Fig. 3. Cerebral expression patterns of CXCR4 mRNA and neuronal and non-neuronal SDF-1 isoforms. Dark-field micrographs of coronal sections hybridized with riboprobes detecting all SDF-1 transcripts (A–F) or CXCR4 (G–L). A–F, In addition to moderate SDF-1 mRNA levels in endothelial cells throughout the brain, high SDF-1 mRNA levels are present in neuronal structures of the forebrain (B–D). G, In the olfactory bulb, CXCR4 mRNA expression is abundant in the glomerular layer (Gl). B–D,H–J, SDF-1 and CXCR4 mRNA-expressing neurons are located in areas 1 and 2 (Cg1, Cg2) of the cingulate cortex (B, H), in the insular cortex (In) (B,H), in the lateral entorhinal and ectorhinal cortex (LEnt, Ect) (C,D, I, J), and in the claustrum (Cl) (B,H). B–D, In the secondary motor cortex (M2) (B, C) and secondary somatosensory cortex (S2) (B,C), the medial aspect of the secondary visual cortex (V2) (D) and the ventral auditory cortex (AuV) (D), cortex neurons expressing SDF-1 mRNA are present, whereas CXCR4 mRNA-expressing neurons are mostly absent (H–J). Lower neuronal SDF-1 mRNA levels and fewer CXCR4 mRNA-expressing neurons are present in the retrosplenial (RS) (C, I) than in the cingulate cortex (B, H). C,D, Cerebrocortical neurons expressing SDF-1 mRNA are frequently located in the deep cortical layers. B,H, Neurons expressing CXCR4 mRNA but none expressing SDF-1 mRNAs are present in the dorsal endopiriform nucleus (DEn) (H). Note SDF-1 mRNA expression in the choroid plexus (CP) of the lateral ventricle (B, C) and CXCR4 mRNA expression in the subfornical organ (SFO) (H) as well as the ependymal layers of the lateral ventricle (LV) (H–J), the dorsal and ventral parts of the third ventricle (D3V, 3V) (H–J), and the fourth ventricle (4V) (K). In the amygdala, neuronal SDF-1 mRNA is selectively located in the anterior (BLA) (C) and posterior (BLP) (D) parts of the basolateral nucleus and in the amygdalohippocampal area (AHi) (D), whereas only few CXCR4 mRNA-expressing neurons without any clear assignment to subnuclei are detectable (I, J). In the hippocampal formation, numerous CXCR4 mRNA-expressing neurons are present in the moleculare lacunosum and molecular layers (Mol) (I, J) as well as the polymorphic layer (PoDG) (I,J), whereas SDF-1 mRNA is expressed only in the granular layer (GrDG) (C,D). K, L, In the cerebellum (CBL), CXCR4 mRNA is expressed in the Purkinje cell layer. K, L, In the brainstem, neuronal CXCR4 mRNA expression cannot be identified. Exposure time, 42 d. 7n, Facial nerve. Scale bar (shown in A for A–L): 2 mm.