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 ichan2.mod  
 
COMMENT
konduktivitas valtozas hatasa- somaban 
ENDCOMMENT
 
UNITS {
        (mA) =(milliamp)
        (mV) =(millivolt)
        (uF) = (microfarad)
	(molar) = (1/liter)
	(nA) = (nanoamp)
	(mM) = (millimolar)
	(um) = (micron)
	FARADAY = 96520 (coul)
	R = 8.3134	(joule/degC)
}
 
? interface 
NEURON { 
SUFFIX ichan2 
USEION nat READ enat WRITE inat VALENCE 1
USEION kf READ ekf WRITE ikf  VALENCE 1
USEION ks READ eks WRITE iks  VALENCE 1
NONSPECIFIC_CURRENT il 
RANGE  gnat, gkf, gks
RANGE gnatbar, gkfbar, gksbar
RANGE gl, el
RANGE minf, mtau, hinf, htau, nfinf, nftau, inat, ikf, nsinf, nstau, iks
}
 
INDEPENDENT {t FROM 0 TO 100 WITH 100 (ms)}
 
PARAMETER {
        v (mV) 
        celsius = 6.3 (degC)
        dt (ms) 
        enat  (mV)
	gnatbar (mho/cm2)   
        ekf  (mV)
	gkfbar (mho/cm2)
        eks  (mV)
	gksbar (mho/cm2)
	gl (mho/cm2)    
 	el (mV)
}
 
STATE {
	m h nf ns
}
 
ASSIGNED {
         
        gnat (mho/cm2) 
        gkf (mho/cm2)
        gks (mho/cm2)

        inat (mA/cm2)
        ikf (mA/cm2)
        iks (mA/cm2)


	il (mA/cm2)

	minf hinf nfinf nsinf
 	mtau (ms) htau (ms) nftau (ms) nstau (ms)
	mexp hexp nfexp nsexp
} 

? currents
BREAKPOINT {
	SOLVE states
        gnat = gnatbar*m*m*m*h  
        inat = gnat*(v - enat)
        gkf = gkfbar*nf*nf*nf*nf
        ikf = gkf*(v-ekf)
        gks = gksbar*ns*ns*ns*ns
        iks = gks*(v-eks)

	il = gl*(v-el)
}
 
UNITSOFF
 
INITIAL {
	trates(v)
	
	m = minf
	h = hinf
      nf = nfinf
      ns = nsinf
	
	VERBATIM
	return 0;
	ENDVERBATIM
}

? states
PROCEDURE states() {	:Computes state variables m, h, and n 
        trates(v)	:      at the current v and dt.
        m = m + mexp*(minf-m)
        h = h + hexp*(hinf-h)
        nf = nf + nfexp*(nfinf-nf)
        ns = ns + nsexp*(nsinf-ns)
        VERBATIM
        return 0;
        ENDVERBATIM
}
 
LOCAL q10

? rates
PROCEDURE rates(v) {  :Computes rate and other constants at current v.
                      :Call once from HOC to initialize inf at resting v.
        LOCAL  alpha, beta, sum
       q10 = 3^((celsius - 6.3)/10)
                :"m" sodium activation system - act and inact cross at -40
	alpha = -0.3*vtrap((v+60-17),-5)
	beta = 0.3*vtrap((v+60-45),5)
	sum = alpha+beta        
	mtau = 1/sum      minf = alpha/sum
                :"h" sodium inactivation system
	alpha = 0.23/exp((v+60+5)/20)
	beta = 3.33/(1+exp((v+60-47.5)/-10))
	sum = alpha+beta
	htau = 1/sum 
        hinf = alpha/sum 
             :"ns" sKDR activation system
        alpha = -0.028*vtrap((v+65-35),-6)
	beta = 0.1056/exp((v+65-10)/40)
	sum = alpha+beta        
	nstau = 1/sum      nsinf = alpha/sum
            :"nf" fKDR activation system
        alpha = -0.07*vtrap((v+65-47),-6)
	beta = 0.264/exp((v+65-22)/40)
	sum = alpha+beta        
	nftau = 1/sum      nfinf = alpha/sum
	
}
 
PROCEDURE trates(v) {  :Computes rate and other constants at current v.
                      :Call once from HOC to initialize inf at resting v.
	LOCAL tinc
        TABLE minf, mexp, hinf, hexp, nfinf, nfexp, nsinf, nsexp, mtau, htau, nftau, nstau
	DEPEND dt, celsius FROM -100 TO 100 WITH 200
                           
	rates(v)	: not consistently executed from here if usetable_hh == 1
		: so don't expect the tau values to be tracking along with
		: the inf values in hoc

	       tinc = -dt * q10
        mexp = 1 - exp(tinc/mtau)
        hexp = 1 - exp(tinc/htau)
	nfexp = 1 - exp(tinc/nftau)
	nsexp = 1 - exp(tinc/nstau)
}
 
FUNCTION vtrap(x,y) {  :Traps for 0 in denominator of rate eqns.
        if (fabs(x/y) < 1e-6) {
                vtrap = y*(1 - x/y/2)
        }else{  
                vtrap = x/(exp(x/y) - 1)
        }
}
 
UNITSON


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