Browse more peptide research, methods and limitations.
Three opioid peptides from different families all inhibited TRH release from rat stomach in a dose-dependent manner, reversible by naloxone.
Mitsuma, T; Hirooka, Y; Nakada, K; Nomura, A; Nogimori, T · In Vitro
All three families of opioid peptides inhibited TRH release from rat cecum tissue in a dose-dependent, naloxone-reversible manner.
Mitsuma, T; Hirooka, Y; Nakata, K; Nogimori, T · In Vitro
Prodynorphin peptide distribution differs substantially between hamster and rat in reproduction and emotion-related brain regions, and hamsters may process the precursor protein differently.
Neal, C R; Newman, S W · Animal Study
Endogenous opioid peptide release from hippocampal slices was demonstrated by competitive radioligand displacement. The strongest release occurred in stratum lacunosum moleculare of CA3.
Neumaier, J F; Chavkin, C · In Vitro
Opioid peptides regulate each other's release through presynaptic cross-receptor mechanisms. Delta receptor blockade increased release of all three peptide types. This 'allelo-receptor' system provides complex feedback regulation.
Nikolarakis, K E; Almeida, O F; Yassouridis, A; Herz, A · In Vitro
The C-terminal residues Met6 and Asp7 of dermenkephalin are the primary determinants of delta-opioid receptor selectivity, overriding the mu-preferring N-terminal domain.
Sagan, S; Amiche, M; Delfour, A; Mor, A; Camus, A; Nicolas, P · In Vitro
Alpha-neoendorphin is the major prodynorphin end product in Xenopus brain. Leu-enkephalin is produced from prodynorphin processing, not from proenkephalin, in this species.
Sei, C A; Richard, R; Dores, R M · Animal Study
No opioid peptide or morphine, across a wide concentration range, affected superoxide formation in human neutrophils or HL-60 cells under defined experimental conditions.
Seifert, R; Burde, R; Schultz, G · In Vitro
A novel endoprotease with high specificity for dynorphin B (Km = 11 µM) was identified in bovine spinal cord. It does not act on other prodynorphin-derived peptides.
Silberring, J; Nyberg, F · In Vitro
Subchronic cocaine selectively increased striatonigral dynorphin through a dopaminergic mechanism requiring both D1 and D2 receptors. Enkephalin and substance P were unaffected.
Sivam, S P · Animal Study
Thymosin alpha 1 modulates an early event in T cell activation. A 30-minute preincubation is sufficient to prime both CD4+ and CD8+ T cells, but macrophage-derived IL-1 is required for the enhanced response.
Sztein, M B; Serrate, S A · In Vitro
Beta-endorphin produces spinal analgesia by selectively releasing met-enkephalin. Morphine does not use this mechanism. The effect is specific to the tail-flick (spinal) but not hot-plate (supraspinal) response.
Tseng, L L; Suh, H H · Animal Study
Dynorphin B mossy fiber terminal fields in the hippocampus vary by mouse genotype, with C57BL/6 mice having larger intra- and infrapyramidal projections than DBA/2 mice.
van Daal, J H; Zanderink, H E; Jenks, B G; van Abeelen, J H · Animal Study
Alpha-methyldopa's hypotensive effect requires opioid receptor activation in the NTS, specifically through beta-endorphin and not through enkephalins or dynorphin.
Van Giersbergen, P L; Roording, P; de Lang, H; de Jong, W · Animal Study
Both beta-endorphin(1-31) and dynorphin(1-13), but not met-enkephalin, mediate alpha-methyldopa's central hypotensive effect. The opioid peptides must be released early in the drug's mechanism.
van Giersbergen, P L; Wiegant, V M; de Jong, W · Animal Study
Clonidine's central hypotensive mechanism involves beta-endorphin and dynorphin only in spontaneously hypertensive rats, not in normotensive Wistar-Kyoto rats.
van Giersbergen, P L; Tierney, S A; Wiegant, V M; de Jong, W · Animal Study
Chronic arthritis activates the prodynorphin gene in spinal cord neurons, increasing both mRNA and peptide levels. Unilateral inflammation produces changes only in the corresponding spinal quadrant.
Weihe, E; Millan, M J; Höllt, V; Nohr, D; Herz, A · Animal Study
All three opioid peptide families selectively blocked the exercise pressor reflex (ergoreceptor) without affecting the baroreceptor reflex, suggesting a specific opioid-catecholamine pathway for exercise blood pressure responses.
