Dental pulp is innervated mostly by unmyelinated axons and small myelinated axons. These axons are implicated pain transmission and contain various neurotransmitters and receptors. However, little information,so far, is available on the distribution pattern and characterization of axons involved in the dental pain. In this study, to enhance understanding of dental pain processing, we observed distribution of axons expressing peripherin, an unmyelinated and small myelinated axonal marker, the in rat maxillary molar pulp.
Peripherin-immunopositive (+) axons are mostly distributed in the peripheral pulp, and a few peripherin+axons ascend into the odontoblast layer. Peripherin+ axons expressing NF200 are more frequently observed in the odontoblast layer (86.3±3.0%) than in the pulpal core region (79.3±2.8%) and nerve plexus region (78.6±1.9%). In contrast, peripherin+ axons expressing CGRP are less frequently observed in the odontoblast layer (17.7±5.0%) than in the pulpal core (37.7±10.1%) and nerve plexus regions (40.0±5.7%).
These findings indicate that small myelinated axons are implicated in the transmission of dental pain arising from the odontoblast layer while peptidergic unmyelinated axons are implicated in the transmission of dental pain arising from central core and nerve plexus regions of the dental pulp.