Early visual changes in reflected light on non-stained brain sections after focal ischemia mirror the area of ischemic damage.

There is no reliable, simple method for delineation of ischemic regions at early time points after ischemia. We propose that at early times after stroke, ischemic regions can be visualized as a subtle change in reflected light directly in thaw-mounted, dried 20 microm brain sections. In 15 male Sprague-Dawley rats, anesthetized with isoflurane, middle cerebral artery transection and permanent bilateral common carotid artery occlusion was performed and brains were processed in five different ways. Areas of reflective change (RC) on non-stained sections were compared with areas on the adjacent sections delineated by microtubule associated protein 2 (MAP2) antibody, a reliable marker for early post-stroke, in five rats each at 1, 3, and 6 h after focal cerebral ischemia. A statistically significant correlation between ischemic areas (IA) measured on non-stained brain sections (IA(RC)) and adjacent sections immunostained (IM) with MAP2 Ab (IA(IM)) (IA(RC)=0.05+0.88.IA(IM); R2=0.8; n=15; P<0.01) and a small mean difference +/-2 S.D. (-0.9+/-6.0%) indicated that the area measured on non-stained sections reflects the IA measured on MAP2 -IM sections. At 1 and 3 h after ischemia, the ratio between ischemic regions measured on the non-stained sections and on the adjacent sections immunostained with MAP2 Ab were not different from 100% (97.6+/-1.7%, 100.9+/-6.0%). At 6 h post-stroke, the IA measured on the non-stained sections was larger than on the IM sections (109.8+/-2.7%, P<0.01, compared to 100% ratio). Our study demonstrated that this quick and simple method for detection of damaged brain permitted the use of brain tissue for other assays and could be very useful for neuroprotective evaluation and for directed micro-sampling of brain tissue at early times after ischemia.