Pancreatic β-cells release insulin in a Ca2+-dependent pulsatile manner to control blood glucose levels. Spatiotemporal kinetics and function of Ca2+ signaling in β-cells have been studied by experiments using in vitro and ex vivo preparations. However, in vivo analysis remains challenging. While β-cell activities in vivo are under the influence of the autonomic nervous system, hormones and other bioactive substances, Ca2+ activities of β-cells under physiological conditions have not been clarified. We here report a method to analyze in vivo β-cell Ca2+ signals using a transgenic mouse line expressing a genetically encoded ratiometric Ca2+ indicator, YC-Nano50. Using the method, we visualized β-cell Ca2+ signals in laparotomized mice under anesthesia, and observed synchronized Ca2+ oscillations in β-cells within individual islets. Furthermore, we succeeded in monitoring Ca2+ activities in multiple islets simultaneously, which may clarify the basis for a pulsatile insulin secretion. Further studies using current method is expected to gain deeper insight in insulin secretion mechanism and the etiology of diabetes.
