Representative drawings of the contralesional C7 and ipsi- and contralesional L5 dorsal horn of unexercised naïve (A), SCI No Allodynia (B), SCI Allodynia (C), and groups that received 5 weeks of exercise beginning at 14 dpi: SCI No Allodynia + Ex (D) and SCI Allodynia + Ex (E) reacted for calcitonin gene-regulated peptide (CGRP) and Isolectin-B4 (IB-4) at 42 dpi. In normal rats, these two types of nociceptive primary afferent fibers show very little overlap. In SCI rats that develop allodynia, there is marked overlap between these two types of nociceptive afferents in the cervical and lumbar dorsal horn (C, D, E) compared to those that do not develop pain after SCI (B). Scale bar = 100 microns.