Development of granule cells of the rat olfactory bulb: an autoradiographic and electron microscopic study.

The rate of migration of immature granule cells of the rat olfactory bulb and polarity of cell-organelles in the migrating granule cells were investigated by 3H-thymidine autoradiographic and electron microscopic methods. The time lag in migration between two points was determined by cross-correlation analysis of labeling indices of the two areas. Granule cells were estimated to take 6 days to migrate rostralwardly from the subependymal layer at the anterior wall of the lateral ventricle to the center of the bulb, and an additional 1 to 6 days to migrate radially from the subependymal layer to the granular layer of the bulb. These results showed that the rate of rostralward migration of granule cells was faster than that of their radial migration. Golgi-electron microscopic as well as routine electron microscopic studies on migrating granule cells revealed that centrioles and Golgi apparatus were located at the base of the leading process that possesses a growth cone at its tip.