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

• Published in: Journal of neurophysiology 2003-06, Vol.89 (6), p.3097-3113
• Main Authors: Rothman, Jason S, Manis, Paul B
• Format: Article
• Language: English
• Subjects: Action Potentials; Animals; Brain Stem - physiology; Cell Culture Techniques; Cochlear Nucleus - physiology; Guinea Pigs; Membrane Potentials; Models, Biological; Nerve Net - physiology; Neurons - physiology; Patch-Clamp Techniques; Potassium Channels - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00127.2002

The Center for Hearing Science, 1 Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; and 2 Department of Otolaryngology/Head and Neck Surgery, and The Curriculum in Neurobiology, University of North Carolina, Chapel Hill, North Carolina 27599 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. Address for reprint requests: Paul B. Manis, Dept. Otolaryngology/Head and Neck Surgery, 1123 Bioinformatics Bldg., CB#7070, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7070 (E-mail: pmanis{at}med.unc.edu ).