What Is DSIP | Delta Sleep-Inducing Peptide for Neuroendocrine Research

DSIP, also known as emideltide, is commonly supplied for research as a synthetic nonapeptide with the sequence H-Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu-OH (WAGGDASGE). The exact identity and physiological role of naturally occurring DSIP-like material remain unresolved.

PubChem lists the unsalted/free form (referred to as “emideltide (free base)” in the FDA briefing document) with CAS number 62568-57-4, the molecular formula C₃₅H₄₈N₁₀O₁₅, an average molecular weight of about 848.8 g/mol, and a monoisotopic mass of 848.3301 Da.^[1]

DSIP was named after early rabbit EEG experiments, but its natural role is still unclear. A 2006 review by Kovalzon and Strekalova found that the identity of naturally occurring DSIP-like material, its source in the body, and its biological role had not been firmly established.

No dedicated DSIP receptor, confirmed mammalian precursor protein, or confirmed encoding gene has been identified in the sources cited here.^[2]

Basic Chemical Information

• Length: 9 amino acids
• Sequence: H-Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu-OH
• One-letter sequence: WAGGDASGE
• Molecular formula: C₃₅H₄₈N₁₀O₁₅ for the unsalted/free form
• Average molecular weight: about 848.8 g/mol for the unsalted/free form
• Monoisotopic mass: 848.3301 Da^[1]
• CAS number: 62568-57-4
• Other name: emideltide

Supplied material may be an acetate or trifluoroacetate form and may also contain water and process-related residuals. Counterion stoichiometry, water content, and other non-peptide mass affect net peptide content and molar calculations.

The average molecular weight of 848.8 g/mol should not be used as the direct high-resolution mass spectrometry (HRMS) target; the monoisotopic neutral mass (848.3301 Da) and the expected charge-state ions should be used for mass-spectrometric identity confirmation.

The chemical connection at the aspartic-acid residue also matters. Schoenenberger et al. (1978) compared the main alpha-aspartyl form with a beta-aspartyl isomer and found that they did not have the same activity in the rabbit test.

Therefore, a matching intact mass alone cannot distinguish these isoaspartyl/isopeptide variants; orthogonal structural confirmation such as MS/MS or peptide mapping may be needed.^[3]

Why DSIP Is Still an Unresolved Research Peptide

DSIP-like signals have been reported with antibody-based tests, but an antibody signal does not prove the exact amino-acid sequence of the detected material. The 2006 review therefore separated the known synthetic peptide from the less certain DSIP-like material reported in tissues.

For that reason, DSIP should not be described as a peptide with a fully known natural pathway or a settled mechanism.^[2]

Early Rabbit EEG Research

Schoenenberger and Monnier (1977) infused the synthetic peptide and several related peptides into the brain ventricles of rabbits under double-blind conditions. Among the tested peptides, synthetic DSIP produced a significant increase in delta and spindle EEG patterns.^[4]

This finding showed activity in one specific rabbit experiment. It did not prove a receptor, a gene, a natural production pathway, or the same effect in every species and study design.

Findings From Laboratory Models

The findings below come only from in-vitro preparations or laboratory animal models. They must not be treated as human, medical, or veterinary-use claims.

• EEG and hormone measurements: Iyer et al. (1988) found that after sleep deprivation in rats, slow-wave sleep and plasma growth hormone (GH) levels increased during recovery sleep. Infusion of DSIP antiserum into the third ventricle blocked these increases, suggesting that endogenous DSIP-like activity may contribute to this response. The result applies to the male-rat model and study conditions used by the researchers, and the interpretation depends on the specificity of the antiserum used and the assumption about the identity of the endogenous material at that time.^[5]
• ACTH release: Okajima et al. (1986) found that DSIP at 10⁻⁹–10⁻⁷ M reduced CRF-stimulated ACTH release in isolated rat anterior-pituitary tissue. This was an in-vitro pituitary experiment. It does not show that DSIP blocks CRH release from the hypothalamus in a whole animal.^[6]
• Somatostatin release: Iyer and McCann (1987) found that DSIP reduced somatostatin release in an in-vitro study using rat hypothalamic median-eminence tissue, and the researchers reported evidence of a dopaminergic component to the response.^[7] That experiment did not directly measure or prove broad changes across growth, thyroid, or pancreatic hormone systems.
• Peptide breakdown: Nakamura et al. (1992) found that when DSIP was incubated with rat brain membranes, it was broken down and the N-terminal tryptophan was released. Aminopeptidase inhibitors reduced this breakdown in the test system.^[8] This result should not be turned into one fixed plasma half-life because tissue-membrane breakdown and whole-body clearance are different measurements.
• Blood-brain barrier studies: Kastin et al. (1981) examined DSIP permeability using a radioimmunoassay-based approach.^[9] Zlokovic et al. (1989) reported a high-affinity, saturable uptake component in a vascularly perfused guinea-pig brain model.^[10] These different experimental models addressed different aspects of DSIP uptake and produced model-specific mechanistic interpretations. Uptake was reported, but a single confirmed transport mechanism has not been established.
• Other animal-model endpoints: DSIP was studied in rodent nociception models by Nakamura et al. (1988)^[11] and in convulsion models by Shandra et al. (1993).^[12] These papers reported changes in the endpoints they measured, but they do not establish DSIP as a pain medicine or anticonvulsant drug.

