Studies on the neural circuit and neurotransmitters in the mammalian retina.

脊椎动物的视网膜是一个小的中枢神经系统，在这里光感受器捕捉到的视觉信息被处理。所有的视觉信号都被编码成动作电位序列，通过视神经传递到更高的视觉中枢。尽管在哺乳动物视网膜上对视神经的光诱发反应进行了大量的研究，但在哺乳动物视网膜上对其视网膜内机制的研究相当有限。相反，低等脊椎动物被用作模型制备，因为哺乳动物和低等脊椎动物具有相似的视网膜结构，视神经的光诱发反应也表现出相似的特征。本研究的目的是阐明离子电流和递质对分离的哺乳动物视网膜细胞的作用。我们完成了以下研究，并得出了如下结论。(1)建立了分离状态良好的哺乳动物视网膜细胞的方法。(2)建立了Dil逆行标记法鉴定孤立神经节细胞的方法。(3)我们发现X细胞和w细胞都含有钠。不同失活动力学电流：I_<Na>的x细胞从失活中恢复较快，而w细胞从失活中恢复较慢。(4)我们发现猫视网膜水平细胞与低等脊椎动物的水平细胞具有相同类型的离子电流。(5)我们在猫视网膜中发现了两种类型的双极细胞。一种类型对l -谷氨酸的反应是向外电流反应，同时电导降低，而另一种类型的反应是向内电流反应，同时电导增加。前者细胞对应于显示去偏振光响应的细胞，后者对应于显示超偏振光响应的OFF双极细胞。

The vertebrate retina is a small central nervous system in which the visual information captured by photoreceptors are processed. All visual signals are encoded into the train of action potentials that travel through the optic nerve to higher visual centers. Despite that a vast amount of studies have been made on mammalian retina on the light-evoked responses of the optic nerve, studies on the underlying intraretinal mechanisms are quite limited in the mammalian retina. In stead, lower vertebrates have been used as model preparations, since mammals and the lower vertebrates have similar structures of the retina and the light-evoked responses of the optic nerve show similar characteristics.The aim of the present study was to elucidate ionic currents and transmitter actions on the isolated retinal cells dissociated from mammals. We achieved following studies and made findings listed below. (1)We established tlie method to dissociate mammalian retinal cells in good condition. (2)We established the method to identify solitary ganglion cells by retrograde labeling using Dil. (3)We found that X- and W-cells has a sodium. current with different inactivation kinetics : I_<Na> of X-cells recover rapidly froin inactivation, while recovery was slow in W-cells. (4)We found that cat retinal horizontal cells have qualitatively the same type of ionic currents as horizontal cells of the lower vertebrates. (5)We found two types of bipolar cells in the cat retina. Tlie one type responded to L-glutamate with an outward current response accompanied by a conductance decrease, while tlie other type responded with an inward current accompanied by a conductance increase. The former cells correspond to those showing depolarizing light responses, while the latter correspond to OFF bipolar cells showing hyperpolarizing light responses.