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  H-current that uses Na ions

:  Updated to use CVode - Carl Gold  08/10/03
:  Updated by Maria Markaki  03/12/03

NEURON {
	SUFFIX h
	USEION na READ ena WRITE ina      
        RANGE  gbar,vhalf, K, taun, ninf,ina
:	NONSPECIFIC_CURRENT i
}

UNITS {
	(um) = (micrometer)
	(mA) = (milliamp)
	(uA) = (microamp)
	(mV) = (millivolt)
}

PARAMETER {              : parameters that can be entered when function is called in cell-setup
        eh     = -10   (mV)
	K      = 8.5   (mV)
	gbar   = 0     (mho/cm2)  : initialize conductance to zero
	vhalf  = -90   (mV)       : half potential
}	

ASSIGNED {             : parameters needed to solve DE
	v              (mV)
        ena            (mV)
	ina            (mA/cm2)
	ninf
	taun           (ms)
}

STATE {                : the unknown parameters to be solved in the DEs
	n
} 


INITIAL {               : initialize the following parameter using states()
	states()	
	n = ninf
}


BREAKPOINT {
	SOLVE states METHOD cnexp
	ina = gbar*n*(v-eh)            
}

DERIVATIVE states {
	rates(v)
        n' = (ninf - n)/taun
}

PROCEDURE rates(v (mV)) {  
 
 	if (v > -30) {
	   taun = 1(ms)
	} else {
           taun = 2(ms)*(1/(exp((v+145)/-17.5(mV))+exp((v+16.8)/16.5(mV))) + 5) :h activation tau

	}  
         ninf = 1 - (1 / (1 + exp((vhalf - v)/K)))                  :steady state value
}




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