Diversity of dendritic morphology and entorhinal cortex synaptic effectiveness in mouse CA2 pyramidal neurons.
Diversity of dendritic morphology and entorhinal cortex synaptic effectiveness in mouse CA2 pyramidal neurons.
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DOI：
10.1002/hipo.23012
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发表时间：
2019-03
期刊：
影响因子：
3.5
通讯作者：
Dudek SM
中科院分区：
文献类型：
--
作者：
Helton TD;Zhao M;Farris S;Dudek SM
来自特定脑区的兴奋性突触输入通常以海马锥体神经元上的不同树突乔木为目标。最近的工作表明，CA2锥体神经元的反应强劲，优先兴奋性输入到层陷窝分子（SLM），与一个相对温和的反应Schaffer侧支兴奋性输入到层辐射（SR）在急性小鼠海马切片，但在何种程度上可以解释这种差异的形态是未知的。为了复制这些发现并更好地了解树突形态在塑造近端和远端突触部位反应中的作用，我们测量了CA 2锥体细胞响应SR和SLM刺激的兴奋性突触后电流和动作电位，并随后分析了共聚焦图像填充细胞。我们发现，与以前的报告相比，SR刺激引起的所有记录的CA2锥体细胞的实质性反应。然而，引人注目的是，我们发现并非所有的神经元都对SLM刺激有反应，并且在那些有反应的神经元中，SLM和SR诱发的反应在诱导动作电位的大小和有效性上是相当的。在一个全面的CA2锥体细胞顶端树突的形态测定分析，我们发现，SLM刺激反应迟钝的神经元是相同的，缺乏实质性的顶端树突分支的SLM。对SR和SLM刺激都有反应的神经元在每层中具有大致相等的树突分支。值得注意的是，我们在小鼠CA2中的研究通常复制了豚鼠海马CA2锥体细胞多样性的工作。我们的结论是，那么，在豚鼠一样，小鼠CA2锥体细胞有一个不同的顶端树突形态，这是可能反映的兴奋性输入到CA2从内嗅皮层和CA3的量和来源。
Excitatory synaptic inputs from specific brain regions are often targeted to distinct dendritic arbors on hippocampal pyramidal neurons. Recent work has suggested that CA2 pyramidal neurons respond robustly and preferentially to excitatory input into the stratum lacunosum moleculare (SLM), with a relatively modest response to Schaffer collateral excitatory input into stratum radiatum (SR) in acute mouse hippocampal slices, but the extent to which this difference may be explained by morphology is unknown. In an effort to replicate these findings and to better understand the role of dendritic morphology in shaping responses from proximal and distal synaptic sites, we measured excitatory postsynaptic currents and action potentials in CA2 pyramidal cells in response to SR and SLM stimulation and subsequently analyzed confocal images of the filled cells. We found that, in contrast to previous reports, SR stimulation evoked substantial responses in all recorded CA2 pyramidal cells. Strikingly, however, we found that not all neurons responded to SLM stimulation, and in those neurons that did, responses evoked by SLM and SR were comparable in size and effectiveness in inducing action potentials. In a comprehensive morphometric analysis of CA2 pyramidal cell apical dendrites, we found that the neurons that were unresponsive to SLM stimulation were the same ones that lacked substantial apical dendritic arborization in the SLM. Neurons responsive to both SR and SLM stimulation had roughly equal amounts of dendritic branching in each layer. Remarkably, our study in mouse CA2 generally replicates the work characterizing the diversity of CA2 pyramidal cells in the guinea pig hippocampus. We conclude, then, that like in guinea pig, mouse CA2 pyramidal cells have a diverse apical dendrite morphology that is likely to be reflective of both the amount and source of excitatory input into CA2 from the entorhinal cortex and CA3.
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