Medial vestibular neuron models (Quadroni and Knopfel 1994)

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Accession:53876
The structure and the parameters of the model cells were chosen to reproduce the responses of type A and type B MVNns as described in electrophysiological recordings. The emergence of oscillatory firing under these two specific experimental conditions is consistent with electrophysiological recordings not used during construction of the model. We, therefore, suggest that these models have a high predictive value.
Reference:
1 . Quadroni R, Knöpfel T (1994) Compartmental models of type A and type B guinea pig medial vestibular neurons. J Neurophysiol 72:1911-24 [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): Vestibular neuron;
Channel(s): I Na,p; I Na,t; I L high threshold; I T low threshold; I A; I K; I h;
Gap Junctions:
Receptor(s): NMDA;
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Oscillations; Action Potentials; Calcium dynamics;
Implementer(s): Morse, Tom [Tom.Morse at Yale.edu];
Search NeuronDB for information about:  NMDA; I Na,p; I Na,t; I L high threshold; I T low threshold; I A; I K; I h;
COMMENT
This T-type calcium current was originally reported in Wang XJ et al 1991
This file supplies a version of this current identical to Quadroni and Knopfel 1994
except for gbar and Erev (see notes below).
ENDCOMMENT

NEURON {
	SUFFIX lva
	: NONSPECIFIC_CURRENT i
	USEION ca WRITE  ica
	RANGE Erev,g, gbar, i
	RANGE k, tee, alpha_1, alpha_2
}

UNITS {
	(S)	=	(siemens)
	(mV)	=	(millivolt)
	(mA)	=	(milliamp)
}

PARAMETER {
	gbar = 166e-6	(S/cm2) < 0, 1e9 > : Quadroni and Knopfel use 166e-6
					   : Wang et al used 0.4e-3
	Erev = 80 (mV)	: orig from Wang XJ et al 1991 was 120
			: Quadroni and Knopfel 1994 table 1 use 80 instead
}

ASSIGNED {
	ica (mA/cm2)
	i (mA/cm2)
	v (mV)
	g (S/cm2)
	k
	tee	: parameter "t" in Quadroni and Knopfel 1994 table 1
	alpha_1	: parameter used for both alpha1 and beta1
	alpha_2	: parameter used for both alpha2 and beta2
}

STATE {	m h d }

BREAKPOINT {
	SOLVE states METHOD cnexp
	g = gbar * m^3 * h
	ica = g * (v - Erev)
	i = ica	: used only to display the value of the current (section.i_lva(0.5))
}

INITIAL {
	LOCAL C, E
	: assume that v has been constant for a long time
	: (derivable from rate equations in DERIVATIVE block at equilibrium)
	rates(v)
	m = alpham(v)/(alpham(v) + betam(v))
	: h and d are intertwined so more complex than above equilib state for m
	C =  beta1(v) /  alpha1(v)
	E =  alpha2(v) /  beta2(v)
	h = E / (E * C + E + C)
	d = 1 - (1 + C) * h
}

DERIVATIVE states{ 
	rates(v)
	m' = alpham(v) * (1 - m) - betam(v) * m
	h' = alpha1(v) * (1 - h - d) - beta1(v) * h
	d' =  beta2(v) * (1 - h - d) - alpha2(v) * d
}

FUNCTION alpham(Vm (mV)) (/ms) {
	UNITSOFF
	alpham = 3.3 /(1.7 + exp(-(Vm + 28.8)/13.5))
	UNITSON
}

FUNCTION betam(Vm (mV)) (/ms) {
	UNITSOFF
	betam =  3.3 * exp(-(Vm + 63)/7.8)/(1.7 + exp(-(Vm + 28.8)/13.5))
	UNITSON
}

FUNCTION alpha1(Vm (mV)) (/ms) {
	UNITSOFF
	alpha1 = alpha_1
	UNITSON
}

FUNCTION beta1(Vm (mV)) (/ms) {
	UNITSOFF
	beta1 =  k * alpha_1
	UNITSON
}

FUNCTION alpha2(Vm (mV)) (/ms) {
	UNITSOFF
	alpha2 = alpha_2
	UNITSON
}

FUNCTION beta2(Vm (mV)) (/ms) {
	UNITSOFF
	beta2 =  k * alpha_2
	UNITSON
}

PROCEDURE rates(Vm(mV)) {
	k = (0.25 + exp((Vm + 83.5)/6.3))^0.5 - 0.5
	tee = 240.0 / (1 + exp((Vm + 37.4)/30))
	alpha_1 = 2.5 / (tee*(1 + k))	: defined since used in alpha1 and beta1
	alpha_2 = 2.5 * exp(-(Vm + 160.3)/17.8)
}

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