Williams, C A · Animal Study
Opioid peptides have differential effects on neonatal cerebral vasculature: enkephalins dilate, beta-endorphin constricts, and dynorphin switches depending on blood pressure status. All effects are prostaglandin-dependent.
Armstead, W M; Mirro, R; Busija, D W; Leffler, C W · Animal Study
Full-length dynorphin A (1-17 or 1-13), leumorphin, and alpha-neo-endorphin induced rapid feeding in pigs. Shorter fragments were ineffective. Naloxone blocked all feeding effects.
Baldwin, B A; de la Riva, C; Ebenezer, I S · Animal Study
Aminopeptidase M in human CSF degrades opioid peptides at rates inversely proportional to chain length. Met-enkephalin is degraded ~13x faster than dynorphin A.
Benter, I F; Hirsh, E M; Tuchman, A J; Ward, P E · In Vitro
Lithium releases all three opioid peptides by inhibiting autoreceptors. Chronic treatment permanently inactivates dynorphin and met-enkephalin autoreceptors through G-protein-dependent mechanisms.
Burns, G; Herz, A; Nikolarakis, K E · In Vitro
All three opioid peptide families are present in the guinea pig endocrine pancreas but in different cell types, with processing pathways distinct from other organs.
Cetin, Y · Animal Study
Prothymosin alpha acts as an accessory signal for T cell activation. It requires macrophage-derived IL-1 for its effect and works through an IL-2-dependent pathway.
Cordero, O J; Sarandeses, C S; Nogueira, M · In Vitro
Researchers constructed a library of 300 million different hexapeptides (6-amino-acid peptides) displayed on the surface of bacteriophage (viruses that infect bacteria). They screened this massive library against a monoclonal antibody specific for beta-endorphin and, through three rounds of panning (affinity selection), isolated 51 clones that bound the antibody. All 51 clones had tyrosine as their first amino acid, and 48 had glycine as the second — matching the known N-terminal sequence of beta-endorphin (Tyr-Gly-Gly-Phe). Binding affinities of synthesized peptides ranged from 0.35 μM to 8.3 μM. Critically, the researchers identified these binding peptides with no prior knowledge of what the antibody recognized, demonstrating that phage display could discover ligands for any receptor in a completely unbiased way.
Cwirla, S E; Peters, E A; Barrett, R W; Dower, W J · Laboratory Study
Prodynorphin and proenkephalin genes are expressed in 16-day embryonic rat brain cultures, earlier than previously known. This is the first evidence of early opioid gene expression in the developing nervous system.
Di Scala-Guenot, D; Strosser, M T; Felix, J M; Richard, P · In Vitro
Dynorphin A(1-8) is extensively converted to leu-enkephalin by metalloendopeptidase EC 3.4.24.15 across all brain regions, effectively switching opioid signaling from kappa to delta receptors.
Dixon, D M; Traynor, J R · In Vitro
Both thymosin alpha 1 and thymosin beta 4 suppress gut lamina propria lymphocyte proliferation through a mechanism that may involve protein kinase C but not calcium flux or ornithine decarboxylase pathways.
Elitsur, Y; Mutchnick, M G; Sakr, W A; Luk, G D · In Vitro
Dynorphin A(1-17) mediates an antianalgesic (pain-relief-opposing) system in the spinal cord. Most analgesics activate both pain relief and this dynorphin-mediated opposition simultaneously.
Fujimoto, J M; Arts, K S; Rady, J J; Tseng, L F · Animal Study
Single-dose morphine pretreatment desensitizes the spinal antianalgesic dynorphin system for up to 18 hours, possibly by triggering dynorphin release that leads to receptor desensitization.
Fujimoto, J M; Holmes, B · Animal Study
Endogenous opioid peptides tonically inhibit dopamine release from both pituitary regions. Opioid peptides show differential potency between the two regions, suggesting different receptor distributions.
Garris, P A; Ben-Jonathan, N · In Vitro
Enkephalins inhibit non-adrenergic, non-cholinergic inhibitory neurotransmission in human colon through prejunctional delta-opioid receptors with high selectivity.
Hoyle, C H; Kamm, M A; Burnstock, G; Lennard-Jones, J E · In Vitro
Enkephalin, beta-endorphin, and dynorphin are not growth factors for ventral spinal cord neurons. They did not affect neurite extension or glial cell proliferation in embryonic cultures.
