De Boer, Jessica; (2003) Electrical properties of Deiters cells of the mammalian cochlea. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Deiters cells provide structural support for outer hair cells within the mammalian organ of Corti, but may also be implicated in local K+ homeostasis. This thesis has investigated electrical properties of Deiters cells of the apical guinea pig cochlea in order to assess their capacity for buffering K+ in the immediate environment of the outer hair cell. A quantitative description of the Deiters cells membrane conductance was formulated according to the Hodgkin-Huxley model, based on whole cell voltage clamp experiments on isolated cells. Using an in situ preparation of the organ of Corti, the network properties of Deiters cells were found to be accurately reproduced by a two dimensional model of parallel sheets of membrane separated by a continuous internal medium. A numerical simulation estimated the electrotonic space constant within the Deiters cell network under in vivo conditions to be in the order of millimetres. The distribution of the K+ conductance along the cell membrane was investigated using focal application of high K+ to isolated cells under whole cell voltage clamp. Over 50 % of the K+ conductance was found to be concentrated in the cup region of the Deiters cells, where they envelop the basal pole of the outer hair cell. Both the network properties of the cell syncitium and the distribution of K+ conductance on individual cells were interpreted as favourable for spatial K+ buffering. However, a simple calculation suggested that K+ uptake by the Deiters cell, as delimited by the membrane conductance, is unlikely to significantly alter extracellular K+ in the environment of the outer hair cell. On the other hand, modulation of the membrane conductance, as observed in isolated cells, could increase K+ uptake enough to allow a significant contribution from Deiters cells to K+ clearance from the narrow space around the outer hair cell base.

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