RPEP-00085 · 1988DADLE (D-Ala2-D-Leu5 enkephalin), a delta-opioid receptor agonist, at 1.50 mg/kg/day induced summer hibernation comparable to that caused by natural Hibernation Induction Trigger (HIT).
Morphine (1.50 mg/kg/day), morphiceptin (0.82 mg/kg/day), and dynorphin A (0.82 mg/kg/day) did not induce hibernation.
Strikingly, morphine, morphiceptin, and dynorphin A actually antagonized HIT-induced hibernation. They blocked the natural hibernation signal.
This suggests delta-opioid receptors promote hibernation while mu and kappa opioid receptors promote the arousal (waking) state. Natural hibernation may involve a shift in the balance between these receptor systems.
Oeltgen, P R; Nilekani, S P; Nuchols, P A; Spurrier, W A; Su, T P · Animal Study
RPEP-00402 · 1997Prolonged oral MK-677 significantly improved sleep quality by increasing stage 4 (deep sleep) and REM sleep in both young (18-30) and older (65+) adults.
Copinschi, G; Leproult, R; Van Onderbergen, A; Caufriez, A; Cole, K Y; Schilling, L M; Mendel, C M; De Lepeleire, I; Bolognese, J A; Van Cauter, E · RCT
RPEP-00574 · 2000Intranasal NPY promoted sleep and reduced ACTH and cortisol in healthy young men, demonstrating CRH-opposing anxiolytic and sedative effects with potential therapeutic applications for depression and insomnia.
Antonijevic, I A; Murck, H; Bohlhalter, S; Frieboes, R M; Holsboer, F; Steiger, A · RCT
RPEP-00606 · 2000Melatonin directly regulates thymosin alpha-1 and thymulin production, driving their nocturnal peaks in serum and thymus. Pinealectomy abolished and melatonin replacement restored the circadian thymic peptide pattern.
Molinero, P; Soutto, M; Benot, S; Hmadcha, A; Guerrero, J M · Animal Study
RPEP-00873 · 2003Intravenous ghrelin administration increased slow-wave sleep (deep sleep) across the total night and enhanced delta-wave activity during the second half of the night. REM sleep was reduced during the second third of the night, while other sleep stages were unaffected.
Ghrelin also stimulated multiple hormonal responses: growth hormone and prolactin levels were elevated throughout the night, and cortisol rose during the first half. Interestingly, the GH response was strongest after the first injection and weakest after the fourth, while cortisol showed the opposite pattern. Leptin levels were unaffected.
Weikel, J C; Wichniak, A; Ising, M; Brunner, H; Friess, E; Held, K; Mathias, S; Schmid, D A; Uhr, M; Steiger, A · Clinical Trial
RPEP-05284 · 2021Antimicrobial peptide gene expression in skin oscillates along day/night rhythms with two distinct patterns: activity-phase peptides controlled by light and sleep-phase peptides controlled by an internal circadian clock.
Bilska, Bernadetta; Zegar, Aneta; Slominski, Andrzej T; Kleszczyński, Konrad; Cichy, Joanna; Pyza, Elzbieta · Animal
RPEP-05353 · 2021Selank and phenibut are poorly studied GABAergic drugs sold as US dietary supplements. Phenibut poison control calls have increased substantially, and both carry risks of dependence, withdrawal, and serious adverse effects when misused.
Doyno, Cassandra R; White, C Michael · Review