Henry KR. Effects of noise, hypothermia and barbiturate on cochlear electrical activity.
AUDIOLOGY : OFFICIAL ORGAN OF THE INTERNATIONAL SOCIETY OF AUDIOLOGY 1980;
19:44-56. [PMID:
7352919 DOI:
10.3109/00206098009072648]
[Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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.
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