Tonic firing in substantia gelatinosa neurons (Melnick et al 2004)

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Accession:62285
Ionic conductances underlying excitability in tonically firing neurons (TFNs) from substantia gelatinosa (SG) were studied by the patch-clamp method in rat spinal cord slices. ... Suppression of Ca2+ and KCA currents ... did not abolish the basic pattern of tonic firing, indicating that it was generated by voltage-gated Na+ and K+ currents. ... on the basis of present data, we created a model of TFN and showed that Na+ and KDR currents are sufficient to generate a basic pattern of tonic firing. It is concluded that the balanced contribution of all ionic conductances described here is important for generation and modulation of tonic firing in SG neurons. See paper for more and details.
Reference:
1 . Melnick IV, Santos SF, Szokol K, Szucs P, Safronov BV (2004) Ionic basis of tonic firing in spinal substantia gelatinosa neurons of rat. J Neurophysiol 91:646-55 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s):
Channel(s): I Na,t; I A; I K;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Activity Patterns;
Implementer(s): Safronov, Boris [safronov at ibmc.up.pt];
Search NeuronDB for information about:  I Na,t; I A; I K;
Readme for the models associated with the paper:

Melnick, Igor V., Sonia F. A. Santos, Karolina Szokol, Peter
Szucs, and Boris V. Safronov. Ionic basis of tonic firing in spinal
substantia gelatinosa neurons of rat. J Neurophysiol 91: 646-655,
2004.. First published October 1, 2003; First published October 1,
2003; 10.1152/jn.00883.2003. 

Abstract:
Ionic conductances underlying excitability in tonically firing neurons
(TFNs) from substantia gelatinosa (SG) were studied by the patch-clamp
method in rat spinal cord slices.  Ca2+-dependent K+ (KCA) conductance
sensitive to apamin was found to prolong the interspike intervals and
stabilize firing evoked by a sustained membrane
depolarization. Suppression of Ca2+ and KCA currents, however, did not
abolish the basic pattern of tonic firing, indicating that it was
generated by voltage-gated Na+ and K+ currents.  Na+ and K+ channels
were further analyzed in somatic nucleated patches. Na+ channels
exhibited fast activation and inactivation kinetics and followed
two-exponential time course of recovery from inactivation. The major
K+ current was carried through tetraethylammonium (TEA)-sensitive
rapidly activating delayed-rectifier (KDR) channels with a slow
inactivation. The TEA-insensitive transient A-type K+ (KA) current was
very small in patches and was strongly inactivated at resting
potential. Block of KDR rather than KA conductance by 1 mM TEA lowered
the frequency and stability of firing.  Intracellular staining with
biocytin revealed at least three morphological groups of
TFNs. Finally, on the basis of present data, we created a model of TFN
and showed that Na+ and KDR currents are sufficient to generate a
basic pattern of tonic firing. It is concluded that the balanced
contribution of all ionic conductances described here is important for
generation and modulation of tonic firing in SG neurons.

How to run model:

Auto-launch from ModelDB (if NEURON is installed)

or

download and extract archive and compile the mod files with
mknrndll (mswin or MAC), nrnivmodl (unix/linux).  Then start
with nrngui mosinit.hoc (linux) or by double clicking mosinit.hoc
(mswin)

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Once the model has started press Init&Run to generate fig 7A (left).
Click on the IClamp button and adjust the current to 0.030 nA
and press Init&Run for the middle fig 7A, and then 0.12 nA and press
Init&Run for fig 7A (right).

5/17/2017  Revised by N.T. Carnevale.  As noted by the senior author
in the readme.html file for ModelDB entry 62284 which is associated
with the paper

Melnick IV, Santos SF, Safronov BV (2004)
Mechanism of spike frequency adaptation in substantia gelatinosa
neurones of rat. J Physiol 559:383-95 

in the original implementation of this model assigning a value of 6.3 
to the parameter "celsius" corresponded to an actual operating temperature
of 23 deg C.  In this new revision of the model, the value assigned to 
celsius is identical to the operating temperature, i.e. a value of 23
means 23 deg C.  The motivation for the current revision is to facilitate 
future attributed reuse of this model and the mechanisms that it employs
by promoting conceptual clarity and making sure that this code "plays nicely"
with other models that involve temperature-dependent mechanisms.


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