How to Read a DSIP Certificate of Analysis

A certificate of analysis, or COA, applies to one batch. It is a quality-control record, not proof of biological activity, safety, or suitability for any use outside laboratory research.

• HPLC purity: This usually shows the relative area of the main chromatographic peak under the stated test method. The result depends on detection wavelength, relative response factors of impurities, column and gradient conditions, and integration rules. It does not automatically equal the actual peptide content by weight and typically excludes water, acetate, TFA, inorganic salts, and non-UV-absorbing components.
• Mass spectrometry: A matching intact mass supports the identity of the peptide, but it does not by itself prove high purity or rule out sequence rearrangements, D/L isomerism, isoaspartyl/β-aspartyl variants, or isobaric sequence isomers. MS/MS, amino acid analysis, or an orthogonal chromatographic method may be needed when these distinctions are material—especially given the known difference in biological activity between the α-aspartyl and β-aspartyl forms of DSIP.
• Peptide content / net peptide content: This is a quantitative measure of the target peptide in the bulk material. It should be determined by a suitable validated or qualified method (e.g., quantitative amino acid analysis, quantitative NMR, elemental analysis, or a validated mass-balance approach) and should not be inferred from HPLC area purity alone.
• Water and counterion: Water, acetate, trifluoroacetate, and other components affect concentration calculations based on powder weight. These should be quantified by methods appropriate to each analyte (e.g., Karl Fischer for water, ion chromatography or other suitable methods for counterions).
• Residual solvents and related substances: These should be reported with the method and acceptance limits when they are part of the batch specification.

For in-vivo studies involving parenteral administration, the applicable protocol should also define requirements for:

• Bacterial endotoxin (e.g., LAL or rFC method, reporting unit, and sample concentration tested);
• Bioburden or sterility, as appropriate to the route of administration;
• Visible and subvisible particulate matter;
• Aggregation or oligomer state, where relevant to the formulation and route;
• Residual coupling reagents, scavengers, or catalysts from synthesis when these may persist.

ICH Q2(R2) (finalized March 2024) provides a general framework for analytical method validation, including accuracy, precision, specificity, range, and robustness. It is cited here as a general analytical reference and does not by itself establish regulatory specifications for research-use-only materials.^[13]

A July 2026 FDA staff briefing document prepared for the Pharmacy Compounding Advisory Committee meeting reviewed example DSIP/emideltide COAs submitted with withdrawn nomination packages. It noted that the COAs described tests such as HPLC, mass spectrometry, Karl Fischer water testing, gas chromatography for residual solvents, amino-acid composition, and related-substance testing, but also identified gaps in reported impurity limits, impurity-profile controls, endotoxin, and bioburden testing.

This document is an FDA staff assessment prepared for advisory committee deliberation; it is not an approval document, a USP/NF monograph, or a universally applicable DSIP specification.^[14]

Laboratory Storage and Sample Preparation

• Dry powder: Follow the batch-specific COA and stability data. In the absence of validated data, sealed and dry storage at a conservative low temperature such as −20°C may be used provisionally, while avoiding repeated freeze–thaw cycles and moisture condensation. This should not be presented as a validated shelf life. The exact peptide form (unsalted/free form vs. acetate or other salt) must be recorded rather than assuming identical stability properties.^[14]
• Solvent: Do not assume that every DSIP form is freely soluble in the same liquid. Solubility depends on the salt form, concentration, pH, temperature, and the needs of the assay. Published supplier data suggest different solubility profiles for the unsalted form and the acetate form; these are not independent batch-specific validated values.
• Sample preparation: Use calibrated laboratory liquid-handling equipment. Any vial, sterile liquid, syringe, or needle used in a laboratory protocol is only a research transfer or sampling tool. It is not for human use or veterinary treatment.
• Concentration: Base molar calculations on the batch-specific net peptide content rather than treating the full powder weight as pure peptide. When peptide content is expressed as the mass fraction of the unsalted/free form, use the molecular weight of the free form (848.8 g/mol) consistently.
• Prepared solution: Do not give every DSIP solution a fixed refrigerated life such as two to four weeks. Solution stability changes with peptide form, solvent, pH, concentration, container, light, temperature, and freeze-thaw history. Peptide formulations may be sensitive to these conditions and may form degradation products or aggregates.^[14]
• When stability data are missing: Prepare only the amount needed for the current laboratory work and record the preparation and storage conditions.

Research Summary

DSIP is a defined synthetic nonapeptide, but its natural source and full mechanism are still unresolved. Laboratory studies have reported changes in EEG, hormone release, peptide breakdown, brain-barrier uptake, nociception, and convulsion-related endpoints in specific models.

These results vary by model and do not support broad claims about one confirmed receptor, one fixed mechanism, or consistent effects across all experiments.

