Changes in neurogenesis with post‑hatching age in the male Japanese quail (Cortunix japonica) brain.

Most avian neurogenesis studies have previously focused on the song control system and little attention has been given to non‑song birds. The objective of this study was to assess changes in neurogenesis associated with post‑hatching age (3‑12 weeks) in the Japanese quail brain using proliferating cell nuclear antigen (PCNA) and doublecortin (DCX) immunohistochemistry. PCNA‑immunoreactive (ir) cells were observed mainly in the olfactory bulb ventricular zone, telencephalic ventricular zones and cerebellum. Fewer PCNA‑ir cells were also observed in the hypothalamus, thalamus and bed nucleus of the stria terminalis. In telencephalic ventricular zones, PCNA‑ir cells were concentrated ventrally and dorsally adjacent to the mesopallium and medial striatum, respectively. DCX‑ir cells were observed in the olfactory bulb, telencephalon and cerebellum. Furthermore, DCX‑ir cells were scattered throughout the pallium except in the entopallium and arcopallium, septal nuclei and striatum. Fewer DCX‑ir cells were also observed in the hippocampus and bed nucleus of stria terminalis. The density of PCNA‑ir cells and DCX‑ir cells in all brain areas declined with post‑hatching age. In conclusion, cell proliferation appears to be restricted to the ventricular zones whereas neuronal recruitment is more widespread in the olfactory bulb, telencephalon and cerebellum. Postnatal neuronal incorporation appears to be absent in the diencephalon and mesencephalon.