The Roles Potassium Currents Play in Regulating the Electrical Activity of Ventral Cochlear Nucleus Neurons

Abstract

Using kinetic data from three different K+currents in acutely isolated neurons, a single electrical compartment representing the soma of a ventral cochlear nucleus (VCN) neuron was created. The K+currents include a fast transient current ( I A), a slow-inactivating low-threshold current ( I LT), and a noninactivating high-threshold current ( I HT). The model also includes a fast-inactivating Na+current, a hyperpolarization-activated cation current ( I h), and 1–50 auditory nerve synapses. With this model, the role I A, I LT, and I HT play in shaping the discharge patterns of VCN cells is explored. Simulation results indicate that I HT mainly functions to repolarize the membrane during an action potential, and I A functions to modulate the rate of repetitive firing. I LT is found to be responsible for the phasic discharge pattern observed in Type II cells (bushy cells). However, by adjusting the strength of I LT, both phasic and regular discharge patterns are observed, demonstrating that a critical level of I LT is necessary to produce the Type II response. Simulated Type II cells have a significantly faster membrane time constant in comparison to Type I cells (stellate cells) and are therefore better suited to preserve temporal information in their auditory nerve inputs by acting as precise coincidence detectors and having a short refractory period. Finally, we demonstrate that modulation of I h, which changes the resting membrane potential, is a more effective means of modulating the activation level of I LT than simply modulating I LT itself. This result may explain why I LT and I h are often coexpressed throughout the nervous system.