Simultaneous demonstration of neuronal somata that innervate the tooth pulp and adjacent periodontal tissues, using two retrogradely transported anatomic markers.

Two axonally transported substances were used to demonstrate the spatial relationships between trigeminal ganglion cells innervating the tooth pulp and adjacent periodontal tissues of the mandibular canine teeth in cats. 4',6-Diamidino-2-phenylindole (DAPI) and horseradish peroxidase (HRP) were applied in the periodontal tissues and in the tooth pulp, respectively. The trigeminal ganglion and brain stem were then examined for the presence of fluorescent DAPI-labeled cells, HRP-labeled cells, and cells containing both labels. Cells containing either DAPI or HRP were observed in the mandibular portion of the ganglion; DAPI-labeled cells were observed in the pontine portion of the mesencephalic nucleus of the trigeminal nerve. Examples of double labeling, indicative of collateralization of single neurons to innervate both the tooth pulp and adjacent tissues, were not commonly observed. Finally, there was no indication of a mesencephalic nucleus contribution to the tooth pulp innervation.