglandins, and renin-angiotension products in response to chemical stimuli such as acetylcholine and bradykinin, to changes in blood pressure and vessel wall stress, to changes in local oxygen levels, and to other local stimuli. These substances are among the most potent vasoconstrictors and vasodilators known. Preliminary investigations suggest a potential role for these substances in endothelial autoregulation of the retinal and choroidal vasculatures.
  
  
  CONCLUSIONS
  Hormonal products of the vascular endothelium may provide the final common pathway for vessel autoregulation in response to varying physiologic stress in many vascular beds, including the retina and choroid. Pharmacologic modulation of this process may provide treatment modalities for diseases such as hypertensive and diabetic retinopathies.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Brown
authors.forename: L M
authors.initials: LM
authors.lastname: Jampol
mesh_terms: D000818:Animals; D016232:Endothelins / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism; D011453:Prostaglandins / Q000378:metabolism; D012084:Renin-Angiotensin System / Q000502:physiology; D012171:Retinal Vessels / Q000502:physiology*
chemical_list: D016232:Endothelins; D011453:Prostaglandins; D009569:Nitric Oxide