A neuro-sedative was a drug designed to keep a patient sedated.

When abducting crew members of the USS Enterprise-D, a species of solanogen-based lifeforms injected them with a strong neuro-sedative, so they would be unconscious when entering their realm through a spatial rupture and wouldn't remember the experiments that were conducted on them.

The neuro-sedative left behind large amounts of serotonin in the abductees' hippocampus and visual cortex, arousing the suspicion of Doctor Beverly Crusher. She devised a neuro-stimulant that would counteract the effects of the sedative, so that the aliens could be stopped by the crew of the Enterprise. (TNG: "Schisms")