Good DSIP research should identify the exact peptide form and batch, check the COA, use suitable controls, record the model and test conditions, and limit the conclusion to what was directly measured.

Authoritative Research References

1. National Center for Biotechnology Information. PubChem Compound Summary: Delta Sleep-Inducing Peptide, CID 68816. https://pubchem.ncbi.nlm.nih.gov/compound/68816
2. Kovalzon VM, Strekalova TV. Delta sleep-inducing peptide (DSIP): a still unresolved riddle. Journal of Neurochemistry. 2006;97(2):303-309. doi:10.1111/j.1471-4159.2006.03693.x. PMID: 16539679. https://pubmed.ncbi.nlm.nih.gov/16539679/
3. Schoenenberger GA, Maier PF, Tobler HJ, Wilson K, Monnier M. The delta EEG (sleep)-inducing peptide (DSIP). XI. Amino-acid analysis, sequence, synthesis and activity of the nonapeptide. Pflügers Archiv: European Journal of Physiology. 1978;376(2):119-129. doi:10.1007/BF00581575. PMID: 568769. https://pubmed.ncbi.nlm.nih.gov/568769/
4. Schoenenberger GA, Monnier M. Characterization of a delta-electroencephalogram (-sleep)-inducing peptide. Proceedings of the National Academy of Sciences of the United States of America. 1977;74(3):1282-1286. doi:10.1073/pnas.74.3.1282. PMID: 265572. https://pmc.ncbi.nlm.nih.gov/articles/PMC430668/
5. Iyer KS, Marks GA, Kastin AJ, McCann SM. Evidence for a role of delta sleep-inducing peptide in slow-wave sleep and sleep-related growth hormone release in the rat. Proceedings of the National Academy of Sciences of the United States of America. 1988;85(10):3653-3656. doi:10.1073/pnas.85.10.3653. PMID: 3368469. https://pubmed.ncbi.nlm.nih.gov/3368469/
6. Okajima T, Kato K, Ibayashi H. Delta-sleep-inducing peptide (DSIP) inhibited CRF-induced ACTH secretion from rat anterior pituitary gland in vitro. Hormone and Metabolic Research. 1986;18(7):497-499. PMID: 3017833. https://pubmed.ncbi.nlm.nih.gov/3017833/
7. Iyer KS, McCann SM. Delta sleep inducing peptide (DSIP) inhibits somatostatin release via a dopaminergic mechanism. Neuroendocrinology. 1987;46(1):93-95. doi:10.1159/000124804. PMID: 2886936. https://pubmed.ncbi.nlm.nih.gov/2886936/
8. Nakamura A, Shiomi H, Harada Y, Ohta S, Koda A. Characterization of the release and metabolism of delta sleep-inducing peptide (DSIP) in the rat brain. Neuropeptides. 1992;23(3):129-135. PMID: 8474631. https://pubmed.ncbi.nlm.nih.gov/8474631/
9. Kastin AJ, Nissen C, Coy DH. Permeability of blood-brain barrier to DSIP peptides. Pharmacology Biochemistry and Behavior. 1981;15(6):955-959. doi:10.1016/0091-3057(81)90060-5. PMID: 6895670. https://pubmed.ncbi.nlm.nih.gov/6895670/
10. Zlokovic BV, Segal MB, Davson H, Jankov RM. Saturable mechanism for delta sleep-inducing peptide (DSIP) at the blood-brain barrier of the vascularly perfused guinea pig brain. Peptides. 1989;10(2):249-254. doi:10.1016/0196-9781(89)90026-0. PMID: 2547200. https://pubmed.ncbi.nlm.nih.gov/2547200/
11. Nakamura A, Shiomi H, Harada Y, Koda A. Potent antinociceptive effect of centrally administered delta-sleep-inducing peptide (DSIP). European Journal of Pharmacology. 1988;155(3):247-253. doi:10.1016/0014-2999(88)90510-9. PMID: 2853064. https://pubmed.ncbi.nlm.nih.gov/2853064/
12. Shandra AA, Godlevsky LS, Bratus NI, Karganov MY, Kelyin AV. The influence of the delta-sleep-inducing peptide on convulsive activity and the functional state of neurons of the reticular part of the substantia nigra. Fiziologicheskii Zhurnal SSSR Imeni I. M. Sechenova. 1993;79(1):76-82. PMID: 8232867. https://pubmed.ncbi.nlm.nih.gov/8232867/
13. U.S. Food and Drug Administration. ICH Q2(R2): Validation of Analytical Procedures. March 2024. FDA Q2(R2)
14. U.S. Food and Drug Administration. Emideltide-Related Bulk Drug Substances. FDA Staff Briefing Document for the Pharmacy Compounding Advisory Committee Meeting, July 23–24, 2026. FDA Briefing Document

Research Use Only Disclaimer

Research Use Only: All NEXALUME LABS products are intended and labeled solely for laboratory research use. They are not intended, manufactured, tested, or released for human or veterinary administration.

This article provides general scientific information regarding standard laboratory in vitro and in vivo research contexts only, and does not constitute a validated experimental protocol, medical guidance, clinical guidance, veterinary guidance, or treatment advice.