P2X3-IR in lumbosacral spinal cord from older postnatal (P21-P28) and adult (A) rats. Low power fluorescence images of the L6 spinal cord showing restricted P2X3-IR in the superficial dorsal horn (DH; A, C, E). Higher power fluorescence images of the dorsal, lateral quadrant of the L6 spinal cord showing restricted P2X3-IR in lamina II (B, D, F). Weak P2X3-IR was present in the lateral collateral pathway (LCP) of Lissauer in the lumbosacral spinal cord (F, arrows) of older postnatal and adult rats. P2X3-IR was observed in the anterior spinal artery (A, C, E, arrow). Calibration bar represents 100 μm in A, C, E and 60 μm in B, D, F.