Excitation Properties of Computational Models of Unmyelinated Peripheral Axons (Pelot et al., 2020)

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Accession:266498
We implemented the single-compartment model of vagal afferents from Schild et al. 1994 and extended the model into a multi-compartment axon, presenting the first C-fiber cable model of a C-fiber vagal afferent. We also implemented the updated parameters from Schild and Kunze 1997. We compared the responses of these novel models to three published models of unmyelinated axons (Rattay and Aberham 1993; Sundt et al. 2015; Tigerholm et al. 2014).
Reference:
1 . Pelot N (2020) Excitation Properties of Computational Models of Unmyelinated Peripheral Axons J Neurophysiology (accepted)
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Simulation Environment: NEURON; Brian 2; MATLAB;
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PelotEtAl_JNP_2020_Models
MultiCompartmentModels
Mod
BK.mod
caext.mod *
caextscale.mod
caint.mod *
CaIntraCellDyn.mod *
caintscale.mod *
cal.mod *
can.mod *
CaPump.mod *
cat.mod *
CaV12.mod
CaV22.mod
DNav18.mod
extrapump.mod
fpump.mod *
h.mod
HCN.mod
im.mod *
k_ion_dynamics.mod
ka.mod *
KA14.mod
KA34.mod
KCa.mod
KCaNT.mod
kd.mod *
kdr.mod *
kdr_Tiger.mod
kdrNT.mod
kds.mod *
kext.mod
kexternal.mod *
kf.mod
KM.mod
kna.mod
ks.mod
KV21.mod
leak.mod
leakSchild.mod *
na_ion_dynamics.mod
NaCaPump.mod *
NaCX.mod
nadifl.mod *
naext.mod
naf.mod *
naf97.mod
naf97mean.mod *
nahh.mod
Nakpump.mod
NakpumpSchild.mod *
nas.mod *
nas97.mod
nas97mean.mod *
nattxs.mod
nav1p9.mod
RattayAberham.mod
SK.mod
                            
TITLE decay of internal calcium concentration
:
: Internal calcium concentration due to calcium currents and pump.
: Differential equations.
:
: Simple model of ATPase pump with 3 kinetic constants (Destexhe 92)
:     Cai + P <-> CaP -> Cao + P  (k1,k2,k3)
: A Michaelis-Menten approximation is assumed, which reduces the complexity
: of the system to 2 parameters: 
:       kt = <tot enzyme concentration> * k3  -> TIME CONSTANT OF THE PUMP
:	kd = k2/k1 (dissociation constant)    -> EQUILIBRIUM CALCIUM VALUE
: The values of these parameters are chosen assuming a high affinity of 
: the pump to calcium and a low transport capacity (cfr. Blaustein, 
: TINS, 11: 438, 1988, and references therein).  
:
: Units checked using "modlunit" -> factor 10000 needed in ca entry
:
: VERSION OF PUMP + DECAY (decay can be viewed as simplified buffering)
:
: All variables are range variables
:
:
: This mechanism was published in:  Destexhe, A. Babloyantz, A. and 
: Sejnowski, TJ.  Ionic mechanisms for intrinsic slow oscillations in
: thalamic relay neurons. Biophys. J. 65: 1538-1552, 1993)
:
: Written by Alain Destexhe, Salk Institute, Nov 12, 1992
:
: "The normal resting [Ca2+]i lies in the range of 30 to 200 nM 
: in living cells." (Hille 2001)
: Parameter changes by Paulo Aguiar and Mafalda Sousa, IBMC, May 2008
: pauloaguiar@fc.up.pt; mafsousa@ibmc.up.pt



INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

NEURON {
	SUFFIX CaIntraCellDyn
	USEION ca READ ica, cai WRITE cai	
        RANGE cai_new, depth, cai_inf, cai_tau
}

UNITS {
	(molar) = (1/liter)		: moles do not appear in units
	(mM)	= (millimolar)
	(um)	= (micron)
	(mA)	= (milliamp)
	(msM)	= (ms mM)
	FARADAY = (faraday) (coulomb)
}


PARAMETER {
	depth	= 0.1	  (um)		: depth of shell
	cai_tau	= 2.0     (ms)		: rate of calcium removal
	cai_inf	= 50.0e-6 (mM)		: equilibrium intracellular calcium concentration
	cai		  (mM)
}

STATE {
	cai_new		(mM) 
}

INITIAL {

	cai_new = cai_inf
}

ASSIGNED {
	ica		(mA/cm2)
	drive_channel	(mM/ms)
}
	
BREAKPOINT {
	SOLVE state METHOD euler
}

DERIVATIVE state { 

	drive_channel =  - (10000) * ica / (2 * FARADAY * depth)
	if (drive_channel <= 0.) { drive_channel = 0.  }   : cannot pump inward 
         
	cai_new' = drive_channel + (cai_inf-cai_new)/cai_tau
	cai = cai_new
}