ATP-induced current in isolated outer hair cells of guinea pig cochlea

Nakagawa, Takashi; Akaike, Norio; Kimitsuki, Takashi; Komune, Shizuo; Arima, Toshio

doi:10.1152/jn.1990.63.5.1068

Cited by 128 publications

(55 citation statements)

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“…These ion channels are non-selective for Na + and K + (Nakagawa et al 1990) and when facing the unique environment of the scala media, with its high K + concentration (approximately 150 mM), activation under normal conditions would result in K + influx with current outflow via basolateral K + channels causing a decline in EP. The pharmacology of the ATP-induced fall in EP supports this P2X receptor-mediated mechanism (Muñoz et al 1995(Muñoz et al , 1999.…”

Section: Discussionmentioning

confidence: 99%

Purinergic Modulation of Cochlear Partition Resistance and Its Effect on the Endocochlear Potential in the Guinea Pig

Thorne

Munoz

Housley

2004

JARO - Journal of the Association for Research in Otolaryngolog

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Introduction of adenosine 5¢-triphosphate (ATP) into the endolymphatic compartment of the guinea-pig cochlea decreases the endocochlear potential (EP). To determine if this is due to an ATP-induced change in compartment resistance, the cochlear partition resistance (CoPR) was measured using constant current injections into scala media before, during, and after microinjection of ATP into the same compartment. The CoPR (mean = 3.13 ± 0.13 kX) decreased with ATP in a dose-dependent manner (25.1 ± 3.0% decrease in relation to baseline values) and this was linearly correlated (R 2 = 0.91) to the magnitude of the ATP-induced decline in EP (41.6 ± 7.0% decline in relation to the baseline). Pyridoxalphosphate-6-azophenyl-2¢,4¢-disulfonic acid (PPADS, a P2X receptor antagonist) injected prior to ATP application blocked this ATP-induced reduction in EP and CoPR. This indicates that ATP-gated ion channels (P2X receptors) provide a latent shunt capable of regulating the majority of the electrical potential across the luminal surface of the sensory hair cells, which is necessary for sound transduction. The results suggest a novel sound transduction regulatory mechanism, which, via extracellular ATP, has the capability of adjusting hearing sensitivity.

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Section: Discussionmentioning

confidence: 99%

Purinergic Modulation of Cochlear Partition Resistance and Its Effect on the Endocochlear Potential in the Guinea Pig

Thorne

Munoz

Housley

2004

JARO - Journal of the Association for Research in Otolaryngolog

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“…The dissection procedure of the guinea pig OHCs was similar to that previously reported (Nakagawa et al 1990). Albino guinea pigs (weight 150-300 g) of either sex with good Preyer's reflexes were decapitated, and the temporal bones were removed.…”

Section: Isolation Of Ohcsmentioning

confidence: 99%

Photometric recording of transmembrane potential in outer hair cells

et al. 2006

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Cochlear outer hair cells (OHCs) are polarized epithelial cells that have mechanoelectrical transduction channels within their apical stereocilia and produce electromotile force along their lateral wall. Phase shifts, or time delays, in the transmembrane voltage occurring at different axial locations along the cell may contribute to our understanding of how these cells operate at auditory frequencies. We developed a method to optically measure the phase of the OHC transmembrane potential using the voltage-sensitive dye (VSD) di-8-ANEPPS. The exit aperture of a fibre-optic light source was driven in two dimensions so that a 24 μm spot of excitation light could be positioned along the length of the OHC. We used the whole-cell patch-clamp technique in the current-clamp mode to stimulate the OHC at the base. The photometric response and the voltage response were monitored with a photodetector and patch-clamp amplifier, respectively. The photometric response was used to measure the regional changes in the membrane potential in response to maintained (dc) and sinusoidal (ac) current stimuli applied at the base of the cell. We used a neutral density filter to lower the excitation light intensity and reduce phototoxicity. A sensitive detector and lock-in amplifier were used to measure the small ac VSD signal. This permitted measurements of the ac photometric response below the noise floor of the static fluorescence. The amplitude and phase components of the photometric response were recorded for stimuli up to 800 Hz. VSD data at 400-800 Hz show the presence of a small phase delay between the stimulus voltage at the base of the cell and the local membrane potential measured along the lateral wall. Results are consistent with the hypothesis that OHCs exhibit inhomogeneous membrane potentials that vary with position in analogy with the voltage in nerve axons.

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“…Studies have shown that extracellularly applied ATP can elicit changes in intracellular Ca2+ concentrations and transmembrane ion conductance in isolated hair cells (Ashmore and Ohmori, 1990;Nakagawa et al, 1990;Shigemoto and Ohmori, 1990;Dulon et al, 1991;Housley et al, , 1993aAshmore et al, 1993). These effects are consistent with a P, purinoceptor classification.…”

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confidence: 99%

Fluorescence imaging of extracellular purinergic receptor sites and putative ecto-ATPase sites on isolated cochlear hair cells

1994

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Fluorescence imaging of extracellular adenosine-5′-triphosphate (ATP) binding sites on inner and outer hair cells isolated from the guinea pig organ of Corti was achieved using the fluorescent analog of ATP, 2′- (or-3′)-O-(trinitrophenyl)adenosine-5′- triphosphate (TNP-ATP; 30–75 microM). This analog, which fluoresces on binding to these sites, was pressure applied by micropipette while hair cells were viewed by fluorescence microscopy. Fluorescence imaging revealed a widespread distribution of extracellular binding sites, including the stereocilia, cuticular plate, and the basolateral margins of the cells, but particularly in infracuticular and infranuclear regions. In support of extracellular binding, simultaneous electrophysiological recordings demonstrated that rapid washout of TNP-ATP-induced fluorescence was dependent upon cell integrity. Suramin, a nonselective P2 purinoceptor antagonist, coapplied with TNP-ATP, reduced the fluorescence observed on the stereocilia and apical surface of the cuticular plate only. This implies that binding sites on the apical surface of hair cells are P2 receptors, consistent with previous electrophysiological evidence for localization of P2 receptors to the apical surface of cochlear hair cells (Housley et al., 1992). Binding of TNP-ATP to P2 purinoceptors was confirmed by its antagonism of the inward current elicited by ATP (10 microM) in voltage-clamped hair cells. Fluorescence from the basolateral margin was significantly quenched when TNP-ATP was applied in divalent cation-free solution. Because divalent cations are required for ATPase activity, this finding provides evidence for the presence of ecto-ATPases on the basolateral membrane of hair cells. The divalent cation-free condition had no significant effect on the ATP-gated P2 purinoceptor conductance. We propose that there are two classes of ATP binding sites on cochlear hair cells: apically located P2 purinoceptors gating nonselective cation channels and basolaterally located ecto- ATPases that may be involved in purine turnover.

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ATP-induced current in isolated outer hair cells of guinea pig cochlea

Cited by 128 publications

References 0 publications

Purinergic Modulation of Cochlear Partition Resistance and Its Effect on the Endocochlear Potential in the Guinea Pig

Purinergic Modulation of Cochlear Partition Resistance and Its Effect on the Endocochlear Potential in the Guinea Pig

Photometric recording of transmembrane potential in outer hair cells

Fluorescence imaging of extracellular purinergic receptor sites and putative ecto-ATPase sites on isolated cochlear hair cells

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