This chapter summarizes the recent development of combination of in vivo microdialysis with selective detection, especially
            electrochemical detection, to form novel online analytical methods for continuously monitoring brain chemistry, without the
            need for sample collection, pretreatment, or separation. While efficient combination of in vivo microdialysis sampling directly
            with selective electrochemical detection is envisaged to provide less technically demanding in vivo and online analytical
            methods for near-real-time monitoring physiologically important neurochemicals in the living animals, which is particularly
            useful for understanding the molecular basis of brain functions, the complexity in the components of the cerebral systems
            and the inherent features of the as-developed integrated online analytical systems (i.e., without sampling collection, pretreatment,
            or separation) virtually puts the selective electrochemical detection into a great challenge with respect to the selectivity,
            sensitivity, stability, and reproducibility. This chapter focuses on the following three aspects: (1) brief introduction of
            in vivo and online analytical methods developed by directly combining in vivo microdialysis sampling with selective electrochemical
            detection; (2) recent developments along with this line both in the method establishment and in their applications in understanding
            brain chemistry through interfacing electroanalytical chemistry with physiology and pathology; and (3) summary and future
            developments in this field.