Orexin A is a 33-amino acid neuropeptide produced in the lateral hypothalamus from the precursor prepro-orexin. It exerts its effects by binding to two G-protein coupled receptors, the Orexin 1 Receptor (OX1R) and Orexin 2 Receptor (OX2R). Orexin A has a high affinity for both receptors. These receptors are widely distributed throughout the central nervous system, including the cerebral cortex, hippocampus, limbic system, and brainstem, as well as in peripheral tissues such as the gut, pancreas, and adrenal glands.

The orexin system plays a crucial role in regulating several physiological functions, most notably the sleep-wake cycle, arousal, appetite, and energy homeostasis. Orexin neurons in the hypothalamus integrate signals from the periphery, such as glucose levels, leptin, and ghrelin, to modulate these functions. The activation of orexin neurons promotes wakefulness and arousal, while a deficiency in orexin signaling is a key factor in narcolepsy.

In addition to its role in arousal and feeding, Orexin A is involved in the gut-brain axis, influencing gut motility, secretions, and the response to gut pain. It also interacts with stress systems and has been implicated in the body's response to stress. The widespread distribution of orexin receptors suggests that Orexin A has a broad range of effects on the body, acting as a key regulator of various physiological and behavioral processes.