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Cerebrospinal fluid absorption in the rabbit. Inner ear pathways
R P Manzo1, D G Gomez, D G Potts
1Department of Radiology, Cornell University Medical College, New York.
Acta Oto-Laryngologica
|May 1, 1990
Summary
Horseradish peroxidase (HRP) injected intrathecally in rabbits reached the inner ear via auditory nerve pathways. This tracer permeated cochlear structures, including the basilar membrane and endolymph, highlighting potential routes for drug delivery.
Area of Science:
- Ototoxicology
- Neuroscience
- Inner Ear Physiology
Background:
- The intrathecal pathway's accessibility to the inner ear is not fully understood.
- Investigating tracer distribution in the cochlea is crucial for understanding drug delivery and ototoxicity.
Purpose of the Study:
- To investigate the distribution of intrathecally administered horseradish peroxidase (HRP) within the cochlea of adult rabbits.
- To identify potential pathways for tracer entry into the inner ear structures.
Main Methods:
- Adult rabbits underwent intrathecal perfusion with HRP under controlled cerebrospinal fluid (CSF) pressure.
- Histological and ultrastructural examinations of cochlear tissues were performed to detect HRP deposits.
Main Results:
- HRP deposits were observed along the cochlear and vestibular nerve branches, within epineural, perineural, and intraneural spaces.
- The tracer permeated to myelinated axons via nodes of Ranvier and extended into lymphatic spaces.
- HRP was found in the basilar membrane, scalae tympani, vestibuli, media, spiral ligament, and endolymph, penetrating sustentacular and hair cells.
Conclusions:
- Intrathecal HRP can access the inner ear structures through the auditory nerve and surrounding spaces.
- The study demonstrates that the intrathecal route allows HRP to reach various compartments of the cochlea and vestibule.
- These findings suggest potential pathways for therapeutic agents delivered intrathecally to the inner ear.