title: Regional dynamics of the fMRI-BOLD signal response to hypoxia-hypercapnia in the rat brain.
abstract: OBJECTIVE
  To examine the regional blood oxygenation level-dependent (BOLD) signal response to rapid changes in arterial oxygen tension.
  
  
  METHODS
  Functional MR imaging (fMRI) was carried out in five male Sprague-Dawley rats anesthetized with Sodium Pentobarbital. Rats were subjected to different durations of apnea as a rapid, graded, and reversible hypoxic-hypercapnic stimulus. Dynamics of the BOLD signal response were studied on a pixel-by-pixel basis in the cerebral cortex, hippocampus, third ventricle, and thalamus in the rat brain.
  
  
  RESULTS
  Apnea induced a BOLD signal drop in all the brain regions studied, the magnitude of which increased with longer durations of the stimulus. The signal recovered to preapnic baseline levels after resumption of normal ventilation. Regional variation in the BOLD signal dynamics was observed with the magnitude of the BOLD signal change in the hippocampus being the least, followed by a relatively larger change in the thalamus, cerebral cortex, and third ventricle. The time (t(0)) for the signal change after the onset of the stimulus was estimated for every pixel. Time delay maps generated show the highest onset time values in the hippocampus followed by the thalamus, cerebral cortex, and third ventricle.
  
  
  CONCLUSIONS
  The regional dynamics of the BOLD signal in the brain in response to apnea may vary depending on the rate of oxygen metabolism in addition to cerebral blood flow (CBF).
authors.affiliation: Department of Radiology, UMDNJ-New Jersey Medical School, Newark, New Jersey 07103, USA.
authors.forename: Sridhar S
authors.initials: SS
authors.lastname: Kannurpatti
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Biswal
authors.forename: A G
authors.initials: AG
authors.lastname: Hudetz
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply* / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D006935:Hypercapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D010100:Oxygen