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Electrophysiological measurements of volume changes in leech neuropile glial cells
Author(s) -
Ballanyi K.,
Grafe P.,
Serve G.,
Schlue W.R.
Publication year - 1990
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/glia.440030302
Subject(s) - depolarization , leech , tetramethylammonium , intracellular , biophysics , hirudo medicinalis , membrane potential , biology , extracellular , hyperpolarization (physics) , electrophysiology , serotonin , membrane , anatomy , biochemistry , chemistry , neuroscience , ion , stereochemistry , receptor , organic chemistry , world wide web , computer science , nuclear magnetic resonance spectroscopy
Double‐barrelled microelectrodes, sensitive to quaternary ammonium ions, were used for simultaneous measurements of the intracellular free concentrations of choline ([Ch] i ) or tetramethylammonium [TMA i ] as well as membrane potential (Em) in neuropile glial cells of the leech, Hirudo medicinalis. Bath application of Ch or TMA (5 mM, 1 min) resulted in a transient membrane depolarization accompanied by a long‐ lasting (0.5–1 h) intracellular accumulation of these compoundsto levels of between 5 and 15 mM. Changes in [Ch] i or [TMA] i were used for the calculation of changes in relative cell volume. Elevation of the extracellular K + concentration ([K + ] e ) from 4 to 9,15,21,27.5, or 40 mM elicited a membrane depolarization and a reversible cell swelling by about 7.5,14, 18.5, 27 and 50%, whereas reduction of [K + ] e to 1.5 mM as well as bath application of serotonin (5‐HT) produced a membrane hyperpolarization and a concomitant shrinkage by about 6 and 14.3%, respectively. The measured alterations in cell volume were compared with calculated data based on the assumption of an osmotic equilibrium disturbed by potential‐dependent changes of the intracellular Cl − concentration. The results indicate, that K + ‐ and serotonin‐induced changes in the cell volume of the neuropile glial cells are due to passive KCl and water fluxes.