The subcellular distribution of T-type Ca2+ channels in LGN interneurons (Allken et al. 2014)

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Accession:156039
" ...To study the relationship between the (Ca2+ channel) T-distribution and several (LGN interneuron) IN response properties, we here run a series of simulations where we vary the T-distribution in a multicompartmental IN model with a realistic morphology. We find that the somatic response to somatic current injection is facilitated by a high T-channel density in the soma-region. Conversely, a high T-channel density in the distal dendritic region is found to facilitate dendritic signalling in both the outward direction (increases the response in distal dendrites to somatic input) and the inward direction (the soma responds stronger to distal synaptic input). ..."
Reference:
1 . Allken V, Chepkoech JL, Einevoll GT, Halnes G (2014) The subcellular distribution of T-type Ca2+ channels in interneurons of the lateral geniculate nucleus. PLoS One 9:e107780 [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): Thalamus lateral geniculate nucleus interneuron;
Channel(s): I L high threshold; I T low threshold; I h; I K,Ca; I CAN; I_AHP;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Dendritic Action Potentials; Active Dendrites; Conductance distributions;
Implementer(s): Allken, Vaneeda [vaneeda at gmail.com];
Search NeuronDB for information about:  I L high threshold; I T low threshold; I h; I K,Ca; I CAN; I_AHP;
TITLE Slow Ca-dependent cation current
:
:   Ca++ dependent nonspecific cation current ICAN
:   Differential equations
:
:   This file was taken the study of Zhu et al.: Neuroscience 91, 1445-1460, 1999,
:   where kinetics were based on Partridge & Swandulla, TINS 11: 69-72, 1988

:   Modified by Geir Halnes, Norwegian University of Life Sciences, June 2011
:   (using only 1 of the two calcium pools applied by Zhu et al. 99)


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

NEURON {
	SUFFIX ican
	USEION other WRITE iother VALENCE 1
	USEION Ca READ Cai VALENCE 2
      RANGE gbar, i, g
	GLOBAL m_inf, tau_m, beta, cac, taumin, erev, x
}


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


PARAMETER {
	v		(mV)
	celsius	= 36	(degC)
	erev = 10	(mV)
	Cai 	= .00005	(mM)	: initial [Ca]i = 50 nM
	gbar	= 1e-5	(mho/cm2)
	beta = 0.003 
	cac	= 1.1e-4	(mM)		: middle point of activation fct
	taumin = 0.1	(ms)		: minimal value of time constant
	x = 8
}


STATE {
	m
}

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

	tadj = 3.0 ^ ((celsius-22.0)/10)
	evaluate_fct(v,Cai)
	m = m_inf
}

ASSIGNED {
	i	(mA/cm2)
	iother	(mA/cm2)
	g       (mho/cm2)
	m_inf
	tau_m	(ms)
	tadj
}

BREAKPOINT { 
	SOLVE states METHOD cnexp
	g = gbar * m*m
	i = g * (v - erev)
	iother = i
}

DERIVATIVE states { 
	evaluate_fct(v,Cai)
	m' = (m_inf - m) / tau_m
}

UNITSOFF

PROCEDURE evaluate_fct(v(mV),Cai(mM)) {  LOCAL alpha
	alpha = beta * (Cai/cac)^x
	tau_m = 1 / (alpha + beta) / tadj
	m_inf = alpha / (alpha + beta)
      if(tau_m < taumin) { tau_m = taumin } 	: min value of time cst
}
UNITSON

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