There is compelling evidence for the involvement of the hippocampal formation in the processing and storage of information by the nervous system. Furthermore, these functions must be accomplished by the basic units of the nervous system, the neurons, along with their various synaptic interconnections. Individual pyramidal neurons in the hippocampus and entorhinal cortex are complex units of integration that dynamically change with their environment. Our long-term objective is to understand how a pyramidal neuron integrates and stores the information it receives from the tens of thousands of excitatory and inhibitory synaptic inputs impinging upon its dendritic tree. Understanding how a pyramidal neuron performs these functions will only come from knowledge about the biophysical properties of these neurons and how they respond to synaptic input. This project focuses on properties, function, and plasticity of voltage-gated ion channels expressed in pyramidal neuron dendrites in hippocampus and entorhinal cortex. During the previous funding period we investigated certain types of potassium, sodium, and inward rectifier (h) channels in dendrites of these neurons and their plasticity under several different conditions. In this renewal application we propose to continue our investigation of dendritic ion channel plasticity by focusing on the bi-directional changes in several ion channels that are highly expressed in pyramidal neuron dendrites and that occur in parallel with long-term potentiation and long-term depression. These channels are responsible for the h current, a transient outward potassium (A) current, and a persistent sodium current. We will be addressing the physiological and biochemical mechanisms underlying the plasticity of these channels and the role they play in the plasticity of intrinsic excitability of these neurons. The experiments will utilize hippocampal brain slices, dendritic patch-clamp electrophysiology, and high-speed fluorescence imaging of Ca2+ and membrane potential.

Public Health Relevance

Neuronal dendrites, and the ionic channels expressed in them, are altered in specific ways in epilepsy, Alzheimer's disease, schizophrenia, and many other neurological and psychiatric disorders. We expect that the results of our studies will provide important information about the functional significance of these disease-related changes in dendrites.

National Institute of Health (NIH)
National Institute of Mental Health (NIMH)
Research Project (R01)
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Neurobiology of Learning and Memory Study Section (LAM)
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Asanuma, Chiiko
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University of Texas Austin
Schools of Arts and Sciences
United States
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Kim, C S; Brager, D H; Johnston, D (2018) Perisomatic changes in h-channels regulate depressive behaviors following chronic unpredictable stress. Mol Psychiatry 23:892-903
Heuermann, Robert J; Jaramillo, Thomas C; Ying, Shui-Wang et al. (2016) Reduction of thalamic and cortical Ih by deletion of TRIP8b produces a mouse model of human absence epilepsy. Neurobiol Dis 85:81-92
Ashhad, Sufyan; Johnston, Daniel; Narayanan, Rishikesh (2015) Activation of InsP? receptors is sufficient for inducing graded intrinsic plasticity in rat hippocampal pyramidal neurons. J Neurophysiol 113:2002-13
Dembrow, Nikolai C; Zemelman, Boris V; Johnston, Daniel (2015) Temporal dynamics of L5 dendrites in medial prefrontal cortex regulate integration versus coincidence detection of afferent inputs. J Neurosci 35:4501-14
Edwards, John; Daniel, Eric; Kinney, Justin et al. (2014) VolRoverN: enhancing surface and volumetric reconstruction for realistic dynamical simulation of cellular and subcellular function. Neuroinformatics 12:277-89
Clemens, Ann M; Johnston, Daniel (2014) Age- and location-dependent differences in store depletion-induced h-channel plasticity in hippocampal pyramidal neurons. J Neurophysiol 111:1369-82
Vaidya, Sachin P; Johnston, Daniel (2013) Temporal synchrony and gamma-to-theta power conversion in the dendrites of CA1 pyramidal neurons. Nat Neurosci 16:1812-20
Brager, Darrin H; Lewis, Alan S; Chetkovich, Dane M et al. (2013) Short- and long-term plasticity in CA1 neurons from mice lacking h-channel auxiliary subunit TRIP8b. J Neurophysiol 110:2350-7
Routh, Brandy N; Johnston, Daniel; Brager, Darrin H (2013) Loss of functional A-type potassium channels in the dendrites of CA1 pyramidal neurons from a mouse model of fragile X syndrome. J Neurosci 33:19442-50
Dougherty, Kelly A; Nicholson, Daniel A; Diaz, Laurea et al. (2013) Differential expression of HCN subunits alters voltage-dependent gating of h-channels in CA1 pyramidal neurons from dorsal and ventral hippocampus. J Neurophysiol 109:1940-53

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