Hair Cells Of Guinea Pig Cochlea Research Articles

Optical Imaging of Synaptic Activity in Inner Hair Cells of Guinea-pig Cochlea

Optical Imaging of Synaptic Activity in Inner Hair Cells of Guinea-pig Cochlea

Active hair bundle motion related to transducer channel in inner hair cells of guinea-pig cochlea

Active hair bundle motion related to transducer channel in inner hair cells of guinea-pig cochlea

CALCIUM ACTION ON THE MEMBRANE CURRENTS POSSESSING THE PROPERTIES OF MECHANO-ELECTRIC TRANSDUCER CURRENTS IN INNER HAIR CELLS OF THE GUINEA-PIG COCHLEA

In free-standing hair bundle, depolarization to +80 mV evoked a stable outward current and repolarization to −80 mV evoked a transient inward current attributable to the opening of mechano-electric transducer channels. The study investigated the Ca2+ dependence of this transducer-like membrane current in isolated inner hair cells of guinea-pig cochlea. The amplitude of outward currents increased and the rate of inward current decay, corresponding to adaptation kinetics, decreasing as the extracellular Ca2+ concentrations lessened, whereas the amplitude of outward current decreased and an adaptation accelerated as the extracellular Ca2+ elevated. Treatment with the cAMP agonist, 8-bromo-cAMP, induced an effect similar to that caused by elevating the extracellular Ca2+.

Glutamate induced currents in isolated inner hair cells from guinea-pig cochlea

We investigated the direct action of glutamate (Glu) on the membrane current of isolated inner hair cells of guinea-pig cochlea. Glu elicited inward currents at a holding potential of −70 mV. Eight of 13 cells showed a steady inward current, while five of 13 cells showed a fast and rapidly desensitized current. I– V relationships demonstrated that the reversal potential of Glu-induced current was near 0 mV. Glu-induced currents were dose-dependent, where the half maximum concentration ( K d) was 41 μM and Hill coefficient ( n) was 1.75.

Membrane current possessing the properties of a mechano-electric transducer current in inner hair cells of guinea-pig cochlea

We measured the membrane current possessing the properties of a mechano-electric transducer current in isolated inner hair cells of guinea-pig cochlea. In a free-standing hair bundle, depolarization to +80 mV evoked a stable outward current attributable to the opening of transducer channels, and repolarization to −80 mV evoked a transient inward current indicating adaptation. The time constant of adaptation increased as the membrane potential depolarized. Dihydrostreptomycin diminished both the outward and inward currents.

Tetraethylammonium effects on cochlear potentials in the guinea pig

Voltage-dependent K + channels in the basolateral membrane of hair cells in guinea-pig cochlea might contribute to the non-linear current-voltage relationships in these hair cells and, thereby, to generation of the extracellular summating potential (SP). To evaluate the role of K + channels in the generation of the SP the perilymphatic perfusion technique was used to introduce the K +-channel blocker tetraethylammonium (TEA) into the cochlea. Sound-evoked cochlear potentials were measured subsequently. Without blocking nerve activity TEA induced reversible shifts of the SP in the negative direction, irrespective of whether we recorded from scala vestibuli or scala tympani. Shifts in the negative direction were probably due to TEA acting directly on the afferent fibres, since removal of nerve activity by the potent Na +-channel blocker tetrodotoxin (TTX) prevented TEA from shifting the SP in the negative direction. Once nerve activity had been removed by TTX, administration of TEA caused a small decrease in the magnitude of the SP, both in scala vestibuli and in scala tympani, irrespective of its polarity. The decrease was significant for the highest test frequencies only (8–12 kHz), and completely reversible. The rapidly activated K + channel in the inner hair cell (IHC) is probably blocked by TEA and this blocking might be responsible for the small decrease in magnitude of the SP. The asymmetric contribution from this K + channel to the IHC's current-voltage relationship seems to be only partly responsible for the generation of the SP, since blocking of this K + channel with TEA caused relatively small decreases in the amplitude of the SP. TEA did not affect the endocochlear potential.

Caffeine rapidly decreases potassium conductance of dissociated outer hair cells of guinea-pig cochlea

The effects of caffeine on the outer hair cells (OHCs) freshly dissociated from guinea-pig cochlea were investigated with the whole-cell patch-clamp technique, in both the conventional and the nystatin perforated patch-clamp configurations under voltage-clamp condition. Application of caffeine (> 1 mM for 10–30 s) induced an inward current ( I caffeine ) with decrease of conductance in a dose-dependent manner at a holding potential ( V H ) of −60 mV. The reversal potential of I caffeine (E caffeine) was close to the K + equilibrium potential. The I caffeine was not affected by Ca 2+-free external solution. The internal perfusion of the Ca 2+ chelator BAPTA had no effect on I caffeine . The I caffeine was not modulated by the external application of H-8 or staurosporine and by the internal perfusion of GDP-βS. The amplitude of I caffeine was the largest at the basal region of OHCs when caffeine was locally applied by the ‘puffer’ method. These results suggest that caffeine induces a decrease in membrane potassium conductance of the OHCs mainly at the basal region without mediating the intracellular signaling pathway.

Cisplatin blocks voltage-dependent calcium current in dissociated outer hair cells of guinea-pig cochlea

The effect of the ototoxic molecule cisplatin ( cis-DDP) on the voltage-dependent Ca 2+ channel in dissociated outer hair cells (OHCs) of guinea-pig cochlea was investigated using a whole-cell pathch-clamp technique. Cis-DDP had antagonistic effect on the Ca 2+ channel and reversibly suppressed the Ca 2+ current in a concentration-dependent manner. These results suggested that one of the ototoxic mechanisms of cis-DDP is involved in the inhibition of the Ca 2+ channel in OHCs.

O-018 - Substance P-induced response in dissociated outer hair cells of guinea-pig cochlea

O-018 - Substance P-induced response in dissociated outer hair cells of guinea-pig cochlea

ATP-induced Current in Isolated Outer Hair Cells of Guinea-pig Cochlea

ATP-induced Current in Isolated Outer Hair Cells of Guinea-pig Cochlea