Korean J Otolaryngol-Head Neck Surg.  2005 May;48(5):589-595.

Changes in Activity of Vestibular Afferents after Intratympanic Gentamicin Single Injection

• Park HJ

Abstract

BACKGROUND AND OBJECTIVES
Aminoglycoside antibiotics are toxic to hair cells of the inner ear. Recently, intratympanic gentamicin injection is widely accepted as a treatment modality for Meniere's disease. SUBJECTS AND METHOD: We treated anesthetized chinchillas with one injection of gentamicin into the middle ear and made extracellular recordings from afferents after three to four weeks. RESULTS: The spontaneous firing rate of regular and irregular afferents was lower (p<0.05) on the treated side than on the untreated side. The relative proportions of regular, intermediate, and irregular afferents did not change after treatment. The majority of the treated afferents did not significantly respond to rotation, and those that did respond had abnormally low levels of sensitivity. Sensitivity to externally applied galvanic currents was unaffected. CONCLUSION: These findings suggest that a single intratympanic gentamicin injection preserves enough hair cell synaptic activity to drive the spontaneous activity of vestibular afferents, and does not damage the afferent spike initiation zones.

Keyword

Aminoglycoside; Electrophysiology; Vestibular afferent; Chinchilla

MeSH Terms

Anti-Bacterial Agents
Chinchilla
Ear, Inner
Ear, Middle
Electrophysiology
Fires
Gentamicins*
Hair
Meniere Disease
Anti-Bacterial Agents
Gentamicins