Cisplatin is known to cause high-frequency neurosensory hearing loss. While reactive oxygen species have been shown to play a role, reactive nitrogen species have been implicated, but not proven to be involved, in cisplatin ototoxicity. The purpose of the present study was to investigate the role of nitric oxide (NO) in cisplatin ototoxicity by administering astragalosides, a natural antioxidant, in conjunction with cisplatin. Guinea pigs were injected with cisplatin, astragalosides or both. Auditory brainstem-evoked responses (ABRs) were measured before and 3 days after cisplatin administration. The cochlear tissue was then assayed for NO and malondialdehyde (MDA), and cochleae were also examined by scanning electron microscopy. Cisplatin alone caused significant ABR threshold shifts at all stimuli tested, whereas astragalosides alone caused no shifts. There was a significant reduction in threshold shift for clicks, 8-kHz and 16-kHz tone bursts (but not 32 kHz) when astragalosides was given with cisplatin. Both the MDA concentration and the NO concentration in the astragalosides/cisplatin group were significantly lower than those of the cisplatin group. Correspondingly, the loss of outer hair cells in the astragalosides/cisplatin group was much less than that in the cisplatin group. This suggests that astragalosides reduces cisplatin ototoxicity by its antioxidant property. Copyright (C) 2011 S. Karger AG, Basel