Blood vessels and nerve fibers in rat incisor pulp. Immunoelectron microscopic observation with anti-substance P antibody.

The distribution of nerve fibers with special reference to their positional relationship with blood vessels in the pulp of the rat mandibular incisor was investigated by light and electron microscopic immunohistochemistry using polyclonal anti-substance P antibody. In the center of the pulp, numerous immunoreactive nerve fibers with varicosities were found along larger blood vessels. In the periphery of the pulp, there were two layers of capillary plexus; an odontoblastic and a subodontoblastic. Many nerve fibers, showing varicosities, were located in the subodontoblastic region, and some revealed a close association with pericytes of capillaries of the subodontoblastic plexus. A few nerve fibers entered the odontoblast layer, but no nerve fibers were seen to be associated with the odontoblastic capillary plexus. The results suggest that the local regulation of blood flow takes place not only in larger blood vessels but also in the capillaries of the rat incisor pulp.