COMMENT
km.mod
Potassium channel, HodgkinHuxley style kinetics
Based on IM (muscarinic K channel)
Slow, noninactivating
Author: Zach Mainen, Salk Institute, 1995, zach@salk.edu
ENDCOMMENT
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
NEURON {
SUFFIX km
USEION k READ ek WRITE ik
RANGE n, gk, gbar
RANGE ninf, ntau
GLOBAL Ra, Rb
GLOBAL q10, temp, tadj, vmin, vmax
}
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
(pS) = (picosiemens)
(um) = (micron)
}
PARAMETER {
gbar = 10 (pS/um2) : 0.03 mho/cm2
v (mV)
tha = 30 (mV) : v 1/2 for inf
qa = 9 (mV) : inf slope
Ra = 0.001 (/ms) : max act rate (slow)
Rb = 0.001 (/ms) : max deact rate (slow)
dt (ms)
celsius (degC)
temp = 23 (degC) : original temp
q10 = 2.3 : temperature sensitivity
vmin = 120 (mV)
vmax = 100 (mV)
}
ASSIGNED {
a (/ms)
b (/ms)
ik (mA/cm2)
gk (pS/um2)
ek (mV)
ninf
ntau (ms)
tadj
}
STATE { n }
INITIAL {
trates(v)
n = ninf
}
BREAKPOINT {
SOLVE states
gk = tadj*gbar*n
ik = (1e4) * gk * (v  ek)
}
LOCAL nexp
PROCEDURE states() { :Computes state variable n
trates(v) : at the current v and dt.
n = n + nexp*(ninfn)
VERBATIM
return 0;
ENDVERBATIM
}
PROCEDURE trates(v) { :Computes rate and other constants at current v.
:Call once from HOC to initialize inf at resting v.
LOCAL tinc
TABLE ninf, nexp
DEPEND dt, celsius, temp, Ra, Rb, tha, qa
FROM vmin TO vmax WITH 199
rates(v): not consistently executed from here if usetable_hh == 1
tadj = q10^((celsius  temp)/10)
tinc = dt * tadj
nexp = 1  exp(tinc/ntau)
}
PROCEDURE rates(v) { :Computes rate and other constants at current v.
:Call once from HOC to initialize inf at resting v.
a = Ra * (v  tha) / (1  exp((v  tha)/qa))
b = Rb * (v  tha) / (1  exp((v  tha)/qa))
ntau = 1/(a+b)
ninf = a*ntau
}
