Otoprotectant minimizes hearing defects caused by Pseudomonas aeruginosa exotoxin A

Exotoxin A, produced by Pseudomonas aeruginosa (PaExoA), penetrates from th e middle ear in to the cochlea and causes sensorineural hearing loss (SNHL) . In this investigation we studied electrophysiological changes in the albi no rat following instillation of PaExoA and N-G-nitro-L-arginine methyl eat er (L-NAME), a known inhibitor of nitric oxide synthesis, into the middle e ar. Hearing thresholds were measured by auditory brainstem response (ABR) t echnique. Latency/intensity curves were constructed to distinguish between cochlear and conductive components of hearing loss. PaExoA caused damage to cochleae and SNHL, mainly at high frequencies. This impairment was blocked by (L-NAME). It would appear that nitric oxide may be a significant link i n the mechanism of SNHL caused by bacterial toxin. L-NAME acts as an otopro tectant against the deleterious action of PaExoA.