Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut.
Biophys J. 2023 Nov 21;122(22):4303-4315. doi: 10.1016/j.bpj.2023.10.008. Epub 2023 Oct 13.
Dendritic spines are small protrusions that mediate most of the excitatory synaptic transmission in the brain. Initially, the anatomical structure of spines has suggested that they serve as isolated biochemical and electrical compartments. Indeed, following ample experimental evidence, it is now widely accepted that a significant physiological role of spines is to provide biochemical compartmentalization in signal integration and plasticity in the nervous system. In contrast to the clear biochemical role of spines, their electrical role is uncertain and is currently being debated. This is mainly because spines are small and not accessible to conventional experimental methods of electrophysiology. Here, I focus on reviewing the literature on the electrical properties of spines, including the initial morphological and theoretical modeling studies, indirect experimental approaches based on measurements of diffusional resistance of the spine neck, indirect experimental methods using two-photon uncaging of glutamate on spine synapses, optical imaging of intracellular calcium concentration changes, and voltage imaging with organic and genetically encoded voltage-sensitive probes. The interpretation of evidence from different preparations obtained with different methods has yet to reach a consensus, with some analyses rejecting and others supporting an electrical role of spines in regulating synaptic signaling. Thus, there is a need for a critical comparison of the advantages and limitations of different methodological approaches. The only experimental study on electrical signaling monitored optically with adequate sensitivity and spatiotemporal resolution using voltage-sensitive dyes concluded that mushroom spines on basal dendrites of cortical pyramidal neurons in brain slices have no electrical role.
树突棘是介导大脑中大部分兴奋性突触传递的小突起。最初，棘突的解剖结构表明它们作为独立的生化和电隔室发挥作用。事实上，大量实验证据表明，棘突的一个重要生理作用是在神经系统中提供信号整合和可塑性的生化分隔。与棘突明确的生化作用形成对比的是，其电作用尚不确定，目前仍存在争议。这主要是因为棘突很小，无法通过传统的电生理学实验方法进行研究。在这里，我重点回顾了有关棘突电特性的文献，包括最初的形态学和理论建模研究、基于棘突颈部扩散电阻测量的间接实验方法、基于双光子胞外谷氨酸光解在棘突突触上的间接实验方法、细胞内钙离子浓度变化的光学成像以及使用有机和基因编码电压敏感探针的电压成像。不同方法在不同制备物中获得的证据的解释尚未达成共识，一些分析方法否定，而另一些则支持棘突在调节突触信号中的电作用。因此，需要对不同方法学方法的优缺点进行批判性比较。唯一一项使用电压敏感染料进行光学监测、具有足够灵敏度和时空分辨率的电信号实验研究得出的结论是，脑片上皮质锥体神经元基底树突上的蘑菇形棘突没有电作用。
