Calcium influx during striatal upstates (Evans et al. 2013)

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Accession:150912
"... To investigate the mechanisms that underlie the relationship between calcium and AP timing, we have developed a realistic biophysical model of a medium spiny neuron (MSN). ... Using this model, we found that either the slow inactivation of dendritic sodium channels (NaSI) or the calcium inactivation of voltage-gated calcium channels (CDI) can cause high calcium corresponding to early APs and lower calcium corresponding to later APs. We found that only CDI can account for the experimental observation that sensitivity to AP timing is dependent on NMDA receptors. Additional simulations demonstrated a mechanism by which MSNs can dynamically modulate their sensitivity to AP timing and show that sensitivity to specifically timed pre- and postsynaptic pairings (as in spike timing-dependent plasticity protocols) is altered by the timing of the pairing within the upstate. …"
Reference:
1 . Evans RC, Maniar YM, Blackwell KT (2013) Dynamic modulation of spike timing-dependent calcium influx during corticostriatal upstates. J Neurophysiol 110:1631-45 [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: Striatum;
Cell Type(s): Neostriatum medium spiny direct pathway GABA cell;
Channel(s): I Na,t; I L high threshold; I N; I A; I K; I K,Ca; I A, slow; I Krp; I R;
Gap Junctions:
Receptor(s): AMPA; NMDA; Gaba;
Gene(s): Cav1.3 CACNA1D; Cav1.2 CACNA1C; Cav2.2 CACNA1B;
Transmitter(s):
Simulation Environment: GENESIS;
Model Concept(s): Oscillations; STDP; Calcium dynamics;
Implementer(s): Evans, Rebekah [Rebekah.Evans at nih.gov];
Search NeuronDB for information about:  Neostriatum medium spiny direct pathway GABA cell; AMPA; NMDA; Gaba; I Na,t; I L high threshold; I N; I A; I K; I K,Ca; I A, slow; I Krp; I R;
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EvansEtAl2013
MScell
channels
ampa_channel.g
BK.g *
CaL12CDI.g
CaL13CDI.g
CaN.g
CaNCDI.g
CaR.g
CaRCDI.g
CaT.g *
gaba_channel.g *
KaF.g *
KaFnew.g *
KaS.g
Kir.g *
Krp.g
NaF.g *
NaFslowinact.g *
nmda_channel.g
SK.g *
synaptic_channel.g
tabchanforms.g *
                            
//genesis

/***************************		MS Model, Version 9.1	*********************
**************************** 	    	CaL13channel.g 		*********************
Rebekah Evans updated 3/20/12	
******************************************************************************
******************************************************************************/


function create_CaL13
	str chanName = "CaL13_channel"
	str compPath = "/library"
	int c, a
	float Ek = 0.140  //(nernst calculated for 35degrees, [Cain] 50nM [Caout]2mM)
			//Ek is overwritten the the GHK object if it is used. 
	float xmin = -0.1
	float xmax = 0.05
	int 	xdivs = 3000
	float mPower = 1.0   //mh is an equally common form to m2h (tuckwell 2012)
	float hPower = 1.0
	if (calciuminact == 1)
		float zpower = 1.0
	else
		float zpower = 0
	end	
	
        float increment ={{xmax}-{xmin}}/{xdivs}
        echo "CaL13 increment:" {increment} "V"
	float x = -0.1
  	float surf = 0
 	float gMax = 0

	float hTauCaL13 	= 44.3e-3
	float mTauCaL13 	= 0.0
	float mvHalfCaL13 = -40.0e-3
	float mkCaL13     = -5e-3
	float hvHalfCaL13 = -37e-3
	float hkCaL13     = 5e-3
	float hInfCaL13	= 0.0
	float mInfCaL13	= 0.0

	//parameters for calcium-dep inactivation (CDI) 
	
	float Ca = 0.0
	float CaMax = 0.005 //5uM
	float CaMin = 0 
	float CaDivs = 3000
	float CaIncrement ={{CaMax}-{CaMin}}/{CaDivs}
        echo "CDIincrement:" {CaIncrement} 


	float theta	= 0.0
	float beta	= 0.0
	float beta_exp	= 0.0
	float mA = 0.0
	float mB = 0.0
	float qFactCaL13 = {qfactCa}
	
	pushe {compPath}

	create tabchannel {chanName}
  	setfield {chanName} Ek {Ek} Xpower {mPower} Ypower {hPower} Zpower {zpower}
	call {chanName} TABCREATE X {xdivs} {xmin} {xmax}
        call {chanName} TABCREATE Y {xdivs} {xmin} {xmax}
		
