No abstract available.
Cochlear Implantation ; Cochlear Implants ; Neurons ; Spiral Ganglion

No abstract available.
Electric Stimulation* ; Evoked Potentials, Auditory, Brain Stem* ; Spiral Ganglion*

Mice ; Animals ; Spiral Ganglion/physiology* ; Cochlea/physiology* ; Neurons

OBJECTIVES: To examine the expression profile of Fas-Fas ligand (FasL) during glutamate (Glu)-induced spiral ganglion cell (SGC) apoptosis. METHODS: Cultured SGCs were treated with 10-mM, 25-mM, and 50-mM concentrations of Glu and incubated for 24 or 48 hours. The expression intensity of FasL, Fas, caspase 3, and morphology of single SGC were evaluated using immunofluorescence staining. RESULTS: In semiquantitative analysis of the Glu-treated SGC, FasL, and caspase 3 expression intensity were increased with concentration- and time-dependent manner. Fas expression intensity did not change with different concentration at 48 hours. In morphologic analysis of the Glu-treated SGC, number of apoptotic cells were increased with concentration- and time-dependent manner. CONCLUSION: FasL was expressed in apoptotic SGCs, suggesting that the Fas-FasL signaling pathway may be involved in the Glu-induced apoptosis of dissociated SGCs.
Apoptosis* ; Caspase 3 ; Fas Ligand Protein ; Fluorescent Antibody Technique ; Glutamic Acid ; Spiral Ganglion*

Animals ; Cells, Cultured ; Electrophysiology ; Mice ; Mice, Inbred Strains ; Neurons ; physiology ; Potassium Channels ; physiology ; Spiral Ganglion ; physiology

OBJECTIVETo establishing the cochlea slice technique and infrared visual slice patch clamp method in order to observe the electrophysiological characteristics of rat spiral ganglion neurons (SGN) METHODS: SD rats were divided into three groups according to postnatal days old (0-2 d, 3-6 d and 7-14 d). Making slice of SD rat cochlear quickly, using infrared differential interference contrast (IR-DIC) technique, together with slice patch clamp, the electrophysiological characteristics of rat spiral ganglion neurons were observed, and factors which affected the quality of cochlear slice and recording of patch clamp were analyzed.

RESULTSThe success rate of 3-6 days SD was the highest, and 2-4 pieces of slice could be made from each cochlea. Cochlea connecting with partial skull and integrity of cochlear hull were the key for making slice, and the angle of modiolus axis should be adjusted to be parallel to the knife and the preparing time should be shorter. The SGN cell of good condition could be easily found and the seal test became easier with the help of infrared visual slice patch clamp method. The rest membrane potential was (-45.6 +/- 5.3) mV (x +/- s, n=52) and the current of Na+ and K+ could be activated.

CONCLUSIONSCochlear slice technique can retain structural integrity, cell viability and their association in cochlea, which suggest that this technique provides carrier for electrophysiological study of rat spiral ganglion neurons, and patch clamp with infrared videomicroscopy method can be used to make direct real-time observation in electrophysiological experiments of SGN, which can provide important technique support and reference for deep study of electrophysiological characteristics of SGN and auditory neurotransmission in cochlea.

Animals ; Cochlea ; physiology ; Microtomy ; Neurons ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Spiral Ganglion ; physiology

OBJECTIVETo assess the protection against cisplatin-induced ototoxicity by adenovirus-mediated overexpression of the bcl-2 gene in cultured spiral ganglion cells (SGC).

METHODSSGC from P3 rats were cultured in vitro and exposed to adenovirus vector carrying green fluorescent protein gene (Ad-GFP), followed by immunocytochemical analysis for expression of the neuron-specific marker Neurofilament 200 (NF200) and detection under laser scanning confocal fluorescence microscope. Then, SGC were transduced by Ad-bcl-2 and the expression of human bcl-2 protein was evaluated by Western Blot. Finally, the cultures of SGC were divided into 4 groups: the group of Ad-bcl-2 transfection followed by cisplatin treatment, the group of Ad-GFP transfection followed by cisplatin treatment, the group of cisplatin treatment only and the untreated group. Cisplatin worked for 48 hours at a concentration of 2 microg/ml. Outcome measures included survival number of SGC and longest neurite length by using ImageJ software.

RESULTSSGC were cultured successfully in vitro and transfected by adenovirus vector safely and efficiently. By Western Blot, human bcl-2 protein was expressed in the group after exposure to Ad-bcl-2, but not in the Ad-GFP transfected SGC. Cisplatin exposure resulted in shrinking of neuritis and pyknosis of cell body, even cell death. Expression of bcl-2 in the SGC provided a significant level of protection against cisplatin-induced SGC degeneration.

