HCRT and narcolepsy: In addition, orexin signaling clearly plays a key role in the regulation of sleep in dogs as chronic loss of orexin signaling due to genetic mutations in orexin receptor 2 causes canine narcolepsy (Lin et al., 1999; Nishino, 2007), while temporary acute pharmacological blockade of orexin signaling by DORA administration can induce sleep in dogs without signs of narcolepsy/cataplexy (Brisbare-Roch et al., 2007; Winrow et al., 2011, 2012).