Characterization of periinfarct flow transients with laser speckle and Doppler after middle cerebral artery occlusion in the rat

Abstract

Little information exists on the role and the characteristics of perfusion changes related to periinfarct depolarization. Our aim was to visualize and monitor periinfarct flow transients (PIFTs) in Sprague-Dawley rats (n = 10) with two different laser methods in a closed-skull model of filament middle cerebral artery occlusion. A laser Doppler probe was placed over the ischemic cortex 5 mm lateral to Bregma, and a 5 x 5 mm area centered 5 mm posterior and 4 mm lateral to Bregma was thinned for laser speckle imaging. Both neurological and histological evaluations were performed at 72 hr postinjury. Mean flow during 90-min ischemia was 29% of baseline measured by laser Doppler and 36-54% by laser speckle. Flow transients occurred in all rats, the number of PIFTs being 4.6 +/- 1.8/90 min. By both methods, 95.6% of them occurred with temporal correlation. The average duration of PIFTs was also identical (162 +/- 24 and 162 +/- 34 sec, respectively). Five different morphologies of flow transients ranging from hypoperfusive to hyperemic were identified by laser speckle. The PIFTs changed their morphology dynamically over certain regions. All of the animals showed an infarct (178.5 +/- 26 mm(3)) in the middle cerebral artery territory. Laser Doppler in itself can be a reliable method for counting/detecting PIFTs, but laser speckle is capable of monitoring the dynamic changes in PIFT morphology over the penumbral and periischemic cortex.