Simultaneous measurements of synaptic input-induced calcium rise and changes in synaptic efficacy in cortical neurons loaded with a low-affinity Ca2+ indicator.
- 作者：Yasuda ; Hiroki ; Tsumoto ; Tadaharu
- 刊名：Neuroscience Research
- 出版年：1996
- 期刊代码：53_01680102
- 类别：neu
- 出版时间：1996
- 卷：25
- 期：Supplement 2
- 页码：S7
- 文件大小：89.3 K
摘要
To test the hypothesis that long-term potentiation (LTP) is induced if an increase in Ca2+ concentration at postsynaptic sites during tetanic synaptic inputs is higher than the certain threshold, while long-term depression (LTD) is induced if it is below the threshold, one can use microscopic fluorometry with a fluorescent Ca2+ indicator. Since high-affinity Ca2+ indicators such as fura-2 may interfere with physiological processes for the induction of LTP or LTD, we used another indicator, rhod-2 which has a much weaker chelating action than fura-2. Initially, rhod-2/AM (membrane-permeable type) was applied to visual cortical slices of young rats. Field responses to test stimulation of layer IV of the cortex were recorded from layer II/III. Fluorescent signal of rhod-2 was detected through a window (50 × 50 μm) placed near the recording electrode in layer II/III. In slices in which LTP of field responses was induced by tetanic stimulation of layer IV, tetanus-induced rise in fluorescent signal was significantly larger than that in LTD-induced slices. Next, we injected rhod-2 directly into pyramidal-cell like neurons of layer II/III through a patch pipette from which excitatory postsynaptic potentials (EPSPs) were recorded. During tetanic stimulation, we often observed a marked increase in fluorescence intensity at apical dendritic areas about 50 μm distal from the soma. In neurons in which LTP of EPSPs was induced, the fluorescent increase at this area was significantly larger than that in neurons in which LTD was observed. These results seem to be consistent with the above-mentioned hypothesis.