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


/***************************		MS Model, Version 9.1	*********************
**************************** 	      Krp.g 	*********************
Rebekah Evans updated 3/22/12
*****************************************************************************/

function make_Krp_channel
	
	float Erev = -0.09
	int m_power = 2 //(Nisenbaum 1996 p 1187)
	int h_power = 1
	
	//table filling parameters	
    float xmin  = -0.1  
    float xmax  = 0.05  
    int  xdivsFiner = 3000
    int c = 0
    float increment =1000*{{xmax}-{xmin}}/{xdivsFiner}
    float x = -100
 


   str path = "Krp_channel" 
    create tabchannel {path} 
    call {path} TABCREATE X {xdivsFiner} {xmin} {xmax} 
	call {path} TABCREATE Y {xdivsFiner} {xmin} {xmax} 
	
//units are mV, ms
//m parameters tuned to fit Nisenbaum 1996 fig6C (minf^2) and fig 8C (mtau)
	float mA_rate = 16
	float mA_slope = 24
	
	float mB_rate = 2.4
	float mB_slope = -45

//h parameters tuned to fit Nisenbaum 1996 fig 9D (hinf, 87% inactivating) and 9B (htau)	
	float hA_rate = 0.01
	float hA_slope = -100
	
	float hB_rate = 0.4
	float hB_slope = 18
	
     for (c = 0; c < {xdivsFiner} + 1; c = c + 1)
		float m_alpha = {exp_form {mA_rate} {mA_slope} {-x}}   //notice x sign is reversed. see tabchanforms.g 
		float m_beta = {exp_form {mB_rate} {mB_slope} {-x}}

		float mtau= {1/(m_alpha+m_beta)}
		float m_inf= {m_alpha/(m_alpha+m_beta)}

		float h_alpha = {exp_form {hA_rate} {hA_slope} {-x}}   
		float h_beta = {exp_form {hB_rate} {hB_slope} {-x}}

		float htau= {(1/(h_alpha+h_beta))+2} //+2 is necessary to fit Nisenbaum fig 9B)
		float h_inf= ((0.87*{h_alpha/(h_alpha+h_beta)})+0.13) //(0.13 non-inact component from Nisenbaum fig 9D)

		//Nisenbaum 1996 does not specify recording temp, so room temp is assumed.
  		setfield {path} X_A->table[{c}] {{mtau}/{qfactorKrp}}
		setfield {path} X_B->table[{c}] {m_inf}
		setfield {path} Y_A->table[{c}] {{htau}/{qfactorKrp}}
		setfield {path} Y_B->table[{c}] {h_inf}
		
		x = x + increment
    end
   
     /* 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 
end
//************************ End Primary Routine ********************************
//*****************************************************************************


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