Detection of apoptotic change in the lipopolysaccharide (LPS)-treated cochlea of guinea pigs

This study was undertaken to examine. electrophysiologically and immunohist ochemically, the effect of endotoxin on the guinea pig cochlea. A bacterial endotoxin (lipopolysaccharide. LPS, 5 mg/ml, 0.2 ml) was injected into the middle ear trans-tympanically. The electrocochleograms were continuously r ecorded from before to 48 h after the injection with an electrode inserted into the facial canal. Then. the animals were sacrificed by intracardiac pe rfusion of a fixative, temporal bones were removed and immunohistochemicall y stained for single-stranded DNA (ssDNA) and caspase 3 (CPP32). ssDNA was detected at 48 h in the stria vascularis and spiral ligament. CPP32 was obs erved in the stria vascularis. the spiral ligament and the organ of Corti. The threshold of the compound action potential increased significantly at 4 8 h in the LPS group. These results suggest that the activation of CPP32 an d fragmentation of DNA are involved in the dysfunction of the cochlea obser ved under inflammatory conditions. (C) 2001 Elsevier Science B.V. All right s reserved.