Periodicity in Na channel properties alters model neuron excitability (Majumdar and Sikdar 2007)

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"... We have shown earlier that the duration and amplitude of a prolonged depolarization alter all the steady state and kinetic parameters of rNav1.2a voltage gated Na channel in a pseudo-oscillatory fashion. In the present study, we show that the Hodgkin–Huxley voltage and time dependent rate constants of activation (am and bm) and fast inactivation (ah and bh), obtained from the analyses of Na currents and steady state activation and inactivation plots, following application of prepulses in both slow (1–100 s) and fast (100–1000 ms) ranges, vary with the duration of a prepulse in a pseudo-oscillatory manner. ..."
1 . Majumdar S, Sikdar SK (2007) Periodicity in Na+ channel properties alters excitability of a model neuron Biochem Biophys Res Commun.
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 K;
Gap Junctions:
Simulation Environment: GENESIS;
Model Concept(s): Ion Channel Kinetics; Epilepsy;
Search NeuronDB for information about:  I Na,t; I K;
// genesis

/* This channel is the Rat Brain type IIA sodium channel modeled as a tab 
channel. The activation and inactivation parameters have been determined for 
these channels in the CHO surrogate system in which the alpha subunit of the 
channel has been heterologously expressed. 

The channel parameters are modeled to m^3h kind of model. The slow inactivation
parameter has to be added to it. 

Model implemented by Sriparna Majumdar, MBU, IISc, '2002 */

include constants.g
//		 Voltage gated Sodium (Na) Channel from Rat Brain 

function make_Na_rat_sm  // Na current
str compartment 
float EREST = -.080 // resting membrane potl.
float ENa = 0.125 + EREST   //reversal potential (V)
float SOMA_A = 2.827e-9 //sq. m

//checking if the channel already exists

if ({exists Na_rat_sm})

// creating the tab channel object

create tabchannel Na_rat_sm
setfield Na_rat_sm Ek {ENa} Gbar {7000.0*SOMA_A} Ik 0 Gk 0 \
Xpower 3 Ypower 1 Zpower 0

//call Na_rat_sm TABCREATE X  40 -0.130 0.070
//setfield Na_rat_sm \
//X_A {file2tab X_A table -skiplines 1}
//X_B {file2tab X_B table -skiplines 1}

//call Na_rat_sm TABCREATE Y 40 -0.130 0.070

//setfield Na_rat_sm \
//Y_A {file2tab Y_A table -skiplines 1}
//Y_B {file2tab Y_B table -skiplines 1}

//alpha for the control data
//setupalpha Na_rat_sm X \
//{0.1705e6*(0.06766+EREST)} -0.1705e6 -1.0 {-1.0*(0.06766+EREST)} \
//-0.0049368 \  //Alpha table
//0.626e3 0.0 0.0 {-1.0*(0.07783+EREST)} 0.02837 //Beta table 

//beta for the control
setupalpha Na_rat_sm Y \  //control data
0.0041e3 0.0 0.0 {-1.0*(0.1189+EREST)} 0.03798 \ //Alpha table
1.411e3 0.0 1.0 {-1.0*(0.07337+EREST)} -0.009042  //Beta table


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