Electron microscopic identification of trigeminal nerve fibers in the ciliary body and the iris.

The trigeminal nerve fibers in the ciliary body and the iris have been identified electron microscopically by using intra-axonally transported horseradish peroxidase injected into the trigeminal ganglion. The tracer revealed unmyelinated fiber profiles in the stroma of the ciliary body and the iris. These were not found to be associated with any particular organ but rather may terminate as free endings. Large profiles of varicosities contained mitochondria. Thin profiles, containing neurotubules, probably represent axons between the varicosities or endings. An interaction between the sensory and the autonomic peripheral fibers in the anterior uvea is suggested.