TITLE gskch.mod calciumactivated potassium channel (nonvoltagedependent)
COMMENT
gsk granule
ENDCOMMENT
UNITS {
(molar) = (1/liter)
(mM) = (millimolar)
(mA) = (milliamp)
(mV) = (millivolt)
}
NEURON {
SUFFIX gskch
USEION sk READ esk WRITE isk VALENCE 1
USEION nca READ ncai VALENCE 2
USEION lca READ lcai VALENCE 2
USEION tca READ tcai VALENCE 2
RANGE gsk, gskbar, qinf, qtau, isk
}
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
PARAMETER {
celsius=6.3 (degC)
v (mV)
dt (ms)
gskbar (mho/cm2)
esk (mV)
cai (mM)
ncai (mM)
lcai (mM)
tcai (mM)
}
STATE { q }
ASSIGNED {
isk (mA/cm2) gsk (mho/cm2) qinf qtau (ms) qexp
}
BREAKPOINT { :Computes i=g*q^2*(vesk)
SOLVE state
gsk = gskbar * q*q
isk = gsk * (vesk)
}
UNITSOFF
INITIAL {
cai = ncai + lcai + tcai
q=qinf
rate(cai)
VERBATIM
ncai = _ion_ncai;
lcai = _ion_lcai;
tcai = _ion_tcai;
ENDVERBATIM
}
PROCEDURE state() { :Computes state variable q at current v and dt.
cai = ncai + lcai + tcai
rate(cai)
q = q + (qinfq) * qexp
VERBATIM
return 0;
ENDVERBATIM
}
LOCAL q10
PROCEDURE rate(cai) { :Computes rate and other constants at current v.
LOCAL alpha, beta, tinc
:q10 = 3^((celsius  6.3)/10)
:"q" activation system
q10 = 1 : BPG
alpha = 1.25e1 * cai * cai
beta = 0.00025
: alpha = 0.00246/exp((12*log10(cai)+28.48)/4.5)
: beta = 0.006/exp((12*log10(cai)+60.4)/35)
: alpha = 0.00246/fctrap(cai)
: beta = 0.006/fctrap(cai)
qtau = 1 / (alpha + beta)
qinf = alpha * qtau
tinc = dt*q10
qexp = 1  exp(tinc/qtau)*q10
}
UNITSON
