TITLE nethhwbm.mod interneuron sodium, potassium, and leak channels
COMMENT
This file is based on the original hh.mod file (see original comment
below). It was modified to match the model that was used in the
simulations of Wang and Buzsaki (1996, J. Neurosci. 16).
***************************************************************************
This is the original Hodgkin-Huxley treatment for the set of sodium,
potassium, and leakage channels found in the squid giant axon membrane.
("A quantitative description of membrane current and its application
conduction and excitation in nerve" J.Physiol. (Lond.) 117:500-544 (1952).)
Membrane voltage is in absolute mV and has been reversed in polarity
from the original HH convention and shifted to reflect a resting potential
of -65 mV.
Remember to set celsius=6.3 (or whatever) in your HOC file.
See squid.hoc for an example of a simulation using this model.
SW Jaslove 6 March, 1992
***************************************************************************
changes:
- m is substituted by it"s steady state value: m_inf - see 'BREAKPOINT'
{as a result mtau is not needed, 'minf' is removed from
GLOBAL declaration and 'm' is included in the RANGE var list
otherwise it will be handled as a GLOBAL var and will not be
evaluated separately for the 'sections'; for 'h' an 'n' this
is not a problem}
- for h and n alpha and beta values are multiplied by 5
(see factor "Phi" in the W&B model)
- USEION removed as we don't want to deal with ions and set eNa and
eK directly. Rev potentials 'egna' and 'egk' are in the PARAMETERS
list
- temp: set to 6.3 Celsius, alpha and beta values are set/manipulated
directly to simulate characteristic firing pattern
I. Vida, Nov. 2000
***************************************************************************
ENDCOMMENT
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
}
? interface
NEURON {
SUFFIX hh_wbm
NONSPECIFIC_CURRENT ina,ik,il
RANGE gnabar,gna,egna,m, gkbar,gk,egk, gl,el
GLOBAL hinf, ninf, htau, ntau
}
PARAMETER {
gnabar = .035 (mho/cm2) <0,1e9>
egna = 55 (mV)
gkbar = .009 (mho/cm2) <0,1e9>
egk = -90 (mV)
gl = .0001 (mho/cm2) <0,1e9>
el = -65 (mV)
}
STATE {
m h n
}
ASSIGNED {
v (mV)
celsius (degC)
gna (mho/cm2)
ina (mA/cm2)
gk (mho/cm2)
ik (mA/cm2)
il (mA/cm2)
minf hinf ninf
htau (ms) ntau (ms)
}
LOCAL mexp, hexp, nexp
? currents
BREAKPOINT {
SOLVE states METHOD cnexp
m = minf
gna = gnabar*m*m*m*h
ina = gna*(v - egna)
gk = gkbar*n*n*n*n
ik = gk*(v - egk)
il = gl*(v - el)
}
INITIAL {
rates(v)
m = minf
h = hinf
n = ninf
}
? states
DERIVATIVE states {
rates(v)
h' = (hinf-h)/htau
n' = (ninf-n)/ntau
}
LOCAL q10
? rates
PROCEDURE rates(v(mV)) { :Computes rate and other constants at current v.
:Call once from HOC to initialize inf at resting v.
LOCAL alpha, beta, sum
TABLE minf, hinf, htau, ninf, ntau DEPEND celsius FROM -100 TO 100 WITH 200
UNITSOFF
q10 = 3^((celsius - 6.3)/10)
:"m" sodium activation system
alpha = .1 * vtrap(-(v+35),10)
beta = 4 * exp(-(v+60)/18)
sum = alpha + beta
minf = alpha/sum
:"h" sodium inactivation system
alpha =.35 * exp(-(v+58)/20)
beta = 5 / (exp(-(v+28)/10) + 1)
sum = alpha + beta
htau = 1/(q10*sum)
hinf = alpha/sum
:"n" potassium activation system
alpha =.05*vtrap(-(v+34),10)
beta = .625*exp(-(v+44)/80)
sum = alpha + beta
ntau = 1/(q10*sum)
ninf = alpha/sum
}
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