Molecular probes of the vestibular nerve. I. Peripheral termination patterns of calretinin, calbindin and peripherin containing fibers.

Vestibular afferents have different physiological properties that can be at least partially correlated with the morphology that the peripheral ending makes with type I and type II hair cells. If the location of the ending in the sensory epithelium is included, the correlations are further improved. It is also known that vestibular afferents can be immunohistochemically stained for a variety of different substances. We have concentrated on three of these markers, calretinin, calbindin and peripherin, because the sources of afferents to the vestibular nuclear complex that contain these substances are restricted, in two cases to the primary afferents. We demonstrate that calretinin is found only in the calyx-only afferents that are located at the apex of the cristae ampullaris and along the striola of the maculae. The area containing stained calyces is equal to or slightly smaller than the central zone of the cristae as defined by the Goldberg group [J. Neurophysiol. 60 (1988) 167]. Calbindin is also found in calyces at the apex of the cristae and along the striola of the otoliths. Examination of adjacent sections of all endorgans indicates that calbindin staining overlaps with calretinin, but is always several hair cells wider on each side. Peripherin also stains fibers in the neuroepithelium. The greatest density of staining is in the peripheral zone of the cristae, i.e. at the base and toward the planum semilunatum. We suggest that these substances are useful markers for specific sets of vestibular afferents.