Thalamic interneuron multicompartment model (Zhu et al. 1999)

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Accession:116862
This is an attempt to recreate a set of simulations originally performed in 1994 under NEURON version 3 and last tested in 1999. When I ran it now it did not behave exactly the same as previously which I suspect is due to some minor mod file changes on my side rather than due to any differences among versions. After playing around with the parameters a little bit I was able to get something that looks generally like a physiological trace in J Neurophysiol, 81:702--711, 1999, fig. 8b top trace. This sad preface is simply offered in order to encourage anyone who is interested in this model to make and post fixes. I'm happy to help out. Simulation by JJ Zhu To run nrnivmodl nrngui.hoc
References:
1 . Zhu JJ, Uhlrich DJ, Lytton WW (1999) Burst firing in identified rat geniculate interneurons. Neuroscience 91:1445-60 [PubMed]
2 . Zhu JJ, Lytton WW, Xue JT, Uhlrich DJ (1999) An intrinsic oscillation in interneurons of the rat lateral geniculate nucleus. J Neurophysiol 81:702-11 [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: Thalamus;
Cell Type(s):
Channel(s): I Na,t; I L high threshold; I T low threshold; I K,leak; I h; I K,Ca; I CAN;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Bursting; Oscillations;
Implementer(s): Zhu, J. Julius [jjzhu at virginia.edu];
Search NeuronDB for information about:  I Na,t; I L high threshold; I T low threshold; I K,leak; I h; I K,Ca; I CAN;
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b09jan13
readme.html
AMPA.mod
cadecay.mod
clampex.mod *
cp.mod *
cp2.mod *
GABAA.mod
GABAB.mod
HH2.mod *
Iahp.mod *
Ican.mod *
Ih.mod *
IL.mod
IL3.mod *
IT.mod *
IT2.mod *
kdr2.mod *
kleak.mod *
kmbg.mod
naf2.mod *
nap.mod *
NMDA.mod
nthh.mod *
ntIh.mod *
ntleak.mod
ntt.mod *
pregencv.mod
vecst.mod
batch_.hoc
bg_cvode.inc
misc.h
mosinit.hoc *
netcon.inc
screenshot.jpg
                            
: $Id: Iahp.mod,v 1.8 2000/01/05 19:55:19 billl Exp $
TITLE Slow Ca-dependent potassium current
:
:   Ca++ dependent K+ current IC responsible for slow AHP
:   Differential equations
:
:   Model of Destexhe, 1992.  Based on a first order kinetic scheme
:      <closed> + n cai <-> <open>	(alpha,beta)
:   Following this model, the activation fct will be half-activated at 
:   a concentration of Cai = (beta/alpha)^(1/n) = cac (parameter)
:   The mod file is here written for the case n=2 (2 binding sites)
:   ---------------------------------------------
:
:   This current models the "slow" IK[Ca] (IAHP): 
:      - potassium current
:      - activated by intracellular calcium
:      - NOT voltage dependent
:
:   A minimal value for the time constant has been added
:
:   Written by Alain Destexhe, Salk Institute, Nov 3, 1992
:

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

NEURON {
	SUFFIX iahp
	USEION k2 WRITE ik2 VALENCE 1
	USEION Ca READ Cai VALENCE 2
	USEION ca READ cai
        RANGE gkbar, i, g, ratc, ratC, minf, taum
	GLOBAL beta, cac, m_inf, tau_m, x
}


UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)
	(molar) = (1/liter)
	(mM) = (millimolar)
}


PARAMETER {
	v		(mV)
	celsius	= 36	(degC)
	erev = -95		(mV)
	Cai 	= 5e-5	(mM)		: initial [Ca]i = 50 nM
	cai 	= 5e-5	(mM)		: initial [Ca]i = 50 nM
	gkbar	= .001	(mho/cm2)
	beta	= 2.5	(1/ms)		: backward rate constant
	cac	= 1e-4	(mM)		: middle point of activation fct
	taumin	= 1	(ms)		: minimal value of the time cst
        ratc    = 0
        ratC    = 0
        x       = 2
}


STATE {
	m
}
ASSIGNED {
	ik2 	(mA/cm2)
	i	(mA/cm2)
	g       (mho/cm2)
	m_inf
	tau_m	(ms)
	minf
        taum
	tadj
}

BREAKPOINT { 
	SOLVE states METHOD cnexp
        minf=m_inf
        taum=tau_m
	g = gkbar * m*m
	i = g * (v - erev)
	ik2  = i
}

DERIVATIVE states { 
	evaluate_fct(v,Cai,cai)

	m' = (m_inf - m) / tau_m
}

UNITSOFF
INITIAL {
:
:  activation kinetics are assumed to be at 22 deg. C
:  Q10 is assumed to be 3
:
	VERBATIM
	cai = _ion_cai;
	Cai = _ion_Cai;
	ENDVERBATIM

	tadj = 3 ^ ((celsius-22.0)/10)

	evaluate_fct(v,Cai,cai)
	m = m_inf
        minf=m_inf
        taum=tau_m
}

PROCEDURE evaluate_fct(v(mV),Cai(mM), cai(mM)) {  LOCAL car, tcar

        tcar = ratC*Cai + ratc*cai
	car = (tcar/cac)^x

	m_inf = car / ( 1 + car )
	tau_m = 1 / beta / (1 + car) / tadj

        if(tau_m < taumin) { tau_m = taumin } 	: min value of time cst
}
UNITSON

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