For example, narcolepsy phenotypes were observed in prepro-orexin knockout (KO) mice, in dogs with mutations in the gene encoding OX2R, and low levels of orexins were detected in the cerebrospinal fluid (CSF) of narcolepsy patients (Chemelli et al., 1999; Lin et al., 1999; Nishino et al., 2000; Adamantidis et al., 2020). This evidence concerns the gene HCRT and narcolepsy.