borgkm.mod

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))
}