TITLE Fast delayed rectifier potassium channel (voltage dependent) COMMENT Fast delayed rectifier potassium channel (voltage dependent) Ions: k Style: quasi-ohmic From: Yuen and Durand, 1991 (squid axon) Updates: 2014 December (Marianne Bezaire): documented ? ? ?: further shifted the voltage dependence by 65 mV ? ? (Aradi): shifted the voltage dependence by 16 mV ENDCOMMENT VERBATIM #include /* Include this library so that the following (innocuous) warning does not appear: In function '_thread_cleanup': warning: incompatible implicit declaration of built-in function 'free' */ ENDVERBATIM UNITS { (mA) =(milliamp) (mV) =(millivolt) (uF) = (microfarad) (molar) = (1/liter) (nA) = (nanoamp) (mM) = (millimolar) (um) = (micron) FARADAY = 96520 (coul) R = 8.3134 (joule/degC) } NEURON { SUFFIX ch_Kdrfast USEION k READ ek WRITE ik VALENCE 1 RANGE g, gmax, ninf, ntau, ik RANGE myi THREADSAFE } PARAMETER { v (mV) celsius (degC) : temperature - set in hoc; default is 6.3 dt (ms) ek (mV) gmax (mho/cm2) } STATE { n } ASSIGNED { g (mho/cm2) ik (mA/cm2) ninf ntau (ms) nexp myi (mA/cm2) } BREAKPOINT { SOLVE states g = gmax*n*n*n*n ik = g*(v-ek) myi = ik } UNITSOFF INITIAL { trates(v) n = ninf } PROCEDURE states() { :Computes state variables m, h, and n trates(v) : at the current v and dt. n = n + nexp*(ninf-n) } LOCAL q10 PROCEDURE rates(v) { :Computes rate and other constants at current v. :Call once from HOC to initialize inf at resting v. LOCAL alpha, beta, sum :q10 = 3^((celsius - 6.3)/10) q10 = 3^((celsius - 34)/10) :"nf" fKDR activation system alpha = -0.07*vtrap((v+65-47),-6) beta = 0.264/exp((v+65-22)/40) sum = alpha+beta ntau = 1/sum ninf = alpha/sum } PROCEDURE trates(v) { :Computes rate and other constants at current v. :Call once from HOC to initialize inf at resting v. LOCAL tinc TABLE ninf, nexp, ntau DEPEND dt, celsius FROM -100 TO 100 WITH 200 rates(v) : not consistently executed from here if usetable_hh == 1 : so don't expect the tau values to be tracking along with : the inf values in hoc tinc = -dt * q10 nexp = 1 - exp(tinc/ntau) } FUNCTION vtrap(x,y) { :Traps for 0 in denominator of rate eqns. if (fabs(x/y) < 1e-6) { vtrap = y*(1 - x/y/2) }else{ vtrap = x/(exp(x/y) - 1) } } UNITSON