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Volume flow rate of perilymph in the guinea-pig cochlea.
Hear Res. 1988 Sep 15; 35(2-3):119-29.HR

Abstract

The rate of longitudinal flow of perilymph has been measured using an ionic tracer technique. Spread of the tracer trimethylphenylammonium (TMPA) along the perilymphatic scalae was monitored with ion-selective microelectrodes following injection of a minute bolus (approximately 50 nl) of 150 mM TMPAC1 one turn away. This amount of TMPA had virtually no toxic effect on cochlear function. The spread of tracer by longitudinal volume flow and passive diffusion were separated by comparing tracer movements in both apical and basal directions along the scalae in two groups of animals. Experimental findings were compared with a mathematical model which combined diffusion and volume flow. Our results demonstrated that when electrodes were completely sealed into the cochlea, the rate of longitudinal volume flow in scala tympani was extremely slow, approximately 1.6 nl/min in the apical direction. Longitudinal flow was not detectable in scala vestibuli. When the otic capsule was perforated, flow rates of over 1 microliter/min were recorded in scala tympani, probably as a result of cerebrospinal fluid entry through the cochlear aqueduct. When the cochlea was sealed (with recording electrodes in place) and cerebrospinal fluid pressure was released, there was no significant basally-directed flow of perilymph in scala tympani. These findings support the concept that perilymph composition is maintained by local, cochlear mechanisms which do not involve longitudinal volume flow. They provide strong evidence that perilymph is not secreted in one region and resorbed at a spatially distant site.

Authors+Show Affiliations

Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO 63110.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

3198505

Citation

Ohyama, K, et al. "Volume Flow Rate of Perilymph in the Guinea-pig Cochlea." Hearing Research, vol. 35, no. 2-3, 1988, pp. 119-29.
Ohyama K, Salt AN, Thalmann R. Volume flow rate of perilymph in the guinea-pig cochlea. Hear Res. 1988;35(2-3):119-29.
Ohyama, K., Salt, A. N., & Thalmann, R. (1988). Volume flow rate of perilymph in the guinea-pig cochlea. Hearing Research, 35(2-3), 119-29.
Ohyama K, Salt AN, Thalmann R. Volume Flow Rate of Perilymph in the Guinea-pig Cochlea. Hear Res. 1988 Sep 15;35(2-3):119-29. PubMed PMID: 3198505.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Volume flow rate of perilymph in the guinea-pig cochlea. AU - Ohyama,K, AU - Salt,A N, AU - Thalmann,R, PY - 1988/9/15/pubmed PY - 1988/9/15/medline PY - 1988/9/15/entrez SP - 119 EP - 29 JF - Hearing research JO - Hear Res VL - 35 IS - 2-3 N2 - The rate of longitudinal flow of perilymph has been measured using an ionic tracer technique. Spread of the tracer trimethylphenylammonium (TMPA) along the perilymphatic scalae was monitored with ion-selective microelectrodes following injection of a minute bolus (approximately 50 nl) of 150 mM TMPAC1 one turn away. This amount of TMPA had virtually no toxic effect on cochlear function. The spread of tracer by longitudinal volume flow and passive diffusion were separated by comparing tracer movements in both apical and basal directions along the scalae in two groups of animals. Experimental findings were compared with a mathematical model which combined diffusion and volume flow. Our results demonstrated that when electrodes were completely sealed into the cochlea, the rate of longitudinal volume flow in scala tympani was extremely slow, approximately 1.6 nl/min in the apical direction. Longitudinal flow was not detectable in scala vestibuli. When the otic capsule was perforated, flow rates of over 1 microliter/min were recorded in scala tympani, probably as a result of cerebrospinal fluid entry through the cochlear aqueduct. When the cochlea was sealed (with recording electrodes in place) and cerebrospinal fluid pressure was released, there was no significant basally-directed flow of perilymph in scala tympani. These findings support the concept that perilymph composition is maintained by local, cochlear mechanisms which do not involve longitudinal volume flow. They provide strong evidence that perilymph is not secreted in one region and resorbed at a spatially distant site. SN - 0378-5955 UR - https://www.unboundmedicine.com/medline/citation/3198505/Volume_flow_rate_of_perilymph_in_the_guinea_pig_cochlea_ L2 - https://linkinghub.elsevier.com/retrieve/pii/0378-5955(88)90111-6 DB - PRIME DP - Unbound Medicine ER -