Journal of Neurophysiology · 2003 · 292 citations · 55 references
K⁺ currents in ventral cochlear nucleus neurons comprise a fast transient current (IA), a slow‑inactivating low‑threshold current (ILT), and a non‑inactivating high‑threshold current (IHT). The study uses a computational model to investigate how IA, ILT, and IHT shape the discharge patterns of VCN cells. A single‑compartment soma model of VCN neurons was built using kinetic data for IA, ILT, and IHT, and incorporated a fast‑inactivating Na⁺ current, a hyperpolarization‑activated cation current (Ih), and 1–50 auditory‑nerve synapses. Simulations show that IHT primarily repolarizes the membrane during action potentials, IA modulates repetitive‑firing rate, ILT generates the phasic discharge of Type II cells and, when its strength is varied, can produce both phasic and regular patterns; Type II cells exhibit a faster membrane time constant than Type I cells, enabling precise coincidence detection, and modulation of Ih more effectively tunes ILT activation than direct ILT modulation, explaining their frequent co‑expression.
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.
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