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Mechanisms Underlying Subthreshold and Suprathreshold Responses in Dorsal Cochlear Nucleus Cartwheel Cells

Tong, Mingjie
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1133806721

Abstract Details

2005, Doctor of Philosophy, University of Toledo, Bioengineering.
Cartwheel cells (CWCs) are a group of interneurons in the dorsal cochlear nucleus (DCN). Unlike other DCN neurons, which respond to stimuli with simple spikes, or trains of individual action potentials, CWCs respond to suprathreshold stimuli with complex spikes, rapid bursts of action potentials superimposed on a slow depolarization, or a combination of simple and complex spikes. In vitro whole-cell current clamp recordings from young rats (P11 – P15) show that CWCs respond to brief suprathreshold stimuli with complex spikes or simple spikes followed by afterdepolarizations (ADPs); and to subthreshold stimuli with subthreshold depolarizations (SDPs). Although complex spikesand ADPs are produced by Ca2+ currents, SDPs are unaffected by Ca2+ current antagonists but are substantially depressed by the Na+ channel antagonist TTX. Voltage clamp recordings reveal that SDPs are produced by a persistent Na+ current activating below spike threshold in CWCs. A hyperpolarization-activated inward current (Ih) is shown to contribute to the repolarization of SDPs; and voltage-gated K+ currents, including transient and Ca2+-activated K+ currents contribute to the repolarization of suprathreshold responses in CWCs. Computational simulations demonstrated that SDPs are produced by persistent Na+ currents; furthermore, these currents are required for the activation of high-threshold Ca2+ channels during suprathreshold responses to produce complex spikes in response to brief suprathreshold stimuli. Delayed-rectifier, transient and Ca2+-activated K+ currents contribute to the repolarization of complex spikes and increase of maximal conductances in any of three K+ currents converts complex spikes into simple spikes. In contrast, removal of the hyperpolarization-activated inward current Ih increases the amplitude and duration of SDPs, but otherwise has little effect on suprathreshold responses of CWCs. These results demonstrate that a combination of voltage-gated conductances that activate over a range of subthreshold and suprathreshold membrane potentials contribute to the unique electrophysiologic responses of CWCs.
Scott Molitor (Advisor)
150 p.
Engineering, Biomedical
DCN; cartwheel; SDP; complex spiking; whole cell; persistent sodium

Recommended Citations

Citations

  • Tong, M. (2005). Mechanisms Underlying Subthreshold and Suprathreshold Responses in Dorsal Cochlear Nucleus Cartwheel Cells [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1133806721

    APA Style (7th edition)

  • Tong, Mingjie. Mechanisms Underlying Subthreshold and Suprathreshold Responses in Dorsal Cochlear Nucleus Cartwheel Cells. 2005. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1133806721.

    MLA Style (8th edition)

  • Tong, Mingjie. "Mechanisms Underlying Subthreshold and Suprathreshold Responses in Dorsal Cochlear Nucleus Cartwheel Cells." Doctoral dissertation, University of Toledo, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1133806721

    Chicago Manual of Style (17th edition)

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© 2005, all rights reserved.
This open access ETD is published by University of Toledo and OhioLINK.