Spontaneous activity of vestibular ganglion neurons recorded in vitro from mouse inner ear explants during postnatal development

Intracellular recordings from neurons in the mouse trigeminal ganglion (TG) in vitro were used to characterize changes in membrane properties that take place from early postnatal stages (P0–P7) to adulthood (>P21). All neonatal TG neurons had uniformly slow conduction velocities, whereas adult neurons could be separated according to their conduction velocity into Aδ and C neurons. Based on the presence or absence of a marked inflection or hump in the repolarization phase of the action potential (AP), neonatal neurons were divided into S- (slow) and F-type (fast) neurons. Their passive and subthreshold properties (resting membrane potential, input resistance, membrane capacitance, and inward rectification) were nearly identical, but they showed marked differences in AP amplitude, AP overshoot, AP duration, rate of AP depolarization, rate of AP repolarization, and afterhyperpolarization (AHP) duration. Adult TG neurons also segregated into S- and F-type groups. Differences in their mean AP amplitude, AP overshoot, AP duration, rate of AP depolarization, rate of AP repolarization, and AHP duration were also prominent. In addition, axons of 90% of F-type neurons and 60% of S-type neurons became faster conducting in their central and peripheral branch, suggestive of axonal myelination. The proportion of S- and F-type neurons did not vary during postnatal development, suggesting that these phenotypes were established early in development. Membrane properties of both types of TG neurons evolved differently during postnatal development. The nature of many of these changes was linked to the process of myelination. Thus myelination was accompanied by a decrease in AP duration, input resistance ( R in), and increase in membrane capacitance (C). These properties remained constant in unmyelinated neurons (both F- and S-type). In adult TG, all F-type neurons with inward rectification were also fast-conducting Aδ, suggesting that those F-type neurons showing inward rectification at birth will evolve to F-type Aδ neurons with age. The percentage of F-type neurons showing inward rectification also increased with age. Both F- and S-type neurons displayed changes in the sensitivity of the AP to reductions in extracellular Ca2+ or substitution with Co2+ during the process of maturation.

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Mechanotransduction and hyperpolarization-activated currents contribute to spontaneous activity in mouse vestibular ganglion neurons

The Journal of General Physiology ◽

10.1085/jgp.201311126 ◽

2014 ◽

Vol 143 (4) ◽

pp. 481-497 ◽

Cited By ~ 23

Author(s):

Geoffrey C. Horwitz ◽

Jessica R. Risner-Janiczek ◽

Jeffrey R. Holt

Keyword(s):

Hair Cell ◽

Spontaneous Activity ◽

Action Potentials ◽

Ex Vivo ◽

Vestibular Neuron ◽

Vestibular Ganglion ◽

Vestibular Hair Cells ◽

Reverse Transcription Pcr ◽

Current Clamp Mode ◽

Ganglion Neurons

The hyperpolarization-activated, cyclic nucleotide–sensitive current, Ih, is present in vestibular hair cells and vestibular ganglion neurons, and is required for normal balance function. We sought to identify the molecular correlates and functional relevance of Ih in vestibular ganglion neurons. Ih is carried by channels consisting of homo- or heteromeric assemblies of four protein subunits from the Hcn gene family. The relative expression of Hcn1–4 mRNA was examined using a quantitative reverse transcription PCR (RT-PCR) screen. Hcn2 was the most highly expressed subunit in vestibular neuron cell bodies. Immunolocalization of HCN2 revealed robust expression in cell bodies of all vestibular ganglion neurons. To characterize Ih in vestibular neuron cell bodies and at hair cell–afferent synapses, we developed an intact, ex vivo preparation. We found robust physiological expression of Ih in 89% of cell bodies and 100% of calyx terminals. Ih was significantly larger in calyx terminals than in cell bodies; however, other biophysical characteristics were similar. Ih was absent in calyces lacking Hcn1 and Hcn2, but small Ih was still present in cell bodies, which suggests expression of an additional subunit, perhaps Hcn4. To determine the contributions of hair cell mechanotransduction and Ih to the firing patterns of calyx terminals, we recorded action potentials in current-clamp mode. Mechanotransduction currents were modulated by hair bundle defection and application of calcium chelators to disrupt tip links. Ih activity was modulated using ZD7288 and cAMP. We found that both hair cell transduction and Ih contribute to the rate and regularity of spontaneous action potentials in the vestibular afferent neurons. We propose that modulation of Ih in vestibular ganglion neurons may provide a mechanism for modulation of spontaneous activity in the vestibular periphery.

