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
                            
TITLE gskch.mod  calcium-activated potassium channel (non-voltage-dependent)

COMMENT

gsk granule

ENDCOMMENT

UNITS {
        (molar) = (1/liter)
        (mM)    = (millimolar)
	(mA)	= (milliamp)
	(mV)	= (millivolt)
}

NEURON {
	SUFFIX gskch
	USEION sk READ esk WRITE isk VALENCE 1
	USEION nca READ ncai VALENCE 2
	USEION lca READ lcai VALENCE 2
	USEION tca READ tcai VALENCE 2
	RANGE gsk, gskbar, qinf, qtau, isk
}

INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

PARAMETER {
	celsius=6.3 (degC)
	v		(mV)
	dt		(ms)
	gskbar  (mho/cm2)
	esk	(mV)
	cai (mM)
	ncai (mM)
	lcai (mM)
	tcai (mM)
}

STATE { q }

ASSIGNED {
	isk (mA/cm2) gsk (mho/cm2) qinf qtau (ms) qexp
}


BREAKPOINT {          :Computes i=g*q^2*(v-esk)
	SOLVE state
        gsk = gskbar * q*q
	isk = gsk * (v-esk)
}

UNITSOFF

INITIAL {
	cai = ncai + lcai + tcai	
	q=qinf
	rate(cai)
	VERBATIM
	ncai = _ion_ncai;
	lcai = _ion_lcai;
	tcai = _ion_tcai;
	ENDVERBATIM
}


PROCEDURE state() {  :Computes state variable q at current v and dt.
	cai = ncai + lcai + tcai
	rate(cai)
	q = q + (qinf-q) * qexp
	VERBATIM
	return 0;
	ENDVERBATIM
}

LOCAL q10
PROCEDURE rate(cai) {  :Computes rate and other constants at current v.
	LOCAL alpha, beta, tinc
	q10 = 3^((celsius - 6.3)/10)
		:"q" activation system
alpha = 1.25e1 * cai * cai
beta = 0.00025 

:	alpha = 0.00246/exp((12*log10(cai)+28.48)/-4.5)
:	beta = 0.006/exp((12*log10(cai)+60.4)/35)
: alpha = 0.00246/fctrap(cai)
: beta = 0.006/fctrap(cai)
	qtau = 1 / (alpha + beta)
	qinf = alpha * qtau
	tinc = -dt*q10
	qexp = 1 - exp(tinc/qtau)*q10
}

UNITSON

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