Regional Differences in the Distribution of Calcitonin-Gene-Related-Peptide-Immunoreactive Nerve Fibers in the Nasal Epithelium of Rat Pup, Guinea Pig, and Cat

ABSTRACT

The distribution pattern of calcitonin gene-related peptide immunoreactive (CGRP-IR) nerve fibers in the epithelial layer was investigated with immunohistochemistry on serial sections of the whole nasal cavities of rat pups, guinea pigs and cats. The distribution pattern of CGRP-IR nerves beneath and within the epithelium demonstrated considerable regional differences in the nasal cavities of the laboratory animals cited above, and appeared to vary according to different compartments of the nasal cavity. In the rat pups, the CGRP-IR nerve fibers were densely distributed in the nasal epithelium lining both surfaces of the nasal septum and the medial sides of the naso-and maxillo-turbinates, whereas the distribution was less dense at the lateral sides of both turbinates and the lateral nasal wall. In particular, these nerve fibers were heavily concentrated in the inferior surface of the nasoturbinate and the superior surface of the maxilloturbinate, where large numbers of nerve fibers were found extending toward the luminal surface from the basal plexus. These features were also noted in the nasal cavity of the guinea pig and cat. The present observations show that one cannot consider the whole nasal cavity as a uniformly innervated region when interpreting the significance of the mucosal CGRP-innervation. Furthermore, in relation to the sensory role of CGRP-IR nerve, these results suggest that the different regions of the nose may have varying significance with respect to the basic protective function of this organ.