Modulation by Zn2+ of GABA responses in bipolar cells of the mouse retina

• Published in: Visual neuroscience 2000-03, Vol.17 (2), p.273-281
• Main Authors: KANEDA, M., ANDRÁSFALVY, B., KANEKO, A.
• Format: Article
• Language: English
• Subjects: Animals; Azo Compounds; Bicuculline - pharmacology; Biological and medical sciences; Bipolar cell; Coloring Agents; Electrophysiology; Eosine Yellowish-(YS); Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; GABA Antagonists - pharmacology; GABAC; gamma-Aminobutyric Acid - pharmacology; Interneurons - metabolism; Mice; Mice, Inbred C57BL; Mouse; Organophosphorus Compounds - pharmacology; Receptors, GABA - metabolism; Receptors, GABA-A - metabolism; Retina; Retina - metabolism; Vertebrates: nervous system and sense organs; Zinc - physiology; Zn2
• ISSN: 0952-5238; 1469-8714
• DOI: 10.1017/S0952523800172098

The localization of endogenous Zn2+ in the mouse retina was examined histochemically and the inhibitory action of Zn2+ on GABA-induced responses was studied in bipolar cells isolated from the mouse retina. Accumulation of endogenous Zn2+ was detected in photoreceptors, bipolar, and/or amacrine cells by either the bromopyridylazo-diethylaminophenol method or the dithizone method. Under whole-cell recording conditions, GABA induced a Cl− current in isolated bipolar cells. The current consisted of two components. The first component was inhibited completely by application of 100 μM bicuculline, suggesting that this is a GABAA-receptor mediated current. The second component was inhibited completely by 100 μM 3-aminopropyl-(methyl)-phosphinic acid, suggesting that this is a GABAC-receptor mediated current. GABAC receptors were present at a higher density on the axon terminal than on dendrites. Zn2+ inhibited both GABAA and GABAC receptors. GABAC receptors were more susceptible to Zn2+; the IC50 for the GABAA receptor was 67.4 μM and that for the GABAC receptor was 1.9 μM. These results suggest that Zn2+ modulates the inhibitory interaction between amacrine and bipolar cells, particularly that mediated by the GABAC receptor.