Electrophysiological measurements of volume changes in leech neuropile glial cells

✍ Scribed by Dr. K. Ballanyi; P. Grafe; G. Serve; W.-R. Schlue

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 682 KB
• Volume: 3
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/glia.440030302

✦ Synopsis

Double-barrelled microelectrodes, sensitive to quaternary ammonium ions, were used for simultaneous measurements of the intracellular free concentrations of choline ([Ch],) or tetramethylammonium ([TMAIJ 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 longlasting (0.5-1 h) intracellular accumulation of these compounds to levels of between 5 and 15 mM. Changes in [Chli or [TMAli were used for the calculation of changes in relative cell volume. Elevation of the extracellular K+ concentration ([K+],) 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+], 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 C1-concentration. The results indicate, that K'and serotonin-induced changes in the cell volume of the neuropile glial cells are due to passive KCI and water fluxes.