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85th Annual Meeting of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery

German Society of Oto-Rhino-Laryngology, Head and Neck Surgery

28.05. - 01.06.2014, Dortmund

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The use of a cochlear implant prevents consequences of deafness for the plasticity response of central auditory neurons

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German Society of Oto-Rhino-Laryngology, Head and Neck Surgery. 85th Annual Meeting of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery. Dortmund, 28.05.-01.06.2014. Düsseldorf: German Medical Science GMS Publishing House; 2014. Doc14hno09

doi: 10.3205/14hno09, urn:nbn:de:0183-14hno091

Published: July 24, 2014

© 2014 Rosskothen-Kuhl et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.

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Introduction: During pre- and postnatal development a high level of growth associated protein 43 (Gap43) is expressed in our brain. This neuron-specific protein is expressed in somata, axons and growth cones and plays a key role in neurite outgrowth and synaptogenesis. With maturation of our brain, Gap43 is down-regulated by most neurons, excepting those in brain areas like the hippocampal CA3 region or the binaural auditory regions lateral superior olive (LSO) and central inferior colliculus (CIC). This study investigated how changes in sensory activity levels and patterns can modulate the adult plasticity response.

Methods: To study the effect of sensory activity on adult Gap43 expression, mRNA and protein levels were determined in LSO and CIC of hearing-experienced rats, unilaterally deafened rats, or rats unilaterally stimulated by a cochlear implant (CI).

Results: Unilateral hearing loss of an adult auditory system causes asymmetrical expression of Gap43 mRNA between ipsi- and contralateral LSOs or CICs of the brainstem. While the mRNA level increased on the contralateral side of the LSO, CIC neurons rose their gap43 transcription ipsilaterally compared to control (p<0.001). Compensation of the lost sensory input by way of CI stimulation results in a bilaterally symmetric but increased Gap43 mRNA expression.

Conclusion: Our data indicate that Gap43 is not only a marker for neuronal growth and synaptogenesis, but also reflects modified patterns of synaptic activities on auditory neurons. Thus, unilateral deafness directly results in an asymmetrical adaptation of the gap43 transcription between both sides of the auditory brainstem. This consequence can be prevented by simple-patterned stimulation of the auditory nerve by way of a CI.

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References

1.
Rosskothen-Kuhl N, Illing RB. Gap43 Transcription Modulation in the Adult Brain Depends on Sensory Activity and Synaptic Cooperation. PLOS One. 2014;9(3): e92624. DOI: 10.1371/journal.pone.0092624 External link
2.
Illing RB, Cao QL, Förster CR, Laszig R. Auditory brainstem: development and plasticity of GAP-43 mRNA expression in the rat. J Comp Neurol. 1999;412(2):353-72.
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Illing RB, Rosskothen-Kuhl N. The Cochlear Implant in Action: Molecular Changes Induced in the Rat Central Auditory System. In: Umat C, Tange RA, editors. Cochlear Implant Research Updates. In Tech; 2012. p. 137-66.
4.
Rosskothen-Kuhl N, Illing RB. Unilateral Cochlear Implant Stimulation Maintains the Molecular Balance of the Plasticity Marker GAP-43 in Auditory Brainstem Circuit. In: 36th annual midwinter meeting of the Association for Research in Otolaryngology; February 16-20 2013; Baltimore, Maryland, USA. Abs. 35. p. 31.
5.
Rosskothen-Kuhl N, Birkenhäger R, Illing RB. Levels of GAP-43 mRNA Reflect Modified Stimulation-Dependent Activity in the Auditory Brainstem of Rats. in: 10th Göttingen Meeting of the German Neuroscience Society 2013. Poster T18-10C.