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 Ca-dependent potassium current (C-current)

COMMENT
        *********************************************
        reference:      Yamada, Koch & Adams (1989) 
			Meth. in Neuronal Modeling, MIT press
        found in:       bullfrog sympathetic ganglion cells
        *********************************************
	Assembled for MyFirstNEURON by Arthur Houweling
Updated to use CVode - N-type VGCC dependent
ENDCOMMENT


NEURON {
	SUFFIX mykca
	USEION k READ ek WRITE ik
:	USEION ca READ cai
	USEION can READ cani
        RANGE gkbar, ik
	GLOBAL m_inf, tau_m
}

UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)
	(mM) = (milli/liter)
}

PARAMETER {
	gkbar= 0.00345	(mho/cm2) 
}

ASSIGNED {
	v		(mV)
	celsius		(degC)
:	cai		(mM)
	cani     	(mM)
	ek		(mV)
	ik		(mA/cm2)
	tau_m		(ms)
	m_inf
	tadj
}

STATE {
	m
}

BREAKPOINT { 
	SOLVE states METHOD cnexp
	ik = gkbar * m * (v - ek)
}

DERIVATIVE states { 
	rates(v,cani)

       m'= (m_inf-m) / tau_m
}

INITIAL {
	tadj = 3^((celsius-23.5)/(10(degC)))
	rates(v,cani)
	m = m_inf
}

PROCEDURE rates( v(mV), cai(mM)) {  LOCAL a,b
	a = 250(/mM) * cai * exp(v/(24(mV))) 
	b = 0.1 * exp(-v/(24(mV)))
	tau_m = 1(ms)/(a+b) / tadj
	m_inf = a/(a+b)
}

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