Vasoactive intestinal polypeptide-like immunoreactive nerves to the human eye

Using immunohistochemical techniques, vasoactive intestinal polypeptide (VIP) is visualized in nerves distributed to the human eye. Immunoreactive nerve fibers occur about limbal blood vessels and within the trabecular meshwork. In the iris, free-running stromal nerves are the most common, but nerves to both dilator and sphincter muscles are present as well. Immunoreactive nerves are seen within the ciliary muscle and occasionally within a ciliary process. Innervation to choroidal blood vessels constitutes a prominent feature; innervation to more anterior uveal blood vessels is seen only irregularly. Immunoreactive to more anterior uveal blood vessels is seen only irregularly. Immunoreactive nerves are apposed to melanocytes throughout the uvea. The present findings extend prior reports in the human eye, indicating a potential role for VIP in ocular physiology. Additional neuroanatomical, biochemical and physiological studies are necessary to define fully the ocular function of VIP and to determine ultimely whether VIP has clinical and pharmacological implications.