Tonotopic Differentiation of Coupling between Ca(2+) and Kv1.1 Expression in Brainstem Auditory Circuit

Tonotopic differentiations of ion channels ensure sound processing across frequencies. Afferent input plays a critical role in differentiations. We demonstrate here in organotypic culture of chicken cochlear nucleus that expression of Kv1.1 was coupled with Ca(2+) to a different degree depending on tonotopic regions, thereby differentiating the level of expression within the nucleus. In the culture, Kv1.1 was down-regulated and not differentiated tonotopically. Chronic depolarization increased Kv1.1 expression in a level-dependent manner. Moreover, the dependence was steeper at higher-frequency regions, which restored the differentiation. The depolarization increased Kv1.1 via activation of Cav1 channels, whereas basal Ca(2+) level elevated similarly irrespective of tonotopic regions. Thus, the efficiency of Ca(2+)-dependent Kv1.1 expression would be fine-tuned in a tonotopic-region-specific manner, emphasizing the importance of neuronal tonotopic identity as well as pattern of afferent input in the tonotopic differentiation of the channel in the auditory circuit.