Light-triggered delivery enables brainwide mapping of intragastric glucose sensory dynamics.

Interoception monitors the gastrointestinal tract for the brain. The intragastric chemical information is embodied in the biological molecules, like nutrients, immune factors, and microbe metabolites, which modulates animal states. Albeit the sensors for these intragastric molecules have been identified and their afferent pathways have been elucidated, their sensory dynamics remains less explored. To fulfill this requirement, a direct manipulation of the gastrointestinal chemical contents, without oral involvement or invasiveness, is needed. Here we have developed a light-triggered intragastric delivery assay and demonstrated its efficacy in modulating the nutrient content of larval zebrafish. Taking the advantage of the larval zebrafish in neural imaging, we succeeded in examining the brainwide responses to the intragastric glucose delivery. Furthermore, a similarly broad response pattern was observed on both the naive and the feeding experienced larval zebrafish, suggesting an innately brainwide network for intragastric glucose sensing.