Autoradiographic study of histogenesis in the mouse olfactory bulb I. Time of origin of neurons and neuroglia

TLDR

Autoradiography with thymidine‑3 injections at various developmental stages, followed by sacrifice near maturity, was used to determine the final cell‑division times of neurons and neuroglia in the mouse olfactory and accessory olfactory formations. Mitral cells arise first (E11–E13), followed by tufted cells (E13–E18) and granule cells (E18–P20), with peripheral tufted cells appearing later than deeper ones, all granule cell types extending into postnatal life, neuroglial precursors dividing mainly between E17 and P10, and accessory olfactory mitral cells appearing earlier (E10–E12) than their olfactory counterparts, supporting a programmed succession of larger to smaller cell types.

Abstract

Abstract Time of origin (final cell division) of neurons and neuroglia of the mouse olfactory and accessory olfactory formations was determined by autoradiography. Animals were injected with thymidine‐H 3 at various developmental stages and killed at or near maturity. In the olfactory formation mitral cells (the largest neurons) arise first, mainly over the three day period from the eleventh day of gestation (E11) to E13, tufted cells chiefly from E13 to E18, and granule cells (the smallest neurons) mainly from E18 to postnatal day 20. Most of the smaller and more superficial peripheral tufted cells arise later than the deeper and larger middle and internal tufted cells. All three types of granule cells have a time of origin extending well into postnatal life, with internal granule cells arising over a longer and later period than periglomerular cells or granule cells of the mitral cell layer. Neuroglial precursors undergo final cell division chiefly between E17 and P10. In the phylogenetically less evolved accessory olfactory formation, mitral cells originate earlier than their homologues in the olfactory formation; mitral cells principally from E10 to E12 and granule cells chiefly from E12 to E18. The results support the concept that some germinal layers of the central nervous system are programmed to produce a succession of cell types, larger cells before smaller ones.