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Specific synaptopathies diversify brain responses and hearing disorders: you lose the gain from early life.

Knipper M, Panford-Walsh R, Singer W, Rüttiger L, Zimmermann U - Cell Tissue Res. (2015)

Bottom Line: With sensory experience, the IHC pre- and post-synapse phenotype matures towards the instruction of low-SR, high-threshold and of high-SR, low-threshold auditory fiber characteristics.Corticosteroid feedback together with local brain-derived nerve growth factor (BDNF) and catecholaminergic neurotransmitters (dopamine) might be essential for this developmental step.In this review, we address the question of whether the control of low-SR and high-SR fiber characteristics is linked to various degrees of vulnerability of auditory fibers in the mature system.

View Article: PubMed Central - PubMed

Affiliation: Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Center (THRC), Molecular Physiology of Hearing, University of Tübingen, Elfriede-Aulhorn-Straße 5, 72076, Tübingen, Germany, marlies.knipper@uni-tuebingen.de.

ABSTRACT
Before hearing onset, inner hair cell (IHC) maturation proceeds under the influence of spontaneous Ca(2+) action potentials (APs). The temporal signature of the IHC Ca(2+) AP is modified through an efferent cholinergic feedback from the medial olivocochlear bundle (MOC) and drives the IHC pre- and post-synapse phenotype towards low spontaneous (spike) rate (SR), high-threshold characteristics. With sensory experience, the IHC pre- and post-synapse phenotype matures towards the instruction of low-SR, high-threshold and of high-SR, low-threshold auditory fiber characteristics. Corticosteroid feedback together with local brain-derived nerve growth factor (BDNF) and catecholaminergic neurotransmitters (dopamine) might be essential for this developmental step. In this review, we address the question of whether the control of low-SR and high-SR fiber characteristics is linked to various degrees of vulnerability of auditory fibers in the mature system. In particular, we examine several IHC synaptopathies in the context of various hearing disorders and exemplified shortfalls before and after hearing onset.

No MeSH data available.


Related in: MedlinePlus

Stress priming affects ABR waveforms and IHC ribbon numbers. a Averaged ABR wave functions before and 2 days after stress priming. Waveforms of stressed animals did not significantly differ from ABR waveforms of control animals, as indicated by a similar CorF but variability was smaller. b Number of IHC ribbons was significantly increased by 22 % in stressed animals. c Northern blot analysis for Arc/Arg3.1 mRNA shows that stress priming alone increased Arc/Arg3.1 mRNA levels in the hippocampus. The housekeeping gene cyclophilin was used as a loading control (for further details, see Singer et al. 2013)
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Fig4: Stress priming affects ABR waveforms and IHC ribbon numbers. a Averaged ABR wave functions before and 2 days after stress priming. Waveforms of stressed animals did not significantly differ from ABR waveforms of control animals, as indicated by a similar CorF but variability was smaller. b Number of IHC ribbons was significantly increased by 22 % in stressed animals. c Northern blot analysis for Arc/Arg3.1 mRNA shows that stress priming alone increased Arc/Arg3.1 mRNA levels in the hippocampus. The housekeeping gene cyclophilin was used as a loading control (for further details, see Singer et al. 2013)

Mentions: We should also consider a possible endogenous protective potential of selected corticosteroid activities of low-SR, high-threshold fibers for the following reasons. Glucocorticoid receptors or mineralocorticoid receptors are expressed in hair cells and the spiral ganglion (Terakado et al. 2011; Yao and Rarey 1996). IHC pre- and post-synapses might thus be the target of elevated cortisol levels whenever the hypothalamic-pituitary-adrenal system triggered by CRH is activated and corticosteroid hormone is secreted by the adrenal glands (De Kloet et al. 1998). Elevated corticosteroid levels triggered by a social stressor paradigm have been shown to induce a long-lasting reduction in ABR wave variations pointing to a strongly consolidated synaptic connection (Fig. 4a), a slightly increased IHC ribbon number (Fig. 4b) and increased expression of the plasticity gene Arc/Arg3.1 in the hippocampus (Fig. 4c; Singer et al. 2013). This indicates that corticosteroid activities can stabilize the auditory circuit activity that also involves, via amygdaloid output projections, hippocampal activity (for a review, see Canlon et al. 2013). Moreover, as stated above, a moderate corticosteroid level is correlated with a higher maintenance of ABR waves after noise exposure (indicating better recovery of ABR waveform), a less pronounced loss of IHC ribbons in high-frequency cochlear turns and more markedly elevated Arc/Arg3.1 levels in the hippocampus (Singer et al. 2013). Endogenous glucocorticoid activities can thus be considered to stabilize the IHC low-SR fiber contacts under traumatic conditions.Fig. 4


Specific synaptopathies diversify brain responses and hearing disorders: you lose the gain from early life.

