title: Neurotrophic receptors as potential therapy targets in postnatal development, in adult, and in hearing loss-affected inner ear.
abstract: OBJECTIVE
  The aim of this investigation was to define the expression of neurotrophic receptors within the developing inner ear of different postnatal ages.
  
  
  BACKGROUND
  Pattern of differential expression of neurotrophic receptors provide molecular target sites for multifunctional nanoparticle-based cell-specific therapeutics delivery to treat hearing diseases.
  
  
  METHODS
  Protein expression of neurotrophic receptors was studied by immune-histochemistry, quantitative polymerase chain reaction, in situ hybridization, Western blot, in early and late postnatal, adult, and aging mice.
  
  
  RESULTS
  There was a high correlation between results obtained at ribonucleic acid and protein levels. TrkB and TrkC gene expression increased during the first 2 weeks and also after the onset of hearing in adult mice. At the onset of hearing, TrkB-immunopositive staining occurred in inner hair cells and in cell bodies of spiral ganglion neurons. TrkC was detected in nerve endings beneath inner and outer hair cells and in supporting cells. Root cells within the spiral ligament and spiral ganglion neurons in the Rosenthal's canal showed high level of TrkC expression. p75NTR was found in organ of Corti similar to TrkC, and scattered neurons showed strong immunoreactivity in the Rosenthal's canal. PD540 mice, a model of age-related hearing loss, showed a complete spiral ganglion cell loss in the basal turn. Although TrkB and TrkC were completely lacking in this region of the Rosenthal's canal, remaining nerve fibers were p75NTR immunopositive.
  
  
  CONCLUSIONS
  We found differential expression pattern of TrkB, TrkC, and p75NTR receptors in the inner ear and could make a receptor expression data base. These findings, in turn, will help to design a study on receptor-specific drug targeting of the mice model of auditory development and aging.
authors.affiliation: Inner Ear Research Laboratory, Department of Otolaryngology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Mario
authors.initials: M
authors.lastname: Bitsche
authors.forename: Jozsef
authors.initials: J
authors.lastname: Dudas
authors.forename: Soumen
authors.initials: S
authors.lastname: Roy
authors.forename: Thomas
authors.initials: T
authors.lastname: Potrusil
authors.forename: Joachim
authors.initials: J
authors.lastname: Schmutzhard
authors.forename: Anneliese
authors.initials: A
authors.lastname: Schrott-Fischer
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D007758:Ear, Inner / Q000378:metabolism*; D006309:Hearing / Q000502:physiology*; D034381:Hearing Loss / Q000378:metabolism*; D051379:Mice; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism*
chemical_list: D017475:Receptors, Nerve Growth Factor