title: [The utilization of brain plasticity by cochlear implants : Molecular and cellular changes due to electrical intracochlear stimulation].
abstract: OBJECTIVE
  During pre- and postnatal development, a high level of growth-associated protein 43 (Gap43) is expressed in the 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 the brain, Gap43 is down-regulated by most neurons, except in brain areas such as 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 and bilaterally 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 brain stem. While the mRNA level rose on the contralateral side of the LSO, CIC neurons increased their gap43 transcription ipsilaterally compared to the control level (p<0.001). Compensation of the lost sensory input by way of CI stimulation resulted in a bilaterally symmetric but increased gap43 transcription.
  
  
  CONCLUSIONS
  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 brain stem. This can be prevented by simple-patterned stimulation of the auditory nerve via a CI.
authors: Neurobiologisches Forschungslabor, Universitäts-HNO-Klinik Freiburg, Killianstr. 5, 79106, Freiburg, Deutschland, nicole.rosskothen@uniklinik-freiburg.de.
authors: N
authors: N
authors: Rosskothen-Kuhl
authors: R-B
authors: RB
authors: Illing
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000503:physiopathology*; D003054:Cochlear Implants; D004599:Electric Stimulation Therapy / Q000379:methods; D005260:Female; D019922:GAP-43 Protein / Q000378:metabolism*; D034381:Hearing Loss / Q000473:pathology / Q000503:physiopathology* / Q000534:rehabilitation; D009416:Nerve Regeneration / Q000502:physiology*; D009473:Neuronal Plasticity; D051381:Rats; D017208:Rats, Wistar
chemical_list: D019922:GAP-43 Protein