Effect of artificial endolymph injection into the cochlear duct on the endocochlear potential. 1998

A Kakigi, and T Takeda
Department of Otolaryngology, Kochi Medical School, Nankoku, Japan.

We investigated the effect of acute endolymphatic hydrops on the positive endocochlear potential (+EP) and negative endocochlear potential (-EP). The +EP was measured in guinea pigs during injection (without outlet) and perfusion (with outlet) of artificial endolymph into the cochlear duct. The -EP was measured during anoxia after the injection or the perfusion had finished. Injection of artificial endolymph produced a slight transient increase in the +EP, and a significant decrease in the magnitude of the -EP. Chronic endolymphatic hydrops produces both +EP and -EP decrease. The +EP decrease in chronic endolymphatic hydrops may cause the chronic change of the inner ear. The +EP increase in acute endolymphatic hydrops may be caused by a shift of the basilar membrane. However, the mechanism of the 'transient' +EP increase is not clear. The -EP decrease was not observed in animals whose cochlear duct was perfused with artificial endolymph. Therefore, the artificial endolymph itself did not cause the decrease in magnitude of the -EP. Dysfunction of the hair cells is a possible explanation for the -EP decrease but the mechanism of such a decrease is not clear in the present study. However, the results of this study support the notion that small increases in endolymphatic pressure below the resolution of recent measurements (DeMott and Salt, 1997) can lead directly to a reduction of the -EP during hydrops. The animal model described here can eliminate the chronic effect of hydrops, therefore, this model is useful for investigations into the effect of hydrops itself on the inner ear and the mechanism of hearing loss in Ménière's disease.

UI MeSH Term Description Entries
D008564 Membrane Potentials The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization). Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D008575 Meniere Disease A disease of the inner ear (LABYRINTH) that is characterized by fluctuating SENSORINEURAL HEARING LOSS; TINNITUS; episodic VERTIGO; and aural fullness. It is the most common form of endolymphatic hydrops. Meniere's Disease,Meniere's Syndrome,Vertigo, Aural,Auditory Vertigo,Aural Vertigo,Ménière Disease,Ménière's Disease,Ménière's Vertigo,Otogenic Vertigo,Auditory Vertigos,Disease, Meniere,Disease, Meniere's,Disease, Ménière,Disease, Ménière's,Diseases, Ménière,Diseases, Ménière's,Meniere Syndrome,Menieres Disease,Menieres Syndrome,Ménière Diseases,Ménière Vertigo,Ménière's Diseases,Ménière's Vertigos,Ménières Disease,Ménières Vertigo,Otogenic Vertigos,Syndrome, Meniere's,Vertigo, Auditory,Vertigo, Ménière's,Vertigo, Otogenic,Vertigos, Auditory,Vertigos, Ménière's,Vertigos, Otogenic
D003051 Cochlea The part of the inner ear (LABYRINTH) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the VESTIBULAR LABYRINTH. Cochleas
D003053 Cochlear Duct A spiral tube that is firmly suspended in the bony shell-shaped part of the cochlea. This ENDOLYMPH-filled cochlear duct begins at the vestibule and makes 2.5 turns around a core of spongy bone (the modiolus) thus dividing the PERILYMPH-filled spiral canal into two channels, the SCALA VESTIBULI and the SCALA TYMPANI. Ductus Cochlearis,Scala Media,Cochlear Ducts,Cochlearis, Ductus,Duct, Cochlear,Ducts, Cochlear,Media, Scala,Medias, Scala,Scala Medias
D003055 Cochlear Microphonic Potentials The electric response of the cochlear hair cells to acoustic stimulation. Cochlear Microphonic Potential,Potential, Cochlear Microphonic,Potentials, Cochlear Microphonic
D004195 Disease Models, Animal Naturally-occurring or experimentally-induced animal diseases with pathological processes analogous to human diseases. Animal Disease Model,Animal Disease Models,Disease Model, Animal
D004594 Electrophysiology The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D004710 Endolymph The lymph fluid found in the membranous labyrinth of the ear. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Endolymphs
D006168 Guinea Pigs A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research. Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D000200 Action Potentials Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli. Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential

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