COMMENT 26 Ago 2002 Modification of original channel to allow variable time step and to correct an initialization error. Done by Michael Hines(michael.hines@yale.e) and Ruggero Scorcioni(rscorcio@gmu.edu) at EU Advance Course in Computational Neuroscience. Obidos, Portugal 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 Accession number: 113732 ENDCOMMENT INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} NEURON { SUFFIX km USEION k READ ek WRITE ik RANGE n, gk, gbar RANGE ninf, ntau RANGE Ra, Rb RANGE q10, temp, tadj, vmin, vmax } UNITS { (mA) = (milliamp) (mV) = (millivolt) (pS) = (picosiemens) (um) = (micron) } PARAMETER { gbar = 10 (pS/um2) : 0.03 mho/cm2 v (mV) tha = -30 (mV) : v 1/2 for inf qa = 9 (mV) : inf slope Ra = 0.001 (/ms) : max act rate (slow) Rb = 0.001 (/ms) : max deact rate (slow) dt (ms) 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 } STATE { n } INITIAL { trates(v) n = ninf } BREAKPOINT { SOLVE states METHOD cnexp gk = tadj*gbar*n ik = (1e-4) * gk * (v - ek) } LOCAL nexp DERIVATIVE states { :Computes state variable n trates(v) : at the current v and dt. n' = (ninf-n)/ntau } PROCEDURE trates(v) { :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 : tinc = -dt * tadj : nexp = 1 - exp(tinc/ntau) } PROCEDURE rates(v) { :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)) tadj = q10^((celsius - temp)/10) ntau = 1/tadj/(a+b) ninf = a/(a+b) }