Additive effects of toxin exposure and destruction of semicircular canal on cochlear function: an auditory brainstem response study in the rat.

Objective: To ascertain whether the severity of toxin-related hearing loss and the interval between instillation of toxin and surgical trauma affect hearing recovery capacity following semicircular canal (SCC) surgery in the rat.

Material And Methods: Twelve rats were injected with Pseudomonas aeruginosa exotoxin A (PaExoA). Auditory brainstem responses (ABRs) were measured 72 h and 3 weeks later.

Age-related hearing changes and effects of exotoxin on inner ear function in aging rat. A frequency-specific auditory brainstem response study.

Frequency-specific auditory brainstem responses to tone bursts (2-31.5 kHz) and tuning curves were recorded in 8 male rats during their entire life. No significant threshold elevation occurred during the 1st year.

Middle ear mucosa changes following exposure to Pseudomonas aeruginosa exotoxin A.

Pseudomonas aeruginosa exotoxin A (1 microgram/20 microliters) was instilled into the middle ear cavity in the rat. Morphological changes of the mucosa were analyzed after various intervals using light (LM) and transmission electron microscopy (TEM). An inflammatory cell reaction was seen in which there was a predominance of polymorphonuclear leukocytes (PMNs) and mononuclear cells that were mostly lymphocytes and monocytes/macrophages.

Interleukin-2 affects cochlear function gradually but reversibly.

Interleukin-2 (IL-2), one of the chemical mediators produced by helper T cells, activates its target cells via its receptor and induces inflammatory reactions indirectly. In this study, IL-2 was instilled into the round window niche of rats and the electrophysiological effects of inflammation on the inner ear were evaluated by a frequency-specific auditory brainstem response (ABR) technique. ABR threshold curves and intensity-latency (I-L) curves were investigated.

Cochlear changes following destruction of semicircular canal in healthy and previously toxin-exposed rats. An electrophysiological and morphological investigation.

One group of Sprague-Dawley rats (group A, n = 6) was treated by instilling Pseudomonas aeruginosa exotoxin A (PaExoA), and another (group B, n = 6) treated similarly with Haemophilus influenzae type b endotoxin (HiBEndo). In group A a 20 dB hearing loss was observed, predominantly in the high-frequency region, which was reversible within 1 month. In group B no significant hearing impairment was noted.