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Dendritic calcium transients in the leech giant glial cell in situ

✍ Scribed by Christian Lohr; Joachim W. Deitmer

Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
232 KB
Volume
26
Category
Article
ISSN
0894-1491

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✦ Synopsis

Glial cells have been shown to respond to neuronal activity with changes in the membrane potential and the intracellular Ca 2ϩ concentration. In order to get closer to glial structures associated with neuronal synapses, we have now looked at Ca 2ϩ signalling in the glial processes (''glial dendrites'') in response to neurotransmitters and neuronal activity. Single giant glial cells in situ of isolated ganglia of the leech Hirudo medicinalis were filled iontophoretically with the Ca 2ϩ -sensitive dyes Oregon green 488 BAPTA-1 or Fluo-3. Relative Ca 2ϩ -dependent fluorescence changes in response to bath and focal application of the ionotropic glutamate receptor agonist kainate (50 µM) and of 5-hydroxytryptamine (5-HT, 100 µM) were recorded in glial dendrites, using confocal laser scanning microscopy. The amplitudes of the [Ca 2ϩ ] i transients in the dendritic processes were 2-4 times larger than those recorded in the cell body. Electrical stimulation of a nerve root (20 Hz for 15 s) elicited [Ca 2ϩ ] i transients in glial dendrites (n ϭ 32) that were reduced by the ionotropic glutamate receptor antagonist 6-cyano-7nitroquinoxaline-2,3-dione (CNQX; n ϭ 14). The results demonstrate that neuronal activity can evoke [Ca 2ϩ ] i transients not only in glial cell bodies but also in glial dendrites, where these transients display regional variation. This may reflect local release of neurotransmitters like glutamate and 5-hydroxytryptamine and/or regional differences in the density of glial receptors.

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