CA1 pyramidal neuron synaptic integration (Bloss et al. 2016)

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Accession:187610
"... We examined synaptic connectivity between molecularly defined inhibitory interneurons and CA1 pyramidal cell dendrites using correlative light-electron microscopy and large-volume array tomography. We show that interneurons can be highly selective in their connectivity to specific dendritic branch types and, furthermore, exhibit precisely targeted connectivity to the origin or end of individual branches. Computational simulations indicate that the observed subcellular targeting enables control over the nonlinear integration of synaptic input or the initiation and backpropagation of action potentials in a branchselective manner. Our results demonstrate that connectivity between interneurons and pyramidal cell dendrites is more precise and spatially segregated than previously appreciated, which may be a critical determinant of how inhibition shapes dendritic computation."
Reference:
1 . Bloss EB, Cembrowski MS, Karsh B, Colonell J, Fetter RD, Spruston N (2016) Structured Dendritic Inhibition Supports Branch-Selective Integration in CA1 Pyramidal Cells. Neuron 89:1016-30 [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): Hippocampus CA1 pyramidal GLU cell;
Channel(s): I Na,t; I K;
Gap Junctions:
Receptor(s): AMPA; NMDA; Gaba;
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Synaptic Integration;
Implementer(s): Cembrowski, Mark S [cembrowskim at janelia.hhmi.org];
Search NeuronDB for information about:  Hippocampus CA1 pyramidal GLU cell; AMPA; NMDA; Gaba; I Na,t; I K;
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arrayTomography
README.txt
dists.mod *
eff.mod *
exc.mod
id.mod *
inh.mod
kad.mod *
kap.mod *
kdr.mod *
na3.mod *
nmdaSyn.mod
syns.mod *
activateExcitation.hoc
activateInhibition.hoc
addChannels.hoc *
addExcitation.hoc
addVgatInhibition.hoc
channelParameters.hoc *
flagVgatInhibition.hoc
getBranchOrder.hoc *
idMorph.hoc
inhibitionBiophysics.hoc
initializationAndRun.hoc *
loadMorph.hoc *
mosinit.hoc *
naceaxon.nrn *
processMorph.hoc *
proofreadMorph.hoc *
resetNSeg.hoc *
start.hoc
synHelperScripts.hoc
twinApical.swc *
                            
COMMENT

Author: Mark Cembrowski, 2012

This is an extension of the Exp2Syn class to incorporate NMDA-like properties,
and incorporates some NMDA features from Elena Saftenku, 2001.

First, Exp2Syn is described:

Two state kinetic scheme synapse described by rise time tau1,
and decay time constant tau2. The normalized peak condunductance is 1.
Decay time MUST be greater than rise time.

The solution of A->G->bath with rate constants 1/tau1 and 1/tau2 is
 A = a*exp(-t/tau1) and
 G = a*tau2/(tau2-tau1)*(-exp(-t/tau1) + exp(-t/tau2))
	where tau1 < tau2

If tau2-tau1 -> 0 then we have a alphasynapse.
and if tau1 -> 0 then we have just single exponential decay.

The factor is evaluated in the
initial block such that an event of weight 1 generates a
peak conductance of 1.

Because the solution is a sum of exponentials, the
coupled equations can be solved as a pair of independent equations
by the more efficient cnexp method.

Next, two extensions have been included:
1.  A switch whether to control whether the condutance is on (isOn)
2.  Voltage gating, mimicking Mg block

ENDCOMMENT

NEURON {
	POINT_PROCESS Exp2SynNmda
	RANGE tau1, tau2, e, i, mgBlock, extMgConc
	NONSPECIFIC_CURRENT i
	RANGE isOn

	RANGE g
}

UNITS {
	(nA) = (nanoamp)
	(mV) = (millivolt)
	(uS) = (microsiemens)
}

PARAMETER {
	tau1=.1 (ms) <1e-9,1e9>
	tau2 = 10 (ms) <1e-9,1e9>
	e=0	(mV)
	alpha_vspom = -0.062 (/mV) :voltage-dependence of Mg2+ block from Maex and De Schutter 1998
	v0_block = 10 (mV)
	extMgConc = 1 (mM) : external Mg concentration
	isOn = 0
}

ASSIGNED {
	v (mV)
	i (nA)
	g (uS)
	factor
	mgBlock
	:extMgConc (mM)
}

STATE {
	A (uS)
	B (uS)
}

INITIAL {
	LOCAL tp
	if (tau1/tau2 > .9999) {
		tau1 = .9999*tau2
	}
	A = 0
	B = 0
	tp = (tau1*tau2)/(tau2 - tau1) * log(tau2/tau1)
	factor = -exp(-tp/tau1) + exp(-tp/tau2)
	factor = 1/factor
}

BREAKPOINT {
	SOLVE state METHOD cnexp
	g = B - A
	mgBlock = vspom(v)
	i = isOn*g*mgBlock*(v - e)

}

DERIVATIVE state {
	A' = -A/tau1
	B' = -B/tau2
}

NET_RECEIVE(weight (uS)) {
	A = A + weight*factor
	B = B + weight*factor
}

FUNCTION vspom (v(mV))( ){
	vspom=1./(1.+0.2801*extMgConc*exp(alpha_vspom*(v-v0_block)))
}

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