TITLE Hodgkin-Huxley like sodium, potassium, and leak channels COMMENT ********************************************* reference: McCormick & Huguenard (1992) J.Neurophysiology 68(4), 1384-1400 found in: cortical pyramidal cells ********************************************* Assembled for MyFirstNEURON by Arthur Houweling ENDCOMMENT INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} UNITS { (mA) = (milliamp) (mV) = (millivolt) } NEURON { SUFFIX HH USEION na READ ena WRITE ina USEION k READ ek WRITE ik NONSPECIFIC_CURRENT il RANGE gnabar,gkbar,gl,el,m_inf,h_inf,n_inf,tau_m,tau_n,tau_h,ina,ik } PARAMETER { v (mV) celsius (degC) dt (ms) gnabar= 0.1 (mho/cm2) ena (mV) gkbar= 0.01 (mho/cm2) ek (mV) gl= 0 (mho/cm2) el (mV) } STATE { m h n } ASSIGNED { ina (mA/cm2) ik (mA/cm2) il (mA/cm2) m_inf h_inf n_inf tau_m tau_h tau_n tadj } BREAKPOINT { SOLVE states ina = gnabar * m*m*m*h * (v - ena) ik = gkbar * n*n*n*n * (v - ek) il = gl * (v-el) } UNITSOFF INITIAL { rates(v) m = m_inf h = h_inf n = n_inf } PROCEDURE states() { rates(v) m = m + (1-exp(-dt/tau_m)) * (m_inf-m) h = h + (1-exp(-dt/tau_h)) * (h_inf-h) n = n + (1-exp(-dt/tau_n)) * (n_inf-n) } PROCEDURE rates(v) { LOCAL alpha, beta, q10, tinc TABLE m_inf, tau_m, h_inf, tau_h, n_inf, tau_n DEPEND dt, celsius FROM -100 TO 100 WITH 200 tadj = 3.0^((celsius-23.5)/10) :"m" sodium activation system alpha = .091 * vtrap(v+38,5) beta = .062 * vtrap(-(v+38),5) tau_m = 1 / (alpha+beta) / tadj m_inf = alpha/(alpha+beta) :"h" sodium inactivation system alpha = .016 * exp(-(v+55)/15) beta = 2.07 / (1+exp((17-v)/21)) tau_h = 1 / (alpha+beta) / tadj h_inf = alpha/(alpha+beta) :"n" potassium activation system alpha = .01*vtrap(v+45,5) beta = .17*exp(-(v+50)/40) tau_n = 1 / (alpha+beta) / tadj n_inf = alpha/(alpha+beta) } FUNCTION vtrap( x, b) { : Traps for 0 in denominator of rate equations if (fabs(x/b) < 1e-6) { vtrap = b+x/2 } else { vtrap = x / (1-exp(-x/b)) } } UNITSON