The roles potassium currents play in regulating the electrical activity of ventral cochlear nucleus neurons

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.