//fill in the voltage act and inact tables

	for(c = 0; c < {xdivs} + 1; c = c + 1)
		/************************ Begin CaL13_mTau *********************/
		//mA = 39800*(vMemb + 67.24e-3)./(exp((vMemb + 67.24e-3)/15.005e-3) - 1);
		//mB = 3500*exp(vMemb/31.4e-3);
		//mTauCaL13 = 1./(mA + mB) / qFactCaL13;
		//parameters tuned to fit Tuckwell 2012 figure 12

		theta = 39800*{ {x} + 67.24e-3}
		beta = {{x} + 67.24e-3}/15.005e-3
		beta_exp = {exp {beta}}
		beta_exp = beta_exp - 1.0
		mA = {{theta}/{beta_exp}}
		
		beta = {{x}/31.4e-3}
		beta_exp = {exp {beta}} 
		mB = 3500*{beta_exp}

		mTauCaL13 = {{1/{mA + mB}}/{qFactCaL13}}	
		setfield {chanName} X_A->table[{c}] {mTauCaL13}
		/************************ End CaL13_mTau ***********************/		

		/************************ Begin CaL13_mInf *********************/
		// mInfCaL13   = 1./(1 + exp((vMemb - mvHalfCaL13)/mkCaL13));
		//parameters tuned to fit Tuckwell 2012 figure 3
		beta = {{x} - {mvHalfCaL13}}/{mkCaL13}
		beta_exp = {exp {beta}} + 1.0
		mInfCaL13 = 1.0/{beta_exp}
		setfield {chanName} X_B->table[{c}] {mInfCaL13}
		/************************ End CaL12_mInf ***********************/	

		/************************ Begin CaL13_hTau *********************/
		// hTauCaL13 
		setfield {chanName} Y_A->table[{c}] {{hTauCaL13}/{qFactCaL13}}
		/************************ End CaL12_hTau ***********************/

		/************************ Begin CaL13_hInf *********************/
		// hInfCaL13   = 1./(1 + exp((vMemb - hvHalfCaL13)/hkCaL13));
		//parameters tuned to fit Tuckwell 2012 figure 12
		beta = {{x} - {hvHalfCaL13}}/{hkCaL13}
		beta_exp = {exp {beta}} + 1.0
		hInfCaL13 = 1.0/{beta_exp}
		setfield {chanName} Y_B->table[{c}] {hInfCaL13}
		/************************ End CaL13_hInf ***********************/	
   	x = x + increment
	end	

	tweaktau {chanName} X
	tweaktau {chanName} Y

//fill in the Z table with CDI values
//equation from Tuckwell review paper 2012 progress in neurobiology table A1.3 
	if (calciuminact == 1)
		
		call {chanName} TABCREATE Z {CaDivs} {CaMin} {CaMax}
	
		int a
		float CDI
		float q, k, b, n
		for(a = 0; a < {CaDivs} + 1; a = a + 1)
			//f= (0.001/(0.001+[Ca]))Poirazi CA1  2003
			//f= (0.0005/(0.0005+[Ca])) Rhodes and Llinas 2001 Cort Pyr
			Ca=a*{CaIncrement}
			k=0.0005
			b={pow {k} 3}
			n={pow {Ca} 3}
			q = {{b}/({b}+{n})}
			CDI = {pow {q} 100}
			setfield {chanName} Z_B->table[{a}] {CDI}
			setfield {chanName} Z_A->table[{a}] {{142e-3}/{cdiqfact}} //CaL1.2 in HEK cells Barrett and Tsien 2007 roomtemp
		end	
		tweaktau {chanName} Z 
	end	

	create ghk {chanName}GHK

  	setfield {chanName}GHK Cout 2 // Carter & Sabatini 2004 uses 2mM, 
											
  	setfield {chanName}GHK valency 2.0
  	setfield {chanName}GHK T {TEMPERATURE}
	
  	setfield {chanName} Gbar {gMax*surf}
  	addmsg {chanName} {chanName}GHK PERMEABILITY Gk	
  	pope
end

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