Kurtz R
Department of Neurobiology, Bielefeld University, P.O. Box 100131, D-33501 Bielefeld, Germany.
Neuroscience. 2007 May 11;146(2):573-83. doi: 10.1016/j.neuroscience.2007.01.058. Epub 2007 Mar 23.
Motion-sensitive neurons in the blowfly brain present an ideal model system to study the cellular mechanisms and functional significance of adaptation to visual motion. Various adaptation processes have been described, but it is still largely unknown which of these processes are generated in the motion-sensitive neurons themselves and which originate at more peripheral processing stages. By input resistance measurements I demonstrate that direction-selective adaptation is generated by an activity-dependent conductance increase in the motion-sensitive neurons. Based on correlations between dendritic Ca(2+) accumulation and slow hyperpolarizing after-potentials following excitatory stimulation, a regulation of direction-selective adaptation by Ca(2+) has previously been suggested. In the present study, however, adaptation phenomena are not evoked when the cytosolic Ca(2+) concentration is elevated by ultraviolet photolysis of caged Ca(2+) in single neurons rather than by motion stimulation. This result renders it unlikely, that adaptation in fly motion-sensitive neurons is regulated by bulk cytosolic Ca(2+).
家蝇大脑中对运动敏感的神经元是研究视觉运动适应的细胞机制和功能意义的理想模型系统。已经描述了各种适应过程，但在很大程度上仍然不清楚这些过程中哪些是在对运动敏感的神经元本身产生的，哪些起源于更外周的处理阶段。通过输入电阻测量，我证明方向选择性适应是由运动敏感神经元中依赖活动的电导增加产生的。基于树突状Ca(2+)积累与兴奋性刺激后缓慢超极化后电位之间的相关性，先前有人提出Ca(2+)对方向选择性适应有调节作用。然而，在本研究中，当通过笼锁Ca(2+)在单个神经元中的紫外光解而非运动刺激来升高胞质Ca(2+)浓度时，并未诱发适应现象。这一结果使得果蝇运动敏感神经元中的适应不太可能受大量胞质Ca(2+)调节。
