Neuroscience research uses peptides to probe specific systems: neurotrophic signaling, stress and anxiety-related behavior, sleep regulation and social memory. The peptides below are research tools for animal and cell models. Their published evidence comes mostly from rodent and rabbit studies, and some areas, especially sleep, remain unresolved.
These compounds are sold for laboratory research only. They are not medicines, are not for human or veterinary use, and nothing here claims an effect on human cognition, mood or sleep.
Leading Cognitive Research Peptides
1. Semax: ACTH(4-10) Analog and BDNF Signaling
Semax is the heptapeptide Met-Glu-His-Phe-Pro-Gly-Pro, an analog of the adrenocorticotropin fragment ACTH(4-10). It keeps the Met-Glu-His-Phe sequence of ACTH(4-7) and adds a C-terminal Pro-Gly-Pro. In rats, a single intranasal application increased hippocampal BDNF protein about 1.4-fold and trkB tyrosine phosphorylation about 1.6-fold, with increases in BDNF exon III and trkB mRNA. Animals given Semax also showed more conditioned avoidance reactions, and the authors proposed that Semax acts on learning through the hippocampal BDNF/trkB system (Dolotov et al., 2006).
2. Selank: A Tuftsin Analog for Stress and Anxiety Research
Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) extends the immunomodulatory tetrapeptide tuftsin (Thr-Lys-Pro-Arg) with the same Pro-Gly-Pro motif found in Semax. Researchers searching for Selank and Semax as nootropic or anxiety peptides will find that the core literature is behavioral and molecular work in rodents. In rats and mice grouped by emotional reactivity, Selank and related tuftsin-family peptides showed anti-stress effects in a conflict-based stress model, with effects varying by molecular structure (Kozlovskaya et al., 2003).
A gene-expression study looked at how Selank might relate to GABAergic signaling. In rat frontal cortex, Selank and GABA each changed the expression of many of 84 neurotransmission-related genes, including GABA receptor subunits, transporters and ion channels. Changes 1 hour after Selank and after GABA were positively correlated (Volkova et al., 2016). This supports a GABA-related mechanism hypothesis, but it does not show direct receptor binding.
3. DSIP: Delta Sleep-Inducing Peptide
DSIP is the nonapeptide Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu. It was isolated from rabbits after it was found to enhance slow-wave (delta) and spindle EEG activity when infused into the brain ventricles. In the original study, only synthetic DSIP, and not its fragments or analogs, specifically enhanced those EEG patterns (Schoenenberger & Monnier, 1977).
Researchers should know that the field is unsettled. A later review concluded that the link between DSIP and sleep was never fully characterized. No DSIP gene, precursor protein or receptor had been isolated, and the authors proposed that a related DSIP-like peptide may explain some of the reported activity (Kovalzon & Strekalova, 2006). DSIP is therefore best suited to exploratory studies of sleep EEG and neuroendocrine regulation, with careful controls.
4. Oxytocin: Social Memory and Attachment
Oxytocin is a neuropeptide central to social neuroscience. Male mice lacking the oxytocin gene failed to develop social memory, while their olfactory detection, spatial memory and behavioral inhibition appeared intact. Oxytocin, but not vasopressin, restored social memory in these mice, and an oxytocin antagonist produced a social amnesia-like effect in wild-type mice (Ferguson et al., 2000). Reviews of attachment biology place oxytocin within a wider set of molecular, cellular and systems-level mechanisms studied across vertebrates (Insel & Young, 2001).
Semax and Selank Compared
Semax and Selank are often discussed together because both are short regulatory peptides that end in the same Pro-Gly-Pro motif. Their starting points differ. Semax is built on an ACTH fragment and has been studied mainly through neurotrophic (BDNF/trkB) and learning endpoints (Dolotov et al., 2006). Selank is built on tuftsin and has been studied mainly through stress-related behavior and GABA-related gene expression (Kozlovskaya et al., 2003; Volkova et al., 2016). Both literatures come largely from rodent models and a small number of research groups, so independent replication using current behavioral standards is a reasonable aim for new work.
Study Design Notes for Neuropeptide Research
- Define behavioral endpoints in advance and score them blind to group.
- Include vehicle controls and, where practical, a scrambled-sequence peptide control.
- Record how solutions were prepared and stored, since short peptides can degrade in solution.
- Check identity and purity on the certificate of analysis for the specific lot before the study starts.
- Consider species and strain: several of the studies above grouped animals by baseline emotional reactivity, which can change results (Kozlovskaya et al., 2003).
Research Strategy: Cognition, Stress, Sleep and Social Behavior
| Peptide | Research area | Example published endpoints |
|---|---|---|
| Semax | Learning and neurotrophic signaling | Hippocampal BDNF, trkB phosphorylation, conditioned avoidance |
| Selank | Stress and anxiety-related behavior | Behavior in conflict-based stress models; cortical gene expression |
| DSIP | Sleep EEG | Delta and spindle EEG activity |
| Oxytocin | Social memory | Social recognition in knockout and antagonist models |
Stress and anxiety-related behavior can confound cognitive tests, and sleep affects memory consolidation, so multi-arm designs need matched controls and standardized behavioral testing. Our guides to neuropeptides in research and neuroplasticity give more background. For the challenges of moving from rodent findings to other species, see species-specific responses to peptides. For another class of centrally acting peptides, see our Melanotan 2 vs PT-141 comparison.
Every lot is third-party tested, with identity confirmed by mass spectrometry, and certificates are published on our COA page.
Browse all Neuropeptide Research peptides →
References
- Dolotov OV, Karpenko EA, Inozemtseva LS, et al. (2006). Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain research, 1117(1), 54-60. PMID: 16996037 · DOI: 10.1016/j.brainres.2006.07.108
- Ferguson JN, Young LJ, Hearn EF, et al. (2000). Social amnesia in mice lacking the oxytocin gene. Nature genetics, 25(3), 284-8. PMID: 10888874 · DOI: 10.1038/77040
- Insel TR, Young LJ (2001). The neurobiology of attachment. Nature reviews. Neuroscience, 2(2), 129-36. PMID: 11252992 · DOI: 10.1038/35053579
- Kovalzon VM, Strekalova TV (2006). Delta sleep-inducing peptide (DSIP): a still unresolved riddle. Journal of neurochemistry, 97(2), 303-9. PMID: 16539679 · DOI: 10.1111/j.1471-4159.2006.03693.x
- Kozlovskaya MM, Kozlovskii II, Val’dman EA, et al. (2003). Selank and short peptides of the tuftsin family in the regulation of adaptive behavior in stress. Neuroscience and behavioral physiology, 33(9), 853-60. PMID: 14969422 · DOI: 10.1023/a:1025988519919
- Schoenenberger GA, Monnier M (1977). Characterization of a delta-electroencephalogram (-sleep)-inducing peptide. Proceedings of the National Academy of Sciences of the United States of America, 74(3), 1282-6. PMID: 265572 · DOI: 10.1073/pnas.74.3.1282
- Volkova A, Shadrina M, Kolomin T, et al. (2016). Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission. Frontiers in pharmacology, 7, 31. PMID: 26924987 · DOI: 10.3389/fphar.2016.00031
Research These Compounds: High-purity research peptides available from BioSim: Semax, Selank, DSIP. All 99%+ purity by HPLC; available certificates are published on our COA page.
