Electrophysiological study of retinal rod-cone interaction

本研究的目的是阐明多巴胺（DA）在视网膜中的功能意义。我们研究了多巴胺和一种有效的D_1-D_2受体阻滞剂氟哌啶醇对白化病兔视网膜功能的影响。玻璃体内注射多巴胺抑制暗视b波，增强振荡电位（OPs）引起的反复明亮的闪光，但没有显着影响明视b波。玻璃体内注射氟哌啶醇抑制明视b波和OP。在氟哌啶醇注射的眼睛中额外玻璃体内注射多巴胺使OP复苏超过氟哌啶醇前状态。这些结果表明，多巴胺介导的暗视系统的光适应过程，最终促进明视系统的功能，通过脱离杆锥抑制。玻璃体内注射D_1受体拮抗剂SCH 23390（50 μ M，100 μ M）可阻断DA对OPs的增强作用，但不能阻断D_2受体拮抗剂舒必利（50 μ M，100 μ M）对OPs的增强作用。这些结果提示D_1受体是DA诱导的OPs增强的主要机制。诺米芬辛（NF），一个有效的DA-摄取阻滞剂，增加的幅度的OP。NF减弱暗视b波的振幅，使暗视b波的峰值潜伏期不变。在任何测试的NF浓度下，暗适应a波和b波均未改变。1 μ M DA和30 μ M NF一起作用，单独应用时，其中每一种都不足以改变暗视b波或OP，减少了暗视b波并增强了OP。这些结果表明，在视网膜中的内在DA释放是足够大的改变ERG。

The purpose of the present study is to elucidate the functional significance of dopamine (DA) in the retina. We studied effects of dopamine and a potent D_1-D_2 blocker, haloperidol, on retinal function in the albino rabbit in vivo. An intravitreal injection of dopamine suppressed the scotopic b-wave and enhanced the oscillatory potentials (OPs) elictited by repeated bright flashes, but did not significantly affect the photopic b-wave. An intravitreal injection of haloperidol suppressed the photopic b-wave and the OPs. An additional intravitreal injection of dopamine to the haloperidol-injected eyes resuscitated the OPs over the pre-haloperidol status. These results suggest that dopamine mediates the light-adaptive processes of the scotopic system, eventually facilitating the photopic system function via disengagement of rod-cone inhibition. Enhancement of the OPs by intravitreal DA injection was blocked by a simultaneous intravitreal injection of SCH 23390 (D_1 antagonist) but not by that of sulpiride (D_2 antagonist) (50muM,100muM). These results suggest that D_1 receptor is mainly responsible for the DA-induced enhancement of the OPs. Nomifensine (NF), a potent DA-uptake blocker, enhanced the amplitude of the OPs. NF attenuated the amplitude of the scotopic b-wave, leaving the peak latency of the scotopic b-wave unaltered. Neither the dark-adapted a- nor b-waves was altered at any NF concentration tested. 1muM DA and 30muM NF together, each of which is insufficient to alter either of the scotopic b-wave or the OPs when applied solely, reduced the scotopic b-wave and enhanced the OPs. These results suggest that the intrinsic DA release in the retina is large enough to alter the ERG.