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87 lines
1.5 KiB
87 lines
1.5 KiB
2 years ago
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: HH P-type Calcium current
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: Created 8/13/02 - nwg
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NEURON {
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THREADSAFE
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SUFFIX cap
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USEION ca READ cai, cao WRITE ica
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RANGE pcabar, ica
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RANGE minf, mtau
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RANGE monovalConc, monovalPerm
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}
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UNITS {
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(mV) = (millivolt)
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(mA) = (milliamp)
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(mM) = (milli/liter)
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F = 9.6485e4 (coul)
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R = 8.3145 (joule/degC)
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}
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PARAMETER {
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v (mV)
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celsius (degC)
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pcabar = 0.00005 (cm/s)
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monovalConc = 140 (mM)
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monovalPerm = 0
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cai (milli/liter)
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cao (milli/liter)
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}
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ASSIGNED {
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ica (mA/cm2)
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minf
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mtau (ms)
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T (degC)
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E (volts)
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}
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STATE {
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m
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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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}
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BREAKPOINT {
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SOLVE states METHOD cnexp
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ica = (1e3) * pcabar * m * ghk(v, cai, cao, 2)
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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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}
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FUNCTION ghk( v(mV), ci(mM), co(mM), z) (coul/cm3) { LOCAL Ci
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T = celsius + 273.19 : Kelvin
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E = (1e-3) * v
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Ci = ci + (monovalPerm) * (monovalConc) : Monovalent permeability
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if (fabs(1-exp(-z*(F*E)/(R*T))) < 1e-6) { : denominator is small -> Taylor series
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ghk = (1e-6) * z * F * (Ci-co*exp(-z*(F*E)/(R*T)))*(1-(z*(F*E)/(R*T)))
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} else {
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ghk = (1e-6) * z^2*(E*F^2)/(R*T)*(Ci-co*exp(-z*(F*E)/(R*T)))/(1-exp(-z*(F*E)/(R*T)))
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}
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}
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PROCEDURE rates (v (mV)) {
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UNITSOFF
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minf = 1/(1+exp(-(v - (-19)) / 5.5))
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mtau = (mtau_func(v)) * 1e3
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UNITSON
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}
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FUNCTION mtau_func( v (mV) ) (ms) {
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UNITSOFF
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if (v > -50) {
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mtau_func = .000191 + .00376*exp(-((v-(-41.9))/27.8)^2)
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} else {
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mtau_func = .00026367 + .1278 * exp(.10327*v)
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}
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UNITSON
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}
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