Distinct current modules shape cellular dynamics in model neurons (Alturki et al 2016)

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Accession:223649
" ... We hypothesized that currents are grouped into distinct modules that shape specific neuronal characteristics or signatures, such as resting potential, sub-threshold oscillations, and spiking waveforms, for several classes of neurons. For such a grouping to occur, the currents within one module should have minimal functional interference with currents belonging to other modules. This condition is satisfied if the gating functions of currents in the same module are grouped together on the voltage axis; in contrast, such functions are segregated along the voltage axis for currents belonging to different modules. We tested this hypothesis using four published example case models and found it to be valid for these classes of neurons. ..."
Reference:
1 . Alturki A, Feng F, Nair A, Guntu V, Nair SS (2016) Distinct current modules shape cellular dynamics in model neurons. Neuroscience 334:309-331 [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: Hippocampus; Amygdala;
Cell Type(s): Abstract single compartment conductance based cell;
Channel(s):
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Simplified Models; Activity Patterns; Oscillations; Methods; Olfaction;
Implementer(s):
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AlturkiEtAl2016
2_Pospischil
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cadecay_destexhe.mod *
HH_traub.mod
IL_gutnick.mod
IM_cortex.mod
IT_huguenard.mod
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demo_PY_IB.hoc *
demo_PY_IBR.hoc *
demo_PY_LTS.hoc *
demo_PY_RS.hoc *
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TITLE High threshold calcium current

COMMENT
-----------------------------------------------------------------------------
	High threshold calcium current
	------------------------------

   - Ca++ current, L type channels
   - Differential equations

   - Model from:

   Reuveni I; Friedman A; Amitai Y; Gutnick MJ.
     Stepwise repolarization from Ca2+ plateaus in neocortical pyramidal cells:
     evidence for nonhomogeneous distribution of HVA Ca2+ channels in
     dendrites.
   Journal of Neuroscience, 1993 Nov, 13(11):4609-21.

   - Experimental data for voltage-dependent activation:

   Sayer RJ; Schwindt PC; Crill WE.
     High- and low-threshold calcium currents in neurons acutely isolated from
     rat sensorimotor cortex.
   Neuroscience Letters, 1990 Dec 11, 120(2):175-8.
 
   - Experimental data for voltage-dependent inactivation:

   Dichter MA; Zona C.
     Calcium currents in cultured rat cortical neurons.
   Brain Research, 1989 Jul 17, 492(1-2):219-29.

   - Calcium-dependent inactivation was not modeled; if interested, see:

   Kay AR.
     Inactivation kinetics of calcium current of acutely dissociated CA1
     pyramidal cells of the mature guinea-pig hippocampus.
   Journal of Physiology, 1991 Jun, 437:27-48.

   - m2h kinetics from:

   Kay AR; Wong RK.
     Calcium current activation kinetics in isolated pyramidal neurones of the
     Ca1 region of the mature guinea-pig hippocampus.
   Journal of Physiology, 1987 Nov, 392:603-16.

   - Reversal potential described by Nernst equation
   - no temperature dependence included (rates correspond to 36 degC)


   Alain Destexhe, Laval University, 1996

-----------------------------------------------------------------------------
ENDCOMMENT

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

NEURON {
	SUFFIX ical
	USEION ca READ eca WRITE ica
        RANGE gcabar, alpha_m, beta_m, alpha_h, beta_h, m, h, carev, i
}


UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)
	(molar) = (1/liter)
	(mM) = (millimolar)
	FARADAY = (faraday) (coulomb)
	R = (k-mole) (joule/degC)
}


PARAMETER {
	v		(mV)
	celsius	= 36	(degC)
	eca		(mV)
	cai 	= .00024 (mM)		: initial [Ca]i = 200 nM
	cao 	= 2	(mM)		: [Ca]o = 2 mM
	gcabar	= 1e-4	(mho/cm2)	: Max conductance
}


STATE {
	m
	h
}

ASSIGNED {
	ica	(mA/cm2)		: current
	i 	(mA/cm2)		: current
	carev	(mV)			: rev potential
	alpha_m	(/ms)			: rate cst
	beta_m	(/ms)
	alpha_h	(/ms)
	beta_h	(/ms)
	tadj
}


BREAKPOINT { 
	SOLVE states METHOD cnexp : see http://www.neuron.yale.edu/phpBB/viewtopic.php?f=28&t=592
	carev = (1e3) * (R*(celsius+273.15))/(2*FARADAY) * log (cao/cai)
	ica = gcabar * m * m * h * (v-carev)
	i = ica
}

DERIVATIVE states { 
	evaluate_fct(v)

	m' = alpha_m * (1-m) - beta_m * m
	h' = alpha_h * (1-h) - beta_h * h
}


UNITSOFF

INITIAL {
	evaluate_fct(v)
:	m = alpha_m / (alpha_m + beta_m)
:	h = alpha_h / (alpha_h + beta_h)
:	tadj = 3 ^ ((celsius-36)/10)
}

PROCEDURE evaluate_fct(v(mV)) {

	: rates at 36 degC
	if (v < -60 ) {           :::::: modification starts here
	alpha_m = 0
	} else{
	alpha_m = 0.055 * (-27-v) / (exp((-27-v)/3.8) - 1)
	}                           :::::: upto here
	
	: alpha_m = 0.055 * (-27-v) / (exp((-27-v)/3.8) - 1)
	beta_m = 0.94 * exp((-75-v)/17)

	alpha_h = 0.000457 * exp((-13-v)/50)
	beta_h = 0.0065 / (exp((-15-v)/28) + 1)
}

UNITSON

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