Ikeda H, Robbins J
Vision Research Unit of Sherrington School, Rayne Institute, St. Thomas' Hospital, London, UK.
Doc Ophthalmol. 1988 Jun;69(2):175-86. doi: 10.1007/BF00153699.
Anatomical and physiological segregation of neurons into ON (brightening detector) and OFF (darkening detector) channels in the retina and subsequent visual system ensure the high sensitivity required for contrast detection and spatial discrimination. This segregation is finest at the visual axis. Neurochemically, ON and OFF ganglion cells at the visual axis seem to be distinguished by different inhibitory transmitters but not excitatory transmitters. Microiontophoretic studies of inhibitory transmitters on the retinal ganglion cells in kittens and adult cats suggest that this neurochemical distinction is poor in immature ganglion cells at the visual axis. Initially both ON and OFF cells seem to be supplied by GABAergic, glycinergic, and catecholaminergic amacrine cells, but in adults, ON cells remain supplied only by GABAergic amacrines, while OFF cells are supplied by glycinergic amacrines. Postnatal elimination of multiple inputs and strengthening of the appropriate inputs, as seen in the central nervous system, also seem to occur at the retinal neurotransmitter synapses during development.
在视网膜及后续视觉系统中，神经元在解剖学和生理学上被分隔为ON（亮度探测器）和OFF（暗度探测器）通道，这确保了对比度检测和空间辨别所需的高灵敏度。这种分隔在视轴处最为精细。从神经化学角度来看，视轴上的ON和OFF神经节细胞似乎是由不同的抑制性递质而非兴奋性递质区分的。对小猫和成年猫视网膜神经节细胞上抑制性递质的微量离子电泳研究表明，在视轴处未成熟的神经节细胞中，这种神经化学差异并不明显。最初，ON和OFF细胞似乎都由γ-氨基丁酸能、甘氨酸能和儿茶酚胺能无长突细胞提供输入，但在成年动物中，ON细胞仅由γ-氨基丁酸能无长突细胞提供输入，而OFF细胞则由甘氨酸能无长突细胞提供输入。正如在中枢神经系统中所见，出生后多种输入的消除和适当输入的强化，在发育过程中似乎也发生在视网膜神经递质突触处。
