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Acute and chronic effects of streptomycin applied to the lateral semicircular canal
C H Norris1, A Aubert, R G Amedee
1Tulane University School of Medicine, Department of Otolaryngology-Head and Neck Surgery, New Orleans, Louisiana.
Abstract:
In developing the technique of selective chemical vestibulectomy, the destructive effect of streptomycin on the hair cells of the inner ear was well established. However, in both animal and human studies, a rapid onset of the drug's vestibular inhibition was observed in addition to a more slowly developing long-term destructive effect. In previous laboratory studies, streptomycin had been given only by a systemic route, and only the chronic long-term effects had been observed. In this study, an isolated semicircular canal was prepared and streptomycin was placed into the perilymph bathing the canal. The spontaneous and evoked afferent nerve activity were recorded prior to streptomycin application, during application, and after a washout period. During streptomycin application, the activity of the semicircular canal was reversibly inhibited in a dose dependent manner. After a sufficient washout period (5-10 min), the preparation had completely recovered from the drug's effect. Thus, there are two phases in the vestibular inhibition by streptomycin: an early reversible phase that subsequently can transform into a later irreversible phase.
Insights
Streptomycin causes reversible vestibular inhibition in the inner ear, which can later become irreversible. This study observed rapid, dose-dependent effects on semicircular canal nerve activity.
Area of Science:
- Ototoxicology
- Neuroscience
- Vestibular System Research
Background:
- Streptomycin's destructive effect on inner ear hair cells is known.
- Previous studies focused on systemic administration and long-term effects.
- Rapid vestibular inhibition by streptomycin has been observed but not fully characterized.
Purpose of the Study:
- To investigate the acute effects of streptomycin on vestibular nerve activity.
- To differentiate between early reversible and late irreversible phases of streptomycin ototoxicity.
- To examine the dose-dependent effects of streptomycin on an isolated semicircular canal preparation.
Main Methods:
- Preparation of an isolated semicircular canal.
- Application of streptomycin directly to the perilymph.
- Recording of spontaneous and evoked afferent nerve activity.
- Observation of effects during application and after washout.
Main Results:
- Streptomycin reversibly inhibited semicircular canal activity in a dose-dependent manner.
- Complete recovery of nerve activity was observed after a 5-10 minute washout period.
- This demonstrates an early, reversible phase of vestibular inhibition.
Conclusions:
- Vestibular inhibition by streptomycin occurs in two phases: an early reversible phase and a later irreversible phase.
- Direct application to the perilymph reveals rapid, reversible effects.
- Understanding these phases is crucial for selective chemical vestibulectomy techniques.