TITLE CA
:Includes changes made by Andreas Schaefer
:ca.mod
:to lead to thalamic ca current inspired by destexhe and huguenrd
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
NEURON {
SUFFIX sit2
USEION ca READ eca WRITE ica
RANGE gca, gamma, eta, deterministic,reff
RANGE N, inactF, actF
GLOBAL v12m, v12h, vwm, vwh, vm1, vm2, vh1, vh2, wm1, wm2, wh1, wh2
GLOBAL amc, ahc, minf, mtau, hinf, htau
GLOBAL vmin, vmax, vshift
GLOBAL P_am, P_bm, P_ah, P_bh, wflag
GLOBAL DONT_VECTORIZE : prevent vectorization to agree with RNG.mod
}
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
(pS) = (picosiemens)
(um) = (micron)
FARADAY = (faraday) (coulomb)
R = (k-mole) (joule/degC)
PI = (pi) (1)
}
PARAMETER {
v (mV)
dt (ms)
area
v12m=50 (mV)
v12h=78 (mV)
vwm =7.4 (mV)
vwh=5.0 (mV)
amc=3 (mV)
ahc=85 (mV)
vm1=25 (mV)
vm2=100 (mV)
vh1=46 (mV)
vh2=405 (mV)
wm1=20 (mV)
wm2=15 (mV)
wh1=4 (mV)
wh2=50 (mV)
gamma = 8 (pS)
eta = 1 (1/um2) : 0.0008 mho/cm2
vshift = 0 (mV) : voltage shift (affects all)
cao = 2.5 (mM) : external ca concentration
cai (mM) celsius (degC)
vmin = -120 (mV)
vmax = 100 (mV)
DONT_VECTORIZE : required declaration
deterministic = 0 : if non-zero, use deterministic variables
}
STATE { m h : deterministic variables
m0h0 m0h1 m1h0 m1h1 m2h0 m2h1 : states
m0h0_m1h0 m1h0_m2h0 m0h1_m1h1 m1h1_m2h1
m2h0_m1h0 m1h0_m0h0 m2h1_m1h1 m1h1_m0h1
m0h0_m0h1 m0h1_m0h0 m1h0_m1h1 m1h1_m1h0 m2h0_m2h1 m2h1_m2h0
}
ASSIGNED {
ica (mA/cm2)
gca (pS/um2)
eca (mV)
minf
hinf
mtau (ms)
htau (ms)
tadj
am (/ms)
bm (/ms)
ah (/ms)
bh (/ms)
N
reff (pS/um2)
scale_dens (pS/um2)
P_am : probability of one channel making am transition
P_bm
P_ah
P_bh
wflag
}
INITIAL {
rates(v+vshift)
m = minf
h = hinf
wflag = 1 : only give a warning once!
scale_dens = gamma/area
reff = eta*gamma
N = floor(eta*area + 0.5) : round to nearest number of channels
m1h0 = floor(2*m*(1-m)*(1-h)*N + 0.5)
m2h0 = floor(m*m*(1-h)*N + 0.5)
m0h1 = floor((1-m)*(1-m)*h*N + 0.5)
m1h1 = floor(2*m*(1-m)*h*N + 0.5)
m2h1 = floor(m*m*h*N + 0.5)
: put tbe rest of tbe channels in the non-conducting & inactivated state
m0h0 = N - (m1h0 + m2h0 + m0h1 + m1h1 + m2h1)
m0h0_m1h0=0
m1h0_m2h0=0
m0h1_m1h1=0
m1h1_m2h1=0
m2h0_m1h0=0
m1h0_m0h0=0
m2h1_m1h1=0
m1h1_m0h1=0
m0h0_m0h1=0
m0h1_m0h0=0
m1h0_m1h1=0
m1h1_m1h0=0
m2h0_m2h1=0
m2h1_m2h0=0
}
BREAKPOINT {
SOLVE states
if (deterministic) {
if (deterministic-1){
gca = m*m*h* N * scale_dens
} else {
gca = floor(m*m*h* N + 0.5) * scale_dens }
} else{
gca = strap(m2h1) * scale_dens
}
ica = (1e-4) * gca * (v - eca) }
PROCEDURE states() {
VERBATIM
extern double BnlDev_RNG();
ENDVERBATIM
rates(v+vshift)
