title: Effects of isoflurane on auditory evoked potentials in the cochlea and brainstem of guinea pigs.
abstract: Electrophysiological recordings of the auditory system are commonly performed in deeply anesthetized animals. This study evaluated the effects of various concentrations of the volatile anesthetic isoflurane (1-3%) on the compound action potential (CAP), cochlear microphonic (CM) and auditory brainstem response (ABR). Recordings were initiated in the awake, lightly restrained animal. Anesthesia was induced with a single dose of Hypnorm (fentanyl and fluanisone). After tracheostomy increasing isoflurane concentrations were applied in N(2)O/O(2) via controlled ventilation. Data were compared to recordings in the awake animal using repeated measures ANOVA and Dunnett's post hoc test. On average, isoflurane dose-dependently suppressed the amplitude and increased the latency of the CAP. CM amplitude was suppressed. These effects were most profound at high frequencies and were typically significant at isoflurane concentrations of 2.5% and 3%. Amplitude and latency of the second negative peak of the CAP (N(2)) were affected to a greater extent compared to the first peak (N(1)). On average, isoflurane dose-dependently reduced the amplitude and increased the latency of the ABR. These effects were typically significant at an isoflurane concentration of 2%. Effects on peak IV and V were more pronounced compared to the early peaks I and III.
authors.affiliation: Department of Otorhinolaryngology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands. c.stronks@umcutrecht.nl
authors.forename: H Christiaan
authors.initials: HC
authors.lastname: Stronks
authors.forename: Mark C J
authors.initials: MC
authors.lastname: Aarts
authors.forename: Sjaak F L
authors.initials: SF
authors.lastname: Klis
mesh_terms: D000161:Acoustic Stimulation; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001933:Brain Stem / Q000187:drug effects* / Q000502:physiology; D003051:Cochlea / Q000187:drug effects* / Q000502:physiology; D003055:Cochlear Microphonic Potentials / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects*; D005260:Female; D006168:Guinea Pigs; D007530:Isoflurane / Q000494:pharmacology*; D011930:Reaction Time / Q000187:drug effects; D013997:Time Factors; D014851:Wakefulness
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane