Reward prediction is encoded by orexin neuron activity during motivated behavior

Orexin neurons regulate physiological functions, such as energy homeostasis, wakefulness, and motivated behaviors. However, studies linking orexin neuron activity to behavior via selectively activating/inactivating these inputs in a temporally controlled manner in rats are scarce. Here, we examined the role that orexin neurons play in motivated behavior in transgenic rats using cell type-specific fiber photometry and optogenetic manipulation. Using chemogenetics, we found that motivation for a reward increased when orexin neurons were activated. Furthermore, during motivated behavior, orexin neuron activity changed dynamically: Activity increased during reward prediction and decreased after reward receipt. When an unexpected event occurred (i.e., not obtaining an expected reward), increased orexin activity was sustained. Notably, orexin activity strengthened with increasing effort. Optogenetic inhibition of orexin neuron activation during reward prediction and treatment with an orexin 1-receptor antagonist reduced reward-seeking behavior. Therefore, orexin is crucial for linking predicted expectations with motivated behavior. Moreover, optimization of orexin activity is necessary to overcome difficulties during motivated behaviors.