"Nature's soft nurse": a sleep-promoting factor isolated from brain.

A sleep promoting factor has been extracted and purified from cerebrospinal fluid of sleep-deprived goats, from whole brains of sleep-deprived rabbits and from brainstems of slaughterhouse cattle. Intraventricular infusion of the purified material into rats, cats, rabbits or squirrel monkeys induces excess slow-wave sleep in the recipients for several hours following the infusion. The excess sleep appears similar to the deep slow-wave sleep which normally follows sleep deprivation; it is characterized by EEG slow waves of greater than normal amplitude and an increase in both the number and duration of sleep episodes. The sleep factor appears to be a small peptide of molecular weight 350--500 daltons and the effective dose is of the order of a few picomols per gram brain. A similar, perhaps identical, factor is present in human urine.