ROLE OF THE OREXIN SYSTEM ON AROUSAL, ATTENTION, FEEDING BEHAVIOUR AND SLEEP DISORDERS

ANTONIETTA MESSINA^1,*, VINCENZO MONDA¹, ROBERTO AVOLA², FIORENZO MOSCATELLI³, ANNA A.VALENZANO³, INES VILLANO¹, MARIA RUBERTO⁵, EMANUELE MONDA¹, MARCO LA MARRA¹, DOMENICO TAFURI⁴, SERGIO CHIEFFI¹, GIUSEPPE CIBELLI¹, MARCELLINO MONDA¹, GIOVANNI MESSINA^1,2

¹Department of Experimental Medicine, Section of Human Physiology and Unit of Dietetic and Sport Medicine, Università degli Studi della Campania, Naples, Italy - ²Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy - ³Department of Clinical and Experimental Medicine, University of Foggia, Foggia, Italy - ⁴Department of Motor Sciences and Wellness, University of Naples “Parthenope”, Naples, Italy - ⁵Department of Medical-Surgical and Dental Specialties, Università degli Studi della Campania-Luigi Vanvitelli, Naples, Italy

The orexin-A/hypocretin-1 and orexin-B/hypocretin-2 are neuropeptides synthesized by a cluster of neurons in the lateral hypothalamus. Orexins play an significant role in regulating arousal and attention. The term “arousal” refers to a person’s general state of alertness or excitation, both physiological and psychological. Arousal levels ranges on a continuum from drowsiness through alertness to excitement. Orexin plays an important role in the regulation of feeding behaviour. The orexin stimulates food intake and reduces the metabolic rate, increasing and maintaining the body's energy reserves. Orexins play also a fundamental role in the regulation of the sleep-wake cycle by increasing arousal levels and maintaining wakefulness. Its deficit can cause narcolepsy. Key to the diagnosis of narcolepsy is the combination of a common symptom, excessive daytime sleepiness, and an uncommon symptom, cataplexy, i.e. a sudden and transient episode of muscle weakness