Indeed, DA levels are high in several brain structures of narcoleptic Dobermans and postmortem brain of humans with narcolepsy (Nishino and Mignot, 1997; Nishino et al., 2001a), consistent with the hypothesis that altered DA accounts for the sleep abnormalities in hypocretin-deficient narcolepsy. This evidence concerns the gene HCRT and narcolepsy.