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COMMENT
USAGE: for most receptors
*****************************************************************************
NEURON {
POINT_PROCESS NAME
}
PARAMETER {
Cdur = 1.08 (ms) : transmitter duration (rising phase)
Alpha = 1 (/ms mM) : forward (binding) rate
Beta = 0.02 (/ms) : backward (unbinding) rate
Erev = -80 (mV) : reversal potential
}
INCLUDE "netsyn.inc"
*****************************************************************************
USAGE: for NMDA receptor
*****************************************************************************
NEURON{ POINT_PROCESS NMDA
RANGE B
}
PARAMETER {
mg = 1. (mM) : external magnesium concentration
Cdur = 1. (ms) : transmitter duration (rising phase)
Alpha = 4. (/ms mM) : forward (binding) rate
Beta = 0.0067 (/ms) : backward (unbinding) rate 1/150
Erev = 0. (mV) : reversal potential
}
ASSIGNED { B }
INCLUDE "netcon.inc"
: EXTRA BREAKPOINT MUST BE BELOW THE INCLUDE
BREAKPOINT {
rates(v)
g = g * B : but don't really need to readjust conductance
i = i * B : i = g*(v - Erev)
}
PROCEDURE rates(v(mV)) {
TABLE B
DEPEND mg
FROM -100 TO 80 WITH 180
B = 1 / (1 + exp(0.062 (/mV) * -v) * (mg / 3.57 (mM)))
}
*****************************************************************************
ENDCOMMENT
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
NEURON {
RANGE g
NONSPECIFIC_CURRENT i
GLOBAL Cdur, Alpha, Beta, Erev, Rinf, Rtau
}
UNITS {
(nA) = (nanoamp)
(mV) = (millivolt)
(umho) = (micromho)
(mM) = (milli/liter)
}
ASSIGNED {
v (mV) : postsynaptic voltage
i (nA) : current = g*(v - Erev)
g (umho) : conductance
Rinf : steady state channels open
Rtau (ms) : time constant of channel binding
R : fraction of open channels
synon
}
STATE {Ron Roff}
INITIAL {
R = 0
Rinf = Alpha / (Alpha + Beta)
Rtau = 1 / (Alpha + Beta)
synon = 0
}
BREAKPOINT {
SOLVE release METHOD cnexp
g = (Ron + Roff)*1(umho)
i = g*(v - Erev)
}
DERIVATIVE release {
Ron' = (synon*Rinf - Ron)/Rtau
Roff' = -Beta*Roff
}
: following supports both saturation from single input and
: summation from multiple inputs
: if spike occurs during CDur then new off time is t + CDur
: ie. transmitter concatenates but does not summate
: Note: automatic initialization of all reference args to 0 except first
NET_RECEIVE(weight, on, nspike, r0, t0 (ms)) {
: flag is an implicit argument of NET_RECEIVE and normally 0
if (flag == 0) { : a spike, so turn on if not already in a Cdur pulse
nspike = nspike + 1
if (!on) {
r0 = r0*exp(-Beta*(t - t0))
t0 = t
on = 1
synon = synon + weight
state_discontinuity(Ron, Ron + r0)
state_discontinuity(Roff, Roff - r0)
}
: come again in Cdur with flag = current value of nspike
net_send(Cdur, nspike)
}
if (flag == nspike) { : if this associated with last spike then turn off
r0 = weight*Rinf + (r0 - weight*Rinf)*exp(-(t - t0)/Rtau)
t0 = t
synon = synon - weight
state_discontinuity(Ron, Ron - r0)
state_discontinuity(Roff, Roff + r0)
on = 0
}
}
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