Impairment of GdnF expression in the Egr-1−/− mouse brain. A, brain sections were prepared, stained with hematoxylin and eosin (upper panel), and immunostained with anti-Gdnf antibody (lower panels). Gdnf immunoreactive cells in the CA1, CA3, and dentate gyrus (DG) regions of the hippocampus (boxes in upper panel) are shown in the lower panels. Arrows indicate immunopositive cells. Scale bar, 500 μm. B, quantification of Gdnf-immunoreactive cells in the CA1, CA3, and dentate gyrus (DG) regions of an 8-month-old mouse brain. Values represent the mean ± S.D. (error bars). *, p < 0.05 (n = 6) for Egr-1+/− versus Egr-1−/− mice (one-way analysis of variance analysis).