title: Drug delivery into the cochlear apex: Improved control to sequentially affect finely spaced regions along the entire length of the cochlear spiral.
abstract: Administering pharmaceuticals to the scala tympani of the inner ear is a common approach to study cochlear physiology and mechanics. We present here a novel method for in vivo drug delivery in a controlled manner to sealed ears.
  
  
  
  Injections of ototoxic solutions were applied from a pipette sealed into a fenestra in the cochlear apex, progressively driving solutions along the length of scala tympani toward the cochlear aqueduct at the base. Drugs can be delivered rapidly or slowly. In this report we focus on slow delivery in which the injection rate is automatically adjusted to account for varying cross sectional area of the scala tympani, therefore driving a solution front at uniform rate.
  
  
  
  Objective measurements originating from finely spaced, low- to high-characteristic cochlear frequency places were sequentially affected. Comparison with existing methods(s): Controlled administration of pharmaceuticals into the cochlear apex overcomes a number of serious limitations of previously established methods such as cochlear perfusions with an injection pipette in the cochlear base: The drug concentration achieved is more precisely controlled, drug concentrations remain in scala tympani and are not rapidly washed out by cerebrospinal fluid flow, and the entire length of the cochlear spiral can be treated quickly or slowly with time.
  
  
  
  Controlled administration of solutions into the cochlear apex can be a powerful approach to sequentially effect objective measurements originating from finely spaced cochlear regions and allows, for the first time, the spatial origin of CAPs to be objectively defined.
authors: Washington University School of Medicine, Department of Otolaryngology, Saint Louis, MO 63110, USA. Electronic address: LichtenhanJ@ent.wustl.edu.
authors: J T
authors: JT
authors: Lichtenhan
authors: Washington University School of Medicine, Department of Otolaryngology, Saint Louis, MO 63110, USA.
authors: J
authors: J
authors: Hartsock
authors: University of Arkansas School of Medicine, Little Rock, AR 72205, USA.
authors: J R
authors: JR
authors: Dornhoffer
authors: Program in Audiology and Communication Sciences, Washington University School of Medicine, Saint Louis, MO 63110, USA.
authors: K M
authors: KM
authors: Donovan
authors: Washington University School of Medicine, Department of Otolaryngology, Saint Louis, MO 63110, USA.
authors: A N
authors: AN
authors: Salt
mesh_terms: D000161:Acoustic Stimulation; D000162:Acoustics; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003911:Dextrans / Q000008:administration & dosage / Q000493:pharmacokinetics; D016503:Drug Delivery Systems; D018690:Excitatory Amino Acid Agonists / Q000008:administration & dosage; D005260:Female; D016650:Fluorescein-5-isothiocyanate / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D006168:Guinea Pigs; D007608:Kainic Acid / Q000008:administration & dosage; D008297:Male; D017084:Otoacoustic Emissions, Spontaneous / Q000187:drug effects; D012533:Scala Tympani / Q000187:drug effects* / Q000378:metabolism*; D013997:Time Factors
chemical_list: D003911:Dextrans; D018690:Excitatory Amino Acid Agonists; C015219:fluorescein isothiocyanate dextran; D016650:Fluorescein-5-isothiocyanate; D007608:Kainic Acid
keywords: Auditory nerve overlapped waveform; Cochlear action potential; Cochlear fluid; Cochlear perfusion; Kainic acid