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
//nmda_channel.g

function make_NMDA_channel (chanpath, Ek, KMg, tau2, gmax, ghk, depr, deprtau)

  str chanpath //what you want the channel to be called (full path)
  float KMg, tau2, gmax  //parameters that differ between NR2A, B, C and D subunits
  float depr
  float deprtau
  float Ek
  int ghk 
  
  float tau1 =  (4.4624e-3)/2 //(5.63e-3)/8 //(4.4624e-3)/2 //  DE Chapman et al 2003, table 1 (5.63ms: wolf) w/qfact of 2 
			     //is (4.4624e-3)/2 in Evans et al., 2012
  float CMg = 1.4  // [Mg] in mM //Kerr and Plenz uses 1.4mM Mg

  float eta = 1/18  // Kmg = 1/eta, (per mM) overwritten by synparams, 3.57 old, 18 new
  float gamma = 99  //99 new //62 old  // per Volt

	echo "XXXXXXXXXXXXXXX make_NMDA_channel XXXXXXXXXXXXXXXX"
	echo "chanpath = "{chanpath}
	echo "caBuffer = "{Ek}
	echo "KMg = "{KMg}
	echo "tau2 = "{tau2}
	echo "gmax = "{gmax}
	echo "XXXXXXXXXXXXXXX make_NMDA_channel XXXXXXXXXXXXXXXX"

	create facsynchan {chanpath}
	setfield {chanpath} \
          Ek   {Ek}   \
          tau1 {tau1} \
          tau2 {tau2} \
          gmax {gmax}  \
	  depr_per_spike {depr}\
	  depr_tau {deprtau}				//why was this gmax/2?? changed back 4/15/12 RCE is overwritten by addNMDAchannel function, so I don't think it matters.
   
//the kinetics of the magnesium block is different for different subunits.  
// NR2A and B are about the same, but C and D are much less affected by the block.  
//these numbers were used because the made the magnesium block curve fit the figures by Moyner et al (1994 figure 7) best by eye.

  create Mg_block {chanpath}/block
  setfield {chanpath}/block CMg {CMg} 
  setfield {chanpath}/block KMg_B {1.0/{gamma}}
  setfield {chanpath}/block KMg_A {KMg}
				
  addmsg {chanpath} {chanpath}/block CHANNEL Gk Ek

  if (ghk==1)  //GHK_yesno is set in Synparams.g
     create ghk {chanpath}/GHK
     setfield {chanpath}/GHK Cout 2 // Carter & Sabatini 2004 uses 2mM, Wolf 5mM
     setfield {chanpath}/GHK valency 2.0
     setfield {chanpath}/GHK T {TEMPERATURE}
     addmsg {chanpath}/block {chanpath}/GHK PERMEABILITY Gk 
  end

end


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