Calcitonin gene-related peptide immunoreactivity in the rat efferent vestibular system during development

The organization of the efferent fiber network during postnatal development was investigated by immunocytochemical detection of the calcitonin gene-related peptide (CGRP) in rat vestibular receptors from postnatal day 0 (PD 0) to adulthood. CGRP was detected at birth in a few efferent fibers below the sensory epithelia of cristae and maculae. Thereafter, the nerve fibers in the cristae progressively invaded the epithelia 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 innervation, such that after reaching the surface of the epithelium, they turned back and moved towards the base of the sensory cells, producing numerous synaptic contacts. Analysis of surface preparations of utricules 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 epithelium at critical stages of development and synaptogenesis suggests that it is involved in the maturation of vestibular receptors. (C) 1998 Elsevier Science B.V. All rights reserved.