Emideltide or delta-sleep-inducing peptide (Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu) is a nonapeptide originally isolated from rabbit cerebral venous blood. It promotes sleep and this has been demonstrated in rabbits, mice, rats, cats and human beings. Emideltide showed significant and specific enhancement/induction of delta and spindle electroencephalogram patterns. In addition to sleep, the peptide also has been observed to affect electrophysiological activity, neurotransmitter levels in the brain, circadian and locomotor patterns, hormonal levels, psychological performance, and the activity of neuropharmacological drugs including their withdrawal.