Dexmedetomidine is a high selective alpha 2 adrenoceptor agonist which produces hypnosis and sedation by activating the alpha 2 adrenoceptor in the locus coeruleus of the brain; it is well known that the locus coeruleus is the key part to adjust sleep and awakening. The study of Nelson et al. showed that dexmedetomidine induces the expression of c-Fos in the locus coeruleus nucleus and ventral lateral nucleus in rats' brain, which is similar to the expression of c-Fos during non-rapid eye movement sleep. They presumed that dexmedetomidine activates the endogenous sleep-promoting pathway to produce sedative effects, which is totally different from benzodiazepines and opiates on the mechanism.