: deterministic versions of state variables
: integrated by relaxing toward the steady state value
m = m + (1 - exp(-dt/mtau)) * (minf-m)
h = h + (1 - exp(-dt/htau)) * (hinf-h)
P_am = strap(am*dt)
P_bm = strap(bm*dt)
: cbeck that will represent probabilities when used
ChkProb( 2.0 * P_am)
ChkProb( 2.0 * P_bm)
ChkProb( P_bm/(1.0-P_am) )
: m gate transitions
m0h0_m1h0 = BnlDev_RNG(2.0*P_am,m0h0)
m1h0_m2h0 = BnlDev_RNG(P_am,m1h0)
m1h0_m0h0 = BnlDev_RNG(P_bm/(1.0-P_am), m1h0 - m1h0_m2h0)
m2h0_m1h0 = BnlDev_RNG(2.0*P_bm, m2h0)
m0h1_m1h1 = BnlDev_RNG(2.0*P_am, m0h1)
m1h1_m2h1 = BnlDev_RNG(P_am, m1h1)
m1h1_m0h1 = BnlDev_RNG(P_bm/(1.0-P_am), m1h1 - m1h1_m2h1)
m2h1_m1h1 = BnlDev_RNG(2.0*P_bm, m2h1)
: new numbers in each state after the a gate transitions
m0h0 = m0h0 - m0h0_m1h0 + m1h0_m0h0
m1h0 = m1h0 - m1h0_m2h0 - m1h0_m0h0 + m2h0_m1h0 + m0h0_m1h0
m2h0 = m2h0 - m2h0_m1h0 + m1h0_m2h0
m0h1 = m0h1 - m0h1_m1h1 + m1h1_m0h1
m1h1 = m1h1 - m1h1_m2h1 - m1h1_m0h1 + m2h1_m1h1 + m0h1_m1h1
m2h1 = m2h1 - m2h1_m1h1 + m1h1_m2h1
: probabilities of making h gate transitions
P_ah = strap(ah*dt)
P_bh = strap(bh*dt)
ChkProb(P_ah)
ChkProb(P_bh)
: number making h gate transitions
m0h0_m0h1 = BnlDev_RNG(P_ah,m0h0)
m0h1_m0h0 = BnlDev_RNG(P_bh,m0h1)
m1h0_m1h1 = BnlDev_RNG(P_ah,m1h0)
m1h1_m1h0 = BnlDev_RNG(P_bh,m1h1)
m2h0_m2h1 = BnlDev_RNG(P_ah,m2h0)
m2h1_m2h0 = BnlDev_RNG(P_bh,m2h1)
m0h0 = m0h0 - m0h0_m0h1 + m0h1_m0h0
m1h0 = m1h0 - m1h0_m1h1 + m1h1_m1h0
m2h0 = m2h0 - m2h0_m2h1 + m2h1_m2h0
m0h1 = m0h1 - m0h1_m0h0 + m0h0_m0h1
m1h1 = m1h1 - m1h1_m1h0 + m1h0_m1h1
m2h1 = m2h1 - m2h1_m2h0 + m2h0_m2h1
}
PROCEDURE rates(v_(mV)) { TABLE minf, hinf, mtau, htau, am, bm, ah, bh
DEPEND v12m,v12h,vwm,vwh,vm1,vm2,vh1,vh2,wm1,wm2,wh1,wh2,amc,ahc
FROM -120 TO 100 WITH 199
UNITSOFF
minf = 1.0 / ( 1 + exp(-(v_+v12m)/vwm) )
hinf = 1.0 / ( 1 + exp((v_+v12h)/vwh) )
mtau = ( amc + 1.0 / ( exp((v_+vm1)/wm1) + exp(-(v_+vm2)/wm2) ) )
htau = ( ahc + 1.0 / ( exp((v_+vh1)/wh1) + exp(-(v_+vh2)/wh2) ) )
ah = hinf/htau
bh = 1/htau - ah
am = minf/mtau
bm = 1/mtau - am
: no temperature adjustment done here
}
UNITSON
: ----------------------------------------------------------------
: sign trap - trap negative numbers and replace with zero
FUNCTION strap(x) {
if (x < 0) {
strap = 0
VERBATIM
fprintf (stderr,"sit2.mod:strap: negative value for state");
ENDVERBATIM
} else {
strap = x
}
}
: ----------------------------------------------------------------
: ChkProb - Check that number represents a probability
PROCEDURE ChkProb(p) {
if (p < 0.0 || p > 1.0) {
if (wflag){
VERBATIM
fprintf(stderr, "sit2.mod:ChkProb: argument not a probability.\n");
ENDVERBATIM
wflag =0}
}
}
