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Fura‐2 signals evoked by kainate in leech glial cells in the presence of different divalent cations
Author(s) -
Munsch Thomas,
Nett Wolfgang,
Deitmer Joachim W.
Publication year - 1994
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.440110407
Subject(s) - kainate receptor , divalent , biophysics , depolarization , membrane potential , biology , glutamate receptor , intracellular , biochemistry , chemistry , ampa receptor , receptor , organic chemistry
The glutamate‐agonist kainate evokes Ca 2+ transients in both neurones and glial cells. Owing to the membrane depolarization elicited by kainate, a Ca 2+ influx could occur through voltage‐gated Ca 2+ channels or through the kainate‐gated cation channels directly. We have measured ratio signals of the calcium indicator dye fura‐2, injected into giant glial cells of the leech Hirudo medicinalis , as response to kainate (5‐20μ) in the presence of different divalent cations. The responses to kainate increased during the first 2‐4 kainate applications, both in unclamped and in voltage‐clamped cells. The fura‐2 fluorescence ratio (F 350 /F 380 ) still increased when Ca 2+ was replaced by Ba 2+ but was suppressed in Ca 2+ ‐free saline and in the presence of Ni 2+ (2 mM). Co 2+ and Mn 2+ (2 mM) also reduced the kainate‐induced fura‐2 fluorescence signals, due to entry of these divalent cations into the cells and subsequent quenching the fluorescence of the intracellular dye. It is concluded that Ni 2+ blocks the kainate‐induced membrane depolarization and Ca 2+ transient but apparently does not enter the cells, while Ba 2+ , Co 2+ , and Mn 2+ appear to permeate the membrane, presumably through the kainategated channels. © 1994 Wiley‐Liss, Inc.