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

Ih current	 - hyperpolarization-activated nonspecific Na and K channel
		 - contributes to the resting membrane potential
		 - controls the afterhyperpolarization
Reference:

1.	Maccaferri, G. and McBain, C.J. The hyperpolarization-activated current
	(Ih) and its contribution to pacemaker activity in rat CA1 hippocampal
	stratum oriens-alveus interneurons, J. Physiol. 497.1:119-130,
	1996.

		V1/2 = -84.1 mV
		   k = 10.2
		reversal potential = -32.9 +/- 1.1 mV

at -70 mV, currents were fitted by a single exponetial of t = 2.8+/- 0.76 s
at -120 mV, two exponentials were required, t1 = 186.3+/-33.6 ms 
t2 = 1.04+/-0.16 s


2.	Maccaferri, G. et al. Properties of the
	Hyperpoarization-activated current in rat hippocampal CA1 Pyramidal
	cells. J. Neurophysiol. Vol. 69 No. 6:2129-2136, 1993.

		V1/2 = -97.9 mV
		   k = 13.4
		reversal potential = -18.3 mV

3.	Pape, H.C.  Queer current and pacemaker: The
	hyperpolarization-activated cation current in neurons, Annu. Rev. 
	Physiol. 58:299-327, 1996.

		single channel conductance is around 1 pS
		average channel density is below 0.5 um-2
		0.5 pS/um2 = 0.00005 mho/cm2 = 0.05 umho/cm2		
4.	Magee, J.C. Dendritic Hyperpolarization-Activated Currents Modify
	the Integrative Properties of Hippocampal CA1 Pyramidal Neurons, J.
	Neurosci., 18(19):7613-7624, 1998

Deals with Ih in CA1 pyramidal cells.  Finds that conductance density
increases with distance from the soma.

soma g = 0.0013846 mho/cm2
dendrite g (300-350 um away) = 0.0125 mho/cm2
see Table 1 in th paper

ENDCOMMENT

 UNITS {
        (mA) = (milliamp)
        (mV) = (millivolt)
}
 
NEURON {
        SUFFIX Ih
        USEION h READ eh WRITE ih VALENCE 1
        RANGE gkhbar,ih
        GLOBAL rinf, rexp, tau_r
}
 
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
 
PARAMETER {
        v (mV)
        p = 5 (degC)
        dt (ms)
        gkhbar = 0.001385 (mho/cm2)			
        eh = -32.9 (mV)
}
 
STATE {
        r
}
 
ASSIGNED {
        ih (mA/cm2)
	rinf rexp
	tau_r
}
 
BREAKPOINT {
        SOLVE deriv METHOD derivimplicit
        ih = gkhbar*r*(v - eh)
}
 
INITIAL {
	rates(v)
	r = rinf
}

DERIVATIVE deriv { :Computes state variable h at current v and dt.
	rates(v)
	r' = (rinf - r)/tau_r
}

PROCEDURE rates(v) {  :Computes rate and other constants at current v.
                      :Call once from HOC to initialize inf at resting v.
        TABLE rinf, rexp, tau_r DEPEND dt, p FROM -200
TO 100 WITH 300
	rinf = 1/(1 + exp((v+84.1)/10.2))
	rexp = 1 - exp(-dt/(tau_r))
	tau_r = 100 + 1/(exp(-17.9-0.116*v)+exp(-1.84+0.09*v))
}
 
UNITSON


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