COMMENT km.mod Potassium channel, Hodgkin-Huxley style kinetics Based on I-M (muscarinic K channel) Slow, noninactivating Author: Zach Mainen, Salk Institute, 1995, zach@salk.edu ENDCOMMENT NEURON { SUFFIX km USEION k READ ek WRITE ik RANGE n, gk, gbar, gmax RANGE ninf, ntau GLOBAL Ra, Rb GLOBAL q10, temp, tadj, vmin, vmax } UNITS { (mA) = (milliamp) (mV) = (millivolt) (pS) = (picosiemens) (um) = (micron) } PARAMETER { v (mV) gbar = 10 (pS/um2) : 0.03 mho/cm2 tha = -30 (mV) : v 1/2 for inf qa = 9 (mV) : inf slope Ra = 0.001 (/ms/mV) : max act rate (slow) Rb = 0.001 (/ms/mV) : max deact rate (slow) celsius (degC) temp = 23 (degC) : original temp q10 = 2.3 : temperature sensitivity vmin = -120 (mV) vmax = 100 (mV) } ASSIGNED { a (/ms) b (/ms) ik (mA/cm2) gk (pS/um2) ek (mV) ninf ntau (ms) tadj gmax (mho/cm2) } STATE { n } INITIAL { trates(v) n = ninf gk = tadj*gbar*n gmax = (1e-4) * gk } BREAKPOINT { SOLVE states METHOD cnexp gk = tadj*gbar*n ik = (1e-4) * gk * (v - ek) if (((1e-4) * gk) > gmax) { gmax = (1e-4) * gk } } LOCAL nexp DERIVATIVE states { trates(v) n' = (ninf-n)/ntau*tadj } PROCEDURE trates(v (mV)) { :Computes rate and other constants at current v. :Call once from HOC to initialize inf at resting v. TABLE ninf, ntau DEPEND celsius, temp, Ra, Rb, tha, qa FROM vmin TO vmax WITH 199 rates(v): not consistently executed from here if usetable_hh == 1 tadj = q10^((celsius - temp)/10(degC)) :temperature adjastment } PROCEDURE rates(v (mV)) { :Computes rate and other constants at current v. :Call once from HOC to initialize inf at resting v. a = Ra * (v - tha) / (1 - exp(-(v - tha)/qa)) b = -Rb * (v - tha) / (1 - exp((v - tha)/qa)) ntau = 1/(a+b) ninf = a*ntau }