Sign-conserving amacrine neurons in the fly's external plexiform layer
Sign-conserving amacrine neurons in the fly's external plexiform layer
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DOI：
10.1017/s095252380522309x
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发表时间：
2005-05-01
影响因子：
1.9
通讯作者：
Strausfeld, NJ
中科院分区：
文献类型：
--
作者：
Douglass, JK;Strausfeld, NJ
首次对果蝇叶片外部丛状层中的无长突细胞进行细胞内记录和染料填充。记录表明，与椎板的短光感受器 R1-R6 一样，I 型椎板无长突神经元响应光照而表现出非尖峰、“符号守恒”的持续去极化。这与代表一阶视网膜专题中继神经元（单极细胞 L1-L5 和 T1 传出神经元）的符号反转反应形成对比。无长突神经元的对比度频率调节与光感受器和大层单极细胞的对比度频率调节相似。初步观察表明，层无长突感受野也是类似光感受器的，这表明它们的输入要么源自少量邻近的视觉采样单元（VSU），要么局部产生的电位随着位移而迅速衰减。无长突层也对运动做出反应，并且在一项记录中，这些反应对于移动边缘的方向是有选择性的。这种功能组织对应于无长突细胞的解剖结构，其中来自几个相邻光感受器末端的突触后输入通过非常薄的远端过程网络连接起来。通过这种方式，每个 VSU 都可以从周围的无长突过程接收收敛输入。这种安排非常适合将局部强度波动的响应从邻近的 VSU 传递到中央 VSU，其中无长突已知位于 T1 传出神经树突的突触前。 T1 终端与从同一光学盒中继的 L2 单极单元的终端在更深层次上会聚。因此，无长突的局部空间反应和类受体时间反应特性与侧抑制、运动处理或定向处理中可能的作用一致。
Amacrine cells in the external plexiform layer of the fly's lamina have been intracellulary recorded and dye-filled for the first time. The recordings demonstrate that like the lamina's short photoreceptors R1-R6, type I lamina amacrine neurons exhibit nonspiking, "sign-conserving" sustained depolarizations in response to illumination. This contrasts with the sign-inverting responses that typify first-order retinotopic relay neurons: monopolar cells L1-L5 and the T1 efferent neuron. The contrast frequency tuning of amacrine neurons is similar to that of photoreceptors and large lamina monopolar cells. Initial observations indicate that lamina amacrine receptive fields are also photoreceptor-like, suggesting either that their inputs originate from a small number of neighboring visual sampling units (VSUs), or that locally generated potentials decay rapidly with displacement. Lamina amacrines also respond to motion, and in one recording these responses were selective for the orientation of moving edges. This functional organization corresponds to the anatomy of amacrine cells, in which postsynaptic inputs from several neighboring photoreceptor endings are linked by a network of very thin distal processes. In this way, each VSU can receive convergent inputs from a surround of amacrine processes. This arrangement is well suited for relaying responses to local intensity fluctuations from neighboring VSUs to a central VSU where amacrines are known to be presynaptic to the dendrites of the T1 efferent. The T1 terminal converges at a deeper level with that of the L2 monopolar cell relaying from the same optic cartridge. Thus, the localized spatial responses and receptor-like temporal response properties of amacrines are consistent with possible roles in lateral inhibition, motion processing, or orientation processing.