title: Retinal artery response to acute systemic blood pressure increase during cold pressor test in humans.
abstract: OBJECTIVE
  The purpose of this study was to investigate the response of the retinal arteriole to an acute increase in systemic blood pressure (BP).
  
  
  METHODS
  Sixteen healthy volunteers underwent a 5-minute cold pressor test (CPT) on the left hand. Retinal blood flow (RBF) was determined using a laser Doppler velocimetry system that enables simultaneous measurements of blood velocity and vessel diameter in a retinal artery every 30 seconds for the duration of the CPT. The mean arterial BP (MABP) was measured every 30 seconds during the test.
  
  
  RESULTS
  The MABP immediately increased and reached the maximum level (from 85.1 +/- 2.7 to 103.7 +/- 5.0 mm Hg; P < 0.01) 1.5 +/- 0.2 minutes after the CPT began. The peak increase in velocity (from 30.6 +/- 1.3 to 46.1 +/- 2.1 mm/sec; P < 0.01) occurred at 1.6 +/- 0.2 minutes, resulting in an increase in RBF (from 10.1 +/- 1.0 to 14.3 +/- 1.4 microL/min; P < 0.01). The peak decrease in diameter (115.8 +/- 5.0 to 105.1 +/- 5.0 microm; P < 0.01) occurred at 2.9 +/- 0.3 minutes and the RBF returned to the baseline value. The increases in MABP significantly correlated with the decreases in diameter (r = -0.674, P = 0.0059).
  
  
  CONCLUSIONS
  The CPT caused an acute increase in MABP that was associated with a transient increase in RBF and blood velocity, followed by constriction of the retinal arterioles and return of RBF to baseline. The results suggest that constriction of the retinal arterioles plays an important role in the maintenance of RBF in response to an acute increase in systemic BP.
authors.affiliation: Department of Ophthalmology, Asahikawa Medical College, Asahikawa, Japan. nagaoka@asahikawa-med.ac.jp
authors.forename: Taiji
authors.initials: T
authors.lastname: Nagaoka
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Mori
authors.forename: Akitoshi
authors.initials: A
authors.lastname: Yoshida
mesh_terms: D000208:Acute Disease; D000328:Adult; D001160:Arterioles / Q000502:physiology; D001341:Autonomic Nervous System; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D003080:Cold Temperature; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D017078:Laser-Doppler Flowmetry; D008297:Male; D015203:Reproducibility of Results; D012161:Retinal Artery / Q000502:physiology*; D012867:Skin / Q000098:blood supply