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	*********************
**************************** 	      BK.g 	*********************
Rebekah Evans updated 3/22/12


function make_BK_channel
    float EK=-0.09  
    float K1=0.003
    float K4=0.009
	//tuned to fit Berkefeld et al., 2006 fig 3C for 10uM Ca, with positive shift for 1uM Ca and negative shift for 100uM Ca. 
    int xdivs = 299
    int ydivs = {xdivs}
    float xmin, xmax, ymin, ymax
    xmin = -0.1; xmax = 0.05; ymin = 0.0; ymax = 0.005 // x = Vm, y = [Ca],mM
    int i, j
    float x, dx, y, dy, a, b
    float Temp = 35
    float ZFbyRT = 23210/(273.15 + Temp)
    if (!({exists BK_channel}))
        create tab2Dchannel BK_channel
        setfield BK_channel Ek {EK} Gbar 0.0  \
            Xindex {VOLT_C1_INDEX} Xpower 1 Ypower 0 Zpower 0
        call BK_channel TABCREATE X {xdivs} {xmin} {xmax} \
            {ydivs} {ymin} {ymax}
    dx = (xmax - xmin)/xdivs
    dy = (ymax - ymin)/ydivs
    x = xmin
    for (i = 0; i <= xdivs; i = i + 1)
        y = ymin
        for (j = 0; j <= ydivs; j = j + 1)
            a = 480*y/(y + {K1}*{exp {-0.84*ZFbyRT*x}}) 
            b = 280/(1 + y/({K4}*{exp {-1.00*ZFbyRT*x}}))
            setfield BK_channel X_A->table[{i}][{j}] {a}
            setfield BK_channel X_B->table[{i}][{j}] {a + b}
            y = y + dy
        x = x + dx
    setfield BK_channel X_A->calc_mode {LIN_INTERP}
    setfield BK_channel X_B->calc_mode {LIN_INTERP}
	//the tau curve that comes out of this is comparable (but not an exact fit) to Berkefeld 2006 figure 4A 10uM, if a qfact of 3 is applied to their figure.  
	//recordings in Berkefeld were at 22-24 degrees (supporting online material)

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