Dendritic low-threshold calcium currents in thalamic relay cells
Alain Destexhe, Mike Neubig, Daniel Ulrich and John R. Huguenard
Journal of Neuroscience 18: 3574-3588, 1998
The low-threshold calcium current (I_T) underlies burst generation in
thalamocortical (TC) relay cells and plays a central role in the genesis of
synchronized oscillations by thalamic circuits. We have here combined in
vitro recordings and computational modeling techniques in order to
investigate the consequences of dendritically-located I_T in TC cells.
Simulations of a reconstructed TC cell were compared to the recordings obtained
in the same cell in order to constrain the values of its passive parameters.
T-current densities in soma and proximal dendrites were then estimated by
matching the model to voltage-clamp recordings obtained in dissociated TC cells,
which lack most of the dendrites. The distal dendritic T-current density was
constrained by recordings in intact TC cells, which show 5-14 times larger peak
T-current amplitudes compared to dissociated cells. Comparison of the model to
the recordings of the same cell constrained further the T-current density in
dendrites, which had to be 4.5-7.6 times higher than in the soma to reproduce all
experimental results. Similar conclusions were reached using a simplified
3-compartment model. Functionally, the model shows that the same amount of
T-channels can lead to different bursting behaviors if they are exclusively
somatic or distributed throughout the dendrites. In conclusion, this combination
of models and experiments shows that dendritic T-currents are necessary to
reproduce low-threshold calcium electrogenesis in TC cells. Dendritic T-current
may also have significant functional consequences, such as an efficient
modulation of thalamic burst discharges by corticothalamic feedback.
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 Neubig M, Ulrich D,
Huguenard JR and Destexhe A. Dendritic calcium currents in thalamic relay
cells. In: Computational Neuroscience. Trends in Research (edited
by J. Bower), Plenum Press, New York, pp. 233-238, 1998.
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