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

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

OBJECTIVE: To study the relationship of distortion product in cochlea with cochlear activity and hearing. METHOD: Time variances of distortion product of basilar membrane vibration in vitro guineapig cochlea were observed by laser interferometry. RESULT: Within half hour after a cochlea was isolated from a guineapig, distortion product accompanied with two-tone inhibition in cochlea, can be observed. As time passed, distortion product and two-tone inhibition effect disappeared at the same time. After that, the membrane contiune vibrating in response to the sound stimulus, but the vibration amplitude decreased obviously and continued decreasing until it disappeared completely. CONCLUSION Distortion product in cochlea is a symbol of cochlear activity which makes the membrane respond in large amplitude vibration to sound stimulus and exhibit two-tone inhibition. The former makes the hearing highly sensitive to sound stimulus, the later makes the hearing perform information abstract well.
Acoustic Stimulation ; Animals ; Basilar Membrane ; physiology ; Cochlea ; physiology ; Guinea Pigs ; Hearing ; physiology ; Hearing Tests ; Interferometry ; Sound

OBJECTIVETo establish a mechanical simulation model for studying the relationship between the characteristic frequency and feature location of the basilar membrane of the cochlea.

METHODSMacro-mechanical methods were used to simplify the details of the model. With simulation tools, the basilar membrane vibration frequency characteristics were analyzed based on the box model.

RESULTSThe basilar membrane had obvious frequency-selective properties, and the basilar membrane from the stapes was sensitive to high frequencies while the farther membrane was sensitive to low frequencies.

CONCLUSIONThe frequency characteristics of the basilar membrane of the cochlea is mainly a result of the longitudinal variations of the geometric dimensions and material properties and is not related with other structures within the cochlea corti.

Basilar Membrane ; physiology ; Cochlea ; physiology ; Computer Simulation ; Mechanics ; Models, Biological ; Vibration

In order to observe the DPOAE of guinea pigs under awake and anesthetic conditions, we invesitigated the amplitude of distortion product emission and I/O function curves and made a comparative analysis of their changes under different conditions. It was found that the amplitude of DPOAE and I/O curves did not show difference in the guinea pigs under awake and anesthetics conditions. We deem it credible and simple to measure DPOAE in the guinea pigs under awake condition, which is similar to measuring DPOAE in the guinea pigs under physiological condition.
Acoustic Stimulation ; Anesthesia ; Animals ; Cochlea ; physiology ; Female ; Guinea Pigs ; Male ; Otoacoustic Emissions, Spontaneous ; physiology

OBJECTIVEA variety of inner ear disease is related to microcirculation disturbance of inner ear, but smooth muscle cells (SMC) and endothelial cells (EC) of the spiral modiolar artery (SMA), which is the main blood supply to the inner ear, physiological feature is not very clear.

METHODSIn this study, two-intracellular microelectrode recording technique and cell staining techniques to study the SMC and EC resting membrane potential characteristics and communication links between cells of SMA.

RESULTSStudy found that SMC and EC have high and low resting membrane potential state, two state of the resting membrane potential of cells to ACh and high K+ response is completely different. The different types of cells, EC-EC, SMC-SMC and SMC-EC, can simultaneously record by two-microelectrode, two cell resting membrane potential can also be a double-high RP, double-low RP and one high- and one low- RP. Experiment recorded in one high- and one low- RP are the SMC-EC types, and ECs initial membrane potential are high potential, SMCs membrane potential are low initial potential. The double-high and double-low RP can be SMC-SMC or EC-EC or SMC-EC types.

CONCLUSIONThe results show that SMC and EC in the 0.3 - 0.5 mm range, similar type of cells have very good communication, can function together to maintain good and consistent, heterogeneous cell performance is more different.

Animals ; Arteries ; cytology ; Cochlea ; blood supply ; physiology ; Endothelial Cells ; physiology ; Guinea Pigs ; Membrane Potentials ; physiology ; Myocytes, Smooth Muscle ; physiology

