COMMENT
k_slow.mod
voltage gated potassium channel, Hodgkin-Huxley style kinetics.
Kinetics were fit to data from recordings of nucleated patches derived
from pyramidal neurons. Data recordings and fits from Alon Korngreen
Author: Alon Korngreen, MPImF Cell Physiology, 1998,
alon@mpimf-heidelberg.mpg.de
last updated 31/7/2002 by AK
ENDCOMMENT
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
NEURON {
SUFFIX kslow
THREADSAFE
USEION k READ ek WRITE ik
RANGE a, b, b1,gk, gbar, vshift, vshift2, ik
RANGE ainf, taua, binf, taub,taub1
GLOBAL a0, a1, a2, a3, a4, a5, a6
GLOBAL b0, b11, b2, b3, b4, b5
GLOBAL bb0,bb1,bb2,bb3,bb4
GLOBAL v05a, za, v05b, zb
GLOBAL q10, temp, tadj, vmin, vmax
}
PARAMETER {
gbar = 0 (S/cm2) :
vshift = 0 (mV) : voltage shift
vshift2 = 0 (mV) : a second voltage shift
v05a = -14.3 (mV) : v 1/2 for act (a)
za = 14.6 (mV) : act slope
v05b = -58 (mV) : v 1/2 for inact (b)
zb = -11 (mV) : inact slope
a0 = 0.0052 (1/ms 1/mV) : parameters for alpha and beta for activation
a1 = 11.1 (mV) : see below
a2 = 13.1 (mV) : see below
a3 = 0.01938 (1/ms) : see below
a4 = -1.27 (mV) : see below
a5 = 71 (mV)
a6 = -0.0053 (1/ms)
b0 = 360 (ms) : fast inact tau (taub) (ms)
b11 = 1010 (ms) : see below
b2 = -75 (mV) : see below
b3 = 48 (mV) : see below
b4 = 23.7 (ms/mV)
b5 = -54 (mV)
bb0 = 2350 (ms) : Slow inactivation tau (taub1)
bb1 = 1380 (ms)
bb2 = 0.01118 (mV)
bb3 = -210 (ms)
bb4 = 0.0306 (mV)
temp = 21 (degC) : original temp
q10 = 2.3 : temperature sensitivity
v (mV)
celsius (degC)
vmin = -120 (mV)
vmax = 1000 (mV)
}
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
(pS) = (picosiemens)
(um) = (micron)
}
ASSIGNED {
ik (mA/cm2)
gk (S/cm2)
ek (mV)
ainf
binf
taua (ms)
taub (ms)
taub1 (ms)
tadj
}
STATE {a b b1}
INITIAL {
rates(v-vshift-vshift2)
a = ainf
b = binf
b1= binf
}
BREAKPOINT {
SOLVE states METHOD cnexp
gk = tadj*gbar*a*a*(0.5*b+0.5*b1)
ik = gk * (v - ek)
}
LOCAL aexp, bexp,b1exp, z
DERIVATIVE states {
rates(v-vshift-vshift2)
a' = (ainf-a)/taua
b' = (binf-b)/taub
b1' = (binf-b1)/taub1
}
PROCEDURE rates(vm) {
LOCAL alpha, beta
TABLE taua, ainf, binf, taub, taub1 DEPEND celsius FROM vmin TO vmax WITH 1600
tadj = q10^((celsius - temp)/10)
alpha=a0*(vm-a1)/(1-exp(-(vm-a1)/a2))
beta=a3*exp(-(vm-a4)/a5)+a6
taua=1/(alpha+beta)
if (taua<1e-7) {
taua=1e-7
}
ainf = alpha/(alpha+beta)
taub = b0 + (b11+b4*(vm-b5))*exp(-(vm-b2)*(vm-b2)/(b3*b3))
if (taub<1e-7) {
taub=1e-7
}
taub1=bb0+bb1*exp(-bb2*vm)+bb3*exp(-bb4*vm)
if (taub1<1e-7) {
taub1=1e-7
}
binf = 1/(1+exp(-(vm-v05b)/zb))
}