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Luo DG, Li GL, Yang XL: Zn (2+) modulates light responses of color-opponent bipolar and amacrine cells in the carp retina. Brain Res Bull. 2002 Sep 15;58(5):461-8.
The effects of Zn (2+) on color-opponent bipolar cells (BCs) and amacrine cells (ACs) were studied in the isolated superfused carp retina using intracellular recording techniques. Bath-applied Zn (2+) (25 micro M) depolarized R (+) G (-)-type BCs and suppressed both depolarizing responses of these cells to red (680 nm) flashes and hyperpolarizing ones to green (500 nm) flashes. Following Zn (2+) application, G (+) R (-)-type BCs were hyperpolarized, which was accompanied by a potentiation of their depolarizing responses to green flashes and a suppression of hyperpolarizing ones to red flashes. Similar Zn (2+) effects were observed in R (+) G (-)- and G (+) R (-)-type ACs. The Zn (2+) effects persisted in the presence of picrotoxin and strychnine, suggesting that modulation by Zn (2+) of GABA and glycine receptors was unlikely involved. Using whole-cell recording techniques, it was found Ca (2+) currents in cone terminals were dose-dependently suppressed by Zn (2+), suggesting that Zn (2+) may reduce glutamate release from cone photoreceptors. Furthermore, lowering extracellular Ca (2+), a procedure that increases glutamate release from photoreceptors, exerted actions on R (+) G (-)- and G (+) R (-)-type BCs, almost opposite to the Zn (2+) effects on these two types of BCs. It is therefore postulated that the Zn (2+) effects reported in the present work may reflect a consequence of the changes in input resistances of color-opponent BCs and driving forces for their light responses resulted from the reduced glutamate release by Zn (2+). |
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