T channel currents (Vitko et al 2005)

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Accession:53965
Computer simulations predict that seven of the SNPs would increase firing of neurons, with three of them inducing oscillations at similar frequencises. 3 representative models from the paper have been submited: a wild-type (WT) recombinant Cav3.2 T-channel, and two of the mutants described in the Vitko et al., 2005 paper (C456S and R788C). See the paper for more and details.
Reference:
1 . Vitko I, Chen Y, Arias JM, Shen Y, Wu XR, Perez-Reyes E (2005) Functional characterization and neuronal modeling of the effects of childhood absence epilepsy variants of CACNA1H, a T-type calcium channel. J Neurosci 25:4844-55 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Channel/Receptor;
Brain Region(s)/Organism:
Cell Type(s):
Channel(s): I T low threshold;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Ion Channel Kinetics; Epilepsy;
Implementer(s):
Search NeuronDB for information about:  I T low threshold;
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zippedModels
Cav32_C456S
cells
README *
capump.mod *
HH2.mod *
IT2.mod
VClamp.mod *
c45601.jpg
c45602.jpg
El.oc *
leak.oc *
loc3.oc *
loc80.oc *
locD.oc *
mosinit.hoc *
re1_cc.oc *
re3_cc.oc *
re3_vc.oc *
re80_cc.oc *
re80_vc.oc *
reD_cc.oc *
reD_vc.oc *
rundemo.hoc *
                            
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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