TITLE STN ion channels for single compartment model
:
: Na+, K, CaT, CaL, A and AHP current
:
NEURON {
SUFFIX stn
NONSPECIFIC_CURRENT ilk
USEION ca READ cai, cao WRITE ica, cai
USEION k READ ki, ko WRITE ik
USEION na READ nai, nao WRITE ina
RANGE ina, ik, ica
RANGE gnabar, ena, m_inf, h_inf, tau_h, tau_m : fast sodium
RANGE gkdrbar, ek, n_inf, tau_n, ikD : delayed K rectifier
RANGE gl, el, ilk : leak
RANGE gcatbar, eca, p_inf, tau_p, q_inf, tau_q : T-type ca current
RANGE gcalbar, eca, c_inf, d1_inf, d2_inf, tau_c, tau_d1, tau_d2, icaT, icaL : L-type ca current
RANGE gkabar, ek, a_inf, tau_a, b_inf, tau_b, ikA : A-type K current
RANGE gkcabar, ek, r_inf, ikAHP : ca dependent AHP K current
RANGE kca, vol, caGain : ca dynamics
}
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
(S) = (siemens)
(molar) = (1/liter)
(mM) = (millimolar)
FARADAY = (faraday) (coulomb) :units are really coulombs/mole
}
PARAMETER {
R = 8.31441 (Gas constant)
T (Absolute temp)
celsius (degC)
:Fast Na channel
gnabar = 49e-3 (S/cm2)
theta_m = -40 (mV)
theta_h = -45.5 (mV)
k_m = -8 (mV)
k_h = 6.4 (mV)
tau_m0 = 0.2 (ms)
tau_m1 = 3 (ms)
tau_h0 = 0 (ms)
tau_h1 = 24.5 (ms)
tht_m = -53 (mV)
tht_h1 = -50 (mV)
tht_h2 = -50 (mV)
sig_m = -0.7 (mV)
sig_h1 = -15 (mV)
sig_h2 = 16 (mV)
: Delayed rectifier K
gkdrbar = 57e-3 (S/cm2)
theta_n = -41 (mV)
k_n = -14 (mV)
tau_n0 = 0 (ms)
tau_n1 = 11 (ms)
tht_n1 = -40 (mV)
tht_n2 = -40 (mV)
sig_n1 = -40 (mV)
sig_n2 = 50 (mV)
:Leakage current
gl = 0.35e-3 (S/cm2)
el = -60 (mV)
:Ca dynamics
kca = 2 (1/ms)
area
vol = 3.355e-11 (L) :~20um radius sphere
caGain = .1
:T-type ca current
gcatbar = 5e-3 (S/cm2)
theta_p = -56 (mV)
theta_q = -85 (mV)
k_p = -6.7 (mV)
k_q = 5.8 (mV)
tau_p0 = 5 (ms)
tau_p1 = 0.33 (ms)
tau_q0 = 0 (ms)
tau_q1 = 400 (ms)
tht_p1 = -27 (mV)
tht_p2 = -102 (mV)
tht_q1 = -50 (mV)
tht_q2 = -50 (mV)
sig_p1 = -10 (mV)
sig_p2 = 15 (mV)
sig_q1 = -15 (mV)
sig_q2 = 16 (mV)
:Ca L current
gcalbar = 15e-3 (S/cm2)
theta_c = -30.6 (mV)
theta_d1 = -60 (mV)
theta_d2 = 0.1e-3 (mM)
k_c = -5 (mV)
k_d1 = 7.5 (mV)
k_d2 = 0.02e-3 (mM)
tau_c0 = 45 (ms)
tau_c1 = 10 (ms)
tau_d10 = 400 (ms)
tau_d11 = 500 (ms)
tht_c1 = -27 (mV)
tht_c2 = -50 (mV)
tht_d11 = -40 (mV)
tht_d12 = -20 (mV)
sig_c1 = -20 (mV)
sig_c2 = 15 (mV)
sig_d11 = -15 (mV)
sig_d12 = 20 (mV)
tau_d2 = 130 (ms)
:A current
gkabar = 5e-3 (S/cm2)
theta_a = -45 (mV)
theta_b = -90 (mV)
k_a = -14.7 (mV)
k_b = 7.5 (mV)
tau_a0 = 1 (ms)
tau_a1 = 1 (ms)
tau_b0 = 0 (ms)
tau_b1 = 200 (ms)
tht_a = -40 (mV)
tht_b1 = -60 (mV)
tht_b2 = -40 (mV)
sig_a = -0.5 (mV)
sig_b1 = -30 (mV)
sig_b2 = 10 (mV)
:AHP current (Ca dependent K current)
gkcabar = 1e-3 (S/cm2)
theta_r = 0.17e-3 (mM)
k_r = -0.08e-3 (mM)
tau_r = 2 (ms)
power_r = 2
}
ASSIGNED {
v (mV)
ina (mA/cm2)
ik (mA/cm2)
ikD (mA/cm2)
ikA (mA/cm2)
ikAHP (mA/cm2)
ica (mA/cm2)
icaT (mA/cm2)
icaL (mA/cm2)
ilk (mA/cm2)
:Fast Na
h_inf
tau_h (ms)
m_inf
tau_m (ms)
