Photoreleased Intracellular Ca2+ Evokes Reversible Mechanical Responses in Supporting Cells of the Guinea-Pig Organ of Corti

Dulon, Didier; Blanchet, Christophe; Laffon, Éric

doi:10.1006/bbrc.1994.1841

Cited by 69 publications

(47 citation statements)

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“…ATP, a potential cochlear neuromodulator, elicits robust increases in intracellular calcium in supporting cells via activation of purinergic receptors (Dulon et al 1993). In Deiters' cells, calcium increases lead to motile responses (Dulon et al 1994). Nothing is known, however, about mechanisms necessary to restore elevated calcium levels to normal.…”

Section: Discussionmentioning

confidence: 99%

Localization of Soluble Guanylate Cyclase Activity in the Guinea Pig Cochlea Suggests Involvement in Regulation of Blood Flow and Supporting Cell Physiology

Fessenden

Schacht

1997

J Histochem Cytochem.

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SUMMARYAlthough the nitric oxide/cGMP pathway has many important roles in biology, studies of this system in the mammalian cochlea have focused on the first enzyme in the pathway, nitric oxide synthase (NOS). However, characterization of the NO receptor, soluble guanylate cyclase (sGC), is crucial to determine the cells targeted by NO and to develop rational hypotheses of the function of this pathway in auditory processing. In this study we characterized guinea pig cochlear sGC by determining its enzymatic activity and cellular localization. In cytosolic fractions of auditory nerve, lateral wall tissues, and cochlear neuroepithelium, addition of NO donors resulted in three-to 15-fold increases in cGMP formation. NO-stimulated sGC activity was not detected in particulate fractions. We also localized cochlear sGC activity through immunocytochemical detection of NO-stimulated cGMP. sGC activity was detected in Hensen's and Deiters' cells of the organ of Corti, as well as in vascular pericytes surrounding small capillaries in the lateral wall tissues and sensory neuroepithelium. sGC activity was not observed in sensory cells. Using NADPH-diaphorase histochemistry, NOS was localized to pillar cells and nerve fibers underlying hair cells. These results indicate that the NO/cGMP pathway may influence diverse elements of the auditory system, including cochlear blood flow and supporting cell physiology.

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Section: Discussionmentioning

confidence: 99%

Localization of Soluble Guanylate Cyclase Activity in the Guinea Pig Cochlea Suggests Involvement in Regulation of Blood Flow and Supporting Cell Physiology

Fessenden

Schacht

1997

J Histochem Cytochem.

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“…The most well-documented is the slow motility of the OHC (37), but motility of isolated Deiters' cells also has been described (38). In some cases (e.g., Fig.…”

Section: Discussionmentioning

confidence: 99%

Acoustic overstimulation increases outer hair cell Ca²⁺concentrations and causes dynamic contractions of the hearing organ

Fridberger

Flock

Ulfendahl

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

165

124

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The dynamic responses of the hearing organ to acoustic overstimulation were investigated using the guinea pig isolated temporal bone preparation. The organ was loaded with the f luorescent Ca 2؉ indicator Fluo-3, and the cochlear electric responses to low-level tones were recorded through a microelectrode in the scala media. After overstimulation, the amplitude of the cochlear potentials decreased significantly. In some cases, rapid recovery was seen with the potentials returning to their initial amplitude. ] changes were not seen in preparations that were stimulated at levels that did not cause an amplitude change in the cochlear potentials. The overstimulation also gave rise to a contraction, evident as a decrease of the width of the organ of Corti. The average contraction in 10 preparations was 9 m (SE 2 m). Partial or complete recovery was seen within 30-45 min after the overstimulation. The [Ca 2؉ ] changes and the contraction are likely to produce major functional alterations and consequently are suggested to be a factor contributing strongly to the loss of function seen after exposure to loud sounds.Noise-induced hearing loss is a common condition that leads to considerable communication problems for affected individuals. Recent research on the physiology of this condition (reviewed in ref. 1) has been mainly focused on damage to the stereocilia (SC) of the sensory cells in the inner ear, important because this is the location of the ion channels converting mechanic vibrations into electric currents. Damage to the SC correlates well with alterations of the tuning curves of auditory nerve fibres (2). A capacity for repair of the SC after acoustic trauma also has been implicated (3), but the mechanisms underlying the stereociliary changes as well as the repair process remain unknown.Acoustic trauma also may cause degeneration of the sensory cells, resulting in an irreversible elevation in hearing thresholds (4). The degeneration most likely involves not only stereociliary changes but also alterations at the cell body level. The events taking place in these cells during and after overstimulation remain largely obscure. Cody and Russell (5) have shown that sustained depolarizations of the outer hair cells (OHCs) occur after moderately intense acoustic overstimulation and that repolarization parallels the recovery of auditory sensitivity. The underlying mechanisms are unclear.In isolated OHCs, mechanical overstimulation results in cytoplasmic [Ca 2ϩ ] increase (6). To investigate how this finding relates to reduced hearing sensitivity after acoustic trauma, the guinea pig isolated temporal bone preparation (7) was used to perform simultaneous investigations of calcium-dependent fluorescence, stimulus-evoked cochlear potentials and cochlear morphology. The sensory cells were visualized in situ in an almost native environment, and the cochlear electric responses were recorded. The preparation was used previously to study changes of organ of Corti mechanics following acoustic trauma (8) and has now been ...

