Department of Pharmacology, and Howard Hughes Medical Institute, University of California at San Diego, La Jolla, CA 92093-0647, USA.
Proc Natl Acad Sci U S A. 2013 Jul 23;110(30):12456-61. doi: 10.1073/pnas.1310158110. Epub 2013 Jul 5.
A hypothesis and the experiments to test it propose that very long-term memories, such as fear conditioning, are stored as the pattern of holes in the perineuronal net (PNN), a specialized ECM that envelops mature neurons and restricts synapse formation. The 3D intertwining of PNN and synapses would be imaged by serial-section EM. Lifetimes of PNN vs. intrasynaptic components would be compared with pulse-chase (15)N labeling in mice and (14)C content in human cadaver brains. Genetically encoded indicators and antineoepitope antibodies should improve spatial and temporal resolution of the in vivo activity of proteases that locally erode PNN. Further techniques suggested include genetic KOs, better pharmacological inhibitors, and a genetically encoded snapshot reporter, which will capture the pattern of activity throughout a large ensemble of neurons at a time precisely defined by the triggering illumination, drive expression of effector genes to mark those cells, and allow selective excitation, inhibition, or ablation to test their functional importance. The snapshot reporter should enable more precise inhibition or potentiation of PNN erosion to compare with behavioral consequences. Finally, biosynthesis of PNN components and proteases would be imaged.
一个假说及其实验测试提出，非常长期的记忆，如恐惧条件反射，是作为围绕成熟神经元并限制突触形成的细胞外基质（ECM）perineuronal 网（PNN）中的孔的模式存储的。PNN 和突触的 3D 交织将通过连续切片 EM 成像。PNN 与突触内成分的寿命将与脉冲追踪（15）N 标记在小鼠和（14）C 含量在人类尸体大脑中进行比较。遗传编码的指示剂和抗新表位抗体应提高局部侵蚀 PNN 的蛋白酶的体内活性的空间和时间分辨率。建议的进一步技术包括基因 KO、更好的药理学抑制剂和遗传快照报告器，该报告器将在由触发照明精确限定的时间内同时捕获一大组神经元的活动模式，驱动效应基因的表达以标记这些细胞，并允许选择性激发、抑制或消融以测试它们的功能重要性。快照报告器应能够更精确地抑制或增强 PNN 侵蚀，以与行为后果进行比较。最后，将对 PNN 成分和蛋白酶的生物合成进行成像。
