Co-localization studies identifying neuronal apoptosis after focal cerebral ischemia. A collage of 40× photomicrographs shows localization of activated caspase-3 (red) in NeuN-positive striatal neurons (green) after focal cerebral ischemia in TNFα-transgenic (TNFα-Tg) and non-Tg rats. Panels a and c are representative images of striatum in the left cerebral hemisphere of a non-Tg (a) and a TNFα-Tg (c) rat subjected to one hour of suture-occlusion of the right middle cerebral artery, followed by 24 hours of reperfusion. Note the absence of activated caspase-3 in NeuN-positive striatal neurons of the cerebral hemisphere contralateral to the ischemic injury in both animals. Panels b and d are taken from the ischemic striatum in the same non-Tg (b) and TNFα-Tg (d) rats. The presence of activated caspase-3 is clearly evident in NeuN-positive striatal neurons (arrows), many of which exhibit morphological changes consistent with ongoing cell death. Scale bar = 100 μm.