Calcium imaging approaches in investigation of pain mechanism in the spinal cord

The continuous advancement of microscopic imaging techniques combined with the discovery and use of more powerful calcium indicators has made calcium imaging technology much more effective and has increased its use in the study of pain circuitry. Using calcium imaging to study spinal pain mechanisms causes less damage to animals compared to electrophysiological techniques and is also able to observe the firing pattern of spinal neurons and the connections between them on a large scale. These advantages allow any changes in spinal cord circuits caused by pain transmission to be observed more effectively. This review will discuss the development of calcium indicators over the past decades as well as the various applications of calcium imaging, from in vitro to in vivo spinal cord experiments, in the study of pain circuits. We will also discuss possible directions for the study of spinal pain circuits in the future.