DISTRIBUTION OF CALBINDIN D-28K IMMUNOREACTIVITY IN THE COCHLEAR NUCLEUS OF THE YOUNG-ADULT CHINCHILLA

Calbindin is a 28 kD calcium-binding protein found in neural tissue. A lthough its functional role in nerve cell physiological processing is still uncertain, previous investigations have suggested that because o f its intracellular calcium buffering and regulation properties, it co uld influence temporal precision of neuronal firing to subserve tempor al processing in the auditory brainstem, or could mediate monaural ver sus binaural coding, or be involved in synaptic plasticity (learning). The present study demonstrates differential calbindin immunoreactivit y in the cochlear nuclear complex of the chinchilla, a rodent with exc eptionally good low-frequency hearing. The most intense labeling in th e cochlear nucleus was in somata of cartwheel and fusiform cells of th e fusiform cell layer, and somata and processes of the molecular layer of the dorsal cochlear nucleus (DCN). Only a relatively few scattered neurons were stained in the deep layers of DCN. In contrast, moderate labeling of neurons and neuropil throughout the ventral cochlear nucl eus was seen. For instance, moderately stained spherical and elongate cells of the anteroventral cochlear nucleus were observed in contact w ith labeled puncta and amidst stained fibers. In the cochlear nerve ro ot region, stained auditory nerve fibers and globular cells were noted . In the posteroventral cochlear nucleus, principal cells of elongate and octopus shape were observed, in contact with labeled swellings and surrounded by labeled neuropil.