TITLE Hcurrent that uses Na ions
NEURON {
SUFFIX h
RANGE gbar,vhalf, K, taun, ninf, g
USEION na READ ena WRITE ina
: NONSPECIFIC_CURRENT i
}
UNITS {
(um) = (micrometer)
(mA) = (milliamp)
(uA) = (microamp)
(mV) = (millivolt)
(pmho) = (picomho)
(mmho) = (millimho)
}
PARAMETER { : parameters that can be entered when function is called in cellsetup
dt (ms)
v (mV)
ena = 50 (mV)
eh = 10 (mV)
K = 8.5 (mV)
gbar = 0 (mho/cm2) : initialize conductance to zero
:vhalf = 90 (mV) : half potential
vhalf = 81 (mV) : half potential
}
STATE { : the unknown parameters to be solved in the DEs
n
}
ASSIGNED { : parameters needed to solve DE
ina (mA/cm2)
ninf
taun (ms)
g
}
INITIAL { : initialize the following parameter using states()
states()
n = ninf
g = gbar*n
ina = g*(veh)
}
BREAKPOINT {
SOLVE h METHOD derivimplicit
g = gbar*n
ina = g*(veh)
}
DERIVATIVE h {
states()
n' = (ninf  n)/taun
}
PROCEDURE states() {
if (v > 30) {
taun = 1
} else {
:taun = 2*(1/(exp((v+145)/17.5)+exp((v+16.8)/16.5)) + 5) :h activation tau
taun = 5*(1/(exp((v+145)/17.5)+exp((v+16.8)/16.5)) + 5) :h activation tau
}
ninf = 1  (1 / (1 + exp((vhalf  v)/K))) :steady state value
}
