HH-ext.ode

# HH-ext.ode: an XppAut file for the Hodgkin-Huxley equations
# + strength of external electrical field
# time in msec, voltage in mV and frequency in Hz

# initial conditions
init V=0, m=0.052, h=0.596, n=0.317

# the parameters
param Vext=8, iapp=1, freq=0.3
param VNa=115,VK=-12,VL=10.599, gNa=120
param gK=36, gL=0.3, cm=1

# time constants and steady state functions for gating variables
am(v)=0.1*(25-v)/(exp((25-v)/10)-1)
bm(v)=4*exp(-v/18)
ah(v)=0.07*exp(-v/20)
bh(v)=1/(exp((30-v)/10)+1)
an(v)=0.01*(10-v)/(exp((10-v)/10)-1)
bn(v)=0.125*exp(-v/80)

vex(t)=vext*(sin(2*pi*(freq/1000)*t))
ik=gk*n^4*(v+vex(t)-vk)
ina=gna*m^3*h*(v+vex(t)-vna)
il=gl*(v+vex(t)-vl)

# the equations
v'=(-ik-ina-il+iapp)/cm
m'=(am(v)*(1-m)-bm(v)*m)
n'=(an(v)*(1-n)-bn(v)*n)
h'=(ah(v)*(1-h)-bh(v)*h)

aux vex=vex(t)

# set xpp parameters
@ total=25000, xp=t, yp=v, xlo=0, xhi=25000, ylo=-20, yhi=120, bounds=10000000, dt=0.01
@ maxstor=10000000
done