Delta sleep-inducing peptide (DSIP, INN emideltide) is a nonapeptide, Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu, isolated in the 1970s by the Schoenenberger and Monnier group in Basel from the cerebral venous blood of rabbits subjected to electrical stimulation of the intralaminar thalamus. The synthetic peptide was characterised by its effect on delta and spindle EEG activity in rabbit studies. Later research broadened to neuroendocrine, pineal and stress models. A 2006 review noted that the gene, precursor protein and receptor for DSIP had not been identified, and that its link to sleep regulation remained poorly documented.