Low Threshold Calcium Currents in TC cells (Destexhe et al 1998)

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Accession:279
In Destexhe, Neubig, Ulrich, and Huguenard (1998) experiments and models examine low threshold calcium current's (IT, or T-current) distribution in thalamocortical (TC) cells. Multicompartmental modeling supports the hypothesis that IT currents have a density at least several fold higher in the dendrites than the soma. The IT current contributes significantly to rebound bursts and is thought to have important network behavior consequences. See the paper for details. See also http://cns.iaf.cnrs-gif.fr Correspondance may be addressed to Alain Destexhe: Destexhe@iaf.cnrs-gif.fr
Reference:
1 . Destexhe A, Neubig M, Ulrich D, Huguenard J (1998) Dendritic low-threshold calcium currents in thalamic relay cells. J Neurosci 18:3574-88 [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): Thalamus geniculate nucleus/lateral principal neuron;
Channel(s): I Na,t; I T low threshold; I K;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Dendritic Action Potentials; Bursting; Ion Channel Kinetics; Parameter Fitting; Simplified Models; Influence of Dendritic Geometry; Detailed Neuronal Models; Calcium dynamics; Rebound firing;
Implementer(s): Destexhe, Alain [Destexhe at iaf.cnrs-gif.fr];
Search NeuronDB for information about:  Thalamus geniculate nucleus/lateral principal neuron; I Na,t; I T low threshold; I K;
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dendtc
cells
README
cadecay.mod *
hh2.mod *
ITGHK.mod *
VClamp.mod *
El.oc *
loc200.oc
loc3.oc *
locD.oc
mosinit.hoc *
rundemo.hoc
tc1_cc.oc
tc200_cc.oc
tc200_vc.oc
tc3_cc.oc
tcD_vc.oc
                            
TITLE svclmp.mod

COMMENT

Single electrode Voltage clamp with three levels
------------------------------------------------

Series Resistance added; backards compatible, except parameters 
e0,vo0,vi0,gain,rstim,tau1,tau2 that no longer exist

Clamp is on at time 0, and off at time dur[0]+dur[1]+dur[2]. When clamp is off
the injected current is 0.  The clamp levels are amp[0], amp[1], amp[2].  i is
the injected current, vc measures the control voltage) Do not insert several
instances of this model at the same location in order to make level changes.
That is equivalent to independent clamps and they will have incompatible
internal state values.

The electrical circuit for the clamp is exceedingly simple:

        rs           Rin
vc ---'\/\/`---o---'\/\/`---o
               |            |
               |____| |_____|
                    | |
                     Cm

Note that since this is an electrode current model v refers to the internal
potential which is equivalent to the membrane potential v when there is no
extracellular membrane mechanism present but is v+vext when one is present. 
Also since i is an electrode current, positive values of i depolarize the
cell. (Normally, positive membrane currents are outward and thus hyperpolarize
the cell)

ENDCOMMENT

INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

DEFINE NSTEP 3

NEURON {
        POINT_PROCESS SEVClamp
        ELECTRODE_CURRENT i
        RANGE dur, amp, rs, vc, i
}

UNITS {
        (nA) = (nanoamp)
        (mV) = (millivolt)
        (uS) = (micromho)
}


PARAMETER {
        v (mV)
        rs = 1 (megohm)		: series resistance
}

ASSIGNED {
        i (nA)
        vc (mV)
        ic (nA)
        tc2 (ms)
        tc3 (ms)
	dur[NSTEP] (ms)
	amp[NSTEP] (mV)
        on
}

INITIAL {
        tc2 = dur[0] + dur[1]
        tc3 = tc2 + dur[2]
        on = 0
}

BREAKPOINT {
        SOLVE vstim
        if (on) {
                i = (vc - v)/rs
        }else{
                i = 0
        }
}

PROCEDURE vstim() {
        on = 1
        if (t < dur[0]) {
                vc = amp[0]
        }else if (t < tc2) {
                vc = amp[1]
        }else if (t < tc3) {
                vc = amp[2]
        }else {
                vc = 0
                on = 0
        }
        if (on) {
        }else{
                ic = 0
        }
        VERBATIM
        return 0;
        ENDVERBATIM
}

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