Modelling reduced excitability in aged CA1 neurons as a Ca-dependent process (Markaki et al. 2005)

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Accession:119266
"We use a multi-compartmental model of a CA1 pyramidal cell to study changes in hippocampal excitability that result from aging-induced alterations in calcium-dependent membrane mechanisms. The model incorporates N- and L-type calcium channels which are respectively coupled to fast and slow afterhyperpolarization potassium channels. Model parameters are calibrated using physiological data. Computer simulations reproduce the decreased excitability of aged CA1 cells, which results from increased internal calcium accumulation, subsequently larger postburst slow afterhyperpolarization, and enhanced spike frequency adaptation. We find that aging-induced alterations in CA1 excitability can be modelled with simple coupling mechanisms that selectively link specific types of calcium channels to specific calcium-dependent potassium channels."
Reference:
1 . Markaki M, Orphanoudakis S, Poirazi P (2005) Modelling reduced excitability in aged CA1 neurons as a calcium-dependent process Neurocomputing 65-66:305-314
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: Hippocampus;
Cell Type(s): Hippocampus CA1 pyramidal GLU cell;
Channel(s): I Na,p; I Na,t; I L high threshold; I N; I A; I K; I M; I K,Ca; I R;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Activity Patterns; Aging/Alzheimer`s;
Implementer(s):
Search NeuronDB for information about:  Hippocampus CA1 pyramidal GLU cell; I Na,p; I Na,t; I L high threshold; I N; I A; I K; I M; I K,Ca; I R;
TITLE R-type calcium channel with high threshold for activation
: used in somatic and dendritic regions 
: 
:  Updated by Maria Markaki  03/12/03

NEURON {
	SUFFIX car
	USEION ca READ cai, eca WRITE ica 
        RANGE gcabar, ica, po
	GLOBAL hinf, minf
}

UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)
	(molar) = (1/liter)
	(mM) =	(millimolar)
}

PARAMETER {           :parameters that can be entered when function is called in cell-setup 
:	gcabar = 0.2e-7   (cm/s)  : initialized conductance
	gcabar = 0   (mho/cm2)  : initialized conductance
	zetam = -3.4		: HVAm Ca++ channels exhibit a fairly
	zetah = 2		: homogenous set of biophysical characteristics
	vhalfm =-21 (mV)	: but present distinctly different unitary openings
	vhalfh =-40 (mV)
	tm0=1.5(ms)
	th0=75(ms)
}



ASSIGNED {     : parameters needed to solve DE
	v            (mV)
	celsius      (degC)
	ica          (mA/cm2)
	po
	cai          (mM)       :5e-5 initial internal Ca++ concentration
	eca             (mV)
        minf
        hinf
}



STATE {	
	m 
	h 
}  

INITIAL {
	rates(v)
        m = minf
        h = hinf
}

BREAKPOINT {
	SOLVE states METHOD cnexp
	po = m*m*h
	ica = gcabar *po* (v-eca)

}


DERIVATIVE states {
	rates(v)
	m' = (minf -m)/tm0
	h'=  (hinf - h)/th0
}


PROCEDURE rates(v (mV)) { 
        LOCAL a, b
        
	a = alpm(v)
	minf = 1/(1+a)
        
        b = alph(v)
	hinf = 1/(1+b)
}



FUNCTION alpm(v(mV)) {
UNITSOFF
  alpm = exp(1.e-3*zetam*(v-vhalfm)*9.648e4/(8.315*(273.16+celsius))) 
UNITSON
}

FUNCTION alph(v(mV)) {
UNITSOFF
  alph = exp(1.e-3*zetah*(v-vhalfh)*9.648e4/(8.315*(273.16+celsius))) 
UNITSON
}


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