LAUSR

Significance The interplay between the anorexigenic and orexigenic neurons in the arcuate nucleus that contributes to the control of feeding remains elusive. Using optogenetic stimulation, we show that activation of POMC neurons rapidly inhibits feeding behavior in fasted animals. However, simultaneous stimulation of both POMC neurons and a subset of the orexigenic neurons that express AgRP is sufficient to reverse that inhibition and trigger intense feeding behavior. We used 3D imaging and functional studies to illuminate the anatomical underpinning of both the inhibitory and excitatory events. Our work suggests that translational applications that aim to control appetite need to target the activation rather than the inhibition mechanisms. Two classes of peptide-producing neurons in the arcuate nucleus (Arc) of the hypothalamus are known to exert opposing actions on feeding: the anorexigenic neurons that express proopiomelanocortin (POMC) and the orexigenic neurons that express agouti-related protein (AgRP) and neuropeptide Y (NPY). These neurons are thought to arise from a common embryonic progenitor, but our anatomical and functional understanding of the interplay of these two peptidergic systems that contribute to the control of feeding remains incomplete. The present study uses a combination of optogenetic stimulation with viral and transgenic approaches, coupled with neural activity mapping and brain transparency visualization to demonstrate the following: (i) selective activation of Arc POMC neurons inhibits food consumption rapidly in unsated animals; (ii) activation of Arc neurons arising from POMC-expressing progenitors, including POMC and a subset of AgRP neurons, triggers robust feeding behavior, even in the face of satiety signals from POMC neurons; (iii) the opposing effects on food intake are associated with distinct neuronal projection and activation patterns of adult hypothalamic POMC neurons versus Arc neurons derived from POMC-expressing lineages; and (iv) the increased food intake following the activation of orexigenic neurons derived from POMC-expressing progenitors engages an extensive neural network that involves the endogenous opioid system. Together, these findings shed further light on the dynamic balance between two peptidergic systems in the moment-to-moment regulation of feeding behavior.