Coincident signals in Olfactory Bulb Granule Cell spines (Aghvami et al 2019)

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"In the mammalian olfactory bulb, the inhibitory axonless granule cells (GCs) feature reciprocal synapses that interconnect them with the principal neurons of the bulb, mitral, and tufted cells. These synapses are located within large excitable spines that can generate local action potentials (APs) upon synaptic input (“spine spike”). Moreover, GCs can fire global APs that propagate throughout the dendrite. Strikingly, local postsynaptic Ca2+ entry summates mostly linearly with Ca2+ entry due to coincident global APs generated by glomerular stimulation, although some underlying conductances should be inactivated. We investigated this phenomenon by constructing a compartmental GC model to simulate the pairing of local and global signals as a function of their temporal separation ?t. These simulations yield strongly sublinear summation of spine Ca2+ entry for the case of perfect coincidence ?t = 0 ms. ..."
1 . Aghvami SS, Müller M, Araabi BN, Egger V (2019) Coincidence Detection within the Excitable Rat Olfactory Bulb Granule Cell Spines. J Neurosci 39:584-595 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Dendrite; Channel/Receptor; Synapse;
Brain Region(s)/Organism: Olfactory bulb;
Cell Type(s): Olfactory bulb main interneuron granule MC GABA cell; Olfactory bulb main interneuron granule TC GABA cell;
Channel(s): Ca pump; I Calcium; I K; I Sodium;
Gap Junctions:
Receptor(s): NMDA; AMPA;
Transmitter(s): Glutamate;
Simulation Environment: NEURON; Python;
Model Concept(s): Active Dendrites; Calcium dynamics; Coincidence Detection;
Implementer(s): Aghvami, S. Sara [ssa.aghvami at];
Search NeuronDB for information about:  Olfactory bulb main interneuron granule MC GABA cell; Olfactory bulb main interneuron granule TC GABA cell; AMPA; NMDA; I K; I Sodium; I Calcium; Ca pump; Glutamate;
: Calcium ion accumulation with radial and longitudinal diffusion + Pump + Buffers
	SUFFIX cadifusnpumpOGBenddif
	USEION ca READ cai,cao,ica WRITE cai,ica
	RANGE ica_pmp, TotalPump 
	RANGE CaBuf01,CaBufav1,caiav 
	RANGE CaBuf02,CaBufav2	
	RANGE Bufferav1,Bufferav2 
	RANGE k1,k2,k3,k4 
	RANGE ica 
	GLOBAL vrat
	RANGE TotalBuffer1,TotalBuffer2,k1buf1,k2buf1,k1buf2,k2buf2   
	RANGE cai0,cai1,cai2,cai3
	GLOBAL DCa,Dbuf1,Dcabuf1 
	GLOBAL Dbuf2,Dcabuf2 
DEFINE Nannuli 4 : must be >=2 (i.e. at least shell and core)
	FARADAY=(faraday) (10000 coulomb)
	PI=(pi) (1)
	(mol) = (1)

	DCa = 0.6 (um2/ms)

	Dbuf1=0.015 (um2/ms)
	Dcabuf1=0.015 (um2/ms) 

	Dbuf2=0.015 (um2/ms)
	Dcabuf2=0.015 (um2/ms) 
	k1buf1 = 100 (/mM-ms) 
	k2buf1 = 0.1 (/ms)
	TotalBuffer1= 0.003 (mM)

	k1buf2 = 100 (/mM-ms) 
	k2buf2 = 0.1 (/ms)
	TotalBuffer2= 0.003 (mM)

	k1 = 1	   (/mM-ms)
	k2 = 0.005 (/ms)
	k3 = 1	   (/ms)
	k4 = 0.005 (/mM-ms)
	TotalPump = 1e-11 (mol/cm2)  

	diam (um)
	ica (mA/cm2)
	cai (mM)

	cai0 (mM)
	cai1 (mM)
	cai2 (mM)
	cai3 (mM)

	CaBuf01 (mM) 
	CaBuf02 (mM)
	caiav (mM) 
	CaBufav1 (mM)
	CaBufav2 (mM) 
	Bufferav1 (mM)
	Bufferav2 (mM)

	vrat[Nannuli] (1) 

	Kd1 (/mM)
	Kd2 (/mM)
	B01 (mM)
	B02 (mM) 

	cao	(mM)
	ica_pmp	(mA/cm2)
	parea	(um) 


