Simulated light response in rod photoreceptors (Liu and Kourennyi 2004)

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Accession:64228
We developed a complete computer model of the rod, which accurately reproduced the main features of the light response and allowed us to demonstrate that it was suppression of Kx channels that was essential for slowing SLR and increasing excitability of rods. The results reported in this work further establish the importance of Kx channels in rod photoreceptor function.
Reference:
1 . Liu XD, Kourennyi DE (2004) Effects of tetraethylammonium on Kx channels and simulated light response in rod photoreceptors. Ann Biomed Eng 32:1428-42 [PubMed]
Citations  Citation Browser
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:
Cell Type(s): Retina photoreceptor cone cell;
Channel(s): I Chloride; I L high threshold; I K; I h; I K,Ca; I Potassium;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Oscillations; Action Potentials; Calcium dynamics;
Implementer(s): Kourennyi, Dmitri E [dek at case.edu]; Liu, Xiaodong [xliu22 at jhmi.edu];
Search NeuronDB for information about:  Retina photoreceptor cone cell; I Chloride; I L high threshold; I K; I h; I K,Ca; I Potassium;
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Liu-Kourennyi_2004
readme.txt
Ca.mod *
Cad.mod
Clca.mod
h.mod
IinjLT.mod *
IinjLTDim.mod *
IinjSin.mod
Kca.mod
Kv.mod
Kx.mod *
Leak.mod *
0222AP_BR.ses
0222AP_DIM.ses
0222Kx_BR.ses
0222Kx_DIM.ses
Fig5_IVCompare.ses
Fig9_AP_Patterns.ses
init.hoc
mosinit.hoc *
rod.hoc
                            
: Rod  Photoreceptor Ca and Calcium  channel
: Ref. Kourenny and  Liu 2002   ABME 30 : 1196-1203
: Modification 2004-02-07
NEURON 
{
	SUFFIX Ca
	
	USEION Ca WRITE iCa VALENCE 2
        RANGE gCabar,VhalfCam,SCam
        RANGE VhalfCah,SCah
        RANGE eCa,aomCa,bomCa
        RANGE gammaohCa,deltaohCa


}

UNITS
{
	(mA) = (milliamp)
	(mV) = (millivolt)
	(mS) = (millimho)
	(mol)= (1)
	(M)  = (mol/liter)
	(uM) = (micro M)
}

PARAMETER
{
       
       : Calcium channel 
       gCabar = 2 (mS/cm2) <0,1e9> :different from ABME paper
       eCa =  40 (mV)
       aomCa = 50  (/s)  : changed from 3.10/s, 20/s
       bomCa = 50  (/s)
       gammaohCa = 1 (/s)
       deltaohCa =1 (/s)  
 
       VhalfCam=-20.0 (mV)
       VhalfCah=10 (mV)
       SCam =6.0      (mV) 
       
       SCah =9        (mV)   
     
}


STATE
{

	mCa
	hCa
	
}

ASSIGNED
{
	gCa (mho/cm2)
    
	v (mV)
	
	iCa (mA/cm2)

	infmCa
	taumCa  (ms) 
	


	infhCa
	tauhCa (ms)



}

INITIAL
{
	rate(v)
	mCa = infmCa
	hCa = infhCa

}




BREAKPOINT
{
	SOLVE states METHOD cnexp
	gCa = (0.001)*gCabar*mCa*hCa
	: g is in unit of S/cm2 ,i is in unit of mA/cm2 and v is in mV
	
	iCa = gCa*(v - eCa)
	: the current is in the unit of mA/cm2
	
	
}

DERIVATIVE states
{
	rate(v)
	mCa' = (infmCa - mCa)/taumCa
	hCa'= (infhCa-hCa)/tauhCa


}




FUNCTION alphamCa(v(mV))(/ms)
{ 
	alphamCa = 0.001*aomCa*exp( (v - VhalfCam)/(2*SCam)   )
}

FUNCTION betamCa(v(mV))(/ms)
{ 
	betamCa = 0.001*bomCa*exp( - ( v-VhalfCam)/(2*SCam) )
}
FUNCTION gammahCa(v(mV))(/ms)
{ 
	gammahCa = 0.001*gammaohCa*exp( (v - VhalfCah)/(2*SCah))
}

FUNCTION deltahCa(v(mV))(/ms)
{ 
	deltahCa = 0.001*deltaohCa*exp( - ( v-VhalfCah)/(2*SCah) )
}


PROCEDURE rate(v (mV))
{
        LOCAL a, b,c, d


	a = alphamCa(v)
	b = betamCa(v)
	taumCa = 1/(a + b)
	infmCa = a/(a + b)
	
	c = gammahCa(v)
	d = deltahCa(v)
	tauhCa = 1/(c + d)
	infhCa = d/(c + d)

}