TITLE Slow Cadependent potassium current
:
: Ca++ dependent K+ current responsible for slow AHP
NEURON {
SUFFIX kca
USEION k READ ek WRITE ik
USEION ca READ cai
RANGE gbar, po, ik
GLOBAL m_inf, tau_m
}
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
(molar) = (1/liter)
(mM) = (millimolar)
}
ASSIGNED { : parameters needed to solve DE
v (mV)
celsius (degC)
ek (mV)
cai (mM) : initial [Ca]i
ik (mA/cm2)
po
m_inf
tau_m (ms)
}
PARAMETER {
gbar = 0 (mho/cm2)
: taumin = 180 (ms) : minimal value of the time cst
taumin = 150 (ms) : minimal value of the time cst
b = 0.004 (/ms)
}
STATE {
m
}
BREAKPOINT {
SOLVE states METHOD cnexp
po = m*m
ik = gbar*po*(v  ek) : potassium current induced by this channel
}
DERIVATIVE states {
rates(cai)
m' = (m_inf  m) / tau_m
}
INITIAL {
rates(cai)
m = m_inf
}
PROCEDURE rates(cai(mM)) { LOCAL a
a = cai/b
m_inf = a/(a+1)
tau_m = taumin+ 1(ms)*1(mM)*b/(cai+b)
}