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Inhibition of MMP-2 but not MMP-9 Influences Inner Ear Spiral Ganglion Neurons In Vitro

Cellular and Molecular Neurobiology ◽

10.1007/s10571-014-0077-2 ◽

2014 ◽

Vol 34 (7) ◽

pp. 1011-1021 ◽

Cited By ~ 2

Author(s):

Michael Sung ◽

Eric Wei ◽

Eduardo Chavez ◽

Neha Jain ◽

Soledad Levano ◽

...

Keyword(s):

Inner Ear ◽

Spiral Ganglion ◽

Spiral Ganglion Neurons ◽

Ganglion Neurons

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Responsiveness of rat vestibular ganglion neurons to exogenous neurotrophic factors during postnatal development in dissociated cultures

Brain Research ◽

10.1016/j.brainres.2011.06.058 ◽

2011 ◽

Vol 1408 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Yasuhiro Chihara ◽

Shinichi Iwasaki ◽

Kenji Kondo ◽

Tatsuya Yamasoba

Keyword(s):

Postnatal Development ◽

Neurotrophic Factors ◽

Vestibular Ganglion ◽

Ganglion Neurons

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A Novel Small Molecule Neurotrophin-3 Analogue Promotes Inner Ear Neurite Outgrowth and Synaptogenesis In vitro

Frontiers in Cellular Neuroscience ◽

10.3389/fncel.2021.666706 ◽

2021 ◽

Vol 15 ◽

Author(s):

Judith S. Kempfle ◽

Marlon V. Duro ◽

Andrea Zhang ◽

Carolina D. Amador ◽

Richard Kuang ◽

...

Keyword(s):

Inner Ear ◽

Neurite Outgrowth ◽

Small Molecule ◽

Hair Cells ◽

Spiral Ganglion ◽

Sensory Hair ◽

Neurotrophin 3 ◽

Sensory Hair Cells ◽

Ganglion Neurons

Sensorineural hearing loss is irreversible and is associated with the loss of spiral ganglion neurons (SGNs) and sensory hair cells within the inner ear. Improving spiral ganglion neuron (SGN) survival, neurite outgrowth, and synaptogenesis could lead to significant gains for hearing-impaired patients. There has therefore been intense interest in the use of neurotrophic factors in the inner ear to promote both survival of SGNs and re-wiring of sensory hair cells by surviving SGNs. Neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF) represent the primary neurotrophins in the inner ear during development and throughout adulthood, and have demonstrated potential for SGN survival and neurite outgrowth. We have pioneered a hybrid molecule approach to maximize SGN stimulation in vivo, in which small molecule analogues of neurotrophins are linked to bisphosphonates, which in turn bind to cochlear bone. We have previously shown that a small molecule BDNF analogue coupled to risedronate binds to bone matrix and promotes SGN neurite outgrowth and synaptogenesis in vitro. Because NT-3 has been shown in a variety of contexts to have a greater regenerative capacity in the cochlea than BDNF, we sought to develop a similar approach for NT-3. 1Aa is a small molecule analogue of NT-3 that has been shown to activate cells through TrkC, the NT-3 receptor, although its activity on SGNs has not previously been described. Herein we describe the design and synthesis of 1Aa and a covalent conjugate of 1Aa with risedronate, Ris-1Aa. We demonstrate that both 1Aa and Ris-1Aa stimulate neurite outgrowth in SGN cultures at a significantly higher level compared to controls. Ris-1Aa maintained its neurotrophic activity when bound to hydroxyapatite, the primary mineral component of bone. Both 1Aa and Ris-1Aa promote significant synaptic regeneration in cochlear explant cultures, and both 1Aa and Ris-1Aa appear to act at least partly through TrkC. Our results provide the first evidence that a small molecule analogue of NT-3 can stimulate SGNs and promote regeneration of synapses between SGNs and inner hair cells. Our findings support the promise of hydroxyapatite-targeting bisphosphonate conjugation as a novel strategy to deliver neurotrophic agents to SGNs encased within cochlear bone.

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The Role of Cyclooxygenase in Multiplication and Reactivation of HSV-1 in Vestibular Ganglion Neurons

The Scientific World JOURNAL ◽

10.1155/2014/912640 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Yuehong Liu ◽

Shufeng Li ◽

Zhengmin Wang

Keyword(s):

Trichostatin A ◽

Vestibular Ganglion ◽

Dependent Inhibition ◽

Latently Infected ◽

Inflammatory Drugs ◽

Ganglion Neurons ◽

New Treatments ◽

Hsv 1

Reactivation of latent herpes simplex type 1 (HSV-1) and nerve inflammation have been shown to be involved in vertigo-related vestibular pathogenesis. Treatments of such diseases have been less than perfect. Nonsteroidal anti-inflammatory drugs (NSAIDs) have been reported to suppress reactivation of HSV-1 in trigeminal ganglions. However, whether this drug can affect reactivation of HSV-1 in vestibular ganglions is unclear. Due to the difficulties of constructingin vivoanimal models, in this study, we developed a vestibular ganglion culture system, in which vestibular neurons were latently or lytically infected with HSV-1. Indomethacin and celecoxib were selected to measure their effects on HSV-1. Trichostatin A was used to reactivate HSV-1 in latently infected neurons. Cycloxygenase-2, which is the target of NSAIDs, was induced by HSV-1 in the lytically infected cultures, with an increase of 14-fold. Although it appeared that indomethacin and celecoxib showed limited but concentration-dependent inhibition effects on viral production under our condition, indomethacin decreased reactivation rate of HSV-1 by about 20%. Though morein vitroorin vivostudies are needed to confirm the effects of the drugs, our study may provide a potential way to investigate the mechanism of HSV-related vestibular pathogenesis as well as new treatments of vertigo-related diseases.

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Pulsed infrared radiation excites cultured neonatal spiral and vestibular ganglion neurons by modulating mitochondrial calcium cycling

Journal of Neurophysiology ◽

10.1152/jn.00253.2014 ◽

2014 ◽

Vol 112 (6) ◽

pp. 1246-1255 ◽

Cited By ~ 25

Author(s):

Vicente Lumbreras ◽

Esperanza Bas ◽

Chhavi Gupta ◽

Suhrud M. Rajguru

Keyword(s):

Plasma Membrane ◽

Infrared Radiation ◽

Ruthenium Red ◽

Neonatal Rat ◽

Functional Improvement ◽

Calcium Cycling ◽

Activation Temperature ◽

Vestibular Ganglion ◽

Ganglion Neurons

Cochlear implants are currently the most effective solution for profound sensorineural hearing loss, and vestibular prostheses are under development to treat bilateral vestibulopathies. Electrical current spread in these neuroprostheses limits channel independence and, in some cases, may impair their performance. In comparison, optical stimuli that are spatially confined may result in a significant functional improvement. Pulsed infrared radiation (IR) has previously been shown to elicit responses in neurons. This study analyzes the response of neonatal rat spiral and vestibular ganglion neurons in vitro to IR (wavelength = 1,863 nm) using Ca2+ imaging. Both types of neurons responded consistently with robust intracellular Ca2+ ([Ca2+]i) transients that matched the low-frequency IR pulses applied (4 ms, 0.25–1 pps). Radiant exposures of ∼637 mJ/cm2 resulted in continual neuronal activation. Temperature or [Ca2+] variations in the media did not alter the IR-evoked transients, ruling out extracellular Ca2+ involvement or primary mediation by thermal effects on the plasma membrane. While blockage of Na+, K+, and Ca2+ plasma membrane channels did not alter the IR-evoked response, blocking of mitochondrial Ca2+ cycling with CGP-37157 or ruthenium red reversibly inhibited the IR-evoked [Ca2+]i transients. Additionally, the magnitude of the IR-evoked transients was dependent on ryanodine and cyclopiazonic acid-dependent Ca2+ release. These results suggest that IR modulation of intracellular calcium cycling contributes to stimulation of spiral and vestibular ganglion neurons. As a whole, the results suggest selective excitation of neurons in the IR beam path and the potential of IR stimulation in future auditory and vestibular prostheses.

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