COMMENT
26 Ago 2002 Modification of original channel to allow variable time step and to correct an initialization error.
Done by Michael Hines(michael.hines@yale.e) and Ruggero Scorcioni(rscorcio@gmu.edu) at EU Advance Course in Computational Neuroscience. Obidos, Portugal
kca.mod
Calcium-dependent potassium channel
Based on
Pennefather (1990) -- sympathetic ganglion cells
taken from
Reuveni et al (1993) -- neocortical cells
Author: Zach Mainen, Salk Institute, 1995, zach@salk.edu
ENDCOMMENT
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
NEURON {
SUFFIX kca
USEION k READ ek WRITE ik
USEION ca READ cai
RANGE n, gk, gbar
RANGE ninf, ntau
GLOBAL Ra, Rb, caix
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)
cai (mM)
caix = 1
Ra = 0.01 (/ms) : max act rate
Rb = 0.02 (/ms) : max deact rate
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 {
rates(cai)
n = ninf
}
BREAKPOINT {
SOLVE states METHOD cnexp
gk = tadj*gbar*n
ik = (1e-4) * gk * (v - ek)
}
LOCAL nexp
DERIVATIVE states { :Computes state variable n
rates(cai) : at the current v and dt.
n' = (ninf-n)/ntau
}
PROCEDURE rates(cai(mM)) {
a = Ra * cai^caix
b = Rb
tadj = q10^((celsius - temp)/10)
ntau = 1/tadj/(a+b)
ninf = a/(a+b)
: tinc = -dt * tadj
: nexp = 1 - exp(tinc/ntau)
}