Quantitative assessment of the balance between oxygen delivery and consumption in the rat brain after transient ischemia with T2 -BOLD magnetic resonance imaging.
The balance between oxygen consumption and delivery in the rat brain after exposure to transient ischemia was quantitatively studied with single-spin echo T2-BOLD (blood oxygenation level-dependent) magnetic resonance imaging at 4.7 T. The rats were exposed to graded common carotid artery occlusions using a modification of the four-vessel model of Pulsinelli. T2, diffusion, and cerebral blood volume were quantified with magnetic resonance imaging, and CBF was measured with the hydrogen clearance method. A transient common carotid artery occlusion below the CBF value of approximately 20 mL x 100 g(-1) x min(-1) was needed to yield a T2 increase of 4.6 +/- 1.2 milliseconds (approximately 9% of cerebral T2) and 6.8 +/- 1.7 milliseconds (approximately 13% of cerebral T2) after 7 and 15 minutes of ischemia, respectively. Increases in CBF of 103 +/- 75% and in cerebral blood volume of 29 +/- 20% were detected in the reperfusion phase. These hemodynamic changes alone could account for only approximately one third of the T2 increase in luxury perfusion, suggesting that a substantial increase in blood oxygen saturation (resulting from reduced oxygen extraction by the brain) is needed to explain the magnetic resonance imaging observation.
Kettunen
Mikko I
MI
National Bio-NMR Facility and Cognitive Neurobiology Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland.
Gröhn
Olli H J
OH
Silvennoinen
M Johanna
MJ
Penttonen
Markku
M
Kauppinen
Risto A
RA
D000818:Animals; D001794:Blood Pressure; D001831:Body Temperature; D001921:Brain / Q000098:blood supply / Q000378:metabolism*; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D002546:Ischemic Attack, Transient / Q000503:physiopathology*; D007700:Kinetics; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010313:Partial Pressure; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow; D013997:Time Factors
D002245:Carbon Dioxide; D010100:Oxygen