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 Kd current

COMMENT Equations from 
		  Lyle J Borg-Graham Interpretation of Data and Mechanisms for Hippocampal Pyramidal Cell Models A Chapter in "Cerebral Cortex, Volumne 13: Cortical Models" Edited by P.S.Ulinski, E.G.Jones and A.Peters,New York:plenum Press,1998
		  
		  The Krasnow Institute
		  George Mason University

Copyright	  Maciej Lazarewicz, 2001
		  (mlazarew@gmu.edu)
		  All rights reserved.
ENDCOMMENT

NEURON {
	SUFFIX kdBG
	USEION k WRITE ik
	RANGE  gbar,ik
	GLOBAL xtau, ytau, xinf, yinf
}

UNITS {
	(S)	= (siemens)
	(mA)	= (milliamp)
	(mV)	= (millivolt)
	FARADAY	= (faraday) (coulombs)
	R	= (k-mole)  (joule/degC)
}

PARAMETER {
	gbar	=   1.0e-3	(S/cm2)
	Ky	=   2.0e-4	(1/ms)
	gammay	=   0.0		(1)
	zettax	=   3.0		(1)
	zettay	=  -2.5		(1)
	vhalfx	= -63.0		(mV)
	vhalfy	= -73.0		(mV)
	taox	=   1.0		(ms)
	taoy	=   0.0		(ms)
}

ASSIGNED {
	v       (mV)
	ik     	(mA/cm2)
	celsius			(degC)
	xtau    (ms)
	ytau    (ms)
	xinf	(1)
	yinf	(1)
	q10	(1)
	T     	(K)
}

STATE { xs ys }

BREAKPOINT { 
	SOLVE states METHOD cnexp
	ik= gbar * xs^4 * ys^4 * ( v + 95.0 ) 
}

DERIVATIVE states {
	rates()
	xs'= (xinf- xs)/ xtau	
	ys'= (yinf- ys)/ ytau
}

INITIAL {
	T  = celsius + 273.15
	q10= 1.0^( (celsius-35.0) / 10.0(K) )
	rates()
	xs= xinf
	ys= yinf
}

PROCEDURE rates() { LOCAL a, b  
	a = q10*exp( (1.0e-3)*  zettax*(v-vhalfx)*FARADAY/(R*T) )
	b = q10*exp( (1.0e-3)* -zettax*(v-vhalfx)*FARADAY/(R*T) )
	xinf = a / ( a + b )
	xtau = taox

	a = q10*Ky*exp( (1.0e-3)*  zettay*     gammay *(v-vhalfy)*FARADAY/(R*T) )
	b = q10*Ky*exp( (1.0e-3)* -zettay*(1.0-gammay)*(v-vhalfy)*FARADAY/(R*T) )
	yinf = a   / ( a + b )
	ytau = 1.0 / ( a + b ) + taoy
}

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