Selank: Published Research

Introduction

Published research on Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) spans approximately three decades of preclinical and clinical investigation, conducted predominantly by groups at the Institute of Molecular Genetics of the Russian Academy of Sciences and associated clinical centers. The literature encompasses rodent behavioral pharmacology, molecular studies of GABAergic and enkephalinergic neurotransmission, neurotrophin regulation, and immunomodulatory gene expression, alongside clinical investigation that contributed to Russian regulatory registration in 2009. Studies below are those available in peer-reviewed English-language publications or as English translations indexed in PubMed. For mechanistic context underlying the studies summarized here, see the Selank mechanism of action article.

Methodology Types in the Published Literature

Published Selank research has employed rodent behavioral pharmacology paradigms — including the elevated plus maze, conditioned active avoidance, and unpredictable chronic mild stress — as primary outcome measures [1,2,3]. Molecular investigations have used qPCR and cDNA microarray methods to characterize gene expression in brain tissue and cell culture [4,5,6]. Enzyme kinetic assays characterized effects on enkephalin-degrading enzymes [7], and ELISA-based methods quantified neurotrophin protein-level changes [8,9]. The principal clinical investigation employed the Hamilton Anxiety Rating Scale, Zung Self-Rating Anxiety Scale, and Clinical Global Impression scale in a parallel-group comparative design [10].

Summary of Published Studies

Behavioral Pharmacology: Stress and Conditioned Learning Models

A 2003 study in Neuroscience and Behavioral Physiology by Kozlovskii and Danchev examined Selank's effects on conditioned active avoidance reflex in rats with initially poor learning ability, reporting that repeated pre-training administration was associated with increased correct solutions compared to vehicle controls, with effects characterized as comparable to piracetam in the same model [1]. A companion 2003 paper by Semenova and colleagues compared Selank and related tuftsin-family peptides across rodent conflict-stress paradigms, documenting Selank's behavioral profile within the broader tuftsin peptide family [2].

A 2017 study in Behavioural Neurology by Kasian and colleagues examined Selank and diazepam co-administration in rats under unpredictable chronic mild stress using the elevated plus maze [3]. Combined Selank-diazepam administration produced anxiety indicator values approaching pre-stress baseline, whereas either compound alone produced incomplete normalization. The study characterized this pattern as additive and noted that combined administration was the most effective condition for restoring pre-stress behavioral parameters [3].

A 2022 study in the Bulletin of Experimental Biology and Medicine by Konstantinopolsky and colleagues examined Selank in a naloxone-precipitated morphine withdrawal model [11]. Single-administration Selank was reported to reduce the total withdrawal index by approximately 40% compared to untreated controls, with statistically significant attenuation of convulsive reactions. The authors characterized the observed attenuation as slightly less complete than that produced by diazepam in the same model, and noted the findings as relevant to the compound's enkephalinergic mechanistic profile [11].

Enkephalinase Inhibition Studies

A 2001 publication in Eksperimental'naia i Klinicheskaia Farmakologiia by Semenova and colleagues reported that Selank inhibited the enzymatic hydrolysis of plasma enkephalin in a concentration-dependent manner in vitro, with inhibitory potency exceeding that of reference peptidase inhibitors bacitracin and puromycin [7]. The authors proposed enkephalinase inhibitory activity as a mechanistic basis for behavioral effects observed in anxiety models. A 2012 study by Narkevich and colleagues in the Journal of Evolutionary Biochemistry and Physiology reported persistent alterations in carboxypeptidase H activity in rat nervous tissue lasting up to 24 hours following Selank administration, demonstrating that the compound's effects on neuropeptide-processing enzymes extend beyond enkephalin catabolism alone [12].

GABAergic Gene Expression Studies

A 2016 study in Frontiers in Pharmacology by Volkova and colleagues used qPCR to assess GABAergic neurotransmission gene expression in rat brain following Selank administration, reporting altered expression of a subset of GABA-A receptor subunit and transporter genes in cortical tissue [4]. These findings were interpreted as consistent with an indirect modulatory influence on GABAergic neurotransmission rather than direct receptor-level action. A 2017 companion investigation in Frontiers in Pharmacology by Filatova and colleagues applied an 84-gene GABAergic expression panel to IMR-32 human neuroblastoma cells [5]. Selank treatment did not produce statistically significant gene expression changes in that monoculture system, a finding the authors interpreted as consistent with in vivo effects depending on intact neural circuit context absent in monoculture — positioning the two studies as complementary rather than contradictory [5].

Hippocampal Transcriptomics and BDNF Regulation

A 2014 cDNA microarray study by Dolotov and colleagues reported that acute Selank administration in rats was associated with greater than two-fold mRNA changes in 36 genes in hippocampal tissue, predominantly encoding plasma membrane and ion-transport proteins; repeated administration produced changes in 20 genes [6]. These transcriptomic findings have informed subsequent pathway-level investigations of the compound's molecular pharmacology.

A 2008 publication in Doklady Biological Sciences by Semenova and colleagues reported concentration-related alterations in hippocampal BDNF mRNA at three hours and BDNF protein at 24 hours following Selank administration in rats [8]. A 2019 study by Laukova and colleagues extended this investigation to chronic ethanol-exposed rats, reporting that Selank-treated animals differed from untreated ethanol controls on BDNF content in both the hippocampus and prefrontal cortex, and on behavioral outcomes in the object recognition test [9]. The authors interpreted these results as consistent with neurotrophin-mediated contributions to the compound's observed effects in the alcohol-exposure model.

Immunomodulatory Gene Expression

A 2011 study in Peptides by Ershov and colleagues examined 35 inflammation-related gene expression changes in murine spleