Journal Article

Modulation of Synaptic Function in Retinal Amacrine Cells1

Brian K. Hoffpauir and Evanna L. Gleason

in Integrative and Comparative Biology

Published on behalf of The Society for Integrative and Comparative Biology

Volume 45, issue 4, pages 658-664
Published in print August 2005 | ISSN: 1540-7063
Published online August 2005 | e-ISSN: 1557-7023 | DOI: https://dx.doi.org/10.1093/icb/45.4.658
Modulation of Synaptic Function in Retinal Amacrine Cells1

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Amacrine cells are interneurons that have diverse functions in retinal signal processing. In order to study signaling and modulation in retinal amacrine cells, we employ a simplified culture system containing identifiable GABAergic amacrine cells. Immunocytochemistry experiments indicate that GABAergic amacrine cells express metabotropic glutamate receptor 5 (mGluR5), a group I mGluR usually linked to the IP3 signaling pathway. Ca2+ imaging experiments using an mGluR5-specific agonist indicate that these receptors are functional and when activated, can stimulate temporally diverse Ca2+ elevations. To begin to establish the role of these receptors in modulating amacrine cell function, we have used electrophysiological methods to ask whether ion channels are the targets of mGluR5-dependent modulation. Here we discuss our results indicating that activation of mGluR5 leads to enhancement of currents through GABAA receptors. This enhancement is dependent upon elevations in cytosolic Ca2+ and activation of protein kinase C (PKC). To explore the consequences of Ca2+ elevations in another context, we have used nitric oxide (NO) donors to mimic the effects of activating the Ca2+-dependent synthetic enzyme for NO, neuronal nitric oxide synthase. We find that exposure to NO donors also enhances the amplitude of currents through GABAA receptors. Together, these results indicate that glutamate from presynaptic bipolar cells has the potential to work through multiple mechanisms to regulate the function of amacrine-to-amacrine cell GABAergic synapses.

Journal Article.  4263 words.  Illustrated.

Subjects: Biological Sciences

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