Next-generation GRAB sensors for monitoring dopaminergic activity in vivo

Abstract

Dopamine (DA) plays a critical role in the brain, and the ability to directly measure dopaminergic activity is essential for understanding its physiological functions. We therefore developed red fluorescent GPCR-activation–based DA (GRAB _DA) sensors and optimized versions of green fluorescent GRAB _DA sensors. In response to extracellular DA, both the red and green GRAB _DA sensors exhibit a large increase in fluorescence, with subcellular resolution, subsecond kinetics, and nanomolar to submicromolar affinity. Moreover, the GRAB _DA sensors resolve evoked DA release in mouse brain slices, detect evoked compartmental DA release from a single neuron in live flies, and report optogenetically elicited nigrostriatal DA release as well as mesoaccumbens dopaminergic activity during sexual behavior in freely behaving mice. Co-expressing red GRAB _DA with either green GRAB _DA or the calcium indicator GCaMP6s allows simultaneously tracking neuronal activity and dopaminergic signaling in distinct circuits in vivo.