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

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"... 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. …"
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;
Simulation Environment: GENESIS;
Model Concept(s): Oscillations; STDP; Calcium dynamics;
Implementer(s): Evans, Rebekah [Rebekah.Evans at];
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;
BK.g *
CaT.g *
gaba_channel.g *
KaF.g *
KaFnew.g *
Kir.g *
NaF.g *
NaFslowinact.g *
SK.g *
tabchanforms.g *

/***************************		MS Model, Version 9.1	*********************
**************************** 	    	KaS.g 			*********************
	Rebekah Evans update 3/22/12

function make_KAs_channel
   //include tabchanforms
  //initial parameters for making tab channel
	float Erev = -0.09
	int m_power = 2  //shen et al., 2004 p 1341
   int h_power = 1
//Activation constants for alphas and betas Shen et al., 2004 fig 3B (minf^2) and 3D (mtau)
	float mA_rate = 0.25 
	float mA_vhalf = 54   
	float mA_slope = -22  
	float mB_rate = 0.05 
	float mB_vhalf = -100  
	float mB_slope = 35
//Inactivation constants for alphas and betas tuned to fit Shen et al., 2004 fig 6B (Inact) hinf and htau.  
	float hA_rate = 2.5 
	float hA_vhalf = -95
	float hA_slope = 16
	float hB_rate = 2 
	float hB_vhalf = 50
	float hB_slope = -70
	//table filling parameters	
    float xmin  = -0.1  /* minimum voltage we will see in the simulation */ 
    float xmax  = 0.05  /* maximum voltage we will see in the simulation */ 
    int  xdivsFiner = 3000 /* the number of divisions between -0.1 and 0.05 */
    int c = 0
    float increment = 1000*{{xmax}-{xmin}}/{xdivsFiner}

    float x = -100
	float m_alpha, m_beta, h_alpha, h_beta
    /* make the table for the activation with a range of -100mV - +50mV
     * with an entry for every 10mV
    str path = "KAs_channel" 
    create tabchannel {path} 
    call {path} TABCREATE X {xdivsFiner} {xmin} {xmax} 
    call {path} TABCREATE Y {xdivsFiner} {xmin} {xmax} 
    /*fills the tabchannel with values for minf, mtau, hinf and htau,
     *from the files.

echo "make kA, qfactor=" {qfactorkAs}	
    for (c = 0; c < {xdivsFiner} + 1; c = c + 1)
		float m_alpha = {sig_form {mA_rate} {mA_vhalf} {mA_slope} {x}}
		float m_beta = {sig_form {mB_rate} {mB_vhalf} {mB_slope} {x}}
		float h_alpha = {sig_form {hA_rate} {hA_vhalf} {hA_slope} {x}}
		float h_beta = {sig_form {hB_rate} {hB_vhalf} {hB_slope} {x}}
		float xa = {1/{{m_alpha}+{m_beta}}}
		float xb = {{m_alpha}/{{m_alpha}+{m_beta}}}
		float ya = {1/{{h_alpha}+{h_beta}}}
		float yb = {{{{h_alpha}/{{h_alpha}+{h_beta}}}*0.8}+0.2}
		//the *0.8+0.2 in yb is to make the channel partially inactivate.  Shen et al., 2004 fig 6B
		// Tables are filled with inf and taus in order to make this channel partially inactivate.
		setfield {path} X_A->table[{c}] {(xa*1e-3)/qfactorkAs}
		setfield {path} X_B->table[{c}] {xb}
		setfield {path} Y_A->table[{c}] {ya/qfactorkAs}
        setfield {path} Y_B->table[{c}] {yb}
		x = x + increment
    /* Defines the powers of m and h in the Hodgkin-Huxley equation*/
    setfield {path} Ek {Erev} Xpower {m_power} Ypower {h_power} 
    tweaktau {path} X 
    tweaktau {path} Y 


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