VGluT2 and CGRP immunoreactivity in the dorsal horn of L3 spinal cord. A: VGluT2-IR labeling occurs throughout the gray matter but labels a dense band of terminals in lamina I which is more prominent laterally. VGluT2-IR is also prominent in the lateral spinal nucleus and lamina II. B: Strong CGRP-IR occurs across lamina I but is especially dense medially. Some CGRP-IR fibers project deeper within the dorsal horn around the mid regions of laminae III-IV. C: Images in (A) and (B) band-pass filtered by Fast Fourier Transformation (FFT), thresholded and merged to reveal larger scale domain organization of the VGluT2-IR (red) and CGRP-IR (green) terminals in lamina I. Domains enriched with VGluT2-IR or CGRP-IR terminals are interspersed with domains containing both types of terminals (yellow). VGluT2-IR domains are superficial to CGRP-IR domains in lateral dorsal horn. D-E: Intensity plots of merged and aligned FFT-filtered images of L3 spinal cord from three animals to show the overall organization of domains enriched for VGluT2-IR or CGRP-IR. The height of the peak represents the mean labeling intensity of the domain; red, VGluT-IR; green, CGRP-IR. D: Ventral view. E: Dorsal view. Domains enriched in VGluT2-IR tend to lie more dorsally, especially in lateral lamina I where it abuts the lateral spinal nucleus. Domains enriched in CGRP-IR tend to lie more deeply, especially in medial lamina I. Scale bar in A represents 100 μm and applies to all panels. The axes indicate the orientation of the transverse sections: D; dorsal, V; ventral, M; medial, L; lateral, and for the 3D plots, I; intensity in arbitrary grayscale units. The approximate location of the superficial laminae are marked in A and B: lamina I; I, lamina II; II, and lamina III; III. The location of the lateral spinal nucleus is also indicated; lsn.