8. Imaging in deep tissues and living organisms
Imaging GPCR signalling in live organisms is the ultimate setting for understanding underlying physiological processes. However, imaging thick tissue samples or whole animals present a unique set of challenges. Major issues include the inability of visible light to penetrate deep into the sample due to high scattering, the strong autofluorescence of many tissue components, complications with targeted ligand delivery, photodamage, and oxidative stress of the samples. These issues are addressed by several techniques including bioluminescence imaging, 2P microscopy, optogenetic signalling regulation, and LSFM (Figures 2 and 3, Supporting Table 1).