Excitability of PFC Basal Dendrites (Acker and Antic 2009)

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Accession:117207
".. We carried out multi-site voltage-sensitive dye imaging of membrane potential transients from thin basal branches of prefrontal cortical pyramidal neurons before and after application of channel blockers. We found that backpropagating action potentials (bAPs) are predominantly controlled by voltage-gated sodium and A-type potassium channels. In contrast, pharmacologically blocking the delayed rectifier potassium, voltage-gated calcium or Ih, conductance had little effect on dendritic action potential propagation. Optically recorded bAP waveforms were quantified and multicompartmental modeling (NEURON) was used to link the observed behavior with the underlying biophysical properties. The best-fit model included a non-uniform sodium channel distribution with decreasing conductance with distance from the soma, together with a non-uniform (increasing) A-type potassium conductance. AP amplitudes decline with distance in this model, but to a lesser extent than previously thought. We used this model to explore the mechanisms underlying two sets of published data involving high frequency trains of action potentials, and the local generation of sodium spikelets. ..."
Reference:
1 . Acker CD, Antic SD (2009) Quantitative assessment of the distributions of membrane conductances involved in action potential backpropagation along basal dendrites. J Neurophysiol 101:1524-41 [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: Neocortex;
Cell Type(s): Neocortex V1 L6 pyramidal corticothalamic GLU cell;
Channel(s): I Na,t; I L high threshold; I T low threshold; I A; I K; I h; I Potassium;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Activity Patterns; Dendritic Action Potentials; Parameter Fitting; Active Dendrites; Detailed Neuronal Models; Calcium dynamics;
Implementer(s): Acker, Corey [acker at uchc.edu];
Search NeuronDB for information about:  Neocortex V1 L6 pyramidal corticothalamic GLU cell; I Na,t; I L high threshold; I T low threshold; I A; I K; I h; I Potassium;
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acker_antic
Model
ca.mod *
Cad.mod
CaT.mod
IL.mod
kadist.mod
kaprox.mod *
kv.mod
na.mod
PlateauConductance.mod
vmax.mod
CA 229.hoc
PFC_L5Pyramid_AckerAntic06.hoc
                            
TITLE decay of internal calcium concentration
:
: Internal calcium concentration calculated from calcium currents 
: and buffered by endogenous buffer and extrusion mechanism.
:
: Uses differential equations from Helmchen 1996
:dCa/dt = (dCa_T delta_t - (gamma*(dCa - Ca_rest)))/kb
: or dCa/dt = (dCa_T delta_t)/kb - (dCa - Ca_rest)/taur 
: with  taur = kb/gamma
:
: to add exogenous buffer kb = 1+kendo+kexo
: for OGB-1 kexo = concOGB1/kd = 200uM/0.2uM => kb=1020
: for OGB-6 kexo = concOGB6/kd = 200uM/3uM   => kb=80
:
: mod file was modified from original version (Destexhe 92)
: use diam/4 instead of depth to calculate [Ca]
: Units checked using "modlunit" -> factor 10000 needed in ca entry
:
: Written by B Kampa May 2006

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

NEURON {
	SUFFIX cad
	USEION ca READ ica, cai WRITE cai
	RANGE ca
	GLOBAL depth,cainf,taur
}

UNITS {
	(molar) = (1/liter)			: moles do not appear in units
	(mM)	= (millimolar)
	(um)	= (micron)
	(mA)	= (milliamp)
	(msM)	= (ms mM)
	FARADAY = (faraday) (coulomb)
}


PARAMETER {
	diam		(um)
	depth	= .1	(um)		: no used anymore, uses diam/4 now
	taur	= 15	(ms)		: Ca decay from Sabatini 2002, uses kb/gamma now
	kb 	= 20			: buffer ratio from Sabatini 2002
	cainf	= 100e-6(mM)	: will be adjusted during init phase
	cai		(mM)
	gamma =1.2	(1/ms)
}

STATE {
	ca		(mM) <1e-5>
}

INITIAL {
	ca = cainf
	cai = ca
}

ASSIGNED {
	ica		(mA/cm2)
	drive_channel	(mM/ms)
}
	
BREAKPOINT {
	SOLVE state METHOD derivimplicit
}

DERIVATIVE state { 
	depth = diam/4
	drive_channel =  - (10000) * ica / (2 * FARADAY * depth)
	if (drive_channel <= 0.) { drive_channel = 0. }	: cannot pump inward
	taur = kb/gamma
	ca' = (drive_channel/kb) + ((cainf-ca)/taur)
	cai = ca
}

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