TITLE Motor Axon Node channels : fast k in juxtaparanodal region model, based on: : : McIntyre CC, Grill WM, Sherman DL, and Thakor NV. 2004. Cellular effects of deep brain : stimulation: model-based analysis of activation and inhibition. J Neurophysiol 91: 1457-1469. NEURON { SUFFIX fastK USEION k READ ek WRITE ik NONSPECIFIC_CURRENT iflut RANGE gkfbar, gflut, eflut RANGE n_inf RANGE tau_n } UNITS { (mA) = (milliamp) (mV) = (millivolt) } PARAMETER { gkfbar = 0.04 (mho/cm2) gflut (mho/cm2) eflut=-70 (mV) } STATE { n } ASSIGNED { v (mV) ek (mV) ik (mA/cm2) iflut (mA/cm2) n_inf tau_n (ms) } BREAKPOINT { SOLVE states METHOD cnexp ik = gkfbar*n*n*n*n*(v - ek) iflut = gflut*(v-eflut) } DERIVATIVE states { evaluate_fct(v) n'= (n_inf - n) / tau_n } UNITSOFF INITIAL { evaluate_fct(v) n = n_inf } PROCEDURE evaluate_fct(v(mV)) { LOCAL a,b a = vtrap(v) b = vtrap0(v) tau_n = 1 / (a + b) n_inf = a / (a + b) } FUNCTION vtrap(x) { if (fabs((x+83.2)/1.1) < 1e-6) { vtrap = 0.0462*1.1 }else{ vtrap = (0.0462*(x+83.2)) / (1 - exp(-(x+83.2)/1.1)) } } FUNCTION vtrap0(x) { if (fabs((x+66)/10.5) < 1e-6) { vtrap0 = 0.0824*10.5 }else{ vtrap0 = (0.0824*(-(x+66))) / (1 - exp((x+66)/10.5)) } } UNITSON