SPLICEIT Fluorescent Sensor for Integrating Dopamine Release with Cellular Resolution.

Dopamine is a neurotransmitter essential for motor control, reward processing, and motivation through G-protein coupled receptor (GPCR) signaling. Recent GPCR-based real-time sensors allow for optical monitoring of dopamine release in behaving animals. However, there is still a need for high resolution mapping of dopamine release across large mouse brain volume for systemic studies. To fill this need, we have developed a new chimeric GPCR-based sensor to detect dopamine with a permanent green fluorescent mark through a combination of computational modeling and rational design. This new sensor, named "Single-chain Protein-based Ligand Indication through a Chimerically-Engineered Integrator Tool" (SPLICEIT), detects dopamine at cellular-resolution with high specificity and a fourfold signal-to-background ratio. We also developed a version of SPLICEIT whose signal can be normalized for varying sensor expression in cell culture and in vivo. This paves the way for further studies into dopamine release across the brain and enables the possibility of whole-brain dopamine mapping.