RESUMO
Histaminergic neurons solely originate from the tuberomammillary nucleus (TMN) in the posterior hypothalamus and send widespread projections to the whole brain. Experiments in rats show that histamine release in the central nervous system is positively correlated with wakefulness and the histamine released is 4 times higher during wake episodes than during sleep episodes. Endogeneous prostaglandin E2 and orexin activate histaminergic neurons in the TMN to release histamine and promote wakefulness. Conversely, prostaglandin D2 and adenosine inhibit histamine release by increasing GABA release in the TMN to induce sleep. This paper reviews the effects and mechanisms of action of the histaminergic system on sleep-wake regulation, and briefly discusses the possibility of developing novel sedative-hypnotics and wakefulness-promoting drugs related to the histaminergic system.
RESUMO
Dopamine(DA) modulates diverse wake-related behaviors including movement,reward, and cognition.Dopaminergic neurons are located in the substantia nigra pars compacta and ventral tegmental area.There are five distinct DA receptors(R):D_1R,D_2R(D_(2S)R and D_(2L)R), D_3R,D_4R and D_5R in the central nervous system, in which D_1R and D_2R are majorly expressed. The affinity of D_2R for endogenous DA is significantly higher than that of D_1R.Re- cently,studies by pharmacological and gene knock-out animals revealed that dopamine D_2R is essential inmaintaining wakefulness.Here,we review the progress on roles of D_2R in sleep-wake regulation.