Chick cochlear efferent neurons are not immunoreactive for calcitonin gene-related peptide

The fluorescent retrograde tracer, rhodamine dextran amine, was unilaterally injected into the cochlear duct of anesthetized chicks. Retrogradely labeled cells were found bilaterally in the brainstem ventromedial to the superior olivary nucleus and to the ventral facial nucleus, and in the caudal pontine reticular formation between the dorsal facial nucleus and the abducens nerve root. Tissue sections containing retrogradely labeled cells were incubated in an antiserum to calcitonin gene-related peptide (CGRP) and a fluorescently labeled secondary antiserum. No double-labeled neurons were found, suggesting that chick cochlear efferent neurons do not contain CGRP or that levels of CGRP in these cells may be too low to be detected immunohistochemically.