Dendro-dendritic synaptic circuit (Shepherd Brayton 1979)

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Accession:144385
A NEURON simulation has been created to model the passive spread of an EPSP from a mitral cell synapse on a granule cell spine. The EPSP was shown to propagate subthreshold through the dendritic shaft into an adjacent spine with significant amplitude (figure 2B).
Reference:
1 . Shepherd GM, Brayton RK (1979) Computer simulation of a dendrodendritic synaptic circuit for self- and lateral-inhibition in the olfactory bulb. Brain Res 175:377-82 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Dendrite;
Brain Region(s)/Organism:
Cell Type(s):
Channel(s):
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Influence of Dendritic Geometry; Olfaction;
Implementer(s): Morse, Tom [Tom.Morse at Yale.edu];
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ShepherdBrayton1979
mod
readme
ampa.mod *
ca.mod
cad.mod *
cadiffus.mod *
canmda.mod *
car.mod *
excite.mod
gabaa.mod *
inhib.mod
kca.mod *
km.mod
kv.mod
na.mod
nmda.mod *
                            
TITLE Calcium ion accumulation with longitudinal and radial diffusion

COMMENT
PROCEDURE factors_cadiffus() sets up the scale factors 
needed to model radial diffusion.
These scale factors do not have to be recomputed
when diam is changed.
The amount of calcium in an annulus is ca[i]*diam^2*vol[i] 
with ca[0] being the 2nd order correct concentration at the exact edge
and ca[NANN-1] being the concentration at the exact center.

ENDCOMMENT

NEURON {
	SUFFIX cadiffus
	USEION ca READ cai, ica WRITE cai
	GLOBAL vrat
}

DEFINE Nannuli  4

UNITS {
	(molar) =	(1/liter)
	(mM) =	(millimolar)
	(um) =	(micron)
	(mA) =	(milliamp)
	FARADAY =	(faraday)	(10000 coulomb)
	PI = (pi)	(1)
}

PARAMETER {
	DCa = 	0.23		(um2/ms) 
}

ASSIGNED {
	diam	(um)
	ica		(mA/cm2)
	cai		(mM)
	vrat[Nannuli]		: numeric value of vrat[i] equals the volume
                        : of annulis i of a 1um diameter cylinder
                        : multiply by diam^2 to get volume per um length
	B0		(mM)
}

CONSTANT { volo = 1e10 (um2)}

STATE {
	ca[Nannuli]		(mM) <1e-6>	: ca[0] is equivalent to cai
}

BREAKPOINT {
	SOLVE state METHOD sparse
}

LOCAL factors_done

INITIAL {
	if (factors_done == 0) {
		factors_done = 1
		factors()
	}

	FROM i=0 TO Nannuli-1 {
		ca[i] = cai
	}
}


LOCAL frat[Nannuli]

PROCEDURE factors() {
	LOCAL r, dr2
	r = 1/2			:starts at edge (half diam)
	dr2 = r/(Nannuli-1)/2	:half thickness of annulus
	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)	:exterior edge of annulus
					: divided by distance between centers
		r = r - dr2
		vrat[i+1] = PI*(r+dr2/2)*2*dr2	:outer half of annulus
	}
}

LOCAL dsq, dsqvol	: can't define local variable in KINETIC block 
			: or use in COMPARTMENT

KINETIC state {
	COMPARTMENT i, diam*diam*vrat[i] {ca CaBuffer Buffer}
	LONGITUDINAL_DIFFUSION i, DCa*diam*diam*vrat[i] {ca}
	~ ca[0] << (-ica*PI*diam/(2*FARADAY))
	FROM i=0 TO Nannuli-2 {
		~ ca[i] <-> ca[i+1] (DCa*frat[i+1], DCa*frat[i+1])
	}
cai = ca[0]
}

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