CALCITONIN-GENE-RELATED PEPTIDE IMMUNOREACTIVITY IN THE RAT EFFERENT VESTIBULAR SYSTEM DURING DEVELOPMENT

The organization of the efferent fiber network during postnatal develo pment was investigated by immunocytochemical detection of the calciton in gene-related peptide (CGRP) in rat vestibular receptors from postna tal day 0 (PD 0) to adulthood. CGRP was detected at birth in a few eff erent fibers below the sensory epithelia of cristae and maculae. There after, the nerve fibers in the cristae progressively invaded the epith elia with an apex to base gradient from PD 2 to PD 4. There was also a rearrangement of the fibers during maturation of the efferent innerva tion, such that after reaching the surface of the epithelium, they tur ned back and moved towards the base of the sensory cells, producing nu merous synaptic contacts. Analysis of surface preparations of utricule s showed the irregular and asymmetric topographic organization of the efferent fiber network and the extensive, complex distribution of this innervation. The presence and broad distribution of CGRP in the epith elium at critical stages of development and synaptogenesis suggests th at it is involved in the maturation of vestibular receptors. (C) 1998 Elsevier Science B.V. All rights reserved.