COMMENT
Sodium current for the soma
References:
1. Martina, M., Vida, I., and Jonas, P. Distal initiation and active
propagation of action potentials in interneuron dendrites,
Science, 287:295-300, 2000.
soma axon-lacking dend axon-bearing dend
Na+ gmax 107 ps/um2 117 ps/um2 107 ps/um2
slope 10.9 mV/e 11.2 mV/e 11.2 mV/e
V1/2 -37.8 mV -45.6 mV -45.6 mV
2. Marina, M. and Jonas, P. Functional differences in Na+ channel
gating between fast-spiking interneurons and principal neurones of rat
hippocampus, J. Physiol., 505.3:593-603, 1997.
*Note* The interneurons here are basket cells from the dentate gyrus.
Na+ Activation V1/2 -25.1 mV
slope 11.5
Activation t (-20 mV) 0.16 ms
Deactivation t (-40 mV) 0.13 ms
Inactivation V1/2 -58.3 mV
slope 6.7
onset of inactivation t (-20 mV) 1.34 ms
onset of inactivation t (-55 mV) 18.6 ms
recovery from inactivation t 2.0 ms
(30 ms conditioning pulse)
recovery from inactivation t 2.7 ms
(300 ms conditioning pulse)
ENDCOMMENT
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
}
NEURON {
SUFFIX Nasoma
USEION na READ ena WRITE ina
RANGE gna, ina
GLOBAL minf, hinf, hexp, mtau, htau
}
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
PARAMETER {
v (mV)
celsius = 24 (degC)
dt (ms)
gna = .0107 (mho/cm2)
ena = 90 (mV)
}
STATE {
m h
}
ASSIGNED {
ina (mA/cm2)
minf
mexp
hinf
hexp
mtau (ms)
htau (ms)
}
INITIAL {
rate(v)
m = minf
h = hinf
}
BREAKPOINT {
SOLVE state METHOD cnexp
ina = gna*m*m*m*h*(v - ena)
}
DERIVATIVE state {
rate(v)
m'=(minf-m)/mtau
h'=(hinf-h)/htau
}
UNITSOFF
PROCEDURE rate(v(mV)) { :Computes rate and other constants at
:current v.
:Call once from HOC to initialize inf at resting v.
LOCAL q10, tinc, alpha, beta
TABLE minf, hinf, hexp, mtau, htau DEPEND celsius FROM -200 TO 100 WITH 300
q10 = 3^((celsius - 24)/10)
tinc = -dt*q10
alpha = 0.1*vtrap(-(v+38),10)
beta = 4*exp(-(v+63)/18)
mtau = 1/(alpha + beta)
minf = alpha*mtau
alpha = 0.07*exp(-(v+63)/20)
beta = 1/(1+exp(-(v+33)/10))
htau = 1/(alpha + beta)
hinf = alpha*htau
hexp = 1-exp(tinc/htau)
}
FUNCTION vtrap(x,y) { :Traps for 0 in denominator of rate eqns.
if (fabs(x/y) < 1e-6) {
vtrap = y*(1 - x/y/2)
}else{
vtrap = x/(exp(x/y) - 1)
}
}
UNITSON