Expression of Kv3.1b in the MNTB of normal hearing in congenitally deaf mice

Abstract

<p>The medial nucleus of the trapezoid body (MNTB) is a key brainstem relay nucleus involved in sound localization. The primary excitatory input to MNTB principal cells is formed by specialized Calyx of Held synapses, arising from axons of globular bushy cells of the of the contralateral anteroventral cochlear nucleus (AVCN). Neurons in the MNTB are topographically organized according to a tonotopic map present throughout the auditory system. Cells responding best to high frequency stimulation are located medially within the nucleus, while cells responding best to low frequency stimulation are located laterally. A variety of mechanisms underlies MNTB synaptic response properties and discharge capabilities in accordance with the tonotopic map. One such mechanism is likely to be rapidly activating K+ currents.The functions of channels containing Kv3.1 subunits have been extensively characterized throughout the central nervous system. Within the MNTB, they contribute to a rapid high voltage activating K+ current that repolarizes action potentials (APs), facilitates high frequency firing, and aids in the faithful propagation of synaptic inputs. Further, tonotopically organized expression gradients of Kv3.1b have been demonstrated in several auditory brainstem nuclei including the rat MNTB, the avian nucleus mangocellularis, and mouse spiral ganglion. That these studies show stronger Kv3.1b expression in portions of the nucleus containing neurons with high characteristic frequency (CF), suggests such expression may correspond with other specializations in higher CF neurons allowing more rapid APs and higher transmission rates. The aim of this study is to determine 1) the distribution of Kv3.1b within the MNTB of normal hearing mice and 2) using a congenitally deaf (dn/dn) mouse model that lacks auditory nerve activity throughout development, if altered neural activity causes changes in the level and or pattern of Kv3.1b expression within the MNTB.</p><p>This presentation occurred at the Wright State University Campus-Wide Celebration of Research, Scholarship and Creative Activities on April 16, 2010</p>