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: ntt.mod,v 1.7 2003/12/11 00:37:51 billl Exp $
TITLE Low threshold calcium current
:
:   Ca++ current responsible for low threshold spikes (LTS)
:   RETICULAR THALAMUS
:   Differential equations 
:
:   Model of Huguenard & McCormick, J Neurophysiol 68: 1373-1383, 1992.
:   The kinetics is described by standard equations (NOT GHK)
:   using a m2h format, according to the voltage-clamp data
:   (whole cell patch clamp) of Huguenard & Prince, J Neurosci.
:   12: 3804-3817, 1992.
:
:    - Kinetics adapted to fit the T-channel of reticular neuron
:    - Q10 changed to 5 and 3
:    - Time constant tau_h fitted from experimental data
:    - shift parameter for screening charge
:
:   ACTIVATION FUNCTIONS FROM EXPERIMENTS (NO CORRECTION)
:
:   Reversal potential taken from Nernst Equation
:
:   Written by Alain Destexhe, Salk Institute, Sept 18, 1992
:

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

NEURON {
	SUFFIX it2
	USEION Ca READ Cai, Cao WRITE iCa VALENCE 2
	RANGE gcabar, g, shift1
	GLOBAL m_inf, tau_m, h_inf, tau_h, shift2, sm, sh, phi_m, phi_h, hx, mx,rat
}

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

	FARADAY = (faraday) (coulomb)
	R = (k-mole) (joule/degC)
}

PARAMETER {
	v		(mV)
	celsius	= 36	(degC)
:	eCa	= 120	(mV)
	gcabar	= .024	(mho/cm2)
	shift1	= -1 	(mV)
        shift2  = -6    (mV) 
        sm      = 7.4
        sh      = 5.0
        hx      = 1.5
        mx      = 3.0
	Cai	= 5e-5 (mM)		: adjusted for eca=120 mV
	Cao	= 2	(mM)
	rat	= 1
}

STATE {
	m h
}

ASSIGNED {
	iCa	(mA/cm2)
	g       (mho/cm2)
	carev	(mV)
	m_inf
	tau_m	(ms)
	h_inf
	tau_h	(ms)
	phi_m
	phi_h
}

BREAKPOINT {
	SOLVE castate METHOD cnexp
	g = gcabar * m*m*h
	iCa = g * ghk(v, Cai, Cao)
}

DERIVATIVE castate {
	evaluate_fct(v)

	m' = (m_inf - m) / tau_m
	h' = (h_inf - h) / tau_h
}

UNITSOFF
INITIAL {
	VERBATIM
	Cai = _ion_Cai;
	Cao = _ion_Cao;
	ENDVERBATIM

:   Activation functions and kinetics were obtained from
:   Huguenard & Prince, and were at 23-25 deg.
:   Transformation to 36 deg assuming Q10 of 5 and 3 for m and h
:   (as in Coulter et al., J Physiol 414: 587, 1989)
:
	phi_m = mx ^ ((celsius-24)/10)
	phi_h = hx ^ ((celsius-24)/10)

	evaluate_fct(v)
	m = m_inf
	h = h_inf
}

PROCEDURE evaluate_fct(v(mV)) { 
:
:   Time constants were obtained from J. Huguenard
:

	m_inf = 1.0 / ( 1 + exp(-(v+shift1+50)/sm) )
	h_inf = 1.0 / ( 1 + exp((v+shift2+78)/sh) )

	tau_m = (2+1.0/(exp((v+shift1+35)/10)+exp(-(v+shift1+100)/15)))/ phi_m
	tau_h = (24.22+1.0/(exp((v+55.56)/3.24)+exp(-(v+383.56)/51.26)))/phi_h
}

FUNCTION ghk(v(mV), Ci(mM), Co(mM)) (.001 coul/cm3) {
	LOCAL z, eci, eco
	z = (1e-3)*2*FARADAY*v/(R*(celsius+273.15))
	eco = Co*efun(z)*rat
	eci = Ci*efun(-z)
	:high Cao charge moves inward
	:negative potential charge moves inward
	ghk = (.001)*2*FARADAY*(eci - eco)
}

FUNCTION efun(z) {
	if (fabs(z) < 1e-4) {
		efun = 1 - z/2
	}else{
		efun = z/(exp(z) - 1)
	}
}
UNITSON

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