Left: Staining of rat hippocampus with chicken anti-calretinin (green, 1:1,000) and mouse anti-parvalbumin (M-1813-100, red, 1:1,000) by Immunohistochemistry. IHC Method: Following transcardial perfusion of rat with 4% paraformaldehyde, brain was post fixed for 24 hours, cut to 45 um, and free-floating sections were stained. The calretinin and parvalbumin antibodies label different classes of interneurons. Blue: Nuclear DNA stain. Right: Western blot analysis of calretinin expression (green, 1:1,000) in rat brain (2) and spinal cord (3), mouse brain (4) and spinal cord (5), and cow spinal cord (6). A band at 29 kDa corresponds to calretinin protein. The same blot was simultaneously probed with a mouse anti-internexin antibody (red).