Category
Sleep & Circadian
Peptides studied for their effects on sleep initiation, slow-wave sleep quality, and circadian rhythm entrainment. DSIP and epithalon represent two distinct mechanisms, one acting on sleep pressure and the other on the circadian clock itself.
5 peptides in this category
What is delta sleep-inducing peptide (DSIP)?
Delta sleep-inducing peptide (DSIP) is a nonapeptide first isolated from rabbit brain in 1977. When administered to humans, it increases the proportion of slow-wave (delta) sleep — the deepest, most restorative sleep stage — without suppressing REM sleep. Unlike sedative drugs that work by GABA-A enhancement, DSIP's receptor mechanism is not fully characterized. It has been studied for insomnia, opiate withdrawal sleep disruption, and stress-related sleep changes. Epithalon is a separate peptide studied for circadian melatonin restoration, addressing the age-related dampening of the pineal melatonin rhythm rather than sleep pressure directly.
Sleep is regulated by two interacting systems: the circadian clock (a roughly 24-hour oscillator driven by the suprachiasmatic nucleus) and sleep homeostasis (the build-up of sleep pressure, primarily signaled by adenosine). Peptides in this category interact with one or both. Delta sleep-inducing peptide (DSIP), a nonapeptide first isolated from rabbit brain by Monnier in 1977, promotes slow-wave (delta) sleep when administered centrally or peripherally. Despite decades of research, its receptor has not been definitively characterized, which has hampered mechanistic clarity. Nevertheless, DSIP has been studied in models of insomnia, opiate withdrawal, and stress-induced sleep disturbance.
Epithalon's relevance here comes from its effects on the pineal gland, where it appears to restore circadian melatonin synthesis that declines with age. The pineal gland produces melatonin in a tightly circadian-regulated pattern, and this rhythm becomes dampened and phase-shifted in older adults, contributing to sleep fragmentation and early waking. Research suggests epithalon can partially restore the amplitude and timing of melatonin secretion, linking it to circadian biology rather than simply hypnotic drug effects.
Compounds
Peptides in this category
DSIP
PreclinicalDelta Sleep Inducing Peptide · Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu
DSIP (Delta Sleep Inducing Peptide) is a nonapeptide first isolated from rabbit cerebral venous blood during electrically induced sleep. Research shows it promotes slow-wave sleep, reduces pain sensitivity, normalizes circadian rhythms, lowers cortisol, and exhibits stress-protective effects. It also stimulates LH release and may influence GH pulsatility. Multiple mechanisms of action are proposed; its receptor has not been fully characterized.
Epithalon
PreclinicalEpitalon · Epithalamin
Epithalon is a synthetic tetrapeptide (Ala-Glu-Asp-Gly) modeled on the endogenous pineal peptide epithalamin. It is one of the most extensively studied longevity peptides, with Russian research demonstrating telomerase activation, telomere elongation, melatonin normalization, and extended lifespan in animal models. Long-term human studies show reduced all-cause mortality rates and improved biomarkers of aging.
Ghrelin
PreclinicalMotilin-related peptide · Growth hormone secretagogue
Ghrelin is a 28-amino-acid acylated peptide hormone primarily produced by gastric X/A-like cells and is the endogenous ligand for the growth hormone secretagogue receptor (GHS-R1a). It stimulates GH release, increases appetite and food intake, promotes energy storage, and modulates sleep and mood. Research explores ghrelin axis manipulation for obesity, cachexia, heart failure, and neurodegenerative diseases.
GHRP-2
Phase IIPralmorelin · Growth Hormone-Releasing Peptide 2
GHRP-2 is a synthetic hexapeptide and potent ghrelin receptor agonist that stimulates growth hormone release from the pituitary. It produces a strong GH pulse with some elevation of cortisol and prolactin at higher doses. Research includes GH deficiency diagnosis, body composition, sleep quality, and appetite stimulation via its ghrelin-mimetic mechanism.
C₄₅H₅₅N₉O₆ · 817.99 Da
Orexin A
PreclinicalHypocretin-1 · OXA
Orexin A (Hypocretin-1) is a 33-amino-acid neuropeptide produced exclusively by lateral hypothalamic neurons. It promotes wakefulness, arousal, and energy expenditure via OX1R and OX2R receptors, and its deficiency (due to autoimmune destruction of orexin neurons) is the cause of narcolepsy with cataplexy. Orexin receptor antagonists (suvorexant, lemborexant) are approved for insomnia; orexin agonists are under development for narcolepsy.
Research applications
What researchers are studying
Slow-wave sleep enhancement
DSIP has been studied in human subjects in several small trials from the 1980s and 1990s, showing increases in delta (slow-wave) sleep percentage and subjective sleep quality in patients with insomnia and disturbed sleep. The peptide appears to be sleep-stage specific in its action, promoting deep sleep without suppressing REM, which distinguishes it from most sedative-hypnotic drugs.
Circadian melatonin restoration
Epithalon's effects on melatonin secretion have been studied in both aged rats and elderly humans. In aged animals with low baseline melatonin, epithalon treatment partially restored the nocturnal melatonin spike that had declined with age. Human studies from Khavinson's group suggest improvements in sleep quality and circadian rhythm amplitude in older subjects receiving epithalon courses.
Stress-related sleep disruption
DSIP has been studied as an adjunct in conditions where sleep is disrupted by physiological stress, including chronic pain, opiate withdrawal, and HPA axis dysregulation. It appears to reduce nighttime cortisol peaks and may normalize stress-hormone circadian patterns in animal models of chronic stress, though human data on this specific application remain sparse.
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