Nens 220 Lecture 5 Beyond HodgkinHuxley John Huguenard

Nens 220, Lecture 5 Beyond Hodgkin-Huxley John Huguenard Stanford University

Integrating with multiple conductances u Use parallel conductance model to determine V and dynamic membrane time constant t. V

Evolution of channel gates during action potential

Repetitive firing in loligo giant axon Stein, 1967

Summary of equilibrium states and time constants for HH gates

Voltage gated channel dynamics Courtesy W Lytton

A new K current, distinct from delayed rectifier Connor & Stevens, 1971

IA is dependent on resting potential

Extraction of IA from total IK

Simulations with I-A reproduce spike trajectories

A role for IA in spike propagation? Debanne et al 1997

Differential regulation of branches Debanne et al 1997

Calcium indicator & axons

M current, a slowly-activating and inactivating current Brown and Adams, 1980

Molecular identity of M current Wang et al 1998

Antagonists of M current alter spike firing Wang et al 1998

Luthi & Mc. Cormick 1998, neural resonators

Parallel conductance model, Hodgkin and Huxley

Thalamic relay neurons have state dependent firing modes Mc. Carley, Benoit & Barrionuevo, J. Neurophysiol, 50: 798, 1983. Hirsch, Fourment & Marc, Brain Res. 259: 308, 1983

Properties of the low threshold spike Llinás and Jahnsen, Nature 297: 406

Paradoxical excitability in thalamic relay neurons

T channels, Low Threshold Spikes (LTSs), and bursts Action potential (High-threshold Na+ spike) Low-threshold Ca 2+ spike Regular Firing Burst Firing Huguenard, JR TINS 21: 451 -452, 1998

b Vm – 55 m. V Vm – 75 m. V

Availability of T channels

T type calcium channel genes in thalamus

Different burst morphologies in thalamic neurons: channel gating cannot completely account for differences e. g. , VB

IT has slow kinetics in n. Rt cells: ITs

The H current (aka the q current): Hyperpolarization induced depolarization Mc. Cormick & Pape, J Physiol 1990 431: 291

The H current, slow kinetics Mc. Cormick & Pape, J Physiol 1990 431: 291

The H current, activation via hyperpolarization Mc. Cormick & Pape, J Physiol 1990 431: 291

The H current, susceptible to neuromodulation Mc. Cormick & Pape, J Physiol 1990 431: 3191

The H current, highly expressed in dendrites of principal (excitatory) cortical neurons Magee 1998 J Neurosci 18: 7613