TrkB-expressing neurons in the dorsomedial hypothalamus are necessary and sufficient to suppress homeostatic feeding

Genetic evidence indicates that brain-derived neurotrophic factor (BDNF) signaling through the TrkB receptor plays a critical role in the control of energy balance. Mutations in the BDNF or the TrkB-encoding NTRK2 gene have been found to cause severe obesity in humans and mice. However, it remains unknown which brain neurons express TrkB to control body weight. Here, we report that TrkB-expressing neurons in the dorsomedial hypothalamus (DMH) regulate food intake. We found that the DMH contains both glutamatergic and GABAergic TrkB-expressing neurons, some of which also express the leptin receptor (LepR). As revealed by Fos immunohistochemistry, a significant number of TrkB-expressing DMH (DMH(TrkB)) neurons were activated upon either overnight fasting or after refeeding. Chemogenetic activation of DMH(TrkB) neurons strongly suppressed feeding in the dark cycle when mice are physiologically hungry, whereas chemogenetic inhibition of DMH(TrkB) neurons greatly promoted feeding in the light cycle when mice are physiologically satiated, without affecting feeding in the dark cycle. Neuronal tracing revealed that DMH(TrkB) neurons do not innervate neurons expressing agouti-related protein in the arcuate nucleus, indicating that DMH(TrkB) neurons are distinct from previously identified LepR-expressing GABAergic DMH neurons that suppress feeding. Furthermore, selective Ntrk2 deletion in the DMH of adult mice led to hyperphagia, reduced energy expenditure, and obesity. Thus, our data show that DMH(TrkB) neurons are a population of neurons that are necessary and sufficient to suppress appetite and maintain physiological satiation. Pharmacological activation of these neurons could be a therapeutic intervention for the treatment of obesity.