BLBP clustered cells and neuroblasts. A, A cluster of dye-coupled cells resectioned in the parasagittal planes. The inset shows a section at the level of the white line in the main image. Notice the mesh-like structure formed by gap junction coupled cells that surrounded noncoupled cells. B, Biocytin-filled cluster with the typical functional phenotype of precursor cells (1). The arrow points to a cell profile that did not belong to the cluster. In the same confocal section, the early neuronal marker HuC/D expressed in cells around the CC (2). The merged images show that the HuC/D⁺ cell pointed by the arrow (2) was surrounded by the cluster (3). Also notice the lack of colocalization indicating the neuroblasts are not coupled to putative precursors (3). C, BLBP and HuC/D immunohistochemistry showing the intimate spatial relationship between BLBP⁺ precursors and neuroblasts. D, A biocytin-filled neuroblast able to generate action potentials surrounded by BLBP⁺ cells. Scale bars: A, 50 μm; inset, 10 μm; B, C, 20 μm; D, 10 μm.