Figure 2. Regional and cell-type specific reduction in the density of interneurons in senescent animals.
A. Coronal cross-section of the macaque temporal lobe showing regions targeted for electrophysiology and immunohistochemistry (blue (CA3) and magenta (PRC), solid boxes) or immunohistochemistry alone (green (Hilus) and yellow (CA1), dashed boxes). Cell bodies stained with DAPI. B. High magnification photomicrographs of GAD67-expressing somatostatin (SOM) interneurons in the stratum oriens of the hippocampal CA3 region of a middle aged animal. Red - somatostatin, Blue – DAPI, Green – GAD67. Yellow indicates the co-localization of somatostatin and GAD67 antibodies. We observed no significant differences in the density of parvalbumin-immunopositive interneurons in any layers of the hilus, CA3 (C), CA1 region or PRC (E). There were significant age-dependent differences in the GAD67 expressing somatostatin (SOM)-immunopositive interneurons in stratum oriens of both the CA3 (D) and CA1 regions. There were no significant differences in the density of SOM neurons in the stratum radiatum of either CA1 (Table 1) or CA3 (D). There were no age differences in density of GAD67-expressing somatostatin- or parvalbumin-immunopositive interneurons in any regions of the perirhinal cortex (F) or the hilus of the dentate gyrus (Table 1). Scale bar for A = 1 mm; for B = 40 microns.