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“…However, it is also possible that ATP-induced changes in conductance and cell shape are not inexorably linked. Indeed, outer supporting cells do not undergo detectable shape changes upon ATP stimulation [10,11] (but see [73]) despite the activation of Ca 2+ -activated Cl − channels [61,70]. An alternative possibility is that these morphological changes result from Ca 2+ -dependent activation of contractile proteins in inner supporting cells.…”

Section: Atp-mediated Morphological Changes In Inner Supporting Cellsmentioning

confidence: 98%

ATP-induced morphological changes in supporting cells of the developing cochlea

Tritsch

Zhang

Ellis‐Davies

et al. 2010

Purinergic Signalling

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The developing cochlea of mammals contains a large group of columnar-shaped cells, which together form a structure known as Kölliker's organ. Prior to the onset of hearing, these inner supporting cells periodically release adenosine 5′-triphosphate (ATP), which activates purinergic receptors in surrounding supporting cells, inner hair cells and the dendrites of primary auditory neurons. Recent studies indicate that purinergic signaling between inner supporting cells and inner hair cells initiates bursts of action potentials in auditory nerve fibers before the onset of hearing. ATP also induces prominent effects in inner supporting cells, including an increase in membrane conductance, a rise in intracellular Ca 2+ , and dramatic changes in cell shape, although the importance of ATP signaling in non-sensory cells of the developing cochlea remains unknown. Here, we review current knowledge pertaining to purinergic signaling in supporting cells of Kölliker's organ and focus on the mechanisms by which ATP induces changes in their morphology. We show that these changes in cell shape are preceded by increases in cytoplasmic Ca 2+ , and provide new evidence indicating that elevation of intracellular Ca 2+ and IP 3 are sufficient to initiate shape changes. In addition, we discuss the possibility that these ATP-mediated morphological changes reflect crenation following the activation of Ca 2+ -activated Cl − channels, and speculate about the possible functions of these changes in cell morphology for maturation of the cochlea.

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Photoreleased Intracellular Ca2+ Evokes Reversible Mechanical Responses in Supporting Cells of the Guinea-Pig Organ of Corti

Cited by 69 publications

References 0 publications

Localization of Soluble Guanylate Cyclase Activity in the Guinea Pig Cochlea Suggests Involvement in Regulation of Blood Flow and Supporting Cell Physiology

Localization of Soluble Guanylate Cyclase Activity in the Guinea Pig Cochlea Suggests Involvement in Regulation of Blood Flow and Supporting Cell Physiology

Acoustic overstimulation increases outer hair cell Ca²⁺concentrations and causes dynamic contractions of the hearing organ

ATP-induced morphological changes in supporting cells of the developing cochlea

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Photoreleased Intracellular Ca2+ Evokes Reversible Mechanical Responses in Supporting Cells of the Guinea-Pig Organ of Corti

Cited by 69 publications

References 0 publications

Localization of Soluble Guanylate Cyclase Activity in the Guinea Pig Cochlea Suggests Involvement in Regulation of Blood Flow and Supporting Cell Physiology

Localization of Soluble Guanylate Cyclase Activity in the Guinea Pig Cochlea Suggests Involvement in Regulation of Blood Flow and Supporting Cell Physiology

Acoustic overstimulation increases outer hair cell Ca2+concentrations and causes dynamic contractions of the hearing organ

ATP-induced morphological changes in supporting cells of the developing cochlea

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Acoustic overstimulation increases outer hair cell Ca²⁺concentrations and causes dynamic contractions of the hearing organ