Ontogeny of calcitonin gene-related peptide in the organ of Corti of the rat.

The ontogeny of calcitonin gene-related peptide (CGRP)-like immunoreactive (CGRPI) fibers in the rat cochlea was examined using immunocytochemistry. It was found that the CGRPI cochlear system developed markedly in the postnatal period; CGRPI fibers first appeared in the inner spiral bundle at postnatal day 8, then at the base of the outer hair cells, tunnel spiral bundle and tunnel radial fibers at postnatal day 19. The ontogenetical profile elucidated by this study suggests that CGRP has a role as a neuromodulator or neurotransmitter in this system.