CONSTANT { volo = 1e10  (um2) }


	ca[Nannuli] (mM) <1e-10> 
	CaBuffer1[Nannuli] (mM)
	Buffer1[Nannuli] (mM)
	CaBuffer2[Nannuli] (mM)
	Buffer2[Nannuli] (mM)

	pump	(mol/cm2)
	pumpca	(mol/cm2)

	     ica = ica_pmp }

LOCAL factors_done
	if (factors_done == 0) { : flag becomes 1 in the first segment
	factors_done = 1 : all subsequent segments will have
	factors() : vrat = 0 unless vrat is GLOBAL
	Kd1 = k1buf1/k2buf1
	Kd2 = k1buf2/k2buf2 
	B01 = TotalBuffer1/(1 + Kd1*cai)
	B02 = TotalBuffer2/(1 + Kd2*cai) 
	FROM i=0 TO Nannuli-1 {
			ca[i] = cai
			Buffer1[i] = B01
			CaBuffer1[i] = TotalBuffer1 - B01
			Buffer2[i] = B02
			CaBuffer2[i] = TotalBuffer2 - B02
	parea = PI*diam
	pump = TotalPump/(1 + (cai*k1/k2))
	pumpca = TotalPump - pump :

LOCAL frat[Nannuli] : scales the rate constants for model geometry

PROCEDURE factors() {
		LOCAL r, dr2
		r = 1/2 : starts at edge (half diam)
		dr2 = r/(Nannuli-1)/2 : full thickness of outermost annulus
					: half thickness of all other annuli
		vrat[0] = 0
		frat[0] = 2*r
		FROM i=0 TO Nannuli-2 {
				vrat[i] = vrat[i] + PI*(r-dr2/2)*2*dr2 : interior half
				r = r - dr2
				frat[i+1] = 2*PI*r/(2*dr2) : outer radius of annulus
				: div by distance between centers
				r = r - dr2
				vrat[i+1] = PI*(r+dr2/2)*2*dr2 : outer half of annulus

LOCAL dsq, dsqvol 

KINETIC state {
		COMPARTMENT i, diam*diam*vrat[i] {ca CaBuffer1 Buffer1}
		COMPARTMENT i, diam*diam*vrat[i] {ca CaBuffer2 Buffer2}

		COMPARTMENT (1e10)*parea {pump pumpca}
		COMPARTMENT volo {cao}
		LONGITUDINAL_DIFFUSION i, DCa*diam*diam*vrat[i] {ca}

		LONGITUDINAL_DIFFUSION i, Dcabuf1*diam*diam*vrat[i] {CaBuffer1}
		LONGITUDINAL_DIFFUSION i, Dbuf1*diam*diam*vrat[i] {Buffer1}
		LONGITUDINAL_DIFFUSION i, Dcabuf2*diam*diam*vrat[i] {CaBuffer2}
		LONGITUDINAL_DIFFUSION i, Dbuf2*diam*diam*vrat[i] {Buffer2}
		~ ca[0] + pump <-> pumpca (k1*parea*(1e10), k2*parea*(1e10))
		~ pumpca <-> pump + cao
		(k3*parea*(1e10), k4*parea*(1e10))
		CONSERVE pump + pumpca = TotalPump * parea * (1e10)
		ica_pmp = 2*FARADAY*(f_flux - b_flux)/parea
		~ ca[0] << (-(ica - ica_pmp)*PI*diam/(2*FARADAY)) 
		FROM i=0 TO Nannuli-2 {
				~ ca[i] <-> ca[i+1] (DCa*frat[i+1], DCa*frat[i+1])
				~ Buffer1[i] <-> Buffer1[i+1] (Dbuf1*frat[i+1], Dbuf1*frat[i+1])
				~ CaBuffer1[i] <-> CaBuffer1[i+1] (Dcabuf1*frat[i+1], Dcabuf1*frat[i+1])
				~ Buffer2[i] <-> Buffer2[i+1] (Dbuf2*frat[i+1], Dbuf2*frat[i+1])
				~ CaBuffer2[i] <-> CaBuffer2[i+1] (Dcabuf2*frat[i+1], Dcabuf2*frat[i+1])
		dsq = diam*diam
		FROM i=0 TO Nannuli-1 {
				dsqvol = dsq*vrat[i]
				~ ca[i] + Buffer1[i] <-> CaBuffer1[i] (k1buf1*dsqvol, k2buf1*dsqvol)
				~ ca[i] + Buffer2[i] <-> CaBuffer2[i] (k1buf2*dsqvol, k2buf2*dsqvol) :this migth cause error
		cai = ca[0]
		cai0 = ca[0]
		cai1 = ca[1]
		cai2 = ca[2]
		cai3 = ca[3]

		caiav = 0.25*(ca[0]+ca[1]+ca[2]+ca[3])

		CaBuf01 = CaBuffer1[0] 
		CaBufav1= 0.25*(CaBuffer1[0]+CaBuffer1[1]+CaBuffer1[2]+CaBuffer1[3]) 

		CaBuf02 = CaBuffer2[0] 
		CaBufav2= 0.25*(CaBuffer2[0]+CaBuffer2[1]+CaBuffer2[2]+CaBuffer2[3]) 

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