Fig. 4.

Unilateral bulbectomy increases the number of secretagogin-expressing cells in the rostral migratory stream. (A and A₁) Secretagogin⁺ cells not only appeared in the otherwise secretagogin-immunonegative axis of the stream but also typically accumulated in its shell region 15 d after olfactory bulbectomy. Saggital sections are shown in B, D, and E. Coronal sections at the rostrocaudal level indicated in A₁ are demonstrated in C₁ and C₂. (B′–B′′′) Olfactory bulbectomy increased the number of secretagogin⁺ neurons both in the marginal zone (black arrowheads) and in the axis (white arrowheads) of the RMS. (F–F′′) Fifteen days after bulbectomy, the number of secretagogin-expressing cells increased robustly in the axis and shell domains of the RMS compared with the number of cells detected in sham-operated controls. Secretagogin⁺ neurons and BrdU⁺ neuroblasts were counted manually, and their density was calculated in the marginal and axial domains (F′) of the distal RMS. To exclude region-specific differences, we carried out identical measurements in three regions of the distal RMS (F). The density secretagogin⁺ neurons increased significantly in both the marginal and axial domains of the RMS. (G and G′) In addition to astroglia and migrating neuroblasts, the rodent RMS contains secretagogin⁺ neurons (P < 0.05, Student’s t test). Images in A, A1, and F were acquired using the tile-and-stitch function. (Scale bars: 300 μm in A and A₁; 200 μm in F; 100 μm in B, C₁, C₂, and D; and 10 μm in B′ and F′.)