Iwasaki, Y; Kinoshita, M; Ikeda, K; Shiojima, T · In Vitro
Opioid peptides selectively inhibit non-cholinergic excitatory neurotransmission in airways via prejunctional receptors, with dynorphin being the most potent endogenous peptide.
Kamikawa, Y; Shimo, Y · In Vitro
Enkephalin and dynorphin systems have opposing effects on stress behavior. The dynorphin system selectively interacts with the met-enkephalin system but not the leu-enkephalin system.
Katoh, A; Nabeshima, T; Kameyama, T · Animal Study
Pancreas and liver contain substantial opioid peptide levels exceeding brain content, with functional delta and kappa receptors on pancreatic islets. These peripheral opioids could regulate blood glucose.
Khawaja, X Z; Green, I C; Thorpe, J R; Titheradge, M A · Animal Study
Thymosin alpha 1 increases high-affinity IL-2 receptor expression with a bimodal dose-response pattern. This directly correlates with enhanced IL-2 production and is only effective during immune activation.
Leichtling, K D; Serrate, S A; Sztein, M B · In Vitro
Lung cancer cells have an opioid-based growth suppression system that nicotine can override. All three opioid receptor types participate, and the cancer cells produce their own opioid peptides.
Maneckjee, R; Minna, J D · In Vitro
Morphine has anti-inflammatory effects on granulocytes through both opioid receptor-dependent (aggregation, ATP) and independent (arachidonic acid metabolism) mechanisms. Natural opioid peptides do not share these effects.
Mazzone, A; Ricevuti, G; Pasotti, D; Fioravanti, A; Marcoli, M; Lecchini, S; Notario, A; Frigo, G M · In Vitro
Beta-endorphin binds to kidney membranes through both opioid (high-affinity, low-capacity) and non-opioid (low-affinity, high-capacity) sites. The non-opioid binding involves the mid-portion of the peptide.
Sato, H; Takeda, K; Terasaki, T; Tsuji, A · In Vitro
Prodynorphin processing matures much faster in the substantia nigra (day 7) than the pituitary (day 21). Late-developing conversion of dynorphin products to leu-enkephalin changes the enkephalin ratio in adults.
Sei, C A; Dores, R M · Animal Study
The marginal division of the striatum has higher densities of zinc, dynorphin B-immunoreactive terminals, and substance P-immunoreactive terminals compared to the rest of the striatum.
Shu, S Y; McGinty, J F; Peterson, G M · Animal Study
Mu and delta opioids increase, while kappa opioids decrease, dopamine release in the nucleus accumbens. This differential modulation explains their opposing motivational effects.
Spanagel, R; Herz, A; Shippenberg, T S · Animal Study
All submucous neurons in guinea pig ileum are immunoreactive for prodynorphin peptides. Multiple distinct populations of opioid neurons with different neurochemical codes project to secretory pathways.
Steele, P A; Costa, M · Animal Study
Immune cells in inflamed tissue release opioid peptides that activate receptors on sensory nerve terminals, producing local pain relief. This represents a newly discovered neuroimmune analgesic pathway.
Stein, C; Hassan, A H; Przewłocki, R; Gramsch, C; Peter, K; Herz, A · Animal Study
Acupuncture and non-acupuncture point stimulation produce analgesia through distinct opioid systems: met-enkephalin/mu pathway for acupuncture points, dynorphin/kappa pathway for non-acupuncture points.
Takeshige, C; Luo, C P; Hishida, F; Igarashi, O · Animal Study
Spinal dynorphin A raises blood pressure through kappa opioid receptors independently from vasopressin. Chain length of at least 13 amino acids is required for the cardiovascular effect.
Thornhill, J A; Pittman, Q J · Animal Study
Both amphetamine (dopamine agonist) and haloperidol (dopamine antagonist) significantly altered levels of prodynorphin peptides in the striatum, substantia nigra, and hippocampus.
Trujillo, K A; Day, R; Akil, H · Animal Study
D-enantiomers of cecropin A, magainin 2, and melittin retained equivalent antibacterial and channel-forming activity, confirming a non-receptor-mediated membrane disruption mechanism.
Wade, D; Boman, A; Wåhlin, B; Drain, C M; Andreu, D; Boman, H G; Merrifield, R B · In Vitro
Physiological-like high-frequency stimulation of opioid-containing pathways releases detectable amounts of endogenous opioids in hippocampal slices. The release is pathway-specific and frequency-dependent.
Wagner, J J; Caudle, R M; Neumaier, J F; Chavkin, C · In Vitro