TITLE HH style channels for spiking retinal ganglion cells
:
: Modified from Fohlmeister et al, 1990, Brain Res 510, 343-345
: by TJ Velte March 17, 1995
: must be used with calcium pump mechanism, i.e. capump.mod
:
:
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
NEURON {
SUFFIX spike
USEION na READ ena WRITE ina
USEION k READ ek WRITE ik
USEION ca READ cai, eca, cao WRITE ica
RANGE gnabar, gkbar, gabar, gcabar, gkcbar,gkc
RANGE m_inf, h_inf, n_inf, p_inf, q_inf, c_inf
RANGE tau_m, tau_h, tau_n, tau_p, tau_q, tau_c,tau_slowh
RANGE m_exp, h_exp, n_exp, p_exp, q_exp, c_exp,slowh_exp
RANGE idrk, iak, icak
GLOBAL vshift_ca,ca50,slowh
RANGE vshift_na_k
GLOBAL tausv,tausd,tausb,Nm,Nh,Nsh
RANGE nkm, gkmbar
RANGE km_inf, tau_km
}
UNITS {
(molar) = (1/liter)
(mM) = (millimolar)
(mA) = (milliamp)
(mV) = (millivolt)
}
PARAMETER {
gnabar = 0.04 (mho/cm2)
gkbar = 0.012 (mho/cm2)
gabar = 0.036 (mho/cm2)
gcabar = 0.002 (mho/cm2)
gkcbar = 0.00005 (mho/cm2)
ena = 65 (mV)
ek = -100 (mV)
eca (mV)
cao = 1.8 (mM)
cai = 0.0001 (mM)
dt (ms)
v (mV)
vshift_na_k=5 (mV)
vshift_ca=5 (mV)
ca50=0.2 (mM)
slowh=1
gkmbar = .002 (mho/cm2) : 0.03 mho/cm2
tausb=0.5
taus=50
tausv=30
tausd=1
Nm=3
Nh=1
Nsh=1
}
STATE {
m h n p q c nkm sh
}
INITIAL {
: The initial values were determined at a resting value of -66.3232 mV in a single-compartment
: m = 0.0155
: h = 0.9399
: n = 0.0768
: p = 0.0398
: q = 0.4526
: c = 0.0016
: at -60 mV
m = 0.0345
h = 0.8594
sh= 1
n = 0.1213
p = 0.0862
q = 0.2534
c = 0.0038
nkm=0.0344
}
ASSIGNED {
ina (mA/cm2)
ik (mA/cm2)
idrk (mA/cm2)
iak (mA/cm2)
icak (mA/cm2)
ikm (mA/cm2)
ica (mA/cm2)
m_inf h_inf n_inf p_inf q_inf c_inf km_inf
tau_m tau_h tau_n tau_p tau_q tau_c tau_km :tau_slowh
m_exp h_exp n_exp p_exp q_exp c_exp km_exp :slowh_exp
gkc
}
BREAKPOINT {
SOLVE states
ina = gnabar * m^Nm*h^Nh*sh^Nsh * (v - ena)
idrk = gkbar * n*n*n*n * (v - ek)
iak = gabar * p*p*p*q * (v - ek)
gkc=((cai / ca50)/ (1 + (cai / ca50)))
icak = gkcbar * gkc * (v - ek)
ikm = 2.3*gkmbar*nkm*(v-ek)
ik = idrk + iak + icak+ikm
ica = gcabar * c*c*c * (v - eca)
}
PROCEDURE states() { : exact when v held constant
LOCAL sigmas
evaluate_fct_nak(v+vshift_na_k)
evaluate_fct_ca(v+vshift_ca)
m = m + m_exp * (m_inf - m)
h = h + h_exp * (h_inf - h)
:sh = sh + slowh_exp * (h_inf - sh)
sigmas=1/(1+exp((v+tausv+vshift_na_k)/tausd))
sh = sh + (1 - exp(-dt/(taus*sigmas+tausb)))*(1 / (1 + exp((v + 44+vshift_na_k)/3)) - sh)
n = n + n_exp * (n_inf - n)
p = p + p_exp * (p_inf - p)
q = q + q_exp * (q_inf - q)
c = c + c_exp * (c_inf - c)
nkm = nkm + km_exp*(km_inf-nkm)
VERBATIM
return 0;
ENDVERBATIM
}
UNITSOFF
PROCEDURE evaluate_fct_ca(v(mV)) { LOCAL a,b
:CA channel
a = (-0.3 * (v+13)) / ((exp(-0.1*(v+13))) - 1)
b = 10 * (exp((-1*(v + 38))/18))
tau_c = 1 / (a + b)
c_inf = a * tau_c
c_exp = 1 - exp(-dt/tau_c)
}
PROCEDURE evaluate_fct_nak(v(mV)) { LOCAL a,b
:NA m
a = (-0.6 * (v+30)) / ((exp(-0.1*(v+30))) - 1)
b = 20 * (exp((-1*(v+55))/18))
tau_m = 1 / (a + b)
m_inf = a * tau_m
:NA h
a = 0.4 * (exp((-1*(v+50))/20))
b = 6 / ( 1 + exp(-0.1 *(v+20)))
tau_h = 1 / (a + b)
:tau_slowh=tau_h*slowh
h_inf = a * tau_h
:K n (non-inactivating, delayed rectifier)
a = (-0.02 * (v+40)) / ((exp(-0.1*(v+40))) - 1)
b = 0.4 * (exp((-1*(v + 50))/80))
tau_n = 1 / (a + b)
n_inf = a * tau_n
:K (inactivating)
a = (-0.006 * (v+90)) / ((exp(-0.1*(v+90))) - 1)
b = 0.1 * (exp((-1*(v + 30))/10))
tau_p = 1 / (a + b)
p_inf = a * tau_p
a = 0.04 * (exp((-1*(v+70))/20))
b = 0.6 / ( 1 + exp(-0.1 *(v+40)))
tau_q = 1 / (a + b)
q_inf = a * tau_q
:Km
a = 0.001 * (v +30) / (1 - exp(-(v +30)/9))
b = -0.001 * (v +30) / (1 - exp((v +30)/9))
tau_km = 1/(a+b)
km_inf = a*tau_km
: State vars to inifinity
m_exp = 1 - exp(-dt/tau_m)
h_exp = 1 - exp(-dt/tau_h)
n_exp = 1 - exp(-dt/tau_n)
p_exp = 1 - exp(-dt/tau_p)
q_exp = 1 - exp(-dt/tau_q)
km_exp= 1 - exp(-dt*2.3/tau_km)
}
UNITSON