A morphometric analysis of protein gene product 9.5-, substance P-, and calcitonin gene-related peptide immunoreactive innervation in the shoulder joint of the Japanese macaque

The shoulder capsule and labrum of Japanese macaque monkeys were studied im munohistochemically with the use of antisera against protein gene product 9 .5 (PGP 9.5), calcitonin gene-related peptide (CGRP), and substance P (SP) to further characterize the innervation of the supporting structures of the shoulder joint With PGP 9.5 immunohistochemistry thick nerve fibers (diame ter greater than or equal to 10 mu m) presumed to be proprioceptive based o n topographic location were found to be abundant in the posterior half of t he capsule. Thinner fibers (diameter < 10 mu m) presumed to contain nocicep tive and autonomic fibers were located in the posterior half of the capsule . Ruffini-like corpuscles were predominantly located in the inferior portio n of the capsule. SP and CGRP immunoreactive thin fibers presumed to be noc iceptive were abundant in the posterior half of the capsule. Thin Fibers th at appeared to be nociceptive fibers were found in the marginal portion and the parenchyma of the labrum, although the number was small. The predomina nt distribution of the Ruffini-like corpuscles in the inferior portion of t he capsule suggest an important role of the inferior portion in generation of the proprioceptive output, which should be advantageous in stabilization of the joint in motion. The abundance of nociceptive fibers in the posteri or half of the capsule may be responsible for the pathophysiological transm ission of pain around the shoulder joint.