To study the modulatory effect of extracellular calcium on the whole cell K(+) currents (I(K)) in isolated Deiters cells, the whole cell K(+) currents were recorded when Deiters cells bathed in normal physiological solutions and calcium-free saline, respectively. The electrophysiological characteristics of I(K) currents were then analyzed with the patch clamp technique. Removing extracellular calcium significantly enhanced the amplitude of the I(K) currents, which increased by 70.2% at +50 mV test pulse. The chord conductance, measured at -30 mV test pulse, also significantly increased from (3.31-/+3.08) ns (n=42) in the normal solutions to (10.81-/+6.01) ns (n=42) in the calcium-free solutions, whereas, the zero current potential of the I(K) currents remained unchanged. In calcium-free solutions, the reversal potential of the I(K) currents was shifted to the direction of hyperpolarization, which was very close to the equilibrium K(+) potential based on the Nernst equation. In addition, both the steady state activation curve and the half activation potential, with the averaged value at (-10.13-/+5.64) mV (n=42), were shifted to the negative. However, the tendency for activation (slope conductances) was the same as that in the normal solutions. Interestingly, both the I-V and the G-V functions deduced from the calcium-inhibited K(+) currents in Deiters cells were "S" shape, implying that at least two different kinds of K(+) conductance were involved in this calcium-inhibited K(+) currents. In summary, we hypothesize that there are two mechanisms for this modulation: one is that the I(K) channels in Deiters cells containing a specific calcium sensitive domain, by which extracellular calcium modulates the structure of the K(+) channels and then the I(K) currents; the other is a novel double gated K(+) channel or an ionotropic receptor coupled to K(+) channels or a new subtype of outward K(+) channels. Removing extracellular calcium activates this novel conductance and then modulates the I(K) currents. These results indicate that a decrease in extracellular calcium not only facilitates the efflux of K(+) out of Deiters cells but also accelerates the repolorization by enhancing the I(K) currents, which in turn can effectively buffer the K(+) concentration around the outer hair cells and maintain the resting membrane potential of Deiters cells.
Animals ; Calcium ; physiology ; Cell Separation ; Cochlea ; cytology ; Extracellular Space ; Guinea Pigs ; Membrane Potentials ; physiology ; Patch-Clamp Techniques ; Potassium Channels ; physiology

OBJECTIVE: To compare the impedance between the modiolus and the inner wall of scala tympani with that between the modiolus and the outer wall of scala tympani. METHOD: The impedances between the modiolus and the inner wall of scala tympani and the impedance between the modiolus and the outer wall of scala tympani were measured, calculated and compared under different stimulating rates 0.1, 1.0, 10.0 kHz. RESULT: The impedance between the modiolus and the inner wall of scala tympani is less than that between the modiolus and the outer wall of scala tympani (P < 0.05). CONCLUSION To effectively stimulate the residual neurons in the spiral ganglion, the electrodes should be kept close to the inner wall of scale tympani.
Adult ; Cochlea ; physiology ; Cochlear Implants ; Electric Impedance ; Electrodes ; Humans ; Scala Tympani ; physiology ; Spiral Ganglion ; Temporal Bone ; physiology

OBJECTIVEThe specific mechanism underlying in the Adenosine triphosphate (ATP) release from the Kölliker's organ is still unknown. The present study was designed to investigate whether the supporting cells in the Kölliker organ in vitro release ATP and to explore the mechanism of ATP releasing from these cells.

METHODSSupporting cells in the Kölliker organ from P1 rats were isolated, purified and cultured with a combinatorial approach of enzymatic digestion and mechanical separation. Quinacrine staining was used to observe the cochlear membranous labyrinth and supporting cells. the bioluminescence assay was chosen to explore the release ATP from supporting cells in the Kölliker organ, when the ATP metabolism of the cells was influenced, the intracellular or extracellular Ca(2)+ concentration changed, the hemichannels blocked, and the phospholipase signaling pathways inhibited.

RESULTSThere were intensely numerous star-like green spots of quinacrine staining in the cytoplasm of supporting cells. There was a strong log-linear relationship in the ATP standard curve generated by the bioluminescence assay. With increasing concentrations of bafilomycin A1, the ATP concentration in the culture medium of the supporting cells in the Kölliker organ decreased, while with adipic acid didecyl, it increased. In a certain concentration range, with increasing extracellular Ca(2)+ concentration, the supporting cells in the Kölliker organ releasing ATP decreased, while the intracellular Ca(2)+ concentration increased, the results showed the elevation of the amount of ATP release. Adding chelerythrine chloride or aristolochid acid into the culture medium of the supporting cells in the Kölliker organ could decrease the ATP release significantly via inhibiting the hemichannels. In addition, by reducing intracellular Ca(2)+ concentration, inhibition of intracellular signaling pathways phospholipase also decreased ATP release.

CONCLUSIONSThis study demonstrated the presence and release of ATP from the supporting cells cultured in vitro. It showed that the changes of the intracellular and extracellular Ca(2)+ concentration could affect on the ATP release from the supporting cells in the Kölliker organ by regulating the hemichannels openings.

Adenosine Triphosphate ; metabolism ; Animals ; Cells, Cultured ; Cochlea ; cytology ; physiology ; In Vitro Techniques ; Rats ; Signal Transduction

Animals ; Auditory Threshold ; Cochlea ; physiology ; Ear, Middle ; surgery ; Evoked Potentials, Auditory, Brain Stem ; Female ; Male ; Rats