dLight1.3b is a genetically encoded fluorescent sensor used to measure endogenous dopamine release with high spatiotemporal resolution in vivo. It is based on the dopamine receptor encoded by the Homo sapiens DRD1 gene (HGNC:3020); the third intracellular loop of DRD1 has been replaced with a circularly permuted form of EGFP (cpEGFP) and a number of additional mutations have also been introduced during optimization of the sensor. Dopamine-dependent conformational changes in the receptor result in a change in fluorescence of the conformationally sensitive cpEGFP (PMID:29853555).