Title: Zinc enhances ionic currents induced in skate Mϋller (glial) cells by the inhibitory neurotransmitter GABA
Abstract: We describe here a novel effect of zinc on GABA receptors of glial cells in the skate retina. The GABA-induced currents of skate Mϋller cells, the radial glia of the retina, are mediated by activation of GABAA receptors (GABAARs). In other parts of the nervous system, GABAA-mediated currents are inhibited by zinc. However, in isolated, voltage-clamped Mϋller cells, coapplication of zinc (10 μM) and GABA (1 μM) resulted in an enhancement of the GABAAR current. Surprisingly, zinc alone induced a current similar in many respects to that elicited by GABA, i. e. the reversal potential was the same as for the GABA-induced current, the current was blocked by bicuculline and picrotoxin, and the current-voltage relation obtained in the presence of 10 μM zinc was virtually identical to that obtained with 1 μM GABA. Both bicuculline and picrotoxin suppressed a current that was present with cells bathed only in Ringer, suggesting that some of the GABA channels were spontaneously open in the absence of externally applied GABA. This possibility was supported by cell-attached patch recordings. Under conditions in which potassium and calcium currents were suppressed, spontaneous channel activity was observed. Moreover, the frequency of these channel openings was greater when zinc was included in the pipette solution, and reduced when bicuculline was added. These findings suggest that zinc acts directly to enhance the GABAA receptor activity of the Mϋller cells, and raise the possibility that the subunit composition of the GABAARs of skate Mϋller cells differs from that of GABAARs identified previously in other neuronal and glial preparations.
Publication Year: 1996
Publication Date: 1996-06-22
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
Access and Citation
Cited By Count: 22
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