Nens220, Lecture 5 Beyond HodgkinHuxley

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Nens220, Lecture 5 Beyond Hodgkin-Huxley

• John Huguenard
• Stanford University

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Integrating with multiple conductances

• Use parallel conductance model to determine V?
  and dynamic membrane time constant tV

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Evolution of channel gates during action
potential
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Repetitive firing in loligo giant axon
Stein, 1967
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Summary of equilibrium states and time constants
for HH gates
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Voltage gated channel dynamics
Courtesy W Lytton
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A new K current, distinct from delayed rectifier
Connor Stevens, 1971
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IA is dependent on resting potential
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Extraction of IA from total IK
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Simulations with I-A reproduce spike trajectories
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A role for IA in spike propagation?
Debanne et al 1997
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Differential regulation of branches
Debanne et al 1997
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Calcium indicator axons
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M current, a slowly-activating and inactivating
current
Brown and Adams, 1980
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Molecular identity of M current
Wang et al 1998
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Antagonists of M current alter spike firing
Wang et al 1998
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Luthi McCormick 1998, neural resonators
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Parallel conductance model, Hodgkin and Huxley
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Thalamic relay neurons have state dependent
firing modes
McCarley, Benoit Barrionuevo, J. Neurophysiol,
50798, 1983. Hirsch, Fourment Marc, Brain Res.
259308, 1983
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Properties of the low threshold spike
Llinás and Jahnsen, Nature 297406
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Paradoxical excitability in thalamic relay neurons
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T channels, Low Threshold Spikes (LTSs), and
bursts
Action potential (High-threshold Na spike)
Low-threshold Ca2 spike
Regular Firing
Burst Firing
Huguenard, JR TINS 21451-452, 1998
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b
Vm 55 mV
Vm 75 mV
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Availability of T channels
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T type calcium channel genes in thalamus
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Different burst morphologies in thalamic neurons
channel gating cannot completely account for
differences
e.g., VB
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IT has slow kinetics in nRt cells ITs
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The H current (aka the q current)
Hyperpolarization induced depolarization
McCormick Pape, J Physiol 1990 431291
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The H current, slow kinetics
McCormick Pape, J Physiol 1990 431291
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The H current, activation via hyperpolarization
McCormick Pape, J Physiol 1990 431291
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The H current, susceptible to neuromodulation
McCormick Pape, J Physiol 1990 4313191
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The H current, highly expressed in dendrites of
principal (excitatory) cortical neurons
Magee 1998 J Neurosci 187613