TITLE slowly inactivating K current COMMENT from "An Active Membrane Model of the Cerebellar Purkinje Cell 1. Simulation of Current Clamp in Slice" ENDCOMMENT UNITS { (mA) = (milliamp) (mV) = (millivolt) } NEURON { SUFFIX KD USEION k WRITE ik RANGE gkbar, ik, gk, minf, hinf, mexp, hexp } INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} PARAMETER { v (mV) celsius = 37 (degC) dt (ms) gkbar = .0045 (mho/cm2) ek = -85 (mV) } STATE { m h } ASSIGNED { ik (mA/cm2) gk minf hinf mexp hexp } BREAKPOINT { SOLVE states gk = gkbar * m*h ik = gk* (v-ek) } UNITSOFF INITIAL { rates(v) m = minf h = hinf } PROCEDURE states() { :Computes state variables m, h rates(v) : at the current v and dt. m = m + mexp*(minf-m) h = h + hexp*(hinf-h) } PROCEDURE rates(v) { :Computes rate and other constants at current v. :Call once from HOC to initialize inf at resting v. LOCAL q10, tinc, alpha, beta, sum TABLE minf, mexp, hinf, hexp DEPEND dt, celsius FROM -100 TO 100 WITH 200 q10 = 3^((celsius - 37)/10) tinc = -dt * q10 :"m" potassium activation system alpha = 8.5/(1+exp((v+17)/(-12.5))) beta = 35/(1+exp((v+99)/14.5)) sum = alpha + beta minf = alpha/sum mexp = 1 - exp(tinc*sum/10) :"h" potassium inactivation system alpha = 0.0015/(1+exp((v+89)/8)) beta = 0.0055/(1+exp((v+83)/(-8))) sum = alpha + beta hinf = alpha/sum hexp = 1 - exp(tinc*sum*1.6) } UNITSON