 In addition to the histaminergic nucleus, the orexin system also projects onto the ventral tegmental area dopamine nucleus, locus ceruleus noradrenergic nucleus, the serotonergic raphe nuclei, and cholinergic pedunculopontine nucleus and laterodorsal tegmental nucleus.The histaminergic, dopaminergic, serotonergic, noradrenergic, and cholinergic nuclei which the lateral hypothalamic orexin neurons project onto constitute the primary components of the ascending reticular activating system.Other output regions include