P2X2-immunoreactive cells lining the central canal (CC) are presumptive ependyme cells, modified glial cells. P2X2-immunoreactive cells lining the CC did not exhibit immunoreactivity to the pan neuronal marker, HuC/D (A-D) and were therefore not neuronal. Numerous HuC/D-immunoreactive cells were present throughout the spinal cord parenchyma (C, arrows) but P2X2-immunoreactive cells did not exhibit HuC/D-IR (C, D). C, D are merged images demonstrating P2X2- (red) and HuC/D-IR (green). In addition, P2X2-IR cells surrounding the CC did not exhibit immunoreactivity to glial fibrillary acidic protein (GFAP) (E, G, H) and were therefore not astrocytes (E-H). G, H are merged images demonstrating P2X2- (red) and GFAP-IR (green) surrounding the CC. Some ependyme cells express immunoreactivity to the protein S-100 (19). S-100-IR cells (I) were observed surrounding the CC and many of these cells expressed a similar morphology to the P2X2-IR cells (D, H versus I) surrounding the CC. Calibration bar represents 60 μm.