Characterization of nitrergic neurons in the porcine and human ciliary nerves.

PURPOSE: To further characterize a subpopulation of choroidal ganglion cells associated with the ciliary nerves.

METHODS: Isolated long ciliary nerves of porcine and human eyes containing ciliary nerve-associated ganglion cells (CNGCs) were embedded in Epon for ultrastructural investigation, or wholemounts were stained with antibodies against nitric oxide synthase (NOS), vasoactive intestinal polypeptide (VIP), vesicular acetylcholine transporter, neuropeptide Y (NPY), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), substance P (SP), and synaptophysin. In addition, wholemount preparations of the choroid and of the anterior segment were stained for reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-D). Serial sections through choroid and anterior segment were stained with the prior antibodies listed.

RESULTS: In the porcine choroid only CNGCs were present. They stained for brain (b)NOS and VIP and were surrounded by SP and VIP-immunoreactive (IR) nerve terminals. The axonal processes of the CNGCs followed the ciliary nerves to the anterior eye segment, where they formed a nerve fiber plexus that terminated in the trabecular meshwork. None of the axons passed into the sparse NOS-IR nerve fiber plexus surrounding the choroidal vasculature. The CNGCs in the human choroid morphologically resembled those seen in the pig.

CONCLUSIONS: The CNGC proportion of choroidal ganglion cells is presumably involved in the intrinsic (peripheral) innervation of the aqueous outflow tissues and of the choroid.