Graded synapse using NMODL

[noorubm]

Hello,

I'm a recent NEURON user. I'm trying to model graded synapse using NMODL. Here is the code.

Code: Select all

: Graded Synaptic Transmission
NEURON {
  POINT_PROCESS GradSyn
  POINTER vpre
  RANGE e, gmax, x0, dx, g, i
  NONSPECIFIC_CURRENT i
}
UNITS {
  (nA) = (nanoamp)
  (mV) = (millivolt)
  (uS) = (microsiemens)
}
PARAMETER {
  e = -70 (mV)
  gmax = -1 (uS)
  x0 = -20 (mV)
  dx = 4 (mV)
}
ASSIGNED {
  v (mV)
  vpre (mV) : presynaptic voltage
  g (uS)
  i (nA)
}
BREAKPOINT {
  g = gmax*(1/(1+exp((x0-v)/dx)))
  i = g*(v-e)
}

I'm trying to voltage clamp the presynaptic cell and look at the synaptic current. However, the model isn't working. I used setpointer notation to equal vpre to the presynaptic voltage. If any of you could help me out I'll really appreciate it.

Thanks,

Yamin

[ted]

vpre is declared in the ASSIGNED block, and made visible to hoc by a POINTER statement in the NEURON block . . . but never used in any expression.

gmax (and the synaptic conductance g) should be >= 0.

Have you checked this mod file with modlunit?

The mod file uses x0 and dx as names for two parameters with voltage units. Is there a reason not to use names that are more suggestive of their meanings, like v0 and kv? (x is most often used to mean anatomical distance or "range", dx to signify a "delta" (small increment) of some distance, whereas k suggests a proportionality or rate).

[noorubm]

Thank you so much. It worked as soon as used vpre in the expression.

Yamin