Trigeminal nerve endings in gingiva, junctional epithelium and periodontal ligament of rat molars as demonstrated by autoradiography.

Tritiated-L-proline was injected into the right Gasserian ganglion of mature rats for incorporation into proteins being carried by rapid axonal transport to nerve endings. The distribution of the nerve endings in molar gingivae and periodontium was subsequently mapped in serial sections by autoradiography. We found that sensory nerve terminals are most prominent in two regions of the free gingiva: (1) In the junctional epithelium there is a rich innervation of the basal epithelial layer with many endings penetrating several cell layers. (2) In the crestal epithelium arborized endings are present, especially on the marginal side of the crest. In the attached gingiva a few terminals are found in the epithelium with more in the lamina propria; the latter appear to be encapsulated. The periodontal ligament is only moderately labeled with silver grains located over nerve bundles, over nerves associated with blood vessels, and over a few apparent endings in the apical region. In the cementum no labeled endings are seen. Labeling of Gasserian cell bodies primarily reveals specific intra-epithelial nerve endings in gingiva crest and junctional epithelium. The absence of major labeling of the periodontal ligament supports the view that many nerves in that region are derived from cell bodies in the mesencephalic nucleus.