Also, we know that lateral hypothalamic neurons synthesize orexin/hypocretin (ox/hcrt) or melanin-concentrating hormone (MCH) peptides and that a lack of ox/hcrt is associated with narcolepsy with cataplexy in rodents, dogs, and humans, that MCH neurons are involved in the generation of REM sleep, and that all these brain structures and neurotransmitters and neuropeptides are interconnected in order to regulate the sleep–wake cycle [Figure 1] [47]. The gene discussed is PMCH; the disease is narcolepsy.