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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;

	str AMPAname = "AMPA"
	float EkAMPA = 0.0
        float AMPAtau1 = 1.1e-3   //wolf with qfact of 2 taken into account (t1 and t2)
        float AMPAtau2 = 5.75e-3  
        float AMPAgmax = 0.171e-9 //0.342e-9  25%or 50% Gsyn for shindou test//593e-12 I changed this to make the NMDA/AMPA ratio more like 2.75/1 which is what Ding 2008 finds int corticalstriatal synapses
	float AMPACaper = 0 //0.001 //percent AMPA conductance that is carried by calcium. value from wolf							//more like 2/1 for thalamus so should be 0.47e-9 for thalamo-striatal syanpnse if NMDA is 0.94e-9 Rebekah Evans 6/25/10
	float AMPAdes = 1 // 1  		//desensitization factor, (depr_per_spike field of facsynchan)
	float AMPAdestau = 100e-3 // 100e-3	// desensitixation t (how fast des recovers)

        str GABAname = "GABA"
        float GABAtau1 = 0.25e-3    // From Galarreta and Hestrin 1997 
        float GABAtau2 = 3.75e-3    //(used in Wolfs model)
        float EkGABA = -0.060  		//calculated Kerr and Plenz 2004 Erev for Cl, is -60 mV 5/2/12 RCE
        float GABAgmax = 900e-12  //was 750, Sri uses 900 //Modified Koos 2004 (Wolf uses 435e-12)

	int GABA2Spine = 0                                // = 0, No GABA; 
                                                  //   1, add GABA to spine head
                                                  //   2, add GABA to spine neck
	int addCa2Spine = 1		// 0, no ca channels in spine, 
					//1, yes ca channels in spine (non-synaptic)
	int ghk_yesno=1  //0 no ghk objects for NMDA, 1 add ghk to NMDA 
			 //ghk reduction factor and hoook ups to calcium shells are in Addsynapticchannels.g

setclock 0 5e-6 //was 5e-6
        // Simulation time step (Second)       
setclock 1 2e-5        //  time step for ascii output
//setclock 1 1e-4 // time step for graphic output

// parameters for NMDA subunits

// cortex
str	    subunit = "NR2A" // A= 50e-3, ctx = 112e-3 B=300e-3 taus
float   EkNMDA   = 0
float	Kmg       = 18 //18 new //3.57 old overwrites 1/eta in nmda_channel.g
float	NMDAtau2      = {(50e-3)/2} //FAST// {(112.5e-3)/2}:	ctx avg for .25 NR2B and .75 NR2A.  (300e-3)/2 (NR2B) (50e-3)/2 (NR2A) 75+37.5 = 112.5
float	NMDAgmax   = {0.47e-9} //0.94e-9 NR2A and B from (Moyner et al., 1994 figure 7)
float   NMDAperCa = 0.00 //HIGH// 0.05: percent calcium influx 
float 	NMDAfactGHK = 35e-9 	//adjustment factor for GHK to calcium shell/pool
float   NMDACaGHK = {{NMDAperCa}*{NMDAfactGHK}}
float   NMDAdes = 0 //1  		//desensitization factor, (depr_per_spike field of facsynchan)
float   NMDAdestau = 0 //200e-3	// desensitixation t (how fast des recovers)

str NMDAname = {subunit}
str outermostshell = "Ca_difshell_1"
str dummyshell = "stupid"

//for saving info on distal or proximal dendrites or massed and spaced. formula typeof dend, # of spines.

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