Researchers can measure the activity of agr p neurons using fiber photometry and calcium sensors.

“so one of the very first experiments we did in my lab was to investigate that to ask for the first time what happens to these arrp neurons when an animal eats and so uh one of my first graduate students yuming Chen he uh he used a technology called fiber fetometry which allows us to put a fiber optic into the mouse's brain so then then we could record fluoresence from these agrp neurons which we could use as a readout of their activity it's basically using a calcium sensor so calcium is a surrogate for neural activity”