CA1 pyramidal neuron: functional significance of axonal Kv7 channels (Shah et al. 2008)

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Accession:112546
The model used in this paper confirmed the experimental findings suggesting that axonal Kv7 channels are critically and uniquely required for determining the inherent spontaneous firing of hippocampal CA1 pyramids, independently of alterations in synaptic activity. The model predicts that the axonal Kv7 density could be 3-5 times that at the soma.
Reference:
1 . Shah MM, Migliore M, Valencia I, Cooper EC, Brown DA (2008) Functional significance of axonal Kv7 channels in hippocampal pyramidal neurons. Proc Natl Acad Sci U S A 105:7869-74 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell; Axon; Channel/Receptor;
Brain Region(s)/Organism:
Cell Type(s): Hippocampus CA1 pyramidal cell;
Channel(s): I Na,t; I T low threshold; I A; I K; I M; I Calcium;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Detailed Neuronal Models; Axonal Action Potentials; Action Potentials;
Implementer(s): Migliore, Michele [Michele.Migliore at Yale.edu];
Search NeuronDB for information about:  Hippocampus CA1 pyramidal cell; I Na,t; I T low threshold; I A; I K; I M; I Calcium;
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km
readme.html
cacumm.mod *
cagk.mod
cal2.mod
can2.mod
cat.mod *
h.mod *
kadist.mod *
KahpM95.mod *
kaprox.mod *
kdrca1.mod *
km.mod *
na3n.mod *
naxn.mod *
fig4a.hoc
fixnseg.hoc *
geo9068802.hoc *
mosinit.hoc *
screenshot.jpg
                            
TITLE n-calcium channel
: n-type calcium channel


UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)

	FARADAY = 96520 (coul)
	R = 8.3134 (joule/degC)
	KTOMV = .0853 (mV/degC)
}

PARAMETER {
	v (mV)
	celsius 		(degC)
	gcanbar=.0003 (mho/cm2)
	ki=.001 (mM)
	cai=50.e-6 (mM)
	cao = 2  (mM)
	q10=5
	mmin = 0.2
	hmin = 3
	a0m =0.055
	zetam = 2
	vhalfm = -75
	gmm=0.6	
}


NEURON {
	SUFFIX can
	USEION ca READ cai,cao WRITE ica
        RANGE gcanbar, ica, gcan       
        GLOBAL hinf,minf,taum,tauh
}

STATE {
	m h 
}

ASSIGNED {
	ica (mA/cm2)
        gcan  (mho/cm2) 
        minf
        hinf
        taum
        tauh
}

INITIAL {
        rates(v)
        m = minf
        h = hinf
}

BREAKPOINT {
	SOLVE states METHOD cnexp
	gcan = gcanbar*m*m*h*h2(cai)
	ica = gcan*ghk(v,cai,cao)

}

UNITSOFF
FUNCTION h2(cai(mM)) {
	h2 = ki/(ki+cai)
}


FUNCTION ghk(v(mV), ci(mM), co(mM)) (mV) {
        LOCAL nu,f

        f = KTF(celsius)/2
        nu = v/f
        ghk=-f*(1. - (ci/co)*exp(nu))*efun(nu)
}

FUNCTION KTF(celsius (degC)) (mV) {
        KTF = ((25./293.15)*(celsius + 273.15))
}


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

FUNCTION alph(v(mV)) {
	alph = 1.6e-4*exp(-v/48.4)
}

FUNCTION beth(v(mV)) {
	beth = 1/(exp((-v+39.0)/10.)+1.)
}

FUNCTION alpm(v(mV)) {
	alpm = 0.1967*(-1.0*v+19.88)/(exp((-1.0*v+19.88)/10.0)-1.0)
}

FUNCTION betm(v(mV)) {
	betm = 0.046*exp(-v/20.73)
}

FUNCTION alpmt(v(mV)) {
  alpmt = exp(0.0378*zetam*(v-vhalfm)) 
}

FUNCTION betmt(v(mV)) {
  betmt = exp(0.0378*zetam*gmm*(v-vhalfm)) 
}

UNITSON

DERIVATIVE states {     : exact when v held constant; integrates over dt step
        rates(v)
        m' = (minf - m)/taum
        h' = (hinf - h)/tauh
}

PROCEDURE rates(v (mV)) { :callable from hoc
        LOCAL a, b, qt
        qt=q10^((celsius-25)/10)
        a = alpm(v)
        b = 1/(a + betm(v))
        minf = a*b
	taum = betmt(v)/(qt*a0m*(1+alpmt(v)))
	if (taum<mmin/qt) {taum=mmin/qt}
        a = alph(v)
        b = 1/(a + beth(v))
        hinf = a*b
:	tauh=b/qt
	tauh= 80
	if (tauh<hmin) {tauh=hmin}
}

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