AP initiation and propagation in type II cochlear ganglion cell (Hossain et al 2005)

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Accession:54903
The model of type II cochlear ganglion cell was based on the immunostaining of the mouse auditory pathway. Specific antibodies were used to map the distribution of voltage-dependent sodium channels along the two unmyelinated axon-like processes of the bipolar ganglion cells. Three distinct hot spots were detected. A high density of sodium channels was present over the entire trajectory of sensory endings beneath the outer hair cells (the most distal portion of the peripheral axon). The other two hot spots were localized in the initial segments of both of the axons that flank the unmyelinated bipolar ganglion cell bodies. A biophysical model indicates that all three hot spots might play important roles in action potential initiation and propagation. For instance, the hot spot in the receptor segment is important for transforming the receptor potentials into a full blown action potential (Supplemental Fig. 1). The hot spots in the two paraganglionic axon initial segments are there to ensure the successful propagation of action potentials from the peripheral to the central axon through the cell body. The Readme.txt file provides step by step instructions on how to recreate Figures 6 and 7 of Hossain et al., 2005 paper.
Reference:
1 . Hossain WA, Antic SD, Yang Y, Rasband MN, Morest DK (2005) Where is the spike generator of the cochlear nerve? Voltage-gated sodium channels in the mouse cochlea. J Neurosci 25:6857-68 [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): Cochlear ganglion cell Type II;
Channel(s): I Na,t; I K; I M;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Dendritic Action Potentials; Audition;
Implementer(s): Antic, Srdjan [antic at neuron.uchc.edu];
Search NeuronDB for information about:  I Na,t; I K; I M; 
: 	Sodium chanel from 
:	Contribution of the Kv3.1 potassium channel to high-frequency firing in mouse auditory neurones
:	Lu-Yang Wang, Li Gan, Ian D. Forsythe and Leonard K. Kaczmarek
:	J. Physiol (1998), 501.9, pp. 183-194

NEURON {
	SUFFIX NaCh
	USEION na READ ena WRITE ina
	RANGE gbar, g, ina
	GLOBAL minf, mtau, hinf, htau, am, bm, ah, bh
}

: area in paper is 1000 (um2) so divide our density parameters by 10

UNITS {
	(mV) = (millivolt)
	(S) = (mho)
	(mA) = (milliamp)
}

PARAMETER {
	gbar = 0.1227 (S/cm2) : .5 (uS)
	gamma = .1

	kam = 76.4 (/ms)
	eam = .037 (/mV)
	:kbm = .0381 (/ms)	: typo in paper
	kbm = 6.930852 (/ms)	: personal communication from L. Kaczmarek
	ebm = -.043 (/mV)

	kah = .00013 (/ms)
	eah = -.1216 (/mV)
	kbh = 1.999 (/ms)
	ebh = .0384 (/mV)
}

ASSIGNED {
	v (mV)
	ena (mV)
	ina (mA/cm2)

	minf
	mtau (ms)
	hinf
	htau (ms)

	am (/ms)
	bm (/ms)
	ah (/ms)
	bh (/ms)
}

STATE {
	m h
}

INITIAL {
	rates(v)
	m = minf
	h = hinf
}

BREAKPOINT {
	SOLVE state METHOD cnexp
	ina = gbar*m^3*h*(v - ena)
}

DERIVATIVE state {
	rates(v)
	m' = (minf - m)/mtau
	h' = (hinf - h)/htau
}

PROCEDURE rates(v(mV)) {
	am = kam*exp(eam*v)
	bm = kbm*exp(ebm*v)

	ah = kah*exp(eah*v)
	bh = kbh*exp(ebh*v)

	minf = am/(am + bm)
	mtau = 1/(am + bm)
	hinf = ah/(ah + bh)
	htau = 1/(ah + bh)
}

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