LOCALIZATION OF A HIGH-THRESHOLD POTASSIUM CHANNEL IN THE RAT COCHLEAR NUCLEUS

Potassium channels play a major role in determining the pattern and fr equency of neuronal firing. In the cochlear nucleus (CN), various morp hologically defined types of neurons have different responses to a sou nd. We have previously identified one type of cloned K+ channel, terme d Kv3.1, which is highly expressed in many auditory neurons. Expressio n studies indicate that Kv3.1 channels have an unusually high threshol d for activation. In this study, we used both in situ hybridization an d immunohistochemistry to examine the expression patterns of the Kv3.1 channel in the CN. In the ventral CN, bushy cells hybridized strongly with Kv3.1 specific probes and a subpopulation of stellate/multipolar cells hybridized with Kv3.1 probes. In the dorsal CN, pyramidal and l arge multipolar/giant cells expressed Kv3.1 mRNA. Abundant Kv3.1 immun olabeling was also observed in the CN. The pattern of immunolabeling r evealed that the Kv3.1 protein is distributed along the soma, proximal dendrites, unmyelinated axons, and axon terminals of stained neurons. In the case of pyramidal and octopus cells, no immunolabeling was det ected at the somata, even though these cells expressed Kv3.1 mRNA. Com puter simulations were used to explore the functional role of the Kv3. 1 channel. The simulations indicate that Kv3.1 conductances may contri bute to repolarization of large synaptic potentials. When stimulated a t high frequencies, the presence of Kv3.1 enhances the ability of a mo del cell with some of the features of bushy cells to follow high frequ ency input with temporal precision. (C) 1997 Wiley-Liss, Inc.