Central projections of the lagena (the third otolith endorgan of the inner ear) in the pigeon

Abstract

Central projections of the lagena were studied in the pigeon using transport of biotinylated dextran amine (BDA) that was locally applied to the lagenar epithelium through the opened cochlear canal. Descending (dorsocaudal part) and superior (middle part) vestibular nuclei were the main rhombencephalon structures with the maximum density of labeled fibers and terminals. Lesser numbers of labeled fibers were observed in the ventral part of the lateral vestibular nucleus and also in the medial vestibular nucleus; single labeled fibers were found in the cochlear nuclei. In the cases where BDA diffused not only in the lagena but also on the basilar papilla after application of the marker to the cochlear canal, considerable numbers of labeled fibers were observed in the cochlear nuclei; apart from this, the pattern of distribution of labeled fibers in the vestibular nuclei did not differ in general from that described above (in the case of a sufficiently local application of BDA only to the lagena). Efferent lagenar neurons were localized ventrally with respect to the vestibular nuclei, in particular in the nucl. reticularis pontis caudalis.