[Nucleus tractus solitarius, serotonin and regulation of vigilance]

A brief historical survey of the vagal influences on sleep is lightly sketched first by analyzing the hypnogenic effects of the medullar area of the solitary tract nucleus (STN) where the vagal afferents terminate. Then the vagal effects and more extensively the sinusal or aortic effects are developed. It is shown that serotonin could play a crucial role in this so-called "vago-aortic" sleep mechanisms. Finally, these results are discussed and confronted with other experimental and human pathological data.