My approach was to modify the file hh.mod found in nrn/src/nrnoc. Here is the revised mod file, hhbuz.mod:

Code: Select all

```
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
(S) = (siemens)
}
? interface
NEURON {
SUFFIX hhbuz
USEION na READ ena WRITE ina
USEION k READ ek WRITE ik
NONSPECIFIC_CURRENT il
RANGE gnabar, gkbar, gl, el, gna, gk
: do not need mtau
: GLOBAL minf, hinf, ninf, mtau, htau, ntau
GLOBAL minf, hinf, ninf, htau, ntau
THREADSAFE : assigned GLOBALs will be per thread
}
PARAMETER {
: modify these values
:gnabar = .12 (S/cm2) <0,1e9>
:gkbar = .036 (S/cm2) <0,1e9>
:gl = .0003 (S/cm2) <0,1e9>
:el = -54.3 (mV)
gnabar = .035 (S/cm2) <0,1e9>
gkbar = .009 (S/cm2) <0,1e9>
gl = .0001 (S/cm2) <0,1e9>
el = -65 (mV)
}
STATE {
: do not need m, since we are just using minf
: m h n
h n
}
ASSIGNED {
v (mV)
celsius (degC)
ena (mV)
ek (mV)
gna (S/cm2)
gk (S/cm2)
ina (mA/cm2)
ik (mA/cm2)
il (mA/cm2)
minf hinf ninf
: do not need mtau
: mtau (ms) htau (ms) ntau (ms)
mtau (ms) htau (ms) ntau (ms)
}
? currents
BREAKPOINT {
SOLVE states METHOD cnexp
: gna = gnabar*m*m*m*h
gna = gnabar*minf*minf*minf*h
ina = gna*(v - ena)
gk = gkbar*n*n*n*n
ik = gk*(v - ek)
il = gl*(v - el)
}
INITIAL {
rates(v)
: m = minf we do not have an 'm' gating variable, since using m_inf
h = hinf
n = ninf
}
? states
DERIVATIVE states {
rates(v)
: m' = (minf-m)/mtau
h' = 5*(hinf-h)/htau
n' = 5*(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, q10
TABLE minf, mtau, hinf, htau, ninf, ntau DEPEND celsius FROM -100 TO 100 WITH 200
:modified value according to Buzsaki model
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
:mtau = 1/(q10*sum)
minf = alpha/sum
:"h" sodium inactivation system
alpha = .07 * exp(-(v+58)/20)
beta = 1 / (exp(-(v+28)/10) + 1)
sum = alpha + beta
htau = 1/(q10*sum)
hinf = alpha/sum
:"n" potassium activation system
alpha = .01*vtrap(-(v+34),10)
beta = .125*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
```

Code: Select all

```
create soma
access soma
// I copied and pasted this from Buzsaki's hoc file on modeldb
soma {
Ra = 100 // geometry
nseg = 1
cm=1
diam = 10.
L = 10./PI
}
insert hhbuz
soma ek=-90
soma ena=55
//insert hh
//soma ek=-77
//soma ena=50
psection()
//set up current to be injected into model neuron
objref clamp
soma clamp = new IClamp(0.5)
clamp.del = 25
clamp.dur = 100
clamp.amp = 0.001
//graphical display
objref g
g = new Graph()
g.size(0,125,-80,40)
g.addvar("soma.v(0.5)")
//simulation control
dt=0.025
tstop=125
v_init=-70
proc initialize() {
finitialize(v_init)
fcurrent()
}
proc integrate() {
g.begin()
while(t<tstop) {
fadvance()
g.plot(t)
}
g.flush()
}
proc go() {
initialize()
integrate()
}
```

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In the above hoc file, if I comment the lines insert hhbuz, soma ek=-90, and soma ena=55, and then uncomment the lines insert hh, soma ek=-77, and soma ena=50, I get the following plot:

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So the code works just fine for the normal HH model, but when I revise it to try to replicate the Wang-Buzsaki neuron, it fails miserably. Any ideas about what I did wrong would be much appreciated. Thanks.