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Deciphering a neuronal circuit that mediates appetite

2012; Nature Portfolio; Volume: 483; Issue: 7391 Linguagem: Inglês

10.1038/nature10899

1476-4687

Qi Wu, Michael Clark, Richard D. Palmiter,

Neuroendocrine regulation and behavior

Dissection of the neuronal circuit driving feeding behaviour in mice shows that suppression of the parabrachial nucleus protects against aphagia and promotes weight gain, and also that the parabrachial nucleus is an integration hub that bidirectionally modulates feeding and body weight. Specific populations of hypothalamic neurons respond to both internal and external signals when promoting feeding and weight gain. A loss of these neurons can lead to fatal aphagia (cessation of feeding) in rodents. Here, Wu et al. dissect the circuit that drives this feeding behaviour, and find that suppression of the parabrachial nucleus (PBN) induced by AgRP-expressing hypothalamic neurons protects against aphagia and promotes weight gain. Furthermore, they reveal that the PBN is an integration hub that bidirectionally modulates feeding and body weight. Understanding the neural circuit involved in modulating feeding behaviour and body weight could be valuable for development of treatments for diverse eating disorders, including anorexia nervosa and nausea. Hypothalamic neurons that co-express agouti-related protein (AgRP), neuropeptide Y and γ-aminobutyric acid (GABA) are known to promote feeding and weight gain by integration of various nutritional, hormonal, and neuronal signals1,2. Ablation of these neurons in mice leads to cessation of feeding that is accompanied by activation of Fos in most regions where they project3,4,5,6. Previous experiments have indicated that the ensuing starvation is due to aberrant activation of the parabrachial nucleus (PBN) and it could be prevented by facilitating GABAA receptor signalling in the PBN within a critical adaptation period5. We speculated that loss of GABA signalling from AgRP-expressing neurons (AgRP neurons) within the PBN results in unopposed excitation of the PBN, which in turn inhibits feeding. However, the source of the excitatory inputs to the PBN was unknown. Here we show that glutamatergic neurons in the nucleus tractus solitarius (NTS) and caudal serotonergic neurons control the excitability of PBN neurons and inhibit feeding. Blockade of serotonin (5-HT3) receptor signalling in the NTS by either the chronic administration of ondansetron or the genetic inactivation of Tph2 in caudal serotonergic neurons that project to the NTS protects against starvation when AgRP neurons are ablated. Likewise, genetic inactivation of glutamatergic signalling by the NTS onto N-methyl d-aspartate-type glutamate receptors in the PBN prevents starvation. We also show that suppressing glutamatergic output of the PBN reinstates normal appetite after AgRP neuron ablation, whereas it promotes weight gain without AgRP neuron ablation. Thus we identify the PBN as a hub that integrates signals from several brain regions to bidirectionally modulate feeding and body weight.