GRAB(DA1m) is a genetically encoded fluorescent sensor for dopamine that can be used for real-time detection of endogenous dopamine dynamics. It is a G-protein-coupled receptor activation-based ('GRAB') sensor based on the dopamine receptor encoded by the Homo sapiens DRD2 gene (HGNC:3023); a circularly permuted form of EGFP (cpEGFP) has been inserted into the third intracellular loop of the DRD2 receptor, and a number of mutations that expand the response range to dopamine have also been introduced. Dopamine-dependent conformational changes in the receptor result in a change in fluorescence of the conformationally sensitive cpEGFP; GRAB(DA1m) shows a large increase in fluorescence in response to extracellular dopamine. GRAB(DA1m) has a medium apparent affinity for dopamine (EC[[50]] is approximately 130nM) (FBrf02040518).

The GRAB(DA1m) sensor shows negligible coupling to downstream signaling pathways and does not cause a measurable alteration in Ca[2+] signaling when expressed in neurons, suggesting that it can used as a reporter of dopamine dynamics without subsequently interfering with cell function. The lack of coupling to downstream pathways is presumably due to steric hindrance from the cEGFP moiety in the third intracellular loop, which is normally the site of interaction of the G-protein-coupled receptor with downstream protein components (FBrf02040518).