The role of melanin-concentrating hormone in the regulation of the sleep/wake cycle: Sleep promoter or arousal modulator?

Abstract

The neuronal system that resides in the perifornical/lateral hypothalamus (Pf/LH) and synthesizes the neuropeptide melanin-concentrating hormone (MCH) participates in critical brain functions across species from fish to human. The MCH system was originally reported to regulate neural activity responsible for the change of skin color in lower vertebrates (such as fish), homeostatic functions (e.g., feeding and energy balance), and complex behaviors (e.g., reward seeking/addiction, depression/ anxiety) in higher animals. The most recent evidence indicates that MCH participates in the regulation of sleep in animals as well. In this chapter, we summarize the evidence supporting the role of MCH in the regulation of sleep homeostasis in animals and discuss its physiological implications in the context of MCH as a central node of the overall brain circuitry controlling physiological functions and complex behaviors in animals.