Influence of atp and atp agonists on the physiology of the isolated semicircular canal of the frog (Rana Pipiens)

Aubert, Anne; Norris, Charles H.; Guth, Paul S.

doi:10.1016/0306-4522(94)90487-1

Cited by 38 publications

(10 citation statements)

References 59 publications

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“…However, the role of adenosine on OHC function is not clear as there is no evidence of the action of adenosine on OHC (Nario et al 1994;Muñoz et al 1995). Adenosine, however, has the potential to protect OHC against a massive membrane depolarisation by downregulating Ca 2+ -activated non-selective cation channels (Van Den Abbeele et al 1996); a similar protective effect of adenosine has been proposed for sensory hair cells in the frog semicircular canal (Aubert et al 1994).…”

Section: Discussionmentioning

confidence: 94%

Differential distribution of adenosine receptors in rat cochlea

et al. 2007

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Adenosine is a constitutive cell metabolite that can be released from cells via specific bi-directional transporters and is an end-point for nucleotide hydrolysis. In the extracellular space, adenosine becomes a signalling molecule for P1 (adenosine) receptors that modulate physiological responses in a wide range of mammalian tissues. Whereas adenosine signalling has been implicated in the regulation of cochlear blood flow and in cochlear protection from oxidative damage, the potential roles for adenosine signalling in the modulation of sound transduction and auditory neurotransmission have not been established. We have characterised the expression and distribution of adenosine receptors in the rat cochlea. mRNA transcripts for all four subtypes of adenosine receptors (A(1), A(2A), A(2B) and A(3)) were detected in dissected cochlear tissue by using reverse transcription/polymerase chain reaction analysis. The protein distribution for the A(1), A(2A) and A(3) receptor subtypes was identified by immunoperoxidase histochemistry and confocal immunofluorescence labelling. These receptors were differentially expressed in the organ of Corti, spiral ganglion neurones, lateral wall tissues and cochlear blood vessels. The distribution of adenosine receptors in sensory and neural tissues and in the vasculature coincided with other elements of purinergic signalling (P2X and P2Y receptors, ectonucleotidases), consistent with the integrative regulation of many physiological processes in the cochlea by extracellular nucleotides and nucleosides. Our study provides a framework for further investigation of adenosine signalling in the inner ear, including putative roles in oxidative stress responses.

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Section: Discussionmentioning

confidence: 94%

Differential distribution of adenosine receptors in rat cochlea

et al. 2007

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“…We employed here ATP to chelate Ca 21 ions (12,26). Although ATP has been shown to gate purinergic receptors in the hair bundles of mammalian outer hair cells (27,28), there is no indication that similar receptors are present in hair bundles from the bullfrog's sacculus (29). If that were the case, ATP would be expected to increase, not decrease, the intracellular Ca 21 concentration.…”

Section: Iontophoresis Of Ca 21 and Ca 21 Chelatorsmentioning

confidence: 99%

Unifying the Various Incarnations of Active Hair-Bundle Motility by the Vertebrate Hair Cell

Tinévez

Jülicher

Martin

2007

Biophysical Journal

133

173

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The dazzling sensitivity and frequency selectivity of the vertebrate ear rely on mechanical amplification of the hair cells' responsiveness to small stimuli. As revealed by spontaneous oscillations and forms of mechanical excitability in response to force steps, the hair bundle that adorns each hair cell is both a mechanosensory antenna and a force generator that might participate in the amplificatory process. To study the various incarnations of active hair-bundle motility, we combined Ca(2+) iontophoresis with mechanical stimulation of single hair bundles from the bullfrog's sacculus. We identified three classes of active hair-bundle movements: a hair bundle could be quiescent but display nonmonotonic twitches in response to either excitatory or inhibitory force steps, or oscillate spontaneously. Extracellular Ca(2+) changes could affect the kinetics of motion and, when large enough, evoke transitions between the three classes of motility. We found that the Ca(2+)-dependent location of a bundle's operating point within its force-displacement relation controlled the type of movement observed. In response to an iontophoretic pulse of Ca(2+) or of a Ca(2+) chelator, a hair bundle displayed a movement whose polarity could be reversed by applying a static bias to the bundle's position at rest. Moreover, such polarity reversal was accompanied by a 10-fold change in the kinetics of the Ca(2+)-evoked hair-bundle movement. A unified theoretical description, in which mechanical activity stems solely from myosin-based adaptation, could account for the fast and slow manifestations of active hair-bundle motility observed in frog, as well as in auditory organs of the turtle and the rat.

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“…Extracellular ATP was also shown to have a neuronal function in the vestibular system in a previous study on an isolated semicircular canal preparation (12). This study suggested that extracellular ATP, which is present in the perilymphatic compartment, may act as a neurotransmitter or neuromodulator in vestibular physiology (12).…”

Section: Introductionmentioning

confidence: 90%

“…This study suggested that extracellular ATP, which is present in the perilymphatic compartment, may act as a neurotransmitter or neuromodulator in vestibular physiology (12). Vestibular ganglion neurons receive excitatory information from the vestibular sensory cells and then transmit it to the vestibular nuclei (13).…”

Section: Introductionmentioning

confidence: 99%

Extracellular Adenosine 5'-ATP-induced Calcium Signaling in Isolated Vestibular Ganglion Cells of the Guinea Pig

Nagata

2000

Acta Oto-Laryngologica

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Extracellular adenosine 5'-triphosphate (ATP)-induced intracellular calcium concentration ([Ca2+]i) changes in acutely isolated vestibular ganglion cells (VGCs) of the guinea pig were investigated using the Ca2+ -sensitive dye Fura-2. Extracellular ATP induced an increase in [Ca2+]i in VGCs in a dose-dependent manner. ATP induced an increase in [Ca2+]i even in the absence of extracellular Ca2+ (1 mM Ethylene Glycol-bis (beta-aminoethyl Ether) N,N,N',N'-Tetraacetic Acid (EGTA)), thus suggesting that ATP induces Ca2+ release from the intracellular stores. The P2-receptor antagonists suramin and reactive blue 2 inhibited the ATP-induced [Ca2+]i increase in a dose-dependent manner. The P1-receptor agonist adenosine did not induce any changes in [Ca2+]i. These results suggest that VGCs may possess a P2-purinergic receptor but not a P1-purinergic receptor. La3+, a receptor-mediated calcium channel blocker, inhibited the ATP-induced [Ca2+]i increase but, in contrast, nifedipine, a L-type calcium channel blocker, did not. These results suggest that ATP induces both a Ca2+ -release from the intracellular stores and a Ca2+ influx from the extracellular space through La3+ -sensitive and nifedipine-insensitive Ca2+ channels in VGCs. Our results also suggest that extracellular ATP may act as a neurotransmitter or neuromodulator of the vestibular peripheral system in the guinea pig.

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Influence of atp and atp agonists on the physiology of the isolated semicircular canal of the frog (Rana Pipiens)

Cited by 38 publications

References 59 publications

Differential distribution of adenosine receptors in rat cochlea

Differential distribution of adenosine receptors in rat cochlea

Unifying the Various Incarnations of Active Hair-Bundle Motility by the Vertebrate Hair Cell

Extracellular Adenosine 5'-ATP-induced Calcium Signaling in Isolated Vestibular Ganglion Cells of the Guinea Pig

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