TITLE HH k channel channel : Hodgkin - Huxley k channel : The model used in Safronov et al. 2000 NEURON { SUFFIX KDR USEION k READ ek WRITE ik RANGE gkbar, ik GLOBAL inf } UNITS { (mA) = (milliamp) (mV) = (millivolt) } INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} PARAMETER { v (mV) dt (ms) gkbar=0 (mho/cm2) <0,1e9> ek = -84 (mV) celsius = 37 (degC) } STATE { n } ASSIGNED { ik (mA/cm2) inf } LOCAL fac INITIAL { rate(v*1(/mV)) n = inf } BREAKPOINT { SOLVE states ik = gkbar*n*n*n*n*(v - ek) } PROCEDURE states() { : exact when v held constant rate(v*1(/mV)) n = n + fac*(inf - n) VERBATIM return 0; ENDVERBATIM } UNITSOFF FUNCTION alp(v(mV)) { LOCAL q10 v = v q10 = 3^((celsius - 23)/10) alp = q10 * .069*expM1(-v - 5, 10) } FUNCTION bet(v(mV)) { LOCAL q10 v = v q10 = 3^((celsius - 23)/10) bet = q10 * .024*exp((-v - 1)/30) } FUNCTION expM1(x,y) { if (fabs(x/y) < 1e-6) { expM1 = y*(1 - x/y/2) }else{ expM1 = x/(exp(x/y) - 1) } } PROCEDURE rate(v) {LOCAL a, b, tau :rest = -70 TABLE inf, fac DEPEND dt, celsius FROM -150 TO 100 WITH 200 a = alp(v) b=bet(v) tau = 1/(a+b) inf = a/(a + b) fac = (1 - exp(-dt/tau)) } UNITSON