I am working with 2 cell connected by an Expsyn. The first cell is 1 comp. (soma), the second cell is 2 comp (soma+dend).

I am using the na and k channels mechanisms by Migliore https://senselab.med.yale.edu/ModelDB/S ... mod#tabs-2 that should work fine at 35-37 degC.

I am using this intialization procedure:

- Code: Select all
`proc init() {`

finitialize(v_init)

forall for (x,0) concentration_init()

forall for (x,0){

if (ismembrane("NaKpump")) {

ic_bias(x) = -(ina + ik + i_leakad +ink_NaKpump )

} else {

ic_bias(x) = -(ina+ik+i_leakad)

}

}

if (cvode.active()) {

cvode.re_init()

} else {

fcurrent()

}

frecord_init()

}

If i uninsert Nakpump the compartments of the model at rest have all the same v_init, but when Nakpump is inserted in the dend of the second cell on;ly the soma of the first cell is correctli initalized, the spoma and dend of the second cell doesn't stabilize at the same v_init.

I had the same problem also using these simple models for na and k channel:

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`:NMODL K+ current:`

NEURON{

SUFFIX kad

USEION k READ ek WRITE ik

RANGE gkbar, ik

}

UNITS{

(S)=(siemens)

(mV)=(millivolt)

(mA)=(milliamp)

}

PARAMETER{gkbar=0.036 (S/cm2)}

ASSIGNED{

v (mV)

ek (mV) : typically ~ -70

ik (mA/cm2)

}

STATE{n}

BREAKPOINT{

SOLVE states METHOD cnexp

ik=gkbar*n^4*(v-ek)

}

INITIAL{

n=alpha(v)/(alpha(v)+beta(v))

}

DERIVATIVE states{

n'=(1-n)*alpha(v)-n*beta(v)

}

FUNCTION alpha(Vm (mV)) (/ms){

UNITSOFF

alpha=(0.01*((-70-Vm)+10))/(exp(((-70-Vm)+10)/10)-1)

UNITSON

}

FUNCTION beta(Vm (mV)) (/ms){

UNITSOFF

beta=0.125*exp((-70-Vm)/80)

UNITSON

}

:cambia 70 con 65

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`:NMODL for Na+ current:`

NEURON{

SUFFIX nad

USEION na READ ena WRITE ina

RANGE gnabar, ina

}

UNITS {

(S) = (siemens)

(mV) = (millivolt)

(mA) = (milliamp)

}

PARAMETER{ gnabar=0.12 (S/cm2)}

ASSIGNED{

v (mV)

ena (mV) : typically ~ +55

ina (mA/cm2)

}

STATE { m h}

BREAKPOINT{

SOLVE states METHOD cnexp

ina=gnabar*m^3*h*(v-ena)

}

INITIAL{

m=alpham(v)/(alpham(v)+betam(v))

h=alphah(v)/(alphah(v)+betah(v))

}

DERIVATIVE states{

m'=alpham(v)*(1-m)-m*betam(v)

h'=alphah(v)*(1-h)-betah(v)*h

}

FUNCTION alpham(Vm (mV)) (/ms){

UNITSOFF

alpham=(0.1*(-70-Vm+25))/(exp((-70-Vm+25)/10)-1)

UNITSON

}

FUNCTION betam(Vm (mV)) (/ms){

UNITSOFF

betam=4*exp((-70-Vm)/18)

UNITSON

}

FUNCTION alphah(Vm (mV)) (/ms){

UNITSOFF

alphah=0.07*exp((-70-Vm)/20)

UNITSON

}

FUNCTION betah(Vm (mV)) (/ms){

UNITSOFF

betah=1/(exp((-70-Vm+30)/10)+1)

UNITSON

}

This is the model of the pump:

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`TITLE sodium potassium pump`

: from Lindblad et al Am J Physiol 1996 275:H1666

NEURON {

SUFFIX NaKpump

USEION k READ ki, ko WRITE ik

USEION na READ nai, nao WRITE ina

RANGE ik, ina , INaKmax, ink, Kmko, Kmnai, n, m

GLOBAL dummy : prevent vectorization for use with CVODE

}

UNITS {

(mA) = (milliamp)

(mV) = (millivolt)

}

PARAMETER {

INaKmax = 2.18660e-3 (mA/cm2) <0,1e6>

Kmnai = 10 (mM) <0,1e6>

Kmko = 1.5 (mM) <0,1e6>

n=1.5

m=1

}

ASSIGNED {

celsius (degC)

v (mV)

ik (mA/cm2)

ina (mA/cm2)

ko (mM)

ki (mM)

nao (mM)

nai (mM)

ink (mA/cm2)

dummy

}

BREAKPOINT { LOCAL q10, fnk

fnk = (v + 150)/(v + 200)

ink= INaKmax*fnk/((1 + (Kmnai/nai)^n)*(1 + (Kmko/ko)^m))

ina = 3*ink

ik = -2*ink

}

how could I initilaize all the comp of the model at the same v_init? I need to customize it for each com? or is something wrong in the mechanisms inserted?

Best

Menica