Coexistence of substance P and calcitonin gene-related peptide-like immunoreactivities in the rat vestibular endorgans.

The immunocytochemical distribution and coexistence of substance P (SP) and calcitonin gene-related peptide (CGRP) in the rat vestibular endorgans were investigated. SP-like immunoreactivity was found in nervous elements beneath and around hair cells. CGRP-like immunoreactivity was also abundantly distributed beneath and within the sensory epithelia. In the present study, double-staining immunocytochemistry revealed that three different types of immunoreactivities: SP-positive/CGRP-negative, SP-negative/CGRP-positive, and SP/CGRP-positive immunostaining can be distinguished. SP/CGRP-immunoreactive fibers were localized within as well as beneath the sensory epithelia. These fibers often penetrated the epithelia and nearly reached the surface. The present immunocytochemical evidence suggests that different types of peripheral nervous systems may exist in the vestibular periphery.