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The Journal of Neuroscience, March 4, 2009, 29(9):2814-2823; doi:10.1523/JNEUROSCI.4667-08.2009
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Neurobiology of Disease
Spatiotemporal Dynamics of Perfusion and Oximetry during Ictal Discharges in the Rat Neocortex
Mingrui Zhao, Hongtao Ma, Minah Suh, andTheodore H. Schwartz Department of Neurological Surgery, Weill Medical College of Cornell University, New York Presbyterian Hospital, New York, New York 10021
Correspondence should be addressed to Dr. Mingrui Zhao, Department of Neurological Surgery, Weill Medical College of Cornell University, 525 East 68th Street, Box 99, New York, NY 10065. Email: miz2003{at}med.cornell.edu
Epileptic events elicit a large focal increase in cerebral blood flow (CBF) to perfuse metabolically active neurons in the focus. Conflicting data exists, however, on whether hemoglobin saturation increases or decreases in the focus and surrounding cortex, and whether CBF increases globally or is decreased in adjacent areas. How these hemodynamic events correlate with actual changes in tissue oxygenation is also not known. Using laser Doppler flowmetry, oxygen microsensors and intrinsic optical imaging spectroscopy, we demonstrate that the dip in hemoglobin in the focus correlates with a profound but temporary decrease in tissue oxygenation despite a large increase in CBF. Furthermore, CBF simultaneously decreases in the cortex immediately adjacent to the focus. These events are then replaced with a longer duration, less focal increase in CBF, cerebral blood volume, and hyperoxygenation, the duration of which correlates with the duration of the seizure. These findings raise the question of whether transient focal hypoxia and vascular steal might contribute to progressive deleterious effects of chronic epilepsy on the adult and developing brain. Possible mechanisms based on recent astrocyte-based models of neurovascular coupling are discussed.
Received Sept. 29, 2008; revised Jan. 23, 2009; accepted Jan. 24, 2009.
Correspondence should be addressed to Dr. Mingrui Zhao, Department of Neurological Surgery, Weill Medical College of Cornell University, 525 East 68th Street, Box 99, New York, NY 10065. Email: miz2003{at}med.cornell.edu
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