Fig. 2.

Mice (n =  3 for each time point) were fed for 6, 10 or 21 days with powdered food containing cuprizone while controls received a cuprizone-free diet. Significantly more apoptotic cells were detected in the corpus callosum on all time points compared to controls. On day 6, almost all apoptotic oligodendrocytes expressed activated caspase 3 (97 ± 5%); on day 10, the percentage is reduced to 58 ± 8% and after 21 days of cuprizone diet none of the dying oligodendrocytes expressed activated caspase 3 (a). Feeding of cuprizone over 21 days induced a significantly reduction of Nogo-A-positive oligodendrocytes on days 6, 10 and 21. (b) Olig2 is expressed in oligodendroglial progenitor cells and mature oligodendrocytes. The number of Olig2-positive cells decreased significantly during the cuprizone diet with lowest numbers observed on day 10; 21 days after the start of the cuprizone diet, a slight recovery of Olig2-positive cells was observed, suggesting a recruitment of progenitor cells. Oligodendroglial cell death was accompanied by a significant increase in the number of microglial cells on day 21 (d). ⁎p < 0.05; ⁎⁎p < 0.01; ⁎⁎⁎p < 0.001. ^###p < 0.001 for activated caspase-3-positive cells compared to controls.