Nerve fibers in trabecular meshwork surface.

The trabecular meshwork surface in the Japanese monkey eye was observed by scanning electron microscopy. Many varicose nerve fibers were recognized in the anterior surface of the trabecular sheets and in the intertrabecular space facing the anterior chamber. The nerve fibers often branched and thus formed a loose-meshed plexus. These varicose nerve fibers were identified by ultrastructural studies after the pretreatment of one animal with 5-hydroxydopamine as an adrenergic agent. Most nerve fibers terminated as free endings without a constant relationship to the endothelial cells of the trabecular sheets. Although the physiological significance of such nerve fibers is not clear, they probably release a transmitter (noradrenaline) into the aqueous humor and have an influence on the aqueous outflow area.