Direct measurement of longitudinal endolymph flow rate in the guinea pig cochlea

Alec N. Salt, Ruediger Thalmann, Daniel C. Marcus, Barbara A. Bohne

Research output: Contribution to journalArticle

62 Scopus citations

Abstract

The rate of longitudinal endolymph flow in the guinea pig cochlea has been measured with a novel tracer technique. The tracer we utilized was the tetramethylammonium (TMA) ion, the movement of which was monitored by ion-sensitive microelectrodes. Extremely small amounts of tracer were required as the electrodes could readily detect TMA concentrations in endolymph as low as 10 μM. TMA was introduced into scala media in the form of a small bolus, varying from 2-20 nl in volume. To examine whether longitudinal flow affects the dispersion of TMA in endolymph, we compared the characteristics of TMA spread to turn I following injection into turn II, with those of TMA spread to turn II following injection into turn I. The comparison of these data with an analytical model combining the processes of diffusion and volume flow demonstrates that the spread of tracer is dominated by passive diffusion processes with very little contribution from longitudinal endolymph flow. The rate of longitudinal endolymph flow between turn I and turn II was estimated to be less than 0.01 mm/min directed towards the basal turn. This value is considerably lower than recently published estimates using other techniques.

Original languageEnglish
Pages (from-to)141-151
Number of pages11
JournalHearing research
Volume23
Issue number2
DOIs
StatePublished - 1986

Keywords

  • cochlea
  • endolymph
  • ion-sensitive microelectrodes

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