COMMENT
IA channel
Reference:
1. Zhang, L. and McBain, J. Voltagegated potassium currents in
stratum oriensalveus inhibitory neurons of the rat CA1
hippocampus, J. Physiol. 488.3:647660, 1995.
Activation V1/2 = 14 mV
slope = 16.6
activation t = 5 ms
Inactivation V1/2 = 71 mV
slope = 7.3
inactivation t = 15 ms
recovery from inactivation = 142 ms
2. Martina, M. et al. Functional and Molecular Differences between
Voltagegated K+ channels of fastspiking interneurons and pyramidal
neurons of rat hippocampus, J. Neurosci. 18(20):81118125, 1998.
(only the gkAbar is from this paper)
gkabar = 0.0175 mho/cm2
Activation V1/2 = 6.2 +/ 3.3 mV
slope = 23.0 +/ 0.7 mV
Inactivation V1/2 = 75.5 +/ 2.5 mV
slope = 8.5 +/ 0.8 mV
recovery from inactivation t = 165 +/ 49 ms
3. Warman, E.N. et al. Reconstruction of Hippocampal CA1 pyramidal
cell electrophysiology by computer simulation, J. Neurophysiol.
71(6):20332045, 1994.
gkabar = 0.01 mho/cm2
(number taken from the work by Numann et al. in guinea pig
CA1 neurons)
ENDCOMMENT
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
}
NEURON {
SUFFIX IA
USEION k READ ek WRITE ik
RANGE gkAbar,ik
GLOBAL ainf, binf, aexp, bexp, tau_b
}
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
PARAMETER {
v (mV)
p = 5 (degC)
dt (ms)
gkAbar = 0.0165 (mho/cm2) :from Martina et al.
ek = 90 (mV)
tau_a = 5 (ms)
}
STATE {
a b
}
ASSIGNED {
ik (mA/cm2)
ainf binf aexp bexp
tau_b
}
BREAKPOINT {
SOLVE deriv METHOD derivimplicit
ik = gkAbar*a*b*(v  ek)
}
INITIAL {
rates(v)
a = ainf
b = binf
}
DERIVATIVE deriv { :Computes state variables m, h, and n rates(v)
: at the current v and dt.
rates(v) : fixes a bug in the original version
a' = (ainf  a)/(tau_a)
b' = (binf  b)/(tau_b)
}
PROCEDURE rates(v) { :Computes rate and other constants at current v.
:Call once from HOC to initialize inf at resting v.
LOCAL alpha_b, beta_b
TABLE ainf, aexp, binf, bexp, tau_a, tau_b DEPEND dt, p FROM 200
TO 100 WITH 300
alpha_b = 0.000009/exp((v26)/18.5)
beta_b = 0.014/(exp((v+70)/(11))+0.2)
ainf = 1/(1 + exp((v + 14)/16.6))
aexp = 1  exp(dt/(tau_a))
tau_b = 1/(alpha_b + beta_b)
binf = 1/(1 + exp((v + 71)/7.3))
bexp = 1  exp(dt/(tau_b))
}
UNITSON
