Calcitonin gene-related peptide immunoreactive nerves in human and rhesus monkey eyes

Using immunohistochemical methods, calcitonin gene-related peptide localizes to peripheral nerve fibers of the human and rhesus monkey eye. Immunoreactive nerve fibers are found in the cornea, about limbal blood vessels and in the trabecular meshwork. Many immunoreactive iris nerve fibers are present, mostly within the stroma. A particularly dense network occurs just anterior to the iris sphincter muscle, but only a small number of immunoreactive nerve fibers are visualized within it. The ciliary muscle and ciliary processes also are innervated. Immunoreactive nerve fibers are associated with uveal blood vessels, most prominently in the choroid and ciliary body. Apposition of immunoreactive nerve fibers to uveal melanocytes is seen. In lower mammalian species, calcitonin gene-related peptide co-localizes with substance P in many ocular nerve fibers. The comparative distribution in human and monkey eyes of nerve fibers immunoreactive to these two peptides is discussed.