Uncoupled Cerebral Blood Flow and Metabolism After Severe Global Ischemia in Rats

• Published in: Journal of cerebral blood flow and metabolism 1992-09, Vol.12 (5), p.802-808
• Main Authors: Singh, Narendra C., Kochanek, Patrick M., Schiding, Joanne K., Melick, John A., Nemoto, Edwin M.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Brain - metabolism; Brain - physiopathology; Brain Ischemia - complications; Brain Ischemia - metabolism; Brain Ischemia - physiopathology; Cerebrovascular Circulation - physiology; Hyperemia - etiology; Hyperemia - metabolism; Male; Medical sciences; Nervous system involvement in other diseases. Miscellaneous; Neurology; Rats; Rats, Inbred Strains; Time Factors
• ISSN: 0271-678X; 1559-7016
• DOI: 10.1038/jcbfm.1992.111

In a rat model of complete global brain ischemia (neck tourniquet) lasting either 3 min or 20 min, we monitored global CBF (sagittal sinus H2 clearance) and CMRO2 for 6 h to test the hypothesis that delayed postischemic hyperemia and uncoupling of CBF and CMRO2 occur depending on the severity of the insult. Early postischemic hyperemia occurred in both the 3-min and 20-min groups (p < 0.05 vs. baseline values) and resolved by 15 min. Hypoperfusion occurred in the 3-min group between 15 and 60 min postischemia (≈23% reduction), and in the 20-min group from 15 to 120 min postischemia (≈50% reduction) (p < 0.05), and then resolved. CMRO2 was not significantly different from baseline at any time after ischemia in the 3-min group. After 20 min of ischemia, however, CMRO2 was decreased (≈60%) throughout the postischemic period (p < 0.05). At 5 min after ischemia, CBF/CMRO2 was increased in both groups but returned to baseline from 60 to 120 min postischemia. In the 3-min group, CBF/CMRO2 remained at baseline throughout the rest of the experiment. However, in the 20-min group, CBF/CMRO2 once again increased (≈100%), reaching a significant level at 180 min and remaining so for the rest of the 6-h period (p < 0.05). These data demonstrate biphasic uncoupling of CBF and CMRO2 after severe (20 min) global ischemia in rats. This relatively early reemergence of CBF/CMRO2 uncoupling after 180 min of reperfusion is similar to that observed after prolonged cardiac arrest and resuscitation in humans.