DISTRIBUTION OF THE CALCIUM-BINDING PROTEINS PARVALBUMIN AND CALRETININ IN THE AUDITORY BRAIN-STEM OF ADULT AND DEVELOPING RATS

Parvalbumin (PV), calretinin (CR), and calbindin (CB) are calcium-bind ing proteins which are presumably involved in the regulation of the in tracellular calcium concentration. Within the rat auditory system, CB is transiently expressed in several nuclei during the period of synaps e refinement, indicating a specific function of CB during development, yet little is known in this regard about PV and CR. In order to gathe r more information about calcium-binding proteins during development, we analyzed the spatiotemporal distribution of PV and CR in the rat au ditory brainstem using immunocytochemistry. In the adult, PV was heavi ly present in somata and neuropil of all nuclei and in fibers of all t racts. CR was found in somata of the cochlear nucleus and peripheral a spects of the inferior colliculus as well as in fibers extending into the superior olivary complex and the nuclei of the lateral lemniscus. The developmental expression of PV was characterized by a relatively l ate appearance in somata (at postnatal day 8), followed by a rapid inc rease to adult levels. In contrast, CR immunoreactivity was already st rong two days before birth, yet the number and intensity of labeled ne urons subsequently decreased and CR disappeared almost completely in t he superior olivary complex, nuclei of the lateral lemniscus, and cent ral aspects of the inferior colliculus. These data, together with thos e on CB, show that CR, CB, and PV are sequentially expressed during au ditory brainstem development. They also suggest that the presence of t he three proteins can be correlated with definite developmental stages . (C) 1996 Wiley-Liss, Inc.