Everything below concerns GABA-A receptor. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-11-25. Numbers and descriptions here follow the published literature rather than marketing material.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
| Property | Value | Notes |
|---|---|---|
| Route studied | Intranasal | Predominant route in published reports |
| Circulation stability | Short, minutes scale | Peptidases cleave it; the tail slows the process |
| Analytical method | RP-HPLC with mass spectrometry | Used for identity and purity assessment |
| Reported outcome domains | Anxiety and cognitive measures | Derived from small, mostly regional trials |
| Regulatory status | Marketed in Russia | Availability outside that market is limited |
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
In November 2007, Merck agreed to pay $4.85 billion to settle most of the pending Vioxx lawsuits. The settlement required that claimants provide medical and pharmacy records confirming the occurrence of a heart attack, ischemic stroke, or sudden cardiac death; the receipt of at least 30 Vioxx pills within 60 days prior to the injury or death; and confirmation of Vioxx being used within 14 days of the Vioxx-related event. The settlement was generally viewed by industry analysts and investors as a victory for Merck, considering that original estimates of Merck's liability reached between $10 billion and $25 billion. As of mid-2008, when the plaintiff class had reached the threshold percentage required by Merck to go through with the settlement, plaintiffs had prevailed in only three of the twenty cases that had reached juries, all with relatively small awards. Merck has refused to consider compensation for Vioxx victims and their families outside the US. This is particularly true in the UK where there are at least 400 victims and the legal protection afforded to the victims and their families is particularly weak. According to internal e-mail traffic released at a later lawsuit, Merck had a list of doctors critical of Vioxx to be "neutralized" or "discredited". "We may need to seek them out and destroy them where they live," wrote an employee. A Stanford Medical School professor said that Merck was engaged in intimidation of researchers and infringement upon academic freedom.
The first and most important measure was the founding of the Kingdom of Italy, proclaimed on 17 March 1861 with Victor Emmanuel II as constitutional monarch. The method of voting between the plebiscite and the parliamentary elections was different: in 1860 all male citizens who were at least 21 years of age and in possession of civil rights was able to vote, while the next round of elections was governed by Piedmontese electoral law, which was census-based and enfranchise only male citizens who were at least 25 years of age, able to read and write and who paid at least 40 liras in taxes. The narrower voting group elected many members of the aristocratic and upper middle class. This included many Calabrian patriots, such as Francesco Stocco and the brothers Antonino Plutino and Agostino Plutino, the historical right with liberal and conservative tendencies, and the historical left with progressive and democratic ideas.
Increased risk of developing knee and hip osteoarthritis was found among those who work with manual handling (e.g., lifting), have physically demanding work, walk at work, and have climbing tasks at work (e.g., climb stairs or ladders). With hip osteoarthritis, in particular, increased risk of development over time was found among those who work in bent or twisted positions. For knee osteoarthritis, in particular, increased risk was found among those who work in a kneeling or squatting position, experience heavy lifting in combination with a kneeling or squatting posture, and work standing up. Women and men have similar occupational risks for the development of osteoarthritis.
Sources: en.wikipedia.org
=== Phenol–chloroform extraction === Phenol-Chloroform extraction is a liquid-liquid method used by biochemists to separate nucleic acids from proteins and lipids after cells have been lysed. This method has fallen out of favor with scientists and microbiologists as there are easier methods available which require less hazardous chemicals.
=== Persufflation === Blood can be replaced with inert noble gases and/or metabolically vital gases like oxygen, so that organs can cool more quickly and less antifreeze is needed. Since regions of tissue are separated by gas, small expansions do not accumulate, thereby protecting against shattering. Pressures of 60 atm can help increase heat exchange rates. Gaseous oxygen perfusion / persufflation can enhance organ preservation relative to static cold storage or hypothermic machine perfusion, since the lower viscosity of gases, may help reach more regions of preserved organs and deliver more oxygen per gram tissue.
Tetrahydroharmine is a harmala alkaloid found in organisms such as Daphnia pulex and Euglena gracilis. Tetrahydroharmine, a component of ayahuasca with weak SSRI properties, has been associated with increased serotonin uptake sites and variable psychoactive effects, with preferences for higher tetrahydroharmine content reported in some ayahuasca-using churches, potentially due to differences in plant composition and preparation methods.
Sources: en.wikipedia.org
This peptide contains two adjacent tryptophan residues, which is unusual, since tryptophan is a fairly uncommon amino acid (about one in a hundred residues in a typical E. coli protein is tryptophan). If the ribosome attempts to translate this peptide while tryptophan levels in the cell are low, it will stall at either of the two trp codons. While it is stalled, the ribosome physically shields sequence 1 of the transcript, thus preventing it from forming the 1-2 secondary structure. Sequence 2 is then free to hybridize with sequence 3 to form the 2-3 structure, which then prevents the formation of the 3-4 termination hairpin. RNA polymerase is free to continue transcribing the entire operon. If tryptophan levels in the cell are high, the ribosome will translate the entire leader peptide without interruption and will only stall during translation termination at the stop codon. At this point the ribosome physically shields both sequences 1 and 2. Sequences 3 and 4 are thus free to form the 3-4 structure which terminates transcription. The result is that the operon will be transcribed only when tryptophan is unavailable for the ribosome, while the trpL transcript is constitutively expressed. To ensure that the ribosome binds and begins translation of the leader transcript immediately following its synthesis, a pause site exists in the trpL sequence. Upon reaching this site, RNA polymerase pauses transcription and apparently waits for translation to begin. This mechanism allows for synchronization of transcription and translation, a key element in attenuation.
For example, some cells in a developing embryo migrate along specific pathways by matching the orientation of their microfilaments to the "grain" of fibers in the ECM. Researchers are also learning that the ECM around a cell can influence the activity of genes in the nucleus. Information about the ECM probably reaches the nucleus by a combination of mechanical and chemical signaling pathways. Mechanical signaling involves fibronectin, integrins, and microfilaments of the cytoskeleton. Changes in the cytoskeleton may in turn trigger chemical signaling pathways inside the cell, leading to changes in the set of proteins being made by the cell and therefore changes in the cells function. In this way, the ECM of a particular tissue may help coordinate the behavior of all the cells within that tissue. Direct connections between cells also function in this coordination.
== Veterinary use == Hydromorphone is used as an intravenous analgesic in cats and dogs. Hydromorphone's potency is 5–10 times greater than morphine when given intravenously and the length of effect is dose dependent with times ranging 1–8 hours. Anaesthetic recovery can be prolonged from long use of hydromorphone. Hydromorphone is not useful compared to morphine when given subcutaenously in cats or epidurally in cats and dogs. Hydromorphone can provide analgesia up to 12 hours when given intravenously in horses and is also effective when given intramuscular. Hydromorphone has minimal adverse effects in horses when compared to other opioids such as morphine.
Sources: en.wikipedia.org
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.
Intranasal delivery is the route described in most published work. It is used because the peptide is degraded quickly once it reaches circulation. Direct evidence of brain penetration in humans is lacking.
Most trials are small, regionally concentrated, and often lack rigorous blinding or placebo control. Independent replication is limited. Reviews in English generally rate the evidence as preliminary.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.