TITLE A-type potassium channel

COMMENT
A-type K+ channel
From: 
Updates:
20100910-MJCASE-documented
ENDCOMMENT

VERBATIM
#include <stdlib.h> /* 	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)
}

PARAMETER {
	v (mV)
        ek (mV)
      celsius (degC) : temperature - set in hoc; default is 6.3
	gmax=.01 (mho/cm2)
        vhalfn=-33.6   (mV)
        vhalfl=-83   (mV)
        a0l=0.08      (/ms)
        a0n=0.02    (/ms)
        zetan=-3    (1)
        zetal=4    (1)
        gmn=0.6   (1)
        gml=1   (1)
}


NEURON {
	SUFFIX ch_KvA
	USEION k READ ek WRITE ik
        RANGE gmax,g, ik
        RANGE myi
        GLOBAL ninf,linf,taul,taun : note that these four are not thread safe
    THREADSAFE
}

STATE {
	n
        l
}

INITIAL {
        rates(v)
        n=ninf
        l=linf
}

ASSIGNED {
	ik (mA/cm2)
        ninf
        linf      
        taul
        taun
        g
	myi (mA/cm2)
}

BREAKPOINT {
	SOLVE states METHOD cnexp
	g = gmax*n*l
	ik = g*(v-ek)
	myi = ik

}


FUNCTION alpn(v(mV)) {
  alpn = exp(1.e-3*zetan*(v-vhalfn)*9.648e4/(8.315*(273.16+celsius))) 
}

FUNCTION betn(v(mV)) {
  betn = exp(1.e-3*zetan*gmn*(v-vhalfn)*9.648e4/(8.315*(273.16+celsius))) 
}

FUNCTION alpl(v(mV)) {
  alpl = exp(1.e-3*zetal*(v-vhalfl)*9.648e4/(8.315*(273.16+celsius))) 
}

FUNCTION betl(v(mV)) {
  betl = exp(1.e-3*zetal*gml*(v-vhalfl)*9.648e4/(8.315*(273.16+celsius))) 
}

DERIVATIVE states { 
        rates(v)
        n' = (ninf - n)/taun
        l' = (linf - l)/taul
}

PROCEDURE rates(v (mV)) { :callable from hoc
        LOCAL a,q10
        q10=3^((celsius-30)/10)
        a = alpn(v)
        ninf = 1/(1 + a)
        taun = betn(v)/(q10*a0n*(1+a))
        a = alpl(v)
        linf = 1/(1+ a)
        taul = betl(v)/(q10*a0l*(1 + a))
}