3H-thymidine injections from E19 to E20 and survival to postnatal day (P)5 (posterior coronal)
Figure 90. This slice through the olfactory peduncle includes the main olfactory bulb (MOB) medially, the accessory olfactory bulb (AOB) dorsally, and the anterior olfactory nucleus (AON) laterally. The AOB output neurons were all generated long before the morning of E19; some granule cells are heavily labeled, and approximately 50% have been generated by the morning of E19; a sprinkling of small cells throughout the rest of the AOB layers are labeled, but many are unlabeled. Labeling patterns in the MOB are nearly identical to the patterns in the more anterior slice in Figure 89. Many labeled young neurons and neuronal precursor cells in the rostral migratory stream are migrating into the MOB granular layer and periglomerular layers (arrows). Most of the tiny cells in the rostral migratory stream are going to the anterior MOB. Nearly all pars externa and superficial cells in the AON pars lateralis are unlabeled on the morning of E19, but heavily-labeled deep cells in the pars lateralis are intermingled with unlabeled cells.