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137 lines
2.8 KiB
137 lines
2.8 KiB
2 years ago
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TITLE jsrnaf.mod VCN Na conductance, fast model
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COMMENT
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gnaf is the modified form used in his
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1993 M.S. thesis (as in Rothman et al., J. Neurophysiol. 70:2562, 1993),
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with rapid recovery from inactivation for potentials below rest.
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Implementation by Paul B. Manis, April and Sept, 1999.
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ENDCOMMENT
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UNITS {
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(mA) = (milliamp)
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(mV) = (millivolt)
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(nA) = (nanoamp)
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}
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? interface
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NEURON {
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THREADSAFE
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SUFFIX jsrna
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USEION na READ ena WRITE ina
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RANGE gbar
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RANGE gna, vsna
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RANGE minf, hinf, mtau, htau
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}
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INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
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PARAMETER {
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v (mV)
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dt (ms)
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ena = 55 (mV)
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gbar = 0.25 (mho/cm2) <0,1e9>
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vsna = 0 (mV)
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q10 = 3.0 (1)
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}
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STATE {
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m h
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}
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ASSIGNED {
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gna (mho/cm2)
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ina (mA/cm2)
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minf hinf
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mtau (ms) htau (ms)
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celsius (degC)
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}
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LOCAL mexp, hexp
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? currents
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BREAKPOINT {
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SOLVE states METHOD cnexp
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gna = gbar*(m^3)*h
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ina = gna*(v - ena)
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}
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UNITSOFF
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INITIAL {
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trates(v)
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m = minf
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h = hinf
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}
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DERIVATIVE states { :Computes state variables m, h, and n
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trates(v) : at the current v and dt.
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m' = (minf - m)/mtau
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h' = (hinf - h)/htau
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}
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LOCAL qt
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PROCEDURE rates(v (mV)) { :Computes rate and other constants at current v.
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:Call once from HOC to initialize inf at resting v.
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LOCAL alpha, beta, sum
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qt = q10^((celsius - 22)/10 (degC)) : R&M'03 used 3
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: Note qt temperature here cancels in minf (a/(a+b))
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:"m" sodium activation system - JSR
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alpha = -0.36*qt*vtrap((v+49),-3)
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beta = 0.4*qt*vtrap((v+58),20)
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sum = alpha + beta
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mtau = 1/sum
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minf = alpha/sum
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:"h" sodium inactivation system - JSR
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alpha = 2.4*qt/(1+exp((v+68-vsna)/3 (mV))) + 0.8*qt/(1+exp(v+61.3-vsna))
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beta = 3.6*qt/(1+exp(-(v+21-vsna)/10 (mV)))
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sum = alpha + beta
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htau = 1/sum
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hinf = alpha/sum
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: jsr modified sodium channel - defined in terms of alpha and beta this time
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: am = (0.36*q10*(v+49))/(1-exp(-((v+49)/3)))
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: am = -(0.36*q10*vtrap(-(v+49),3))
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: bm = -(0.40*q10*(v+58))/(1-exp((v+58)/20))
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: bm = (0.40*q10*vtrap((v+58),20))
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: ah = ((2.4*q10)/(1+exp((v+68)/3))) + (0.8*qten/(1+exp(v+61.3)))
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: bh = (3.6*q10)/(1+exp(-(v+21)/10))
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: minf = am/(am+bm)
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: hinf = ah/(ah+bh)
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: mtau = 1/(am+bm)
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: htau = 1/(ah+bh)
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}
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PROCEDURE trates(v (mV)) { :Computes rate and other constants at current v.
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:Call once from HOC to initialize inf at resting v.
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LOCAL tinc
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rates(v) : not consistently executed from here if usetable_hh == 1
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: so don't expect the tau values to be tracking along with
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: the inf values in hoc
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tinc = -dt : * q10 # handled in rates now
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mexp = 1 - exp(tinc/mtau)
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hexp = 1 - exp(tinc/htau)
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}
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FUNCTION vtrap(x,y) { :Traps for 0 in denominator of rate eqns.
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if (fabs(x/y) < 1e-6) {
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vtrap = y*(1 - x/y/2)
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}else{
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vtrap = x/(exp(x/y) - 1)
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}
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}
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