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197 lines
4.3 KiB
197 lines
4.3 KiB
2 years ago
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TITLE Rsg sodium channel
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: Resurgent sodium channel (with blocking particle)
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: with updated kinetic parameters from Raman and Bean
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NEURON {
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SUFFIX naRsg
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USEION na READ ena WRITE ina
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RANGE gna, gbar
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}
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UNITS {
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(mV) = (millivolt)
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(S) = (siemens)
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}
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PARAMETER {
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gbar = .015 (S/cm2)
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: kinetic parameters
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Con = 0.005 (/ms) : closed -> inactivated transitions
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Coff = 0.5 (/ms) : inactivated -> closed transitions
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Oon = .75 (/ms) : open -> Ineg transition
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Ooff = 0.005 (/ms) : Ineg -> open transition
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alpha = 150 (/ms) : activation
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beta = 3 (/ms) : deactivation
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gamma = 150 (/ms) : opening
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delta = 40 (/ms) : closing, greater than BEAN/KUO = 0.2
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epsilon = 1.75 (/ms) : open -> Iplus for tau = 0.3 ms at +30 with x5
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zeta = 0.03 (/ms) : Iplus -> open for tau = 25 ms at -30 with x6
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: Vdep
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x1 = 20 (mV) : Vdep of activation (alpha)
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x2 = -20 (mV) : Vdep of deactivation (beta)
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x3 = 1e12 (mV) : Vdep of opening (gamma)
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x4 = -1e12 (mV) : Vdep of closing (delta)
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x5 = 1e12 (mV) : Vdep into Ipos (epsilon)
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x6 = -25 (mV) : Vdep out of Ipos (zeta)
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}
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ASSIGNED {
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alfac : microscopic reversibility factors
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btfac
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: rates
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f01 (/ms)
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f02 (/ms)
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f03 (/ms)
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f04 (/ms)
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f0O (/ms)
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fip (/ms)
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f11 (/ms)
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f12 (/ms)
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f13 (/ms)
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f14 (/ms)
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f1n (/ms)
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fi1 (/ms)
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fi2 (/ms)
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fi3 (/ms)
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fi4 (/ms)
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fi5 (/ms)
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fin (/ms)
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b01 (/ms)
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b02 (/ms)
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b03 (/ms)
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b04 (/ms)
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b0O (/ms)
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bip (/ms)
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b11 (/ms)
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b12 (/ms)
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b13 (/ms)
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b14 (/ms)
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b1n (/ms)
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bi1 (/ms)
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bi2 (/ms)
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bi3 (/ms)
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bi4 (/ms)
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bi5 (/ms)
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bin (/ms)
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v (mV)
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ena (mV)
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ina (milliamp/cm2)
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gna (S/cm2)
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}
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STATE {
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C1 FROM 0 TO 1
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C2 FROM 0 TO 1
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C3 FROM 0 TO 1
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C4 FROM 0 TO 1
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C5 FROM 0 TO 1
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I1 FROM 0 TO 1
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I2 FROM 0 TO 1
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I3 FROM 0 TO 1
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I4 FROM 0 TO 1
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I5 FROM 0 TO 1
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O FROM 0 TO 1
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B FROM 0 TO 1
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I6 FROM 0 TO 1
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}
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BREAKPOINT {
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SOLVE activation METHOD sparse
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gna = gbar * O : O is "open state"
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ina = gna * (v - ena)
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}
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INITIAL {
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rates(v)
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SOLVE seqinitial
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}
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KINETIC activation
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{
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rates(v)
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~ C1 <-> C2 (f01,b01)
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~ C2 <-> C3 (f02,b02)
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~ C3 <-> C4 (f03,b03)
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~ C4 <-> C5 (f04,b04)
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~ C5 <-> O (f0O,b0O)
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~ O <-> B (fip,bip)
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~ O <-> I6 (fin,bin)
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~ I1 <-> I2 (f11,b11)
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~ I2 <-> I3 (f12,b12)
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~ I3 <-> I4 (f13,b13)
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~ I4 <-> I5 (f14,b14)
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~ I5 <-> I6 (f1n,b1n)
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~ C1 <-> I1 (fi1,bi1)
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~ C2 <-> I2 (fi2,bi2)
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~ C3 <-> I3 (fi3,bi3)
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~ C4 <-> I4 (fi4,bi4)
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~ C5 <-> I5 (fi5,bi5)
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CONSERVE C1 + C2 + C3 + C4 + C5 + O + B + I1 + I2 + I3 + I4 + I5 + I6 = 1
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}
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LINEAR seqinitial { : sets initial equilibrium
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~ I1*bi1 + C2*b01 - C1*( fi1+f01) = 0
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~ C1*f01 + I2*bi2 + C3*b02 - C2*(b01+fi2+f02) = 0
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~ C2*f02 + I3*bi3 + C4*b03 - C3*(b02+fi3+f03) = 0
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~ C3*f03 + I4*bi4 + C5*b04 - C4*(b03+fi4+f04) = 0
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~ C4*f04 + I5*bi5 + O*b0O - C5*(b04+fi5+f0O) = 0
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~ C5*f0O + B*bip + I6*bin - O*(b0O+fip+fin) = 0
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~ O*fip + B*bip = 0
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~ C1*fi1 + I2*b11 - I1*( bi1+f11) = 0
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~ I1*f11 + C2*fi2 + I3*b12 - I2*(b11+bi2+f12) = 0
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~ I2*f12 + C3*fi3 + I4*bi3 - I3*(b12+bi3+f13) = 0
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~ I3*f13 + C4*fi4 + I5*b14 - I4*(b13+bi4+f14) = 0
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~ I4*f14 + C5*fi5 + I6*b1n - I5*(b14+bi5+f1n) = 0
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~ C1 + C2 + C3 + C4 + C5 + O + B + I1 + I2 + I3 + I4 + I5 + I6 = 1
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}
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PROCEDURE rates(v(mV) )
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{
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alfac = (Oon/Con)^(1/4)
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btfac = (Ooff/Coff)^(1/4)
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f01 = 4 * alpha * exp(v/x1)
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f02 = 3 * alpha * exp(v/x1)
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f03 = 2 * alpha * exp(v/x1)
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f04 = 1 * alpha * exp(v/x1)
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f0O = gamma * exp(v/x3)
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fip = epsilon * exp(v/x5)
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f11 = 4 * alpha * alfac * exp(v/x1)
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f12 = 3 * alpha * alfac * exp(v/x1)
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f13 = 2 * alpha * alfac * exp(v/x1)
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f14 = 1 * alpha * alfac * exp(v/x1)
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f1n = gamma * exp(v/x3)
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fi1 = Con
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fi2 = Con * alfac
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fi3 = Con * alfac^2
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fi4 = Con * alfac^3
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fi5 = Con * alfac^4
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fin = Oon
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b01 = 1 * beta * exp(v/x2)
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b02 = 2 * beta * exp(v/x2)
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b03 = 3 * beta * exp(v/x2)
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b04 = 4 * beta * exp(v/x2)
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b0O = delta * exp(v/x4)
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bip = zeta * exp(v/x6)
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b11 = 1 * beta * btfac * exp(v/x2)
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b12 = 2 * beta * btfac * exp(v/x2)
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b13 = 3 * beta * btfac * exp(v/x2)
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b14 = 4 * beta * btfac * exp(v/x2)
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b1n = delta * exp(v/x4)
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bi1 = Coff
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bi2 = Coff * btfac
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bi3 = Coff * btfac^2
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bi4 = Coff * btfac^3
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bi5 = Coff * btfac^4
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bin = Ooff
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}
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