Firing properties of GABAergic vs. non-GABAergic vestibular nucleus neurons conferred by a differential balance of potassium currents Abbreviated title: Balance of potassium currents in MVN neurons

Neural circuits are composed of diverse cell types whose firing properties reflect their intrinsic ionic currents. GABAergic and non-GABAergic neurons in the medial vestibular nuclei, identified in GIN and YFP-16 lines of transgenic mice, respectively, exhibit different firing properties in brain slices. The intrinsic ionic currents of these cell types were investigated in acutely dissociated neurons from 3-4 week-old mice, where differences in spontaneous firing and action potential parameters observed in slice preparations are preserved. Both GIN and YFP-16 neurons express a combination of four major outward currents: Ca 2+-dependent K + currents (I KCa), 1 mM TEA-sensitive delayed rectifier K + currents (I 1TEA), 10 mM TEA-sensitive delayed rectifier K + currents (I 10TEA), and A-type K + currents (I A). The balance of these currents varied across cells, with GIN neurons tending to express proportionately more I KCa and I A and YFP-16 neurons tending to express proportionately more I 1TEA and I 10TEA. Correlations in charge densities suggested that several currents were coregulated. Variations in the kinetics and density of I 1TEA could account for differences in repolarization rates observed both within and between cell types. These data indicate that diversity in the firing properties of GABAergic and non-GABAergic vestibular nucleus neurons arises from graded differences in the balance and kinetics of ionic currents.