Confocal images showing PPD-immunoreactive cells in lamina I and IIo. a: Part of the L4 segment scanned to reveal PPD (red). b: The same field scanned for NeuN (blue) and Sytox (green). c: Merged image, with the solid line representing the dorsal border of the grey matter, and the two dashed lines the dorsal and ventral borders of lamina II. Three PPD-immunoreactive cells (asterisks) are present, one in lamina I and 2 in lamina IIo. Note that these are stained with NeuN, indicating that they are neurons. Many other neurons that are not PPD-immunoreactive are also visible. The nuclei of non-neuronal cells lack NeuN, and therefore appear green. The small red profiles include PPD-immunoreactive axons and dendrites. The images were obtained from a single optical section. Note that some neuronal nuclei appear very small, because the optical section does not go through their maximum diameter. Scale bar = 20 μm.