Slack and Slick K _Na Channels Regulate the Accuracy of Timing of Auditory Neurons

Abstract

The Slack (sequence like a calcium-activated K channel) and Slick (sequence like an intermediate conductance K channel) genes, which encode sodium-activated K ⁺ (K _Na) channels, are expressed at high levels in neurons of the medial nucleus of the trapezoid body (MNTB) in the auditory brainstem. These neurons lock their action potentials to incoming stimuli with a high degree of temporal precision. Channels with unitary properties similar to those of Slack and/or Slick channels, which are gated by [Na ⁺] _i and [Cl ⁻] _i and by changes in cytoplasmic ATP levels, are present in MNTB neurons. Manipulations of the level of K _Na current in MNTB neurons, either by increasing levels of internal Na ⁺ or by exposure to a pharmacological activator of Slack channels, significantly enhance the accuracy of timing of action potentials at high frequencies of stimulation. These findings suggest that such fidelity of timing at high frequencies may be attributed in part to high-conductance K _Na channels.