NES and Stroke: By labeling YFP+ oligodendrocyte progenitor cells and YFP+ neural stem cells in the SVZ of the Nestin-CreERT2/+;R26R-stop-YFP/+ mouse prior to induction of stroke, the present study shows that inhibition of PDE5 by Sildenafil increased nestin lineage oligodendrocytes in ischemic boundary regions of the corpus callosum of middle-aged mice.