Decrease in tissue oxygenation during interictal epileptic spikes in a rodent model depends on intensity of epileptic activity
Abstract number :
3.046;
Submission category :
1. Translational Research
Year :
2007
Submission ID :
7792
Source :
www.aesnet.org
Presentation date :
11/30/2007 12:00:00 AM
Published date :
Nov 29, 2007, 06:00 AM
Authors :
A. S. Geneslaw1, T. H. Schwartz1, M. Suh1, M. Zhao1, C. Perry1, H. Mah1
Rationale: We have previously demonstrated a decoupling between cerebral blood volume and hemoglobin oxygenation and an enlarged “epileptic dip” during interictal spikes (IIS) with intrinsic optical imaging in a rodent model. To confirm and quantify these results we used laser-Doppler flowmetry (LDF) and tissue oxygen measurements to look directly at tissue oxygenation.Methods: Simultaneous field potential (fp) and either tissue oxygen or cerebral blood flow (CBF) were measured with a Clark-style tissue oxygen microelectrode or laser-Doppler flowmeter. An adult rat was anesthetized under isoflurane and IIS were induced with bicuculline iontophoresis. IIS were classified as either singlet (n1), doublet (n2), triplet (n3), etc. according to the number of peaks. The mean maximum dip in oxygenation, mean maximum increase in cortical perfusion, and the timing of each signal change was calculated from the averaged data.Results: Three-hundred thirty total IIS were recorded with the oxygen electrode (n2 = 73 spikes, n2 = 101, n3 = 101, n4 = 43, n5 = 12). A negative linear trend was observed between the number of spikes and the mean oxygenation dip from baseline (R2 = 0.981, slope = -0.36), while a positive linear trend was observed between the number of spikes and mean time of the oxygen dip maximum (R2 = 0.919, slope = 0.358). Eighty-six total spikes were detected by the LDF probe (n1 = 6 spikes, n2 = 37, n3 = 26, n4 = 12, n5 = 5). A positive linear trend was observed between the number of spikes and the mean perfusion increase (R2 = 0.885, slope = 2.71), and an additional positive linear trend was observed between the time of max perfusion and number of spikes (R2 = 0.888, slope = 0.371).Conclusions: These findings support the assertion that the increased metabolic demand invoked by interictal spiking is not adequately met by cerebral perfusion, causing a brief focal decrease in tissue oxygenation. Moreover, it appears that IIS can have an aggregate effect, in which the number of spikes shows a strong linear relationship to both the increase in perfusion and the decrease in tissue oxygenation.
Translational Research