Figure 1

TrkB-expressing cells surround neurons during sympathetic gangliogenesis. Chicken embryos at St. 25, 26, 27, and 28/29 were sectioned through the trunk and the patterns of Hu C/D-(white or red) and TrkB-(green) immunoreactivity were determined. (A) Low and (B) high power images demonstrating that at St. 25 (early E5) very few Hu C/D-positive cells are found in the region where sympathetic ganglia form, ventral to the spinal cord (SC) and dorsal root ganglion (DRG) and lateral to the dorsal aorta (DA). (C) At St. 26, migrating Hu C/D-positive cells are present, but TrkB is still not expressed. (D) At St. 27, TrkB-positive cells "cluster" around Hu C/D-expressing cells, although TrkB is not expressed in the neuronal cells. (E) Sympathetic ganglia coalesce at St. 28/29, and TrkB-expressing cells remain adjacent to Hu C/D expressing cells. The box in (A) indicates the region where we obtained high power images. Calibration bars: Low power image: 200 μ; high power images: 20 μ.