TITLE Kdr.mod   delayed rectifier potassium channel
 
COMMENT
This is the original Hodgkin-Huxley treatment for the set of potassium channel found
in the squid giant axon membrane.
Some parameters have been changed to correspond to McIntyre and Grill (2002) "Extracellular
stimulation of central neurons"
Author: Balbi
ENDCOMMENT
 
UNITS {
        (mA) = (milliamp)
        (mV) = (millivolt)
		(S) = (siemens)
}
 
NEURON {
        SUFFIX Kdr
        USEION k READ ek WRITE ik
        RANGE gkmax, gk
        RANGE ninf, ntau
}
 
PARAMETER { : value for soma
        gkmax = .5 (S/cm2)	  <0,1e9>
}
 
STATE {
        n
}
 
ASSIGNED {
        v (mV)
        ek (mV)

		gk (S/cm2)
        ik (mA/cm2)
        ninf
		ntau (ms)
}
 
BREAKPOINT {
        SOLVE states METHOD cnexp
        gk = gkmax*n*n*n*n
		ik = gk*(v - ek)
} 
 
INITIAL {
	rates(v)
	n = ninf
}

DERIVATIVE states {
        rates(v)
        n' = (ninf-n)/ntau
}
 
PROCEDURE rates(v(mV)) {  
		:Call once from HOC to initialize inf at resting v.
        LOCAL  alpha, beta, sum

UNITSOFF
                :"n" potassium activation system
        ntau = 5/(exp((50+v)/40)+exp(-(50+v)/50))
        ninf = 1/(1+exp((38+v)/-15))
}
 
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