Heterogeneous Voltage Dependence of Inward Rectifier Currents in Spiral Ganglion Neurons

Mo, Zun-Li; Davis, Robin L.

doi:10.1152/jn.1997.78.6.3019

Cited by 71 publications

(76 citation statements)

References 50 publications

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“…5) is indicative of the presence of the hyperpolarization-activated currents (I h ). Previous studies have shown that spiral ganglion neurons possess I h currents with a wide range of steady state voltages of activation in spiral ganglion neurons isolated from restricted regions of the cochlea (Mo and Davis, 1997b). We wished to determine, therefore, whether NT-3 would affect the magnitude or time course of voltage changes in response to step hyperpolarizing constant-current injections that reflect the activity of the I h currents.…”

Section: Resultsmentioning

confidence: 99%

Complex Regulation of Spiral Ganglion Neuron Firing Patterns by Neurotrophin-3

Zhou

Liu²,

Davis³

2005

J. Neurosci.

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Auditory information is conveyed into the CNS via the spiral ganglion neurons, cells that possess distinctive electrophysiological properties that vary according to their cochlear innervation. Neurons from the base of the cochlea fire action potentials with shorter latencies and durations with more rapid accommodation than apical neurons (Adamson et al., 2002b). Interestingly, these features are altered by exposure to brain-derived neurotrophic factor and neurotrophin-3 (NT-3), suggesting that the electrophysiological diversity is not preprogrammed into the neurons but instead results from extrinsic regulation. In support of this, gradients of neurotrophins exist in the cochlea that could account for the apex-base differences in firing. To understand the determinants of spiral ganglion function, we characterized the NT-3 concentration dependence and mode of action on spiral ganglion neurons. Whole-cell current-clamp recordings were made from mouse basal spiral ganglion neurons (postnatal day 5) exposed to different concentrations of NT-3 for 3 d in vitro. Measurements of accommodation, latency, onset time course, and action potential latency revealed a nonmonotonic dependence on NT-3 concentration, with a peak effect occurring at 10 ng/ml. Addition of NT-3 at different time points showed that neurotrophin exposure altered the firing features of existing neurons rather than supporting differential survival. These experiments establish that the electrophysiological phenotype of spiral ganglion neurons depends critically on the precise concentration of NT-3 and that the functional organization of this component of the peripheral auditory system results from a complex interplay between multiple kinds of neurotrophins and their cognate receptors.

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Section: Resultsmentioning

confidence: 99%

Complex Regulation of Spiral Ganglion Neuron Firing Patterns by Neurotrophin-3

Zhou

Liu²,

Davis³

2005

J. Neurosci.

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“…The characteristic "sag" in the voltage observed for spiral ganglion neurons (Mo and Davis, 1997b) was slowed in the type II neuron (Fig. 2 F) compared with the neighboring type I (Fig.…”

Section: Basal Type II Spiral Ganglion Neuronsmentioning

confidence: 89%

Firing Patterns of Type II Spiral Ganglion NeuronsIn Vitro

Reid¹,

Flores‐Otero²,

Davis³

2004

J. Neurosci.

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Type I and type II spiral ganglion neurons convey auditory information from the sensory receptors in the cochlea to the CNS. The numerous type I neurons have been extensively characterized, but the small population of type II neurons with their unmyelinated axons are undetectable with most recording methods. Despite the paucity of information about the type II neurons, it is clear that they must have a significant role in sound processing because they innervate the large number of outer hair cells that are critical for maintaining normal responses to stimuli. To elucidate the function of type II neurons, we have developed an approach for studying their electrophysiological features in vitro.Type II neurons obtained from postnatal day 6 -7 mice displayed distinctly different firing properties than type I neurons. They showed slower accommodation, lower action potential thresholds, and more prolonged responses to depolarizing current injection than the type I neurons. These differences were most evident in neurons from the basal, high-frequency region of the cochlea. The basal type I neurons displayed uniformly fast firing features, whereas the basal type II neurons showed particularly slow accommodation and responses to depolarization. Interestingly, neurons from the apical, low-frequency region of the cochlea showed the opposite trend. These data suggest that the type I and type II neurons have specialized electrophysiological characteristics tailored to their different roles in auditory signal processing. In particular, the type II neuron properties are consistent with cells in other sensory systems that receive convergent synaptic input for high-sensitivity stimulus detection.

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“…In other cells, too, reversal potentials of this mixed cation current generally lie between -30 and -44 mV (Bal and Oertel 2000;Banks et al 1993;Chen 1997;Maccaferri and McBain 1996;McCormick and Pape 1990b;Mo and Davis 1997;Saitow and Konishi 2000;Spain et al 1987). This reversal potential reflects a permeability ratio P Na /P K of ϳ0.3 (Wollmuth and Hille 1992).…”

Section: Characteristics Of I H In Neurons From the Vcnmentioning

confidence: 98%

Hyperpolarization-Activated Currents Regulate Excitability in Stellate Cells of the Mammalian Ventral Cochlear Nucleus

Rodrigues¹,

Oertel²

2006

Journal of Neurophysiology

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Rodrigues, Aldo Rogelis A. and Donata Oertel. Hyperpolarizationactivated currents regulate excitability in stellate cells of the mammalian ventral cochlear nucleus. J Neurophysiol 95: 76 -87, 2006. First published September 28, 2005 doi:10.1152/jn.00624.2005. The differing biophysical properties of neurons the axons of which form the different pathways from the ventral cochlear nucleus (VCN) determine what acoustic information they can convey. T stellate cells, excitatory neurons the axons of which project locally and to the inferior colliculus, and D stellate cells, inhibitory neurons the axons of which project to the ipsi-and contralateral cochlear nuclei, fire tonically when they are depolarized, and, unlike other cell types in the VCN, their firing rates are sensitive to small changes in resting currents. In both types of neurons, the hyperpolarization-activated current (I h ) reversed at -40 mV, was activated at voltages negative to Ϫ60 mV, and half-activated at approximately Ϫ88 mV; maximum hyperpolarization-activated conductances (g h max ) were 19.1 Ϯ 2.3 nS in T and 30.3 Ϯ 2.6 nS in D stellate cells (means Ϯ SE). Activation and deactivation were slower in T than in D stellate cells. In both types of stellate cells, 50 M 4(N-ethyl-N-phenylamino)1,2-dimethyl-6-(methylamino) pyridinium chloride (ZD7288) and 2 mM Cs ϩ blocked a 6-to 10-fold greater conductance than the voltage-dependent g h determined from Boltzmann analyses at -62 mV. The voltageinsensitive, ZD7288-sensitive conductance was proportional to g h max and g input . 8-Br-cAMP shifted the voltage dependence of I h in the depolarizing direction, increased the rate of activation, and slowed its deactivation in both T and D stellate cells. Reduction in temperature did not change the voltage dependence but reduced the maximal g h with a Q 10 of 1.3 and slowed the kinetics with a Q 10 of 3.3.

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Heterogeneous Voltage Dependence of Inward Rectifier Currents in Spiral Ganglion Neurons

Cited by 71 publications

References 50 publications

Complex Regulation of Spiral Ganglion Neuron Firing Patterns by Neurotrophin-3

Complex Regulation of Spiral Ganglion Neuron Firing Patterns by Neurotrophin-3

Firing Patterns of Type II Spiral Ganglion NeuronsIn Vitro

Hyperpolarization-Activated Currents Regulate Excitability in Stellate Cells of the Mammalian Ventral Cochlear Nucleus

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