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;
//genesis

/***************************		MS Model, Version 9.4	**********************
**************************** 	     AddSynapticChannels.g 	**********************

******************************************************************************/


function addNMDAchannel(compPath, chanpath,caBuffer, gbar, ghk)

  str compPath, chanpath
  float gbar
  str caBuffer 
  int ghk

  copy /library/{chanpath} {compPath}/{chanpath}
  addmsg {compPath} {compPath}/{chanpath}/block VOLTAGE Vm
  addmsg {compPath} {compPath}/{chanpath} VOLTAGE Vm
  addmsg {compPath}/{chanpath}/block {compPath} CHANNEL Gk Ek
  

  if (ghk==1)
    addmsg {compPath} {compPath}/{chanpath}/GHK VOLTAGE Vm
  end

  // Set the new conductance
  float len = {getfield {compPath} len}
  float dia = {getfield {compPath} dia}
  float pi = 3.141592653589793
  float surf = {len*dia*pi}

/*
    echo "XXXXXXXXXXXXXXX addNMDAchannel XXXXXXXXXXXXXXXX"
	echo "compPath = "{compPath}
	echo "chanpath = "{chanpath}
	echo "caBuffer = "{caBuffer}
	echo "gbar = "{gbar}
	echo "NMDACaGHK=" {NMDACaGHK}
	echo "XXXXXXXXXXXXXXX addNMDAchannel XXXXXXXXXXXXXXXX"
*/

  setfield {compPath}/{chanpath} gmax {gbar}



//while the block object always controls the voltage, either the block object or the ghk object controls the calcium. 
//ghk_yesno set in SynParams.g
// adds NMDA to Ca buffer in difshell or concen 
	if (ghk==0)
		if ({isa difshell  {compPath}/{caBuffer}} )         // dif_shell 
	 		addmsg {compPath}/{chanpath}/block {compPath}/{caBuffer} FINFLUX Ik {NMDAperCa}  //set in SynParams.g
		elif ({isa Ca_concen {compPath}/{caBuffer}})      // Ca_conc
			addmsg {compPath}/{chanpath}/block {compPath}/{caBuffer} fI_Ca Ik {NMDAperCa}
		end
	elif (ghk==1)
		if ({isa difshell  {compPath}/{caBuffer}})         // dif_shell 
	 		addmsg {compPath}/{chanpath}/GHK {compPath}/{caBuffer} FINFLUX Ik {NMDACaGHK}  //set in SynParams.g
			addmsg {compPath}/{caBuffer} {compPath}/{chanpath}/GHK CIN C
		elif ({isa Ca_concen {compPath}/{caBuffer}})      // Ca_conc
			addmsg {compPath}/{chanpath}/GHK {compPath}/{caBuffer} fI_Ca Ik {NMDACaGHK}  //0.35e-8 is necessary because GHK reads in Gk from block and interprets it as permeability.  this results in calcium that is ridiculous. a factor of e-9 reduces calcium back to normal levels. 
			addmsg {compPath}/{caBuffer} {compPath}/{chanpath}/GHK CIN Ca
		end
	end

end


function addSynChannel (compPath, chanpath, gbar, caBuffer)

  str compPath, chanpath, caBuffer
  float gbar

  copy /library/{chanpath} {compPath}/{chanpath}

  addmsg {compPath} {compPath}/{chanpath} VOLTAGE Vm
  addmsg {compPath}/{chanpath} {compPath} CHANNEL Gk Ek

  // Set the new conductance
  float len = {getfield {compPath} len}
  float dia = {getfield {compPath} dia}
  float pi = 3.141592653589793
  float surf = {len*dia*pi}

/*	echo "XXXXXXXXXXXXXXX addSynChannel XXXXXXXXXXXXXXXX"
	echo "compPath = "{compPath}
	echo "chanpath = "{chanpath}
	echo "gbar = "{gbar}
	echo "XXXXXXXXXXXXXXX addSynchannel XXXXXXXXXXXXXXXX"
*/

//  setfield {compPath}/{chanName} gmax {surf*gbar}
  setfield {compPath}/{chanpath} gmax {gbar}
  
  if ({chanpath} == "AMPA")
	if ({NMDABufferMode == 1} && {isa difshell {compPath}/{caBuffer}}) 
		//echo spine calcium model is difshell
		addmsg {compPath}/{chanpath} {compPath}/{caBuffer} FINFLUX Ik {AMPACaper}
	end
  end
end
 
 

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