SPECIES-DIFFERENCES IN CHOROIDAL VASODILATIVE INNERVATION - EVIDENCE FOR SPECIFIC INTRINSIC NITRERGIC AND VIP-POSITIVE NEURONS IN THE HUMANEYE

Purpose. There is evidence that vasodilation of choroidal vessels resu lts from facial nerve stimulation. To obtain more information about th e role of the innervation, the authors examined the presence and spati al organization of nitrergic and vasoactive intestinal peptide (VIP) i mmunoreactive nerves in the human choroid. For comparison, the choroid of rabbit and rat eyes, with different types of retinal vascularizati on and no fovea, were studied. Methods. Whole mounts of five human, ni ne, rat, and two rabbit choroids were stained for NADPH-diaphorase. In addition, immunocytochemical staining was carried out on tangential f rozen sections of two human choroids using antibodies against nitric o xide synthase (NOS), synaptophysin, and VIP. Results. In all species, a perivascular network of diaphorase-positive nerve fibers with varico se terminals accompanied the arteries and arterioles of the choroidal stroma. A striking difference to rat and rabbit choroids was the prese nce of numerous positively stained ganglion cells in human choroids. P ositively stained axons connected the neurons with each other and with the perivascular network. Most of the ganglion cells were concentrate d in the temporal-central region, adjacent to the fovea. Immunocytoche mically, the choroidal ganglion cells were immunoreactive for NOS. Som e ganglion cells stained for VIP. Staining for synaptophysin demonstra ted varicose terminals innervating the perikarya of the ganglion cells . Many of these terminals stained for NOS and VIP. Conclusions. The pr esence of an intrinsic nerve cell plexus that is specifically localize d in human eyes in the temporal-central portion of the choroid indicat es a functional significance of the nitrergic choroidal innervation fo r the fovea.