What Is DSIP?

Delta sleep-inducing peptide (DSIP) is a linear neuropeptide of nine amino acids, Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu, first isolated from rabbit blood and described in PNAS in 1977. It has a molecular weight of about 849 g/mol and takes its name from the slow delta brain waves recorded in the donor animals. Nearly five decades later no gene encoding it and no dedicated receptor have been confirmed, so laboratories use it as an investigational probe in EEG, stress hormone and neuroendocrine studies.

What Does DSIP Stand For?

DSIP stands for delta sleep-inducing peptide, a label that describes the original rabbit experiment, not a confirmed biological role. Delta refers to delta waves, the slow, high-amplitude EEG rhythm of 0.5 to 4 cycles per second that marks deep non-REM sleep. Swiss investigators electrically stimulated the thalamus of rabbits to produce that rhythm, collected cerebral venous blood and identified a factor that appeared to transfer the pattern to recipient animals. Later work showed the picture was far less tidy than the name suggests.

What Is DSIP Made Of?

DSIP is made of nine unmodified amino acids in a single linear chain, with no cysteine and no disulfide bond. Four of the residues are glycine or alanine, the two smallest amino acids, so the chain is flexible and has no fixed fold in water. The tryptophan at the amino end absorbs ultraviolet light and is the residue most sensitive to light and oxidation, which is why vials are best kept boxed. Its acidic groups, one aspartic acid, one glutamic acid and the free C-terminus, leave it negatively charged in neutral solution, so it dissolves readily in bacteriostatic water.

What Is the DSIP Mechanism of Action?

The DSIP mechanism of action is still unresolved, because without a known receptor the peptide can only be described by what it does in a given model. The main lines of work are:

• EEG studies in rabbits, rats and cats that recorded changes in delta and spindle activity after administration, with results that varied between laboratories.
• Neuroendocrine work on the pituitary, measuring corticotropin, luteinising hormone and somatostatin release.
• Stress research examining how the peptide interacts with the hypothalamic-pituitary-adrenal axis.
• Reports of interaction with glutamate NMDA receptors and with alpha-1 adrenergic signalling in brain tissue preparations.

A further complication emerged when antibodies raised against the peptide were found to recognise a separate protein, glucocorticoid-induced leucine zipper or GILZ; the two share an antibody-binding region, yet GILZ is not a precursor. Writing in 2006, a Journal of Neurochemistry review called the whole field as a still unresolved riddle.

What Is the Half-Life of DSIP?

The half-life of DSIP in plasma and blood incubation studies is in the order of minutes, with a figure of about 15 minutes often cited. Breakdown is driven largely by aminopeptidase activity at the tryptophan end. Some work suggests binding to carrier proteins protects part of it in circulation, and a phosphorylated form has been described that resists degradation. For laboratory solutions the relevant measure is stability in the vial rather than in plasma: reconstituted in bacteriostatic water and kept at 2 to 8 °C, it is handled like other short linear peptides.

How Does DSIP Differ From Melatonin?

DSIP differs from melatonin in chemical class, origin and receptor: DSIP is a nine residue peptide with no confirmed receptor, while melatonin is a small indoleamine hormone acting through MT1 and MT2.

Melatonin has a clear biosynthetic pathway, two well-mapped G protein-coupled receptors and a defined role in signalling darkness to the circadian clock. DSIP has none of those anchors, which is why it remains a research probe rather than a reference compound. Melatonin is a non-peptide molecule, and we do not supply it.

What Is the Difference Between Epitalon and DSIP?

Epitalon is a synthetic four residue pineal bioregulator studied for telomerase and cellular ageing, whereas DSIP is a natural nine residue neuropeptide studied for EEG activity and pituitary hormones. Epitalon tetrapeptide, Ala-Glu-Asp-Gly, is based on epithalamin, a pineal extract, and has been examined for telomerase activity in cell culture and for pineal hormone rhythms in ageing animals. The two are often grouped because both are linked to the pineal gland and to circadian research, but their structures and research questions barely overlap. Laboratories comparing them usually do so in models of circadian or age-related change, with each peptide in its own vial. Both belong to our longevity and cognitive research range.

DSIP Reconstitution Chart

We stock DSIP in 5mg and 10mg vials. To find the concentration, divide the vial milligrams by the millilitres of diluent; a U-100 syringe holds 100 units in each mL.

Let the bacteriostatic water trickle along the vial wall, then swirl rather than shake. The DSIP starter kit pairs a vial with diluent and consumables.

When Is DSIP a Suitable Research Tool?

DSIP suits studies that approach it as an open question rather than a characterised tool, so we recommend designs with clear controls, precisely recorded EEG or hormone endpoints and an expectation that results may differ from older papers. The 5mg vial suits pilot work, and the 10mg vial covers longer series from a single lot. Our DSIP batches are checked by HPLC at 98% or higher purity and by mass spectrometry for identity, and the lot number links to a certificate of analysis. The full paper list is in our DSIP research library, and another short peptide with a tissue-extract history is covered in what Cartalax is.

Questions about what is DSIP

More reading

What Is Cartalax?What Is the BPC-157 Half-Life, and How Do Other Peptides Compare?Are Research Peptides Legal in Australia? Every guide on the research peptide blog

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