Brainstem orexigenic neurons drive long-term energy balance via distributed hypothalamic circuits.

Chronic activation of brainstem NPY neurons in the nucleus of solitary tract drives persistent hyperphagia and weight gain, independently of hypothalamic AgRP/NPY neurons.

• Why it matters: Hypothalamic neurons are known for energy balance, but the physiological role of brainstem feeding circuits in sustained long-term hyperphagia and weight gain is unclear.
• What they did: Using viral tracing, optogenetics, chronic chemogenetics, and targeted ablation, the study mapped NTS NPY projections to hypothalamus and tested feeding and body-weight effects after hypothalamic and/or NTS NPY neuron removal.
• The result: Ablating hypothalamic AgRP/NPY did not eliminate NTS NPY orexigenic effects, and single or dual NTS NPY plus AgRP/NPY ablation did not disrupt baseline energy homeostasis, implying redundant brain orexigenic networks.

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