Ciliary processes

Abstract: The nutrition of the intraocular tissues is accomplished by the retinal vessels, the uveal vessels, and by the aqueous humor. Both morphologically and physiologically the retinal vessels are similar to those in the brain. The endothelial cells of the capillaries are attached to each other by tight junctions, the resistance vessels respond poorly to a large number of drugs, and the blood flow through the retina is autoregulated and very little affected by the sympathetic nervous system. The blood vessels of the iris also have morphological and permeability characteristics similar to those in the brain but they are under a strong influence from the sympathetic nerves and react to many drugs. The blood flow is autoregulated. The blood vessels of the choroid and the ciliary processes are similar to those in the small intestine and in the kidney. The endothelial cells of the capillaries are fenestrated; the vessels respond to sympathetic nervous stimulation and to a large number of vasoactive drugs. Autoregulation of the blood flow is intermediate in the ciliary body and very poor or absent in the choroid...

Abstract: The autonomic innervation to the eye of monkey, cat and rabbit was studied using a sensitive histofluorometric method for adrenergic nerves and the acetylcholinesterase technique for cholinergic nerves. In the monkey cornea adrenergic nerves are absent while they are numerous in both the cat and rabbit. There is marked species variation in the amount of autonomic innervation to the filtration area. The iris sphincter and the ciliary muscle have a dual innervation but the relative amount of the adrenergic component to these structures varies widely. The ciliary process in every case has a plentiful adrenergic nerve supply. In the choroid a heavy adrenergic innervation apparatus approaches the choriocapillaris. A layer of fluorescent terminals is found in the retina at the junction of the inner nuclear and inner plexiform layers in all three species. In the adjoining part of the inner nuclear layer lie scattered catecholamine-containing amacrine cells.

Abstract: The bulk of aqueous humor entering the eye is produced through an active secretory process by the nonpigmented epithelial cells of the ciliary process. Carbonic anhydrase is present in these cells, and following inhibition of the enzyme, bicarbonate formation is decreased, which, in turn, diminishes sodium and fluid secretion into the eye. The biological profile of the thienothiopyrans was assessed through in vitro, ex vivo, and in vivo studies. In vitro determination of I 50 and K i values utilized HCA-II, the isozyme found in the human ciliary process

Abstract: Vasoactive intestinal polypeptide (VIP), a neuronal peptide of ubiquitous occurrence in the body, is known to have strong vasodilatory effects and to promote secretion from many exocrine glands. Nerves displaying VIP immunoreactivity (VIP nerves) were detected in several orbital structures of the cat. Such nerves were numerous in the lacrimal glands and somewhat less numerous in the Harderian glands and the tarsal glands. The nerves surrounded glandular acini and small blood vessels. Intraocularly, VIP nerves were seen in the ciliary processes, in the posterior third of the ciliary muscle, and around small to medium-sized blood vessels in the posterior uvea. VIP nerve fibers were absent from vessels in the anterior uvea. This distribution may explain why intracranial stimulation in the oculomotor nerve exit region dilates the vessels of the choroid but not those of the iris. A large number of VIP-immunoreactive nerve cell bodies were observed in the pterygopalatine ganglion. Extirpation of this ganglion resulted in the disappearance of VIP nerves from the intraocular structures and from the lacrimal and Harderian glands. Removal of the superior cervical ganglion and the ciliary ganglion did not affect the VIP nerve supply. The results suggest that the VIP nerves originate in the pterygopalatine ganglion.