3H-thymidine injections from E16 to E17 and survival to postnatal day (P)5 (posterior coronal)
Figure 43. 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. In the AOB, the output neurons stand out as the biggest unlabeled population; the granule cells are heavily labeled, and small cells throughout the rest of its layers are nearly all labeled. Labeling patterns in the MOB are nearly identical to the patterns in the more anterior slice in Figure 42. The only difference is the core of the peduncle is heavily labeled—many of these are labeled young neurons and neuronal precursor cells in the rostral migratory stream migrating into the MOB granular layer and periglomerular layers (arrows). Most of these tiny cells are migrating perpendicular to the plane of the section to the more anterior parts of the MOB. Cells in the AON are mostly labeled. The AON is a prominent nucleus extending from the anterolateral olfactory peduncle through the entire peduncle to blend into the anterior basal telencephalon. On the morning of E16, most cells in the pars externa and pars lateralis are labeled, indicating that most neuronal populations are still in the proliferating phase and have not yet been generated.