Modulation Of Signal Processing Of Retinal Neurons By Zinc

Modulation of Signal Processing of Retinal Neurons by Zinc Dong-Gen Luo (Neurobiology) Directed by Prof. Xiong-Li Yang Abstract It has been reported that Zn~2+ modulates not only inhibitory and excitatory amino acid receptors, but also the voltage-gated channels in the central nervous system (CNS). In the retina, Zn~2+ is abundantly localized to the outer and inner plexiform layers and may act as an endogenous neuromodulator. In the present work, modulation by Zn~2+ of activities of retinal horizontal cells, bipolar cells and amacrine cells is studied in the isolated, superfused carp retina, using intracellular recording techniques. In darkness, 25 μM Zn~2+ hyperpolarizes L-type horizontal cells (LHCs) and potentiates responses of these cells to green (500 nm) flashes, but decreases those to red (680 nm) flashes. On the other hand, 25 μM Zn~2+ hyperpolarizes R/G HCs (a type of chromaticy-type horizontal cells, depolarizing to red flashes but hyperpolarizing to green flashes) and potentiate hyperpolarizing responses to green flashes, but decrease depolarizing responses to red flashes. However, 25 μM Zn~2+ does not change photopic electroretinographic PIII responses, which reflect the activities of cone photoreceptors. These results suggest that the differential modulation by Zn~2+ observed in LHCs does not result from changes in cone activities. The differential modulation by Zn~2+ persists when the Zn~2+ -induced membrane hyperpolarization is compensated by lowering Ca concentration in the perfusate, but abolished in the presence of background illumination. Furthermore, the differential modulation no longer exists in the presence of Bicuculline, suggesting the involvement of γ- 5 锌离子对视网膜神经元信号传递的调制 aminobutyric acid A (GABA A ) receptors. We speculate that the differential modulation...