HCRT and chronic obstructive pulmonary disease: In a rat model of smoke-induced chronic obstructive pulmonary disease (COPD), the synthesis of orexin-A is increased in hypothalamic neurons; the content of orexin-A is increased in both the hypothalamus and medulla; and the expression of OX1R and orexin receptor type 2 (OX2R) in neurons of the ventrolateral medulla is up-regulated (Liu et al., 2010).