TITLE Cardiac Ito current : Hodgkin-Huxley type k channel from Courtemanche et al Am J Physiol Am J Physiol 1998 275:H301 NEURON { SUFFIX Ito USEION k READ ek WRITE ik RANGE gto, ik, Tauact, Tauinact GLOBAL minf, ninf, mtau, ntau } UNITS { (mA) = (milliamp) (mV) = (millivolt) (mM) = (milli/liter) } PARAMETER { gto=0.3304e-3 (S/cm2) <0,1e9> Tauact=1 (ms) Tauinact=1 (ms) } STATE { m n } ASSIGNED { v (mV) celsius (degC) : 37 ik (mA/cm2) minf ninf mtau (ms) ntau (ms) ek (mV) } LOCAL k INITIAL { rates(v) m = minf n = ninf } BREAKPOINT { SOLVE states METHOD derivimplicit ik = gto*m*m*m*n*(v - ek) } DERIVATIVE states { : exact when v held constant rates(v) m' = (minf - m)/mtau n' = (ninf - n)/ntau } UNITSOFF FUNCTION alp(v(mV),i) { LOCAL q10 : order m n v = v q10 = 2.2^((celsius - 37)/10) if (i==0) { alp = q10*0.65/(exp(-(v + 10)/8.5) + exp(-(v - 30)/59)) } else if (i==1) { alp = q10/(18.53 + exp((v + 113.7)/10.95)) } } FUNCTION bet(v(mV),i) (/ms) { LOCAL q10 : order m n v = v q10 = 2.2^((celsius - 37)/10) if (i==0){ bet = q10*0.65/(2.5 + exp((v + 82)/17)) }else if (i==1){ bet = q10/(35.56 + exp(-(v + 1.26)/7.44)) } } FUNCTION ce(v(mV),i)(/ms) { : order m n v = v if (i==0) { ce = 1/(1 + exp(-(v + 20.47)/17.54)) }else if (i==1){ ce = 1/(1 + exp((v + 43.1)/5.3)) } } PROCEDURE rates(v) {LOCAL a,b,c :rest = -70 :TABLE minf, ninf, mtau, ntau DEPEND celsius FROM -100 TO 100 WITH 200 a = alp(v,0) b=bet(v,0) c = ce(v,0) mtau = 1/(a + b)/3*Tauact minf = c a = alp(v,1) b=bet(v,1) c = ce(v,1) ntau = 1/(a + b)/3*Tauinact ninf = c } UNITSON