Internal and external modulation factors of the orexin system (REVIEW)
Source : https://www.sciencedirect.com/science/article/abs/pii/S0196978123000712?via=ihub
Orexin-A and -B (identical to hypocretin-1 and -2) are synthesized in the neurons project their broadly throughout the entire central nervous system (CNS). The activity of orexins is mediated by two specific G protein-coupled receptors (GPCRs), termed orexin type1 receptor (OX1R) and orexin type2 receptor (OX2R).
Conclusions/Relevance: In this review, we summarize the modulating factors of orexin neurons in the feeding behavior, energy homeostasis, circadian rhythm, body fluid regulation and nutritional factors (Fig. 1). Further understanding of such modulating mechanisms of the orexin system will contribute to the control of sleep/wakefulness, metabolic regulation and emotional condition for physical and mental well-being. A more detailed mechanism and neural pathway of the orexin system and its application in humans is expected in future research.
• Source: Peptides
• Conclusions/Relevance: “In this review, we summarize the modulating factors of orexin neurons in the feeding behavior, energy homeostasis, circadian rhythm, body fluid regulation and nutritional factors. Further understanding of such modulating mechanisms of the orexin system will contribute to the control of sleep/wakefulness, metabolic regulation and emotional condition for physical and mental well-being.”
• Circadian signaling regulates orexin neuron activity, therefore influencing wakefulness and motor activity in nocturnal animals. The release and expression of prepro-orexin, orexins A and B, and orexin receptors demonstrate diurnal rhythmicity
• The orexin system contributes to various different functions, including arousal, feeding, reward, and thermogenesis. Orexin neurons field signals related to environmental, physiological, and emotional stimuli. Previous research has shown that various neurotransmitters and neuromodulators affect the activation or inhibition of orexin neuron activity.
• “Several neurotransmitters and neuromodulators influence the activation or inhibition of orexin neuronal activity, many of which have been identified in electrophysiological studies and experiments using transgenic animal models,” the authors wrote. “A previous study reported that glutamate, cholecystokinin, neurotensin, oxytocin, and vasopressin (AVP) activate orexin neurons via modulation of adenosine and CO2 concentrations. Inhibitory factors of orexin neurons include GABA, noradrenaline, adrenaline, serotonin and dopamine directly hyperpolarize orexin neurons through activation of α2-adrenoceptors, while catecholamines regulate orexin neurons in a complex manner.”