title: Blockade of opioid-induced changes in auditory function at the level of the cochlea.
abstract: OBJECTIVE
  We have previously investigated the auditory neural effects of the kappa-opioid receptor agonist, (-)pentazocine. When administered intravenously (i.v.), this drug temporarily alters auditory nerve compound action potential (CAP) amplitudes. To test the hypothesis that the observed neural effects of i.v. (-)pentazocine occur via kappa-receptor interactions within the cochlea, we attempted to block these effects by employing a specific kappa-opioid receptor antagonist applied directly to the cochlear round window (RW) membrane.
  
  
  METHODS
  In 31 normal-hearing, male pigmented chinchillas, amplitude changes in the click-evoked auditory CAP (N1) were tracked at six stimulus intensities during a baseline and a postbaseline period in which i.v. (-)pentazocine (8 mg/kg) was administered. (-)Pentazocine administration was preceded by the delivery to the cochlear RW membrane of an artificial perilymph solution given alone or containing the kappa-opioid receptor selective antagonist, norbinaltorphimine (Nor-BNI), which was administered at two concentrations in separate groups of animals.
  
  
  RESULTS
  The amplitude increase in the CAP after (-)pentazocine was significantly reduced when i.v. (-)pentazocine was preceded by RW-administered Nor-BNI (4 mM).
  
  
  CONCLUSIONS
  The reversibility of agonist effects by Nor-BNI indicates direct or indirect opioid kappa-receptor-mediated auditory neural effects at the level of the cochlea and suggests a connection between kappa-receptors and auditory neural function.
authors.affiliation: Department of Speech & Hearing and Biology, Cleveland State University, Ohio, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Sahley
authors.forename: R H
authors.initials: RH
authors.lastname: Nodar
authors.forename: F E
authors.initials: FE
authors.lastname: Musiek
mesh_terms: D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects; D002682:Chinchilla; D003051:Cochlea / Q000187:drug effects*; D007275:Injections, Intravenous; D008297:Male; D009292:Narcotic Antagonists / Q000494:pharmacology*; D010423:Pentazocine / Q000008:administration & dosage / Q000494:pharmacology*; D012405:Round Window, Ear / Q000187:drug effects; D000159:Vestibulocochlear Nerve / Q000187:drug effects
chemical_list: D009292:Narcotic Antagonists; D010423:Pentazocine