Orexin and pupillary modulation for hunger control.

Hypocretin/orexin neurons in fasted mice rapidly suppress AgRP/NPY neuron activity, linked to pupil dilation, and sensory stimulation recruits this pathway to reduce eating.

• Why it matters: Hunger signals during fasting can limit adherence, and the neural mechanisms linking arousal state to AgRP/NPY-driven eating are not well defined.
• What they did: The study used HON ablation and HON optostimulation with combined recordings of AN activity and pupil size, then tested sensory stimulation in fasted mice.
• The result: HON ablation increased AN activity, while optostimulation rapidly suppressed it; sensory-driven pupil dilation recruited HONs, suppressing AN activity and eating, suggesting pupillometry-guided hunger control during fasting.