The Journal of Neuroscience, February 2, 2005, ():
Brain-Derived Neurotrophic Factor and Antidepressant Drugs Have Different But Coordinated Effects on Neuronal Turnover, Proliferation, and Survival in the Adult Dentate Gyrus
J. Neurosci. Sairanen et al.
25: 1089
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Hippocampal sections of saline and imipramine treated trkB.T1 transgenic animals double labeled with anti-BrdU and anti-GFAP. A and B: The merged confocal images demonstrate that in the saline-treated transgenic mice (A), BrdU (red) and GFAP (green) were mainly located in the same cells (indicated by arrows). By contrast, in the imipramine treated transgenic mice (B), BrdU and GFAP were mainly located in different cells (arrows). Magnification is 1000 X. C: Quantitative analysis confirmed that the great majority of BrdU-labeled cells in saline-treated transgenic animals were GFAP-positive glial cells (presented in gray), whereas fewer BrdU positive cells stained with GFAP in imipramine treated cells. The numbers of BrdU positive/GFAP negative cells (black, also shown in Figure 3C) in the saline and imipramine treated transgenic mice correspond to the numbers of TUC-4 positive new-born neurons (Figure 3E). The preferential survival of GFAP positive cells in the saline-treated transgenic mice may reflect the fact that the dominant-negative trkB transgene, which was driven by the Thy1 promoter, is highly expressed in neurons, but not in glial cells (T. Saarelainen and E.C., unpublished). Therefore, the long-term survival of glial cells was not influenced by the transgene whereas the survival of neurons was compromised. Moreover, our results suggest that when trkB signaling is inhibited, chronic imipramine treatment preferentially directs neuronal progenitor cell differentiation towards neurons and reduces glial differentiation. The mechanism of this effect is currently unclear. Methods: Sections were pretreated as in BrdU immunohistochemistry and blocked in 10% serum/0,5% Triton X-100/PBS for 1h at RT. Slices were incubated with the mouse anti-BrdU antibody (Sigma, 1:400) in 1% NGS/0,5% Triton X-100/PBS for 48 h at +4°C, and then with Texas Red labeled anti-mouse IgG (Sigma, 1:250) for 1 h at RT. After washes and blocking in 10% NGS/0,5% Triton X-100/PBS for 1 h at RT, the sections were incubated with the rabbit anti-GFAP antibody (Sigma, 1:1000) for 48 h at +4°C and then with FITC-labeled anti-rabbit IgG (Sigma, 1:250). Sections were dried and mounted on glass slides with Vectastain mounting medium (Vector Laboratories) and analyzed with confocal microscopy (BioRadRadiance 2100 & Olympus IX70).
