TITLE Borg-Graham K-M channel UNITS { (mA) = (milliamp) (mV) = (millivolt) (mM) = (milli/liter) } PARAMETER { cai (mM) v (mV) ek (mV) celsius (degC) gkmbar=.003 (mho/cm2) vhalf=-55 (mV) a0=0.006 (/ms) zeta=-10 (1) gm=0.06 (1) st=1 } NEURON { SUFFIX borgkm USEION k READ ek WRITE ik RANGE gkmbar GLOBAL inf,tau } STATE { m } ASSIGNED { ik (mA/cm2) inf tau } INITIAL { rate(v) m=inf } BREAKPOINT { SOLVE state METHOD cnexp ik = gkmbar*m^st*(v-ek) } FUNCTION alp(v(mV)) { alp = exp( 1.e-3*zeta*(v-vhalf)*9.648e4/(8.315*(273.16+celsius))) } FUNCTION bet(v(mV)) { bet = exp(1.e-3*zeta*gm*(v-vhalf)*9.648e4/(8.315*(273.16+celsius))) } DERIVATIVE state { rate(v) m' = (inf - m)/tau } PROCEDURE rate(v (mV)) { :callable from hoc LOCAL a,q10 q10=5^((celsius-23)/10) a = alp(v) inf = 1/(1 + a) tau = bet(v)/(q10*a0*(1+a)) }