Basket cell extrasynaptic inhibition modulates network oscillations (Proddutur et al., 2013)

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Accession:155601
Among the rhythmic firing patterns observed in brain, gamma oscillations, which are involved in memory formation and retrieval, are generated by networks of fast-spiking basket cells (FS-BCs) with robust interconnectivity through fast GABA synapses. Recently, we identified presence of extrasynaptic tonic GABA currents in FS-BCs and showed that experimentally-induced seizures enhance extrasynaptic tonic GABA currents and render GABA reversal potential (EGABA) depolarizing (Yu et al., 2013). Extrasynaptic GABA currents are mediated by extra- and peri-synaptically located GABAARs and can contribute to synaptic decay kinetics. Additionally, shunting rather than hyperpolarizing EGABA has been shown to increase the frequency and reduce coherence of network oscillations. Using homogeneous networks of biophysically-based, multi-compartmental model FS-BCs, we examined how the presence of extrasynaptic GABA currents and the experimentally identified seizure-induced alterations in GABA currents and EGABA modify the frequency and coherence of network firing.
Reference:
1 . Proddutur A, Yu J, Elgammal FS, Santhakumar V (2013) Seizure-induced alterations in fast-spiking basket cell GABA currents modulate frequency and coherence of gamma oscillation in network simulations. Chaos 23:046109 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s): Dentate gyrus basket cell;
Channel(s):
Gap Junctions: Gap junctions;
Receptor(s): GabaA;
Gene(s):
Transmitter(s): Gaba;
Simulation Environment: NEURON;
Model Concept(s): Oscillations;
Implementer(s):
Search NeuronDB for information about:  GabaA; Gaba;
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ProdduturEtAl2013
readme.html
bgka.mod *
CaBK.mod *
ccanl.mod *
gap.mod
Gfluct2.mod *
gskch.mod *
hyperde3.mod *
ichan2.mod *
izap.mod
LcaMig.mod *
markov.mod *
nca.mod *
tca.mod *
tonic.mod *
IClamp 50% gaps 30 SYNAPSES tonicspill -74mV_0.6nA.hoc
PPSTIM 50% gaps 30 SYNAPSES tonicspill -74mV.hoc
screenshot1.png
                            
: $Id: izap.mod,v 1.3 2010/06/22 06:40:59 ted Exp $

COMMENT
izap.mod

Delivers an oscillating current that starts at t = del >= 0.
The frequency of the oscillation increases linearly with time
from f0 at t == del to f1 at t == del + dur, 
where both del and dur are > 0.

Uses event delivery system to ensure compatibility with adaptive integration.

Original implementation 12/4/2008 NTC
ENDCOMMENT

NEURON {
  POINT_PROCESS Izap
  RANGE del, dur, f0, f1, amp, f, i
  ELECTRODE_CURRENT i
}

UNITS {
  (nA) = (nanoamp)
  PI = (pi) (1)
}

PARAMETER {
  del (ms)
  dur (ms)
  f0 (1/s)  : frequency is in Hz
  f1 (1/s)
  amp (nA)
}

ASSIGNED {
  f (1/s)
  i (nA)
  on (1)
}

INITIAL {
  f = 0
  i = 0
  on = 0

  if (del<0) { del=0 }
  if (dur<0) { dur=0 }
  if (f0<=0) { f0=0 (1/s) }
  if (f1<=0) { f1=0 (1/s) }

  : do nothing if dur == 0
  if (dur>0) {
    net_send(del, 1)  : to turn it on and start frequency ramp
  }
}

COMMENT
The angular velocity in radians/sec is w = 2*PI*f, 
where f is the instantaneous frequency in Hz.

Assume for the moment that the frequency ramp starts at t = 0.
f = f0 + (f1 - f0)*t/dur

Then the angular displacement is
theta = 2*PI * ( f0*t + (f1 - f0)*(t^2)/(2*dur) ) 
      = 2*PI * t * (f0 + (f1 - f0)*t/(2*dur))
But the ramp starts at t = del, so just substitute t-del for every occurrence of t
in the formula for theta.
ENDCOMMENT

BREAKPOINT {
  if (on==0) {
    f = 0
    i = 0
  } else {
    f = f0 + (f1 - f0)*(t-del)/dur
    i = amp * sin( 2*PI * (t-del) * (f0 + (f1 - f0)*(t-del)/(2*dur)) * (0.001) )
  }
}

NET_RECEIVE (w) {
  : respond only to self-events with flag > 0
  if (flag == 1) {
    if (on==0) {
      on = 1  : turn it on
      net_send(t+dur, 1)  : to stop frequency ramp, freezing frequency at f1
    } else {
      on = 0  : turn it off
    }
  }
}

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