TITLE nax : Na current for axon. No slow inact. : M.Migliore Jul. 1997 : added sh to account for higher threshold M.Migliore, Apr.2002 : WVG @ BBP 2018: add ttx sensitivity NEURON { SUFFIX nax USEION na READ ena WRITE ina USEION ttx READ ttxo, ttxi VALENCE 1 RANGE gbar, sh GLOBAL minf, hinf, mtau, htau,thinf, qinf } PARAMETER { sh = 0 (mV) gbar = 0.010 (mho/cm2) tha = -30 (mV) : v 1/2 for act qa = 7.2 (mV) : act slope (4.5) Ra = 0.4 (/ms) : open (v) Rb = 0.124 (/ms) : close (v) thi1 = -45 (mV) : v 1/2 for inact thi2 = -45 (mV) : v 1/2 for inact qd = 1.5 (mV) : inact tau slope qg = 1.5 (mV) mmin=0.02 hmin=0.5 q10=2 Rg = 0.01 (/ms) : inact recov (v) Rd = .03 (/ms) : inact (v) thinf = -50 (mV) : inact inf slope qinf = 4 (mV) : inact inf slope ena (mV) : must be explicitly def. in hoc celsius v (mV) } UNITS { (mA) = (milliamp) (mV) = (millivolt) (pS) = (picosiemens) (um) = (micron) } ASSIGNED { ttxo (mM) ttxi (mM) ina (mA/cm2) thegna (mho/cm2) minf hinf mtau (ms) htau (ms) } STATE { m h} BREAKPOINT { SOLVE states METHOD cnexp thegna = gbar*m*m*m*h ina = thegna * (v - ena) } INITIAL { if (ttxi == 0.015625 && ttxo > 1e-12) { minf = 0.0 mtau = 1e-12 hinf = 1.0 htau = 1e-12 } else { trates(v,sh) } m=minf h=hinf } DERIVATIVE states { if (ttxi == 0.015625 && ttxo > 1e-12) { minf = 0.0 mtau = 1e-12 hinf = 1.0 htau = 1e-12 } else { trates(v,sh) } m' = (minf-m)/mtau h' = (hinf-h)/htau } PROCEDURE trates(vm,sh2) { LOCAL a, b, qt qt=q10^((celsius-24)/10) a = trap0(vm,tha+sh2,Ra,qa) b = trap0(-vm,-tha-sh2,Rb,qa) mtau = 1/(a+b)/qt if (mtau 1e-6) { trap0 = a * (v - th) / (1 - exp(-(v - th)/q)) } else { trap0 = a * q } }