DSIP

Delta sleep-inducing peptide (DSIP, emideltide) is a nonapeptide with the sequence Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu, a formula of C35H48N10O15 and a molar mass of about 848.8 g/mol. It was isolated in 1977 by the Schoenenberger and Monnier group in Basel from the cerebral venous blood dialysate of rabbits subjected to electrical stimulation of the intralaminar thalamic area, and was named for the slow-wave (delta) EEG activity it produced in those animals. Its structure differs from other known peptide families, and no dedicated gene, precursor protein or receptor has been isolated.

DSIP in the research literature

In the original rabbit experiments, synthetic DSIP increased delta and spindle EEG activity in the neocortex and limbic archicortex, whereas five candidate metabolic fragments, two nonapeptide analogues and a related tripeptide did not; only the alpha-aspartyl form was highly active, not its beta-Asp isomer. In rat pineal tissue in vitro, DSIP and a phosphorylated analogue augmented norepinephrine-stimulated N-acetyltransferase activity, an effect eliminated by prazosin and attributed to modulation of the alpha1-adrenergic receptor. DSIP-like immunoreactivity has also been characterized in ovine pineal extracts, in both small and large molecular forms.

Reviews describe circadian phase-dependent effects on thermoregulation, heart rate and pain threshold in animal models, while noting that the natural occurrence and mechanism of the peptide remain unresolved.