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KD.mod
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KD.mod
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TITLE slowly inactivating K current
COMMENT
from "An Active Membrane Model of the Cerebellar Purkinje Cell
1. Simulation of Current Clamp in Slice"
ENDCOMMENT
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
}
NEURON {
SUFFIX KD
USEION k WRITE ik
RANGE gkbar, ik, gk, minf, hinf, mexp, hexp
}
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
PARAMETER {
v (mV)
celsius = 37 (degC)
dt (ms)
gkbar = .0045 (mho/cm2)
ek = -85 (mV)
mon = 1
hon = 1
}
STATE {
m h
}
ASSIGNED {
ik (mA/cm2)
gk minf hinf mexp hexp
}
BREAKPOINT {
SOLVE states
gk = gkbar * m*h
ik = gk* (v-ek)
}
UNITSOFF
INITIAL {
rates(v)
m = minf
h = hinf
}
PROCEDURE states() { :Computes state variables m, h
rates(v) : at the current v and dt.
m = mon * (m + mexp*(minf-m))
h = hon * (h + hexp*(hinf-h))
}
PROCEDURE rates(v) { :Computes rate and other constants at current v.
:Call once from HOC to initialize inf at resting v.
LOCAL q10, tinc, alpha, beta, sum
TABLE minf, mexp, hinf, hexp DEPEND dt, celsius FROM -400 TO 300 WITH 700
q10 = 3^((celsius - 37)/10)
tinc = -dt * q10
:"m" potassium activation system
alpha = 8.5/(1+exp((v+17)/(-12.5)))
beta = 35/(1+exp((v+99)/14.5))
sum = alpha + beta
minf = alpha/sum
mexp = 1 - exp(tinc*sum/10)
:"h" potassium inactivation system
alpha = 0.0015/(1+exp((v+89)/8))
beta = 0.0055/(1+exp((v+83)/(-8)))
sum = alpha + beta
hinf = alpha/sum
hexp = 1 - exp(tinc*sum*1.6)
}
UNITSON