A developmental study of the mouse neostriatum.

The development of the mouse neostriatum was studied from 11 days postconception to 180 days postnatum in semithin sections, Golgi-stained sections and electron micrographs. The neostriatum was first visible in 12 day embryos. Neuroblasts, glioblasts and microglia were first identified at 13 days and by 16 days sufficient cells were differentiated to carry out differential cell counts. Astrocyte processes were identified in the electron micrographs at 15 days but astrocytes were only identified in semithin sections at birth. Oligodendrocytes were first observed 5 days after birth. No glioblasts were present later than 15 days after birth. Astrocytes were present in adult numbers by 5 days after birth; microglia were present in adult numbers by 15 days but oligodendrocytes increased in number up to 90 days. By 5 days after birth all neurons appeared fairly well differentiated in electron micrographs, but Golgi preparations showed a marked increase in dendritic spines between 5 and 90 days.