Active dendrites and spike propagation in a hippocampal interneuron (Saraga et al 2003)

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Accession:28316
We create multi-compartment models of an Oriens-Lacunosum/Moleculare (O-LM) hippocampal interneuron using passive properties, channel kinetics, densities and distributions specific to this cell type, and explore its signaling characteristics. We find that spike initiation depends on both location and amount of input, as well as the intrinsic properties of the interneuron. Distal synaptic input always produces strong back-propagating spikes whereas proximal input could produce both forward and back-propagating spikes depending on the input strength. Please see paper for more details.
Reference:
1 . Saraga F, Wu CP, Zhang L, Skinner FK (2003) Active Dendrites and Spike Propagation in Multi-compartment Models of Oriens-Lacunosum/Moleculare Hippocampal Interneurons. J Physiol 552(3):673-689 [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 interneuron oriens alveus cell;
Channel(s): I Na,t; I A; I K; I h;
Gap Junctions:
Receptor(s): AMPA;
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Dendritic Action Potentials; Active Dendrites; Influence of Dendritic Geometry; Detailed Neuronal Models; Action Potentials;
Implementer(s): Saraga, Fernanda [Fernanda.Saraga at utoronto.ca];
Search NeuronDB for information about:  Hippocampus CA1 interneuron oriens alveus cell; AMPA; I Na,t; I A; I K; I h;
COMMENT

Potassium current for the dendrites
ENDCOMMENT
UNITS {
        (mA) = (milliamp)
        (mV) = (millivolt)
}
 
NEURON {
        SUFFIX Kdend
        USEION k READ ek WRITE ik
        RANGE gkdend, ik
        GLOBAL ninf, nexp, ntau
}
 
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
 
PARAMETER {
        v (mV)
        celsius = 24 (degC)
        dt (ms)
        gkdend = .0230 (mho/cm2)
        ek = -100 (mV)
}
 
STATE {
        n 
}
 
ASSIGNED {
        ik (mA/cm2)
        ninf 
	nexp 
	ntau (ms)
}
 
INITIAL {
	n = ninf
}

BREAKPOINT {
        SOLVE states
	ik = gkdend*n*n*n*n*(v - ek)    
}

PROCEDURE states() {	:exact when v held constant
	evaluate_fct(v)
	n = n + nexp*(ninf - n)
	VERBATIM
	return 0;
	ENDVERBATIM 
}
UNITSOFF
PROCEDURE evaluate_fct(v(mV)) {  :Computes rate and other constants at 
		      :current v.
                      :Call once from HOC to initialize inf at resting v.
        LOCAL q10, tinc, alpha, beta
        TABLE ninf, nexp, ntau DEPEND dt, celsius FROM -200 TO 
100 WITH 300
		q10 = 3^((celsius - 24)/10)
		tinc = -dt*q10
		alpha = 0.018*vtrap(-(v-20),21)
		beta = 0.0036*vtrap(v-30,12)
		ntau = 1/(alpha + beta)
		ninf = alpha*ntau
		nexp = 1-Exp(tinc/ntau)
}
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)
		}
}
FUNCTION Exp(x) {
		if (x < -100) {
			Exp = 0
		}else{
			Exp = exp(x)
		}
}
UNITSON

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