(a) Isoflurane increased the number of TUNEL-positive cells in the hippocampi of wild type neonatal mice compared with wild type control mice. FAS knockout had no effect on baseline TUNEL staining. Isoflurane did not increase TUNEL-positive cells in FAS-knockout mice compared to wild type isoflurane-treated mice. The scale bar represents 50 μm. (b) FASL knockout had no effect on baseline TUNEL staining. Isoflurane did not increase TUNEL-positive cells in FASL-knockout mice compared to wild type isoflurane-treated mice. The scale bar represents 50 μm.