In addition to the usages defined below, Modern English also allows the use of "sedate" as a transitive verb: to bring a person into a state of sedateness.
When used as a verb, "sedate" is probably a retronym, being medical jargon for the application of a calming or sleep-inducing drug (a "sedative"):
"Nurse, sedate the patient with 200 milligrams of Demerol."
"I Wanna Be Sedated" - title of a Ramones song containing a drug reference
Of course, such usage has spilled over into the general culture, and can describe any time a person or animal is calmed or put to sleep:
"Skippy barked and snarled at the stranger in his house, but his owner's calm reassurance eventually sedated him."
"Continuing prosperity sedated the populace, lulling them away from their vigilance against an attack."