Amperometric Monitoring of Sensory-Evoked Dopamine Release in Awake Larval Zebrafish

Dopamine plays crucial roles in a broad spectrum of brain functions, and neural circuit mechanisms underlying dopaminergic regulation have been intensively studied in the past decade. As larval zebrafish have relatively simple and highly conserved dopaminergic systems, it can serve as an ideal vertebrate animal model to tackle this issue at a whole-brain scale. For this purpose, it is important to develop methods for monitoring endogenous dopamine release in intact larval zebrafish. Here, we developed a real-time method to monitor dopamine release at high spatiotemporal resolution in the brain of awake larval zebrafish using carbon fiber microelectrodes. As an example for application, we combined this method with genetic tools and in vivo calcium imaging and found that food extract can activate pretectal dopaminergic neurons, which in turn release dopamine at the visual center through their projection, providing a dopaminergic circuit mechanism for olfactory modulation of visual functions. Thus, our study demonstrates, for the first time, the utility of carbon fiber microelectrodes for monitoring sensory-evoked dopamine release in the brain of an awake small organism.