Fig. 5. ( A ) Calcitonin gene–related peptide (CGRP) immunohistochemical labeling in mouse dorsal horn after application of KACGRP to one hind paw. Low magnification (5×) photomicrograph of CGRP immunoreactivity demonstrates a decrease in labeling in the primary afferents terminating in the dorsal horn ipsilateral to vector application ( black arrows ). Black lines represent the selected regions of interest. ( B ) Semiquantitative evaluation of CGRP immunoreactivity in the superficial dorsal horn of mice 6 weeks after treatment of one paw with KACGRP. KACGRP treatment significantly ( P < 0.05, analysis of variance, as indicated by the asterisk ) but unilaterally decreased labeling for CGRP (measured in optical density) in the lower lumbar spinal dorsal horn (L4–L5) but not in lower cervical/upper lumbar segments (C13–L1). Results were averaged across five animals per group, 10 sections per segment. KACGRP = antisense CGRP viral vector.