Sympathetic fibers associated with a blood vessel express PGP9.5 while mostly lacking neurofilament heavy (NFH). A-D. Confocal micrographs showing PGP9.5 (B, red), tyrosine hydroxylase (C, green) and NFH (D, purple)-identified nerve fibers associated with a blood vessel identified with von Willebrand Factor (vWF; A, blue). The PGP9.5-identified nerve fibers include sympathetic fibers that express TH and fibers with NFH. Fibers with TH are prominently associated with the blood vessel (V) and many of these fibers lack NFH (arrow). Most of the PGP9.5-identified fibers located within the two nerve bundles (N) next to the blood vessel express NFH. The asterisk indicates the lumen of the blood vessel. Scale bar, 50 μm.