5-FU treatment causes reduced cellularity and loss of myelin basic protein (MBP) at 6 months after treatment. Representative images of hematoxylin and eosin staining from the periventricular region of (a,c) a control animal and (b,d) a 5-FU-treated animal. (c) Partial enlargement of the CC shown in (a); (d) partial enlargement of the CC shown in (b). (a) Normal cellular density is seen in the CC of the control; (b) in the CC from a 5-FU-treated animal, the cellular density in the CC has decreased markedly. (e,f) The expression of MBP seen in control animals (e) (the fiber-like green fluorescence staining in the CC and white-matter tracts in the peri-ventricular striatum) is greatly reduced in treated animals (f). The bright green punctuated fluorescent staining is BrdU+ cells, which are present in control animals but greatly depleted in treated animals. All sections were processed at the same time and all images were taken under equal exposure times. The scale bar represents 100 μm.