Grødem et al (preprint, 2021): doi: https://doi.org/10.1101/2021.05.14.443815
Short story with videoclips on twitter.
We have struggled to get GCaMP from systemic administration to work reliably, the signal was just not bright enough. So, after lots of failed experiments with various GECIs, we decided to do a more rigorous screening.
We tested a range of GCaMPs for suitability in two-photon imaging using retro-orbital and local injections of PHP.eb AAVs.
Ribo-jGCaMP8s also works with ROI but takes up to 6 weeks for viable imaging brightness. However, local injections of Ribo-jGCaMP8m and s give rise to incredible labeling density and highly improved brightness compared to previous versions
RO injections of GCaMP come with several advantages; no need for driver lines or intricate breeding, no injection surgery, and can be combined with transgenic lines. We demonstrate the latter by cell-type targeted chemogenetics combined with brain-wide GCaMP in PV-Cre mice.
All plasmids are currently in processing at Addgene and will be available soon. The original jGCaMP8 sensors from the Looger lab and the GENIE project are already available on Addgene @addgene @janeliagenie.