Immunohistochemical localization of γ and β subunits of epithelial Na+ channel in the rat molar tooth pulp

The distribution of γ and β subunits of epithelial Na+ channel (ENaC), markers for low-threshold mechanoreceptors in peripheral tissues, was examined in the tooth pulp. In the root pulp, γENaC- and βENaC-immunoreactive (IR) nerve fibers showed a thick smooth appearance. These nerve fibers ascended toward the pulp horn and formed subodontoblastic nerve plexuses. Immunoelectron microscopic method revealed that 63% of axons were immunoreactive for γENaC in the root pulp. Virtually all myelinated axons showed γENaC-IR (97%), whereas unmyelinated axons were mostly devoid of it (12%). These findings suggest that myelinated tooth pulp nociceptors respond to mechanical stimuli.