In vivo, in vitro and computational analysis of dendritic calcium
currents in thalamic reticular neurons
Alain Destexhe, Diego Contreras, Mircea Steriade, Terrence J. Sejnowski
and John R. Huguenard
Journal of Neuroscience 16: 169-185, 1996
Thalamic reticular (RE) neurons are involved in the genesis of synchronized
thalamocortical oscillations, which depend in part on their complex bursting
properties. We have investigated the intrinsic properties of RE cells using
computational models based on morphological and electrophysiological data.
Simulations of a reconstructed RE cell were compared directly to recordings
from the same cell to obtain precise values for the passive parameters. In a
first series of experiments, the low-threshold calcium current (IT) was
studied with voltage-clamp in acutely dissociated RE cells which lack most of
their dendrites. Simulations based on a cell with truncated dendrites and
Hodgkin-Huxley kinetics reproduced these recordings with a relatively low
density of IT. In a second series of experiments, voltage-clamp recordings
obtained in intact RE cells in slices showed a higher amplitude and slower
kinetics of IT. These properties could be reproduced from the reconstructed
cell model assuming higher densities of IT in distal dendrites. In a third
series of experiments, current-clamp recordings were obtained in RE cells
in vivo. The marked differences with in vitro recordings could
be reconciled by simulating synaptic bombardment in the dendrites of RE cells,
but only if they contained high distal densities of IT. In addition, simpler
models with as few as three compartments could reproduce the same behavior
assuming dendritic IT. These models and experiments show how intrinsic
bursting properties of RE cells, as recorded in vivo and in
vitro, may be explained by dendritic calcium currents.
Several movie files illustrate the dynamics of membrane potential in soma and
dendrites of thalamic reticular neurons. They are an excellent complement to
the figures of the paper. The somatodendritic distribution of membrane
potential is shown by colors during a burst of action potentials. In
particular, see how distal dendrites are maintained at a depolarized level,
"feeding" the soma with current during the burst.
dendritRE_full.mpg (large size movie, also contains a plot of the
membrane potential at the soma)
The original NEURON programs that served to simulate this model are also
available. They provide a useful way to learn how to design compartmental
models using NEURON.
This package creates a directory containing programs for running the
compartmental model of thalamic reticular neuron using NEURON. The
simulations reproduce some of the figures of the paper, in which all
the details are given. There are also instructions in a README
See also the book chapter A. Destexhe, D. Contreras, M.
Steriade, T.J. Sejnowski and J.R. Huguenard. Computational models constrained
by voltage-clamp data for investigating dendritic currents. In:
Computational Neuroscience , Edited by Bower, J., Academic Press, New
York, pp. 53-58, 1996.
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