ena (mV) := 60
:Delayed rectifier
n_inf
tau_n (ms)
ek (mV) := -90
:ca T current
p_inf
q_inf
tau_p (ms)
tau_q (ms)
eca (mV) :calc from Nernst
:ca L current
c_inf
tau_c (ms)
d1_inf
tau_d1 (ms)
d2_inf
:tau_d2 (ms) :in PARAMETERS
:A current
a_inf
tau_a (ms)
b_inf
tau_b (ms)
:AHP (Ca dependent K current)
r_inf
}
STATE {
m h n
p q
c d1 d2
cai (mM) <1e-10>
cao (mM) <1e-10>
nai (mM) <1e-10>
nao (mM) <1e-10>
ki (mM) <1e-10>
ko (mM) <1e-10>
a b
r
}
BREAKPOINT {
SOLVE states METHOD cnexp
T = 273 + celsius - 9.5
ena = -(R*T)/FARADAY*log(nai/nao)*1000
ek = (R*T)/FARADAY*log(ko/ki)*1000
eca = -(R*T)/FARADAY*log(cai/cao)*1000/2
:printf("%f %f %f\n", ena, ek, eca)
ina = gnabar * m*m*m*h * (v - ena)
ikD = gkdrbar * n^4 * (v - ek)
ikA = gkabar * a*a*b * (v - ek)
ikAHP = gkcabar * (v - ek)*r^(power_r)
ik=ikD+ikA+ikAHP
icaT = gcatbar * p*p*q * (v - eca)
icaL = gcalbar * c*c*d1*d2 * (v - eca)
ica=icaT+icaL
ilk = gl * (v - el)
}
DERIVATIVE states {
evaluate_fct(v)
h' = (h_inf - h)/tau_h
m' = (m_inf - m)/tau_m
n' = (n_inf - n)/tau_n
p' = (p_inf - p)/tau_p
q' = (q_inf - q)/tau_q
evaluate_fct2(cai)
c' = (c_inf - c)/tau_c
d1' = (d1_inf - d1)/tau_d1
d2' = (d2_inf - d2)/tau_d2
:(Ica mA/cm2)*(area um2)*(1e-8 cm2/um2)*(1e-3 A/mA)*(1/(2*F) mol/C)*(1e-3 sec/msec)*(1e3 mMol/mol)(1/volume 1/L)=(mM/msec)
cai' = caGain*(-ica*area*1e-11/(2*FARADAY*vol) - kca*cai)
: cai' = -ica*area*somaAreaFrac*1e-11/(2*FARADAY*vol*shellVolFrac) + (5e-6 - cai)/kca
a' = (a_inf - a)/tau_a
b' = (b_inf - b)/tau_b
r' = (r_inf - r)/tau_r
}
UNITSOFF
INITIAL {
evaluate_fct(v)
m = m_inf
h = h_inf
n = n_inf
p = p_inf
q = q_inf
evaluate_fct2(cai)
c = c_inf
d1 = d1_inf
d2 = d2_inf
a = a_inf
b = b_inf
r = r_inf
}
PROCEDURE evaluate_fct(v(mV)) {
:Fast Na current
h_inf = 1/(1+exp((v-theta_h)/k_h))
m_inf = 1/(1+exp((v-theta_m)/k_m))
tau_h = tau_h0 + tau_h1/(exp(-(v-tht_h1)/sig_h1) + exp(-(v-tht_h2)/sig_h2))
tau_m = tau_m0 + tau_m1/(1+exp(-(v-tht_m)/sig_m))
:Delayed rectifier K
n_inf = 1/(1+exp((v-theta_n)/k_n))
tau_n = tau_n0 + tau_n1/(exp(-(v-tht_n1)/sig_n1) + exp(-(v-tht_n2)/sig_n2))
:Ca T current
p_inf = 1/(1+exp((v-theta_p)/k_p))
q_inf = 1/(1+exp((v-theta_q)/k_q))
tau_p = tau_p0 + tau_p1/(exp(-(v-tht_p1)/sig_p1) + exp(-(v-tht_p2)/sig_p2))
tau_q = tau_q0 + tau_q1/(exp(-(v-tht_q1)/sig_q1) + exp(-(v-tht_q2)/sig_q2))
:Ca L current
c_inf = 1/(1+exp((v-theta_c)/k_c))
d1_inf = 1/(1+exp((v-theta_d1)/k_d1))
tau_c = tau_c0 + tau_c1/(exp(-(v-tht_c1)/sig_c1) + exp(-(v-tht_c2)/sig_c2))
tau_d1 = tau_d10 + tau_d11/(exp(-(v-tht_d11)/sig_d11) + exp(-(v-tht_d12)/sig_d12))
:A current
a_inf = 1/(1+exp((v-theta_a)/k_a))
b_inf = 1/(1+exp((v-theta_b)/k_b))
tau_a = tau_a0 + tau_a1/(1+exp(-(v-tht_a)/sig_a))
tau_b = tau_b0 + tau_b1/(exp(-(v-tht_b1)/sig_b1) + exp(-(v-tht_b2)/sig_b2))
}
PROCEDURE evaluate_fct2(cai(mM)) {
:Ca L current
d2_inf = 1/(1+exp((cai-theta_d2)/k_d2))
:AHP current
r_inf = 1/(1+exp((cai-theta_r)/k_r))
}
UNITSON