CALCIUM ACCUMULATION IN VISUAL INTERNEURONS OF THE FLY - STIMULUS DEPENDENCE AND RELATIONSHIP TO MEMBRANE-POTENTIAL
CALCIUM ACCUMULATION IN VISUAL INTERNEURONS OF THE FLY - STIMULUS DEPENDENCE AND RELATIONSHIP TO MEMBRANE-POTENTIAL
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DOI：
10.1152/jn.1995.73.6.2540
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发表时间：
1995-06-01
影响因子：
2.5
通讯作者：
BORST, A
中科院分区：
文献类型：
--
作者：
EGELHAAF, M;BORST, A
1.果蝇第三视觉神经元中的大型运动敏感切向神经元在空间上汇集了许多局部元件的突触后信号。采用光学和细胞内电压同步记录技术，分析了视觉运动引起的细胞膜电位和钙离子浓度的变化.视觉运动的首选方向导致去极化的细胞和钙的积累，主要在轴突末端，索马，和树突树。在零方向的运动过程中，细胞超极化，几乎没有钙浓度的变化可以被忽略。树突状钙的积累首先限于那些接近直接突触输入位点的树突状分支。在枝晶的其他部分中，钙浓度增加较慢，通常仅达到较低的水平。钙在运动开始时就开始积累。然而，钙浓度达到其最终稳态水平远晚于相应的膜电位变化。即使这些在模式运动的高时间频率下是完全瞬态的，钙信号也会保持高水平，直到刺激模式停止移动。钙信号的幅度以与相应的膜电位变化类似的方式取决于模式运动的时间频率。然而，存在可以归因于两种信号的不同时间过程的差异。通过微电极电流注入树突树的去极化导致钙积累的类似变化，因为突触输入激活，这表明钙通过电压依赖性通道进入细胞。钙通道的突触输入的树突整合的可能功能进行了讨论。
1. The large motion-sensitive tangential neurons in the fly third visual neuropil spatially pool the postsynaptic signals of many local elements. The changes in membrane potential and calcium concentration induced in these cells by visual motion are analyzed in vivo by simultaneous optical and intracellular voltage recording techniques.2. Visual motion in the preferred direction leads to depolarization of the cell and to calcium accumulation mainly in the axon terminal, the soma, and the dendritic tree. During motion in the null direction, the cell hyperpolarizes and virtually no changes in calcium concentration can be observed.3. Dendritic calcium accumulation is first restricted to those dendritic branches that are close to the sites of direct synaptic input. In other parts of the dendrite the calcium concentration increases more slowly and usually reaches only lower levels.4. Calcium starts accumulating at the onset of motion. However, the calcium concentration reaches its final steady-state level much later than the corresponding membrane potential changes. Even if these are completely transient at high temporal frequencies of pattern motion, the calcium signal stays high until the stimulus pattern stops moving.5. The amplitude of the calcium signal depends on the temporal frequency of pattern motion in a similar way as do the corresponding membrane potential changes. However, there exist differences that can be attributed to the different time courses of both signals.6. Depolarization of the dendritic tree by current injection through a microelectrode leads to similar changes in calcium accumulation as does activation by synaptic input, suggesting that calcium enters the cell via voltage-dependent channels. The possible function of calcium channels for dendritic integration of synaptic input is discussed.