Nitrergic and secretagogin-expressing neurons in the olfactory neurogenic region of intact and maternally separated rats.

Maternal separation (MS), a source of early-life stress, may influence postnatal neurogenesis, including proliferation, cell death, or migration of progenitor cells in the olfactory neurogenic region-the ventricular-subventricular zone (V-SVZ) and the rostral migratory stream (RMS). In this study, we investigated the impact of MS on populations of nitric oxide (NO)-producing neurons and neurons expressing secretagogin (SCGN) within the V-SVZ/RMS of adult rats. The aim was to obtain new morphological data on these neuronal populations in intact rats and rats subjected to MS during the first three neonatal weeks (3 hours/day). We analyzed their distribution, number, and mutual relationships within the V-SVZ and in specific anatomical subregions of the RMS. Double immunofluorescence labeling for neuronal nitric oxide synthase (nNOS) and SCGN confirmed the presence of nNOS+ and SCGN+ neurons in the V-SVZ/RMS, each exhibiting distinct morphological features and distribution patterns. The response to MS differed between the two neuronal populations. Quantitative analysis revealed an increased number of nNOS+ cells in the V-SVZ/RMS of MS rats, with a statistically significant increase observed specifically in the V-SVZ. In contrast, the typical caudo-rostral decrease in SCGN+ cell numbers-seen in intact rats, with the lowest count in the rostral part of the RMS-was absent in MS animals. Instead, MS rats showed a significant decrease in SCGN+ neuron numbers in the caudal part of the RMS and a significant increase in the rostral part of the migratory pathway. These findings indicate that nitrergic and SCGN-expressing neurons in the V-SVZ/RMS respond differently to early-life stress induced by MS, exhibiting distinct changes in both cell number and spatial distribution.