Spike timing in pyramidal cells of the dorsal cochlear nucleus Public Deposited

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  • March 22, 2019
  • Street, Sarah Elizabeth
    • Affiliation: School of Medicine, Department of Cell Biology and Physiology
  • The cochlear nucleus is the termination point for all axons of the auditory nerve. In addition to input from the auditory nerve, the dorsal cochlear nucleus (DCN) receives input from other sensory systems. The principal neurons of the DCN, the pyramidal cells, process information from both the auditory and non-auditory inputs and relay this information to the inferior colliculus. While it is known that pyramidal cells can use spike timing to encode some auditory information such as frequency modulation, these neurons are usually described in terms of average rate. This study examines the spike timing characteristics of DCN pyramidal cells. We first investigated the spike timing characteristics of pyramidal cells by presenting the cells with Gaussian distributed white noise currents. In response to such stimuli, pyramidal cells fired trains of action potentials with precisely timed spikes. In addition, when an inhibitory event, such as an IPSP was added at the midpoint of the stimulus, the spike times became more precise after the IPSP than they were without the inhibitory event. Intrinsic conductances can shape the output of neurons. One important conductance is a transient outward current known as an A-current. A-currents arise from potassium channels such as Kv1.4, Kv3.4 and the entire Kv4 family. It has been hypothesized that an A-current leads to the build-up response pattern in pyramidal cells, which is characterized by a long latency to the first spike. Using heteropodatoxin-2, a specific blocker of Kv4 channels, we determined that Kv4 channels are responsible for the long delay to the first spike after a hyperpolarizing pre-pulse. To confirm this result, we also subtracted a model of the Acurrent using dynamic clamp and observed the same effect. Finally, the identity of this potassium current was determined using in situ hybridization and immunofluoresence. Pyramidal cells were labeled by injecting a retrograde dye into the inferior colliculus. Labeled pyramidal cells expressed Kv4.3 but not Kv4.2 potassium channels. From these results we concluded that Kv4.3 is essential for the characteristic response patterns observed in DCN pyramidal cells.
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  • In Copyright
  • Manis, Paul B.
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  • University of North Carolina at Chapel Hill
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