Analysis using optical recording for synaptic plasticity of non-LTP type in hippocampal slices

利用光学和场电位记录，我们发现在大鼠海马斜面脑片中有两种不同的信号传播模式，即CA3-CA1和CA3-CA2-CA1。在快传播时，活动直接从CA3流向CA1的辐射层，而在慢传播时，在CA2中产生光信号，然后传播到CA1。我们的数据显示，CA2神经元可以将延迟的兴奋信号传递给CA1神经元。因此，我们的结论是，除了传统的齿状回-CA3-CA1三突触回路外，考虑通过海马区的电信号传播应该包括通过CA2区的流动。当用腺苷拮抗剂(2μM8-CPT)处理脑片时，几乎所有的横切片都在CA1和CA2层的锥体层记录到群峰电位(Pss)，而在没有8-CPT的情况下大多数脑片没有记录到PS。这一数据表明，存在较强的Puri…在CA2/CA3a中有更多的神经抑制作用，提示CA2细胞在海马区横面起着信号传递门的作用。我们进一步描述了腺苷A1受体在大鼠海马区的免疫细胞化学分布。腺苷A1受体阳性反应见于锥体细胞胞体和树突，颗粒细胞胞体和树突近端，胶质细胞未见腺苷A1受体样免疫反应。在成年大鼠的海马区，旋转尾部检查发现CA2/CA3a的免疫反应最强。共聚焦显微镜显示腺苷A1受体和突触素的染色模式不同，突触前终末的标记物。这提示腺苷A1受体可能具有突触后的生理功能。腺苷A1受体和乳头上核顺行标记纤维的双标结果表明，乳头上核的纤维直接终止于CA2/CA3a和齿状回A1受体免疫阳性神经元的胞体上。这些结果表明，CA2/CA3a内的腺苷A1受体和齿状回处于调节海马体活动的位置，由此产生的CA2/CA3a内强烈的突触抑制可能在调节CA3和CA1之间的内在信号流动中发挥作用。较少

Using optical and field potential recordings, we have shown that there were two distinguished patterns of signal propagation, CA3-CA1 and CA3-CA2-CA1, in oblique slices obtained from rat hippocampus ; the, and the slow propagation. In the fast propagation, activity flowed directly from CA3 to the stratum radiatum of CA1, and in the slow propagation optical signals were generated in CA2 before spreading to CA1. Our data reveal that CA2 neurons can transmit delayed excitatory signals to CA1 neurons. We therefore conclude that consideration of electrical signal propagation through the hippocampus should include flow through the CA2 region in addition to the traditional dentate gyrus-CA3-CA1 trisynaptic circuit. When slices were treated with an adenosine antagonist (2 μM 8-CPT), population spikes (PSs) were recorded in the stratum pyramidale of CA1 and CA2 in almost all of transverse slices, where no PS was recorded without 8-CPT in most cases. This data indicated that there is strong puri … More nergic inhibition in CA2/CA3a and suggest that CA2 cells act as a gate of signal propagation in the transverse plane of hippocampus.We further described the immunocytochemical distribution of adenosine A1 receptors in the rat hippocampus. Adenosine A1 receptor-like immunoreactivity was seen on the cell soma and dendrites of pyramidal cells and the cell soma and proximal part of dendrites of granule cells, but not on glial cells. In the adult rat hippocampus, rostrocaudal inspection revealed that immunoreactivity in CA2/CA3a was greatest. Confocal microscopy revealed differences in the staining patterns for the adenosine A1 receptor and synaptophysin, a marker of presynaptic terminals. This suggests that the adenosine A1 receptor might have postsynaptic physiological functions. Double-labeling of adenosine A1 receptors and anterogradely labeled fibers from the supramammillary nucleus showed that the fibers from the supramammillary nucleus terminate directly on the cell soma of the A1 receptor immunopositive neurons in CA2/CA3a and the dentate gyrus.These results indicate that the adenosine A1 receptor in CA2/CA3a and the dentate gyrus are in a position to regulate hippocampal theta activity and that resultant strong synaptic depression in CA2/CA3a could play a role in regulating the intrinsic signal flow between CA3 and CA1. Less