Improved dual-color GRAB sensors for monitoring dopaminergic activity in vivo

Dopamine (DA) is a crucial monoamine neurotransmitter involved in many physiological and pathological processes through a complex network of dopaminergic projections, and the ability to directly monitor DA dynamics is essential for understanding its physiological functions. Despite the widespread use of genetically-encoded dopamine fluorescent sensors in vivo, the detection of DA is often limited to highly innervated regions. Consequently, cortical DA detection has received comparatively little attention due to a lake of sensitivity of current generations of sensors. To address this gap, we have developed a series of green and red fluorescent G-protein-coupled receptor (GPCR) activation-based DA (GRABDA) sensors employing different DA receptor subtypes. These sensors display highly improved sensitivity, selectivity, and signal-to-noise properties, with subsecond response kinetics and the ability to detect a broad range of DA concentrations. Using these sensors, we have measured optogenetically-evoked and behaviorally-relevant DA release in mice, while concurrently monitoring neurochemical signaling in the nucleus accumbens, amygdala, and cortex. Furthermore, with these sensors, we have identified spatially-resolved heterogeneous cortical DA release during various behavioral tasks. Thus, these new DA sensors provide an extended toolbox for multifaceted in vivo DA imaging under a variety of complex behavior contexts, which can in turn promote the understanding of diverse aspects of dopamine biology.