Masson G, Mestre D, Blin O
UA CNRS 1166 "Cognition & Mouvement", Université Aix-Marseille II, France.
Fundam Clin Pharmacol. 1993;7(8):449-63. doi: 10.1111/j.1472-8206.1993.tb01041.x.
A large body of experimental evidence supports the hypothesis that dopamine is a functional neuromodulator at many levels of the visual system. Intrinsic dopaminergic neurons were characterized in most mammalian retina, including man. These neurons give rise to a dendritic plexus covering the retina. Thus, dopamine seems to be involved in the organization of the ganglion cell and the bipolar cell receptive fields and modulates physiological activity of photoreceptors, both processes which underlie sensitivity and spatial selectivity of visual processing in the early stage of the visual system. Moreover, few data are now available concerning the functional significance of dopaminergic modulation of visual sensitivity in man. Parkinson's disease is a specific disorder of central dopaminergic systems. Abnormalities in the pattern-evoked potentials and electroretinogram have been found in parkinsonian patients. Contrast sensitivity, a useful tool for measuring visual spatio-temporal sensitivity in man, has also been shown to be modified due to this affection. Dynamic contrast sensitivity is primarily decreased in these patients, distinguishing them from the normal aging process. Because these modifications in shape of the contrast sensitivity function are reversed by L-Dopa, and that neuroleptic administration could reproduce them in schizophrenia patients, it was suggested that dopamine might tune the contrast sensitivity function in man. We have recently shown that subcutaneous apomorphine induces changes in contrast sensitivity in healthy volunteers, which preferentially affect motion sensitivity. These dopaminergic sensitive modifications in the shape of the contrast sensitivity function might reflect a change in the range of sensitivity of the visual system, both in dynamic and spatial properties. This could be explained by a modification in the spatial and dynamic properties of the ganglion cell responses in the retina. Moreover, we suggest both from our results and from the review of the literature that human psychophysical data confirm the hypothesis that dopamine may be involved in light retinal adaptation, as light-induced and dopamine-induced modifications in the shape in the contrast sensitivity function are quite similar.
大量实验证据支持多巴胺在视觉系统多个层面作为功能性神经调节剂的假说。在包括人类在内的大多数哺乳动物视网膜中，已鉴定出内在多巴胺能神经元。这些神经元形成覆盖视网膜的树突丛。因此，多巴胺似乎参与了神经节细胞和双极细胞感受野的组织，并调节光感受器的生理活动，这两个过程是视觉系统早期视觉处理的敏感性和空间选择性的基础。此外，目前关于多巴胺能调节人类视觉敏感性的功能意义的数据很少。帕金森病是中枢多巴胺能系统的一种特定疾病。帕金森病患者已发现模式诱发电位和视网膜电图异常。对比敏感度是测量人类视觉时空敏感性的有用工具，也已被证明因这种疾病而发生改变。这些患者的动态对比敏感度主要降低，这将他们与正常衰老过程区分开来。由于对比敏感度函数形状的这些改变可被左旋多巴逆转，并且在精神分裂症患者中给予抗精神病药物可重现这些改变，因此有人提出多巴胺可能调节人类的对比敏感度函数。我们最近表明，皮下注射阿扑吗啡会使健康志愿者的对比敏感度发生变化，这优先影响运动敏感性。对比敏感度函数形状的这些多巴胺能敏感改变可能反映了视觉系统在动态和空间特性方面敏感性范围的变化。这可以通过视网膜中神经节细胞反应的空间和动态特性的改变来解释。此外，我们从我们的结果以及文献综述中都表明，人类心理物理学数据证实了多巴胺可能参与视网膜光适应的假说，因为光诱导和多巴胺诱导的对比敏感度函数形状的改变非常相似。
