Zn(2+) modulates light responses of color-opponent bipolar and amacrine cells in the carp retina.
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+).
Luo
Dong-Gen
DG
Institute of Neurobiology, Fudan University, 220 Han-Dan Road, Shanghai, PR China.
Li
Geng-Lin
GL
Yang
Xiong-Li
XL
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D025042:Amacrine Cells / Q000187:drug effects* / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002347:Carps; D003118:Color Perception / Q000187:drug effects / Q000502:physiology; D004596:Electroretinography; D007477:Ions; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000187:drug effects* / Q000502:physiology*; D014785:Vision, Ocular / Q000187:drug effects / Q000502:physiology*; D015032:Zinc / Q000494:pharmacology*
D007477:Ions; D015032:Zinc; D002118:Calcium