Aitken P G, Fayuk D, Somjen G G, Turner D A
Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Methods. 1999 Jun;18(2):91-103. doi: 10.1006/meth.1999.0762.
Optical imaging techniques have the potential to bring a combination of high spatial and temporal resolution to studies of brain function. Many optical techniques require the addition of a dye or fluorescent marker to the tissue, and such methods have proven extremely valuable. It is also known that the intrinsic optical properties of neural tissue are affected by certain physiological changes and that these intrinsic optical signals can provide information not available by other means. Most authors attribute the intrinsic optical change to alterations in cell volume and concomitant change in the concentration of the cytosol. In this article we review the literature on intrinsic optical signals, covering both the mechanisms of the optical change and its use in various branches of neurophysiology. We also discuss technical aspects of the technique as used with hippocampal slices, including illumination methods, cameras, experimental methods, and data collection and analysis procedures. Finally we present data from investigations in which we used intrinsic optical signals in hippocampal slices to study the extent of spread of synaptic activation, propagation of spreading depression, extent and severity of the response to hypoxia, and tissue response to osmotic challenges. We conclude that (1) at least two processes generate intrinsic optical signals in hippocampal slices, one of which causes light scattering to change inversely with cell volume and is related to dilution of the cytoplasm, while the other, opposite in sign, may be due to mitochondrial swelling; and (2) the intrinsic optical signal can be a useful tool for spatial mapping of relatively slow events, but is not suitable for study of fast physiological processes.
光学成像技术有潜力为脑功能研究带来高空间分辨率和高时间分辨率的结合。许多光学技术需要向组织中添加染料或荧光标记，并且这些方法已被证明极具价值。人们还知道神经组织的固有光学特性会受到某些生理变化的影响，并且这些固有光信号可以提供其他方法无法获得的信息。大多数作者将固有光学变化归因于细胞体积的改变以及随之而来的胞浆浓度变化。在本文中，我们回顾了有关固有光信号的文献，涵盖了光学变化的机制及其在神经生理学各个分支中的应用。我们还讨论了用于海马切片的该技术的技术方面，包括照明方法、相机、实验方法以及数据收集和分析程序。最后，我们展示了一些研究的数据，在这些研究中我们使用海马切片中的固有光信号来研究突触激活的传播范围、扩散性抑制的传播、对缺氧反应的程度和严重性以及组织对渗透压挑战的反应。我们得出以下结论：（1）至少有两个过程在海马切片中产生固有光信号，其中一个过程导致光散射与细胞体积成反比变化，并且与细胞质的稀释有关，而另一个过程，其信号相反，可能是由于线粒体肿胀；（2）固有光信号可以成为相对缓慢事件空间映射的有用工具，但不适合用于快速生理过程的研究。
