HCRT and narcolepsy: Studies of narcolepsy (in dogs, mice, humans) caused by loss of orexin neurons, type-2 receptors, or orexin peptides, illustrate that orexin cells are vital for arousal cruise-control (Chemelli et al., 1999; Lin et al., 1999; Peyron et al., 2000; Willie et al., 2003).