Knipper M, Panford-Walsh R, Singer W, Rüttiger L, Zimmermann U - Cell Tissue Res. (2015)

Stress priming affects ABR waveforms and IHC ribbon numbers. a Averaged ABR wave functions before and 2 days after stress priming. Waveforms of stressed animals did not significantly differ from ABR waveforms of control animals, as indicated by a similar CorF but variability was smaller. b Number of IHC ribbons was significantly increased by 22 % in stressed animals. c Northern blot analysis for Arc/Arg3.1 mRNA shows that stress priming alone increased Arc/Arg3.1 mRNA levels in the hippocampus. The housekeeping gene cyclophilin was used as a loading control (for further details, see Singer et al. 2013)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig4: Stress priming affects ABR waveforms and IHC ribbon numbers. a Averaged ABR wave functions before and 2 days after stress priming. Waveforms of stressed animals did not significantly differ from ABR waveforms of control animals, as indicated by a similar CorF but variability was smaller. b Number of IHC ribbons was significantly increased by 22 % in stressed animals. c Northern blot analysis for Arc/Arg3.1 mRNA shows that stress priming alone increased Arc/Arg3.1 mRNA levels in the hippocampus. The housekeeping gene cyclophilin was used as a loading control (for further details, see Singer et al. 2013)
Mentions: We should also consider a possible endogenous protective potential of selected corticosteroid activities of low-SR, high-threshold fibers for the following reasons. Glucocorticoid receptors or mineralocorticoid receptors are expressed in hair cells and the spiral ganglion (Terakado et al. 2011; Yao and Rarey 1996). IHC pre- and post-synapses might thus be the target of elevated cortisol levels whenever the hypothalamic-pituitary-adrenal system triggered by CRH is activated and corticosteroid hormone is secreted by the adrenal glands (De Kloet et al. 1998). Elevated corticosteroid levels triggered by a social stressor paradigm have been shown to induce a long-lasting reduction in ABR wave variations pointing to a strongly consolidated synaptic connection (Fig. 4a), a slightly increased IHC ribbon number (Fig. 4b) and increased expression of the plasticity gene Arc/Arg3.1 in the hippocampus (Fig. 4c; Singer et al. 2013). This indicates that corticosteroid activities can stabilize the auditory circuit activity that also involves, via amygdaloid output projections, hippocampal activity (for a review, see Canlon et al. 2013). Moreover, as stated above, a moderate corticosteroid level is correlated with a higher maintenance of ABR waves after noise exposure (indicating better recovery of ABR waveform), a less pronounced loss of IHC ribbons in high-frequency cochlear turns and more markedly elevated Arc/Arg3.1 levels in the hippocampus (Singer et al. 2013). Endogenous glucocorticoid activities can thus be considered to stabilize the IHC low-SR fiber contacts under traumatic conditions.Fig. 4

Bottom Line: With sensory experience, the IHC pre- and post-synapse phenotype matures towards the instruction of low-SR, high-threshold and of high-SR, low-threshold auditory fiber characteristics.Corticosteroid feedback together with local brain-derived nerve growth factor (BDNF) and catecholaminergic neurotransmitters (dopamine) might be essential for this developmental step.In this review, we address the question of whether the control of low-SR and high-SR fiber characteristics is linked to various degrees of vulnerability of auditory fibers in the mature system.

View Article: PubMed Central - PubMed

Affiliation: Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Center (THRC), Molecular Physiology of Hearing, University of Tübingen, Elfriede-Aulhorn-Straße 5, 72076, Tübingen, Germany, marlies.knipper@uni-tuebingen.de.

ABSTRACT
Before hearing onset, inner hair cell (IHC) maturation proceeds under the influence of spontaneous Ca(2+) action potentials (APs). The temporal signature of the IHC Ca(2+) AP is modified through an efferent cholinergic feedback from the medial olivocochlear bundle (MOC) and drives the IHC pre- and post-synapse phenotype towards low spontaneous (spike) rate (SR), high-threshold characteristics. With sensory experience, the IHC pre- and post-synapse phenotype matures towards the instruction of low-SR, high-threshold and of high-SR, low-threshold auditory fiber characteristics. Corticosteroid feedback together with local brain-derived nerve growth factor (BDNF) and catecholaminergic neurotransmitters (dopamine) might be essential for this developmental step. In this review, we address the question of whether the control of low-SR and high-SR fiber characteristics is linked to various degrees of vulnerability of auditory fibers in the mature system. In particular, we examine several IHC synaptopathies in the context of various hearing disorders and exemplified shortfalls before and after hearing onset.

No MeSH data available.


Related in: MedlinePlus