What is DSIP? The delta sleep-inducing peptide explained.

The short version

What is the delta sleep inducing peptide? DSIP is a tiny natural peptide — a chain of just nine amino acids, the same units that build proteins. Its sequence is Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu. The body makes it; it has been found in blood, spinal fluid, and even milk. Scientists isolated it in 1977 from the blood of sleeping rabbits and named it for the slow "delta" brain waves of deep sleep that it seemed to boost ^[1]. That name oversells the certainty. Despite decades of work, no one has found the receptor DSIP acts on, or the gene that codes for it ^[3]. It is not a medicine — it is an endogenous peptide that is also sold, unapproved, as a research chemical. This page explains what it is and what it is studied for.

What is DSIP peptide, structurally

The DSIP peptide is a linear nonapeptide — a single unbranched chain of nine amino acids: Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu (shorthand WAGGDASGE). Molecular formula C35H48N10O15. Molecular weight 848.8 Da. It was first isolated by Schoenenberger and Monnier from the cerebral venous blood of rabbits during electrically induced sleep, and characterized as the peptide that enhanced delta and spindle EEG activity when infused into the brain ^[1].

A naturally phosphorylated form, DSIP-P, also appears in the literature and is reported as more potent in some assays. DSIP is endogenous — found in mammalian plasma, cerebrospinal fluid, and milk, often bound to a carrier protein. Yet no DSIP gene, precursor protein, or specific receptor has ever been conclusively identified ^[3].

What is DSIP peptide used for

What is the DSIP peptide used for, in research? Three threads. First, sleep: the founding work showed it enhances slow-wave EEG activity ^[1], and a small human study reported improved sleep in chronic insomniacs ^[2]. Second, the longevity-antioxidant thread this site foregrounds: in mice a DSIP preparation extended lifespan and reduced tumors ^[5], and in rats it protected mitochondria and antioxidant defenses under stress ^[7]. Third, neuroendocrine signaling: effects on the stress (HPA) axis ^[4] and, in animals, growth hormone and reproductive hormones ^[15]. Important: these are research uses and findings, not approved medical uses. DSIP is not approved to treat anything, and it does not treat insomnia or any sleep disorder ^[3].

Endogenous, yet unexplained

The strange thing about DSIP is that the body clearly makes it, yet its biology resists explanation. DSIP-like immunoreactivity has been found beyond the brain — in gut endocrine cells of humans, pigs, and rats, with the human gut the richest source, located in cells that also make gastrin, secretin, and other gut hormones ^[13]. It has been found alongside serotonin in certain tumor cells, though it failed as a clinical tumor marker ^[14]. So DSIP is widely distributed and co-located with known hormones, while its own receptor, gene, and precursor remain unidentified ^[3]. Endogenous, broadly present, mechanistically blank — that contradiction is the heart of the DSIP story.

Emideltide: the name that went nowhere

DSIP was assigned an International Nonproprietary Name — Emideltide — the formal designation given to a candidate drug substance. It is the signal that a molecule was on a path toward becoming a medicine. No Emideltide-branded product was ever developed or approved by any regulator, and there is no Emideltide-specific clinical literature ^[3]. The name is a fossil of an approval that never happened. Today DSIP exists as an endogenous curiosity and an unapproved research peptide at the margins of peptide discussion.