Optical Mapping of Translucence Changes in Rat Hippocampal Slices During Hypoxia

We have evaluated the effects of hypoxia on changes in light transmittance (delta T/T) in rat hippocampal interface slices at 36 degrees C, using a digital imaging system. Slice translucence increased only slightly (delta T/T = 4.65% in CA1; control 2.27%) during brief hypoxia in which hypoxic spreading depression-like depolarization was not induced. If hypoxia duration was sufficient to trigger spreading depression in CA1, slice translucence increased rapidly in CA1 (delta T/T = 27.5%) and smaller, delayed changes were noted in other regions. These spreading depression-induced changes reversed slowly to control levels upon reoxygenation. Measurement of intrinsic optical signals revealed both spatial and temporal patterns of cell volume changes associated with hypoxia and spreading depression in hippocampus.