title: Effects  of noise, hypothermia and barbiturate on cochlear electrical activity.
abstract: Pentobarbital has been reported as both increasing and decreasing the effects of noise trauma on the inner ear. In the C57BL/6 laboratory mouse, the effects depend upon which electrical events are measured and whether or not the hypothermic effects of pentobarbital are counteracted. Pentobarbital-induced hypothermia per se increased the latency of both the high-intensity-threshold, short-latency (H) and low-intensity-threshold, long-latency (L) waves by approximately 60 mus per degrees C decrease, had no significant effect on H-wave amplitude, but caused a severe reduction of the L-wave amplitude. As little as 1 min of 120 dB SPL high-frequency noise can temporarily reduce the cochlear microphonic (CM) amplitude, abolish the H and reduce the amplitude of the L waves of the click-evoked, volume-conducted gross auditory nerve action potential (AP). 1 week later, CMs were more depressed in subjects which had been anesthetized during 5 min noise exposure, regardless of body temperature during the exposure. The long-term decrement of the L-wave amplitude did not consistently differ as a function of anesthetic state or body temperature at exposure. However, hypothermia protected from, while barbiturate increased the effects of noise stress on the H wave. It was hypothesized that metabolic factors differentially affect the various electrical generators in the inner ear.
mesh_terms: D000818:Animals; D001831:Body Temperature; D003051:Cochlea / Q000187:drug effects / Q000502:physiology*; D003055:Cochlear Microphonic Potentials / Q000187:drug effects; D051379:Mice; D009622:Noise; D010424:Pentobarbital / Q000494:pharmacology*; D011930:Reaction Time
chemical_list: D010424:Pentobarbital