Modulation by Zn2+ of GABA responses in bipolar cells of the mouse retina.
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 microM bicuculline, suggesting that this is a GABA(A)-receptor mediated current. The second component was inhibited completely by 100 microM 3-aminopropyl-(methyl)-phosphinic acid, suggesting that this is a GABA(C)-receptor mediated current. GABA(C) receptors were present at a higher density on the axon terminal than on dendrites. Zn2+ inhibited both GABA(A) and GABA(C) receptors. GABA(C) receptors were more susceptible to Zn2+; the IC50 for the GABA(A) receptor was 67.4 microM and that for the GABA(C) receptor was 1.9 microM. These results suggest that Zn2+ modulates the inhibitory interaction between amacrine and bipolar cells, particularly that mediated by the GABA(C) receptor.
Kaneda
M
M
Department of Physiology, Keio University School of Medicine, Tokyo, Japan. mkaneda@physiol.med.keio.ac.jp
Andrásfalvy
B
B
Kaneko
A
A
D000818:Animals; D001391:Azo Compounds; D001640:Bicuculline / Q000494:pharmacology; D004396:Coloring Agents; D004594:Electrophysiology; D004801:Eosine Yellowish-(YS); D018756:GABA Antagonists / Q000494:pharmacology; D007395:Interneurons / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009943:Organophosphorus Compounds / Q000494:pharmacology; D018079:Receptors, GABA / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D015032:Zinc / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D001391:Azo Compounds; D004396:Coloring Agents; D018756:GABA Antagonists; C087200:GABA-C receptor; D009943:Organophosphorus Compounds; D018079:Receptors, GABA; D011963:Receptors, GABA-A; C068457:3-aminopropyl(methyl)phosphinic acid; C037882:2-(5-bromo-2-pyridylazo)-5-diethylaminophenol; D005680:gamma-Aminobutyric Acid; D015032:Zinc; D004801:Eosine Yellowish-(YS); D001640:Bicuculline