The allocation of nerve fibres to the anterior eye segment and peripheral ganglia of rats. I. The sensory innervation.

The distribution of sensory trigeminal nerve fibres in the anterior eye segment and the autonomic eye related ganglia, i.e. the parasympathetic ciliary and pterygopalatine ganglia and the sympathetic superior cervical ganglion, was studied in rats. For this the trigeminal ganglion was injected with tritiated leucine and wheat germ agglutinin coupled to horseradish peroxidase (WGA-HRP). After injection of WGA-HRP into the trigeminal ganglion, ganglion cell somata in the superior cervical and the pterygopalatine ganglion were labelled. As labelling of these cell bodies with WGA-HRP is the result of retrograde transport it must be assumed that cell bodies in these ganglia project to the trigeminal ganglion. [3H]Leucine injection into the trigeminal ganglion revealed the presence of labelled nerve fibres in the pterygopalatine ganglion and the nodose ganglion i.e. the sensory ganglion of the vagus nerve. Labelled nerve fibres were absent in the ciliary and superior cervical ganglion. As [3H]leucine labelling of nerve fibres is the result of anterograde transport exclusively, it can be concluded that trigeminal nerve fibres project to the nodose ganglion and the pterygopalatine ganglion, but not to the ciliary and superior cervical ganglion. In the retrobulbar structures, sensory nerve fibres occurred between the inferior oblique and the lateral rectus muscle and were present medial to the medial rectus muscle. Within the anterior eye segment, sensory nerve fibres were found in the cornea epithelium, stroma and adjacent to the endothelium. In addition, labelled fibres were found in the anterior stroma of the ciliary body, throughout the iris up to the pupillary border and in the conjunctiva. Most sensory nerve fibres which innervate the cornea, the iris and the ciliary body traverse the ciliary cleft.