Elk2 and elk3 expression in rat brain have overlapping expression in the cerebral cortex and hippocampus.A–B, Dual labeling of elk2 and PV in rat cerebellar cortex. A, Bright-field image showing elk2 expression localized to the granule cell layer (Gr) of the cerebellum. B, Immunofluorescent detection of PV-labeled Purkinje neurons within the Purkinje layer (PL) and inhibitory cells within the molecular layer (ML). Comparison of A and B shows that elk2 is not expressed within the Purkinje cell layer as demarcated by PV staining. C–D, Low- and high-magnification bright-field images, respectively, showing no elk3 expression within the cerebellar cortex. E–F, Low- and high-magnification bright-field images, respectively, showing strong elk2 expression in the olfactory bulb. Elk2 was abundant in the internal granule (IGr) and mitral cell (Mi) layers but not within the periglomerular area (Gl).G–H, Elk3 expression in the caudate/putamen (CPu). G, Low-magnification image showing elk3-positive neurons in the CPu. H, Higher magnification of G showing that most neurons in the CPu were elk3 positive (as compared with erg1) (Fig.8A,B). I–J, Localization of elk2 and elk3 transcripts, respectively, in the hippocampus. Note that both genes were found in the CA1 subfield and the DG, with elk3 expression being weaker than that of elk2.K–L, Elk2 expression in the cerebral cortex.K, Low-power bright-field image showing weak elk2 expression throughout all the cortical lamina with higher levels in upper layers II/III. L, High-power image ofK showing cortical layer II. Note large number of weakly stained neurons. M–N, Elk3 expression in cerebral cortex. M, Similar to elk2, elk3 expression was found throughout the cortex with higher levels within upper lamina.N, High-power image of M showing elk3 in a large proportion of layer II neurons. Scale bar (shown inN): A, B,D, F, H, L,N, 200 μm; I,J, 550 μm; G, 2000 μm;C, E, K, M, 500 μm.