Immunohistochemical Analysis of Maxillary Nerve Distribution in Rats

Previous studies of nerve distribution in the orofacial complex have focused primarily on the anatomic courses of nerve fibers and have rarely addressed the density of nerve distribution. The nerve distribution in the mandible was described in only one report which showed an increase in nerve distribution density moving from the alveolar crest toward the inferior alveolar nerve. However, no previous reports have focused on the nerve distribution density in the maxilla.

In this study involving 6 Wistar rats, tissue samples from the maxillary molar region were obtained and sectioned for staining and analysis. All nerves including nociceptive nerves in 5 regions of the maxilla samples, ranging from the alveolar crest to the superior alveolar nerve, were immunohistochemically stained with antibodies to protein gene product (PGP) and calcitonin gene-related peptide (CGRP) to identify and measure the vertical and horizontal nerve distribution densities in the 5 regions under an optical microscope. We also determined the ratio of nociceptive (CGRP-positive) nerves to all (PGP-positive) nerves.

The densities of both PGP- and CGRP-positive nerves increased vertically from the alveolar crest to the superior alveolar nerve and horizontally from the periosteal side to the periodontal ligament side within the maxilla. The ratio of CGRP- to PGP-positive nerves was on average greater than 80%.

These findings were consistent with those of the previous report on mandibular nerve distribution. However, our results suggest that the overall nerve distribution density in the maxilla is approximately one-third of that in the mandible. The results of this study, which report the nerve distribution density in the posterior maxilla, may support future research on pain and local anesthesia.