OBJECTIVETo investigate the detrimental effects of ouabain on cochlear spiral ganglion neurons (SGCs) in vivo and in vitro.

METHODSSeventy-five male SD rats were randomly divided into 5 groups. In addition to the normal control group, rats in other 4 groups received 0.01, 0.02, 0.05 mmol/L of Ouabain or saline through cochlear scala tympani drilling. Seven days after surgery, the hearing threshold was measured by distortion product otoacoustic emissions (DPOAE) and auditory brainstem response (ABR) in rats. In the in vitro study, SGNs were isolated from SD rats (E14) and treated with 1 × 10(-8) mmol/L of Ouabain. The damaged of SGCs were detected after ouabain treatment using immunohistochemistry, transmission electron microscope and scanning electron microscope in vitro.

RESULTSAfter administration of Ouabain, DPOAE did not change significantly. No significant difference in the amplitude of DPOAE could be observed among all the groups (P > 0.05). Compared with saline and normal control, ABR threshold was significantly increased in the Ouabain treated groups (P < 0.05), which correlated with the concentration of Ouabain. Electron microscopy showed that after treated with Ouabain, SGCs presented degenerative changes, including collapse of organelle structures, the karyotheca dissolved, myelin sheath disintegrating. Ouabain could damage type I SGCs but not type II SGNs.

CONCLUSIONSOuabain can damage SGCs, either in the in vivo or in vitro conditions.