114 lines
2.7 KiB
Modula-2
114 lines
2.7 KiB
Modula-2
COMMENT
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This is the original Hodgkin-Huxley treatment for the set of sodium,
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potassium, and leakage channels found in the squid giant axon membrane.
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("A quantitative description of membrane current and its application
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conduction and excitation in nerve" J.Physiol. (Lond.) 117:500-544 (1952).)
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Membrane voltage is in absolute mV and has been reversed in polarity
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from the original HH convention and shifted to reflect a resting potential
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of -65 mV.
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Remember to set a squid-appropriate temperature
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(e.g. in HOC: "celsius=6.3" or in Python: "h.celsius=6.3").
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See squid.hoc for an example of a simulation using this model.
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SW Jaslove 6 March, 1992
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ENDCOMMENT
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NEURON {
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SUFFIX hhqt
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USEION na READ ena WRITE ina
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USEION k READ ek WRITE ik
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NONSPECIFIC_CURRENT il
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RANGE gnabar, gkbar, gl, el, gna, gk, celsius
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}
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UNITS {
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(mA) = (milliamp)
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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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gnabar = .12 (S/cm2) <0,1e9>
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gkbar = .036 (S/cm2) <0,1e9>
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gl = .0003 (S/cm2) <0,1e9>
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el = -54.3 (mV)
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celsius = 29 (degC)
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}
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ASSIGNED {
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v (mV)
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ena (mV)
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ek (mV)
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gna (S/cm2)
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gk (S/cm2)
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ina (mA/cm2)
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ik (mA/cm2)
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il (mA/cm2)
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minf hinf ninf
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mtau (ms) htau (ms) ntau (ms)
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}
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STATE {
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m h n
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}
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BREAKPOINT {
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SOLVE states METHOD cnexp
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gna = gnabar*m*m*m*h
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ina = gna*(v - ena)
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gk = gkbar*n*n*n*n
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ik = gk*(v - ek)
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il = gl*(v - el)
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}
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DERIVATIVE states {
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rates(v)
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m' = (minf-m)/mtau
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h' = (hinf-h)/htau
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n' = (ninf-n)/ntau
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}
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INITIAL {
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rates(v)
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m = minf
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h = hinf
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n = ninf
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}
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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, q10
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q10 = 3^((celsius - 6.3)/10)
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UNITSOFF
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:"m" sodium activation system
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alpha = .1*vtrap(-(v+40),10)
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beta = 4*exp(-(v+65)/18)
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sum = alpha + beta
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mtau = 1/(q10*sum)
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minf = alpha/sum
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:"h" sodium inactivation system
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alpha = .07*exp(-(v+65)/20)
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beta = 1/(exp(-(v+35)/10) + 1)
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sum = alpha + beta
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htau = 1/(q10*sum)
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hinf = alpha/sum
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:"n" potassium activation system
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alpha = .01*vtrap(-(v+55),10)
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beta = .125*exp(-(v+65)/80)
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sum = alpha + beta
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ntau = 1/(q10*sum)
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ninf = alpha/sum
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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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UNITSON
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