Lateral Hypothalamic Area Neurotensin Neurons Are Required for Control of Orexin Neurons and Energy Balance.

The lateral hypothalamic area (LHA) is essential for motivated ingestive and locomotor behaviors that impact body weight, yet it remains unclear how the neurochemically defined subpopulations of LHA neurons contribute to energy balance. In particular, the role of the large population of LHA neurotensin (Nts) neurons has remained ambiguous due to the lack of methods to easily visualize and modulate these neurons. Because LHA Nts neurons are activated by leptin and other anorectic cues and they modulate dopamine or local LHA orexin neurons implicated in energy balance, they may have important, unappreciated roles for coordinating behaviors necessary for proper body weight. In this study, we genetically ablated or chemogenetically inhibited LHA Nts neurons in adult mice to determine their necessity for control of motivated behaviors and body weight. Genetic ablation of LHA Nts neurons resulted in profoundly increased adiposity compared with mice with intact LHA Nts neurons, as well as diminished locomotor activity, energy expenditure, and water intake. Complete loss of LHA Nts neurons also led to downregulation of orexin, revealing important cross-talk between the LHA Nts and orexin populations in maintenance of behavior and body weight. In contrast, chemogenetic inhibition of intact LHA Nts neurons did not disrupt orexin expression, but it suppressed locomotor activity and the adaptive response to leptin. Taken together, these data reveal the necessity of LHA Nts neurons and their activation for controlling energy balance, and that LHA Nts neurons influence behavior and body weight via orexin-dependent and orexin-independent mechanisms.