HCRT and neurodegenerative disease: Some animal studies suggest a tentative link between neurodegenerative disease symptoms and deficits in orexin signaling in monoaminergic and cholinergic neurons in the brainstem and forebrain (Drouot et al., 2003; Wu et al., 2004; Sakurai et al., 2005; Zhang et al., 2005a,b; Downs et al., 2007; Stanley and Fadel, 2012; Fadel et al., 2013; Yang et al., 2013).