Hunger modulates exploration through suppression of dopamine signaling in the tail of the striatum

Caloric depletion induces behavioral changes that help an animal find food and restore its homeostatic balance. Hunger increases exploration and risk-taking behavior, allowing an animal to forage for food despite risks; however, it is unknown which neural systems coordinate such behavioral adaptations. Here, we characterize how hunger restructures an animal's spontaneous behavior as well as its directed exploration of a novel object. We show that hunger-induced changes in exploration are accompanied by and result from the modulation of dopamine signaling in the tail of the striatum (TOS). Dopamine signaling in the TOS is in turn modulated by hunger through the activity of agouti-related peptide (AgRP) neurons, putative "hunger neurons" in the arcuate nucleus of the hypothalamus that are polysynaptically connected to the TOS through the lateral hypothalamus. Thus, we delineate how hypothalamic systems modulate dopaminergic circuitry to mediate changes in exploratory behavior in the hungry state.