The Journal of Neurophysiology Vol. 85 No. 2 February 2001, pp. 523-538
Copyright ©2001 by the American Physiological Society

A Physiologically Based Model of Discharge Pattern Regulation by Transient K⁺ Currents in Cochlear Nucleus Pyramidal Cells

 ¹The Center for Hearing Sciences and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; and  ²Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7070

Kanold, Patrick O. and Paul B. Manis. A Physiologically Based Model of Discharge Pattern Regulation by Transient K⁺ Currents in Cochlear Nucleus Pyramidal Cells. J. Neurophysiol. 85: 523-538, 2001. Pyramidal cells in the dorsal cochlear nucleus (DCN) show three characteristic discharge patterns in response tones: pauser, buildup, and regular firing. Experimental evidence suggests that a rapidly inactivating K⁺-current (I_KIF) plays a critical role in generating these discharge patterns. To explore the role of I_KIF, we used a computational model based on the biophysical data. The model replicated the dependence of the discharge pattern on the magnitude and duration of hyperpolarizing prepulses, and I_KIF was necessary to convey this dependence. Phase-plane and perturbation analyses show that responses to depolarization are critically controlled by the amount of inactivation of I_KIF. Experimentally, half-inactivation voltage and kinetics of I_KIF show wide variability. Varying these parameters in the model revealed that half-inactivation voltage, and activation and inactivation rates, controls the voltage and time dependence of the model cell discharge. This suggests that pyramidal cells can adjust their sensitivity to different temporal patterns of inhibition and excitation by modulating the kinetics of I_KIF. Overall, I_KIF is a critical conductance controlling the excitability of DCN pyramidal cells.