Changes of the compound action potential (CAP) and the expression of inducible nitric oxide synthase (iNOS/NOS II) in the cochlea under the inflammatory condition(1).
In this study, the effect of endotoxin on the guinea pig cochlea has been examined electrophysiologically and immunohistochemically. Bacterial lipopolysaccharide (LPS, 5 mg/ml, 0.2 ml) was injected into the middle ear trans-tympanically. The electrocochleograms were measured before, immediately upon, and 3, 6 and 12 h after the injection continuously with an electrode inserted into the facial canal. After each measurement, some of the animals were killed with an intracardiac perfusion of fixative, temporal bones were removed and were immunohistochemically examined for inducible nitric oxide synthase (iNOS/NOS II). On serial paraffin section, iNOS could be detected first after 3 h in the lateral wall, the supporting cells of the organ of Corti and in cells of the spiral ganglion and was observed up to 12 h. After the injection of LPS, the threshold of compound action potential became significantly worse after 12 h in the LPS group. These changes became evident first at higher frequency (8 kHz). These results suggest that iNOS-generated NO is involved in the cochlea dysfunction under inflammatory conditions.
Watanabe
K
K
Department of Oto-Rhino-Laryngology, Nippon Medical School, Tokyo, Japan. bxp02646@nifty.ne.jp
Hess
A
A
Zumeger
C
C
Stennert
E
E
Bloch
W
W
Addicks
K
K
Michel
O
O
D000200:Action Potentials; D000818:Animals; D001300:Audiometry, Evoked Response; D003051:Cochlea / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology*; D015834:Cochlear Diseases / Q000139:chemically induced / Q000201:enzymology* / Q000503:physiopathology*; D004056:Differential Threshold; D006168:Guinea Pigs; D007249:Inflammation / Q000201:enzymology / Q000503:physiopathology; D008070:Lipopolysaccharides / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D014018:Tissue Distribution
D008070:Lipopolysaccharides; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II