title: Age-related impairment in choroidal blood flow compensation for arterial blood pressure fluctuation in pigeons.
abstract: OBJECTIVE
  Choroidal vessels compensate for changes in systemic blood pressure (BP) so that choroidal blood flow (ChBF) remains stable over a BP range of approximately 40 mm Hg above and below basal. Because of the presumed importance of ChBF regulation for maintenance of retinal health, we investigated if ChBF compensation for BP fluctuation in pigeons fails with age.
  
  
  METHODS
  Transcleral laser Doppler flowmetry was used to measure ChBF during spontaneous BP fluctuation in anesthetized pigeons ranging in age from 0.5 to 17 years (pigeons can live approximately 20 years in captivity).
  
  
  RESULTS
  ChBF in <8-year-old pigeons remained near 100% of basal ChBF at BPs ranging 40 mm Hg above and below basal BP (95 mm Hg). Baroregulation failed below approximately 50 mm Hg BP. In ≥8-year-old pigeons, ChBF compensation was absent at >90 mm Hg BP, with ChBF linearly following BP. Over the 60 to 90 mm Hg range, ChBF in ≥8-year-old pigeons was maintained at 60-70% of young basal ChBF. Below approximately 55 mm Hg, baroregulation again followed BP linearly.
  
  
  CONCLUSIONS
  Age-related ChBF baroregulatory impairment occurs in pigeons, with ChBF linear with above-basal BP, and ChBF failing to adequately maintain ChBF during below-basal BP. Defective autonomic sympathetic and parasympathetic neurogenic control, or defective myogenic control, may cause these baroregulatory defects. In either case, overperfusion during high BP may cause oxidative injury to the outer retina, whereas underperfusion during low BP may result in deficient nutrient supply and waste removal, with both abnormalities contributing to age-related retinal pathology and vision loss.
authors.affiliation: Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA. areiner@uthsc.edu
authors.forename: Anton
authors.initials: A
authors.lastname: Reiner
authors.forename: Nobel
authors.initials: N
authors.lastname: Del Mar
authors.forename: Yuri
authors.initials: Y
authors.lastname: Zagvazdin
authors.forename: Chunyan
authors.initials: C
authors.lastname: Li
authors.forename: Malinda E C
authors.initials: ME
authors.lastname: Fitzgerald
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D017704:Baroreflex / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D002829:Choroid / Q000098:blood supply*; D010856:Columbidae / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D017078:Laser-Doppler Flowmetry; D011311:Pressoreceptors; D012039:Regional Blood Flow