Distribution and possible origin of galanin-like immunoreactive nerve fibers in the mammalian dental pulp.

Human, dog, cat and rat dental pulps were investigated for the presence and distribution of galanin-like immunoreactive (-IR) nerve fibers, and the possible origin of pulpal galanin-IR nerve fibers in the rat was examined. Galanin-IR nerve fibers were present in the dental pulps of all species examined. Two types of galanin-IR nerve fibers were distinguished with regard to morphology; thin varicose nerve fibers and thick smooth-surfaced nerve fibers. Thin varicose galanin-IR nerve fibers were seen to run along the blood vessel in the human, dog and cat root pulp. In the coronal pulp, galanin-IR nerve fibers ran toward the odontoblastic layer but they did not form the subodontoblastic nerve plexus. In rat molar pulp, few galanin-IR nerve fibers were observed; the distribution of these nerve fibers was similar to those in human, dog and cat pulp. In contrast, many thick smooth-surfaced galanin-IR nerve fibers were observed near the blood vessels in incisor pulp of the rat; occasionally a few varicose galanin-IR nerve fibers were also observed. Transection of the inferior alveolar nerve or mandibular nerve caused complete disappearance of galanin-IR nerve fibers in rat dental pulp, while surgical sympathectomy of the superior cervical ganglion did not affect their distribution. The present results indicate that galanin-IR nerve fibers are present in the mammalian dental pulp, and that the intrapulpal galanin-IR nerve fibers in the rat originate from the trigeminal ganglion and are primary afferents.