Spine neck plasticity controls postsynaptic calcium signals (Grunditz et al. 2008)

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Accession:116769
This model was set up to dissect the relative contribution of different channels to the spine calcium transients measured at single spines.
Reference:
1 . Grunditz A, Holbro N, Tian L, Zuo Y, Oertner TG (2008) Spine Neck Plasticity Controls Postsynaptic Calcium Signals through Electrical Compartmentalization J Neurosci 28(50):13457-13466 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Synapse;
Brain Region(s)/Organism:
Cell Type(s): Hippocampus CA1 pyramidal cell;
Channel(s): I Calcium; I R;
Gap Junctions:
Receptor(s): AMPA; NMDA;
Gene(s):
Transmitter(s): Glutamate;
Simulation Environment: NEURON;
Model Concept(s): Calcium dynamics;
Implementer(s): Mueller, Asa [asa.mueller at fmi.ch];
Search NeuronDB for information about:  Hippocampus CA1 pyramidal cell; AMPA; NMDA; I Calcium; I R; Glutamate;
TITLE Ca R-type channel with high threshold for activation

: HVA calcium channels are inserted in the spine head
: Activation and inactivation parameters taken from
: Foehring RC, Mermelstein PG, Song W, Ulrich S and Surmeier DJ
: Unique properities of R-type calcium currents in neucortical and neostriatal neurons
: J Neurophysiol (2000) 84: 2225 - 2236
:
: written by Lei Tian on 04/11/06 

NEURON {
	SUFFIX car
	USEION ca  WRITE ica
    RANGE gcabar, m, h, g, p, eca
	RANGE inf, fac, tau, k
	GLOBAL irtype
	EXTERNAL Area_canmda
}

UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)
}

INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

PARAMETER {	: parameters that can be entered when function is called in cell-setup
    v               (mV)
    celsius = 30	(degC)
	dt              (ms)
    gcabar = 0.351  (mho/cm2) : initialized conductance 
	eca = 10		(mV)      : Ca++ reversal potential was choosen to best fit the GHK between -40 and -10 mV	

	Area            (cm2)
	k = 1e-06		(mA/nA)

        }  

STATE {	m h }               

ASSIGNED {                  
	ica             (mA/cm2)
    inf[2]
	fac[2]
	tau[2]
	irtype
	g                       :R_type channel total conductance
	p
	
}

BREAKPOINT {
	SOLVE states
	ica = gcabar*m*m*m*h*(v - eca)
	irtype= -gcabar*m*m*m*h*(v - eca)
	g = gcabar*m*m*m*h*Area*1e6	:[uS]
	p = m*m*m*h
	}

INITIAL {
	Area = Area_canmda
    m = 0                               : initial activation parameter value
	h = 0.5                             : initial inactivation parameter value
	states()
	ica = gcabar*m*m*m*h*(v - eca)      : initial Ca++ current value
    irtype=-gcabar*m*m*m*h*(v - eca) 	: the ca current through R_type channel
	g = gcabar*m*m*m*h*Area*1e6 		:[uS]
	p = m*m*m*h
	}

PROCEDURE calcg() {
	mhn(v*1(/mV))
	m = m + fac[0]*(inf[0] - m)
	h = h + fac[1]*(inf[1] - h)
	}	

PROCEDURE states() {                    : exact when v held constant
	calcg()
	VERBATIM
	return 0;
	ENDVERBATIM
}

FUNCTION varss(v, i) {
	if (i==0) {
           varss = 1 / (1 + exp((v+14)/(-6.7)))	: Ca activation
	}
	else if (i==1) {    
        varss = 1/ (1 + exp((v+65)/(11.8)))     : Ca inactivation
	}
}

FUNCTION vartau(v, i) {
	if (i==0) {
           vartau = 3.6		: activation variable time constant 
        }
	else if (i==1) {
           vartau = 200		: inactivation variable time constant 
       }
	
}	

PROCEDURE mhn(v) {LOCAL a, b :rest = -70
:	TABLE inf, fac DEPEND dt, celsius FROM -100 TO 100 WITH 200
	FROM i=0 TO 1 {
		tau[i] = vartau(v,i)
		inf[i] = varss(v,i)
		fac[i] = (1 - exp(-dt/tau[i]))
	}
}



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