CONCLUSIONSOur results suggest that SGC can be transduced by adenovirus vector safely and efficiently in vitro. Adenovirus-mediated delivery of the bcl-2 gene attenuates cisplatin-induced SGC degeneration.

Adenoviridae ; genetics ; Animals ; Apoptosis ; drug effects ; Cisplatin ; pharmacology ; Genes, bcl-2 ; Humans ; Spiral Ganglion ; cytology

Animals ; Apoptosis ; Cochlea ; Estrogens/pharmacology* ; Mice ; Mice, Inbred C57BL ; Neurons ; Spiral Ganglion

The endolymph and perilymph of the inner ear have unique ionic composition and electrical potential. It is widely accepted that normal auditory function depends on them and Na/K-ATPase plays a central role in production and maintenance of them. The distribution of five Na/K-ATPase subunit isoform (alpha1, alpha2, alpha3, beta1, and beta2) in rat inner ear was determined by immunohistochemistry after decalcifying the temporal bone with Gooding and Stewart's solution. In the cochlear regions, Na/K-ATPase alpha1beta1 isozyme was abundantly expressed in the infrastrial fibrocytes, suprastrial fibrocytes, spiral prominence, outer sulcus cells and spiral ganglion, and also detected in cochlear nerve and interdental cells. alpha1beta2 isozyme was abundantly expressed in all layers of stria vascularis and alpha3beta1 isozyme was detected in cochlear nerve and spiral ganglion. alpha3beta2 isozyme was expressed in spiral ganglion. In vestibular regions, Na/K-ATPase alpha1b1 isozyme was expressed in macular sacculi hair cell, transitional cells of ampulla, and vestibular ganglion, and alpha1b2 isozyme was abundantly expressed in ampullary dark cells and transitional cells and vestibular ganglion. a3b1 isozyme was abundantly expressed in crista ampularis, macula utriculi, and macula sacculi hair cells, and also moderately detected in ampullary, utricular, and saccular nerves, and vestibular ganglion. alpha3beta2 isozyme also detected in ampullary, utricular, and saccular nerves, and vestibular ganglion. But, alpha2beta1 and alpha2beta2 isozymes were not detected in any regions of inner ear. These findings suggest the possibility of four unique Na/K-ATPase isozymes deferentially expressed among the various cell types of the inner ear. This structural diversity imparts considerable biological versatility to the Na/K-ATPase and would be provided the explanations for the differences in fluid and ion transport and its regulation among the inner ear regions.
Animals ; Cochlear Nerve ; Ear, Inner* ; Endolymph ; Ganglion Cysts ; Hair ; Immunohistochemistry ; Ion Transport ; Isoenzymes ; Perilymph ; Protein Isoforms* ; Rats* ; Spiral Ganglion ; Stria Vascularis ; Temporal Bone

OBJECTIVEThe present study was to investigate the effects of acute hypoxia on the electrophysiological properties and outward current of spiral ganglion cell (SGC).

METHODSSGC of newborn's Sprague Dawley (SD) rats were isolated and digested, primary cultured neurons for 8 h. By perfusion with physical saline solution containing no glucose and low oxygen, SGNs model of acute hypoxia was established. The whole-cell patch clamp recording was used to clarify the effect of hypoxia on the outward currents of SGC.

RESULTSThe outward current of SGC showed characteristics of outward rectification, which contained two major components, one sensitive to the big conductance Ca²⁺-activated K⁺ channels (BKCa) which blocked by TEA, and the other could be suppressed by the KV channel blocker 4-AP. When holding at -60 mV, acute hypoxia increased the outward current of SGC in a voltage-dependent manner, which mainly increased the amplitude of the current activated by the votage ranged from 0 mV to +60 mV, and increased the amplitude of outward current from (1 160.0 ± 129.1) pA to (2 428 ± 239.3) pA (n = 9, P < 0.01) at holding potential of -60mV. By perfusion with the Potassium channel blocker TEA or 4-AP, the former could significantly reduced the increasing of outward currents induced by hypoxia on the SGC, the latter had no significant effect on the outward current increased by the hypoxia.

CONCLUSIONSThese results suggest that acute hypoxia causes neuron hyperpolarization possibly by activating big conductance BKCa of the SGC. When the BKca channels are activated, K⁺ effluxes increase, which induces cell membrane hyperpolarization, and decreases cell excitability, which may affect the conducting function of SGC.

Animals ; Hypoxia ; physiopathology ; Neurons ; cytology ; metabolism ; Patch-Clamp Techniques ; Potassium Channels ; metabolism ; Rats ; Rats, Sprague-Dawley ; Spiral Ganglion ; cytology ; physiopathology