Electroanalytical methods, especially, fast-scan cyclic voltammetry (FSCV) coupled with carbon-fiber microelectrodes, have been widely used to study rapid changes in neurochemical concentrations and provide a local view of neurotransmission in real time. However, electroanalytical methods alone are limited to understand the distinct roles of local neural circuits in different brain areas or even subregions of the same brain area. In recent years, the development of novel genetic approaches such as optogenetics and chemogenetics have made it possible to selectively target and control (excite or inhibit) specific neural circuits in a neurochemically heterogeneous brain without affecting surrounding cells or fibers of passage.

In this study, we demonstrate that a novel combination of in vivo FSCV coupled with chemogenetics permits us to determine local catecholamine transmission by individually manipulating dopamine (DA) or norepinephrine (NE) neurons and how chemogenetic modulation of DA or NE transmission is correlated with behavioral changes. These findings will be the fundamental framework to understand how individual local catecholamine circuits are distinctly linked to essential brain functions as well as common psychiatric and neurodegenerative diseases.