Kai Helling, Sebastian Strieth and Ulf-Rudiger Heinrich
Scientific Tracks Abstracts: Commun Disord Deaf Stud Hearing Aids
Introduction: Intratympanic medication might alter cochlear NO-production resulting in damage or protection, respectively. In this
study, the quantitative distribution patterns of gentamicin and doxycycline were determined after intratympanic application in the
guinea pig animal model.
Materials & Methods: Gentamicin or Doxycycline were injected into both middle ears of male animals (n=24 and n=3, respectively).
The cochleae were removed 1, 2 and 7 days after gentamicin injection or 1, 6 and 24 h after doxycycline application, transferred into
fixative and embedded in paraffin. The cellular staining reactions by specific antibodies against gentamicin and doxycycline were
quantified computer-assisted on sections for seven different cochlear regions.
Results: Gentamicin was identified in all experimental groups in numerous regions of the cochlea but with quantitative cellspecific
differences. An intense accumulation was observed within the spiral ligament, organ of Corti, nerve fibers, interdental cells
and fibrocytes in the limbus-area. A low gentamicin accumulation was seen in spiral ganglion cells and no accumulation in the
striavascularis. Statistic analysis revealed fixed effects of cell type and an interaction between treatment and cell type, but no effects
of cochlea turn and of treatment. Analysis over time identified a reduction of gentamicin within the spiral ligament and nerve fibers.
Doxycycline was preferentially located in the striavascularis and in hair cells.
Conclusion: In respect to the route of infiltration, a contribution of the vessel systems is discussed. The identified accumulation of
gentamicin in those cochlea regions which are responsible for potassium recycling might result in a local NO-increase leading finally
to cochlear damage. The specific accumulation of doxycycline in the striavascularis and hair cells might prevent an NO up-regulation
in stress situations in these areas. Knowledge of cell specific accumulation of different pharmaceutical products offers a promising
approach for human medication.
Kai Helling is presently working in Johannes Gutenberg University Medical School, Department of Otorhinolaryngology, Head and Neck Surgery and Neuro-Otology. His
research interest includes vestibular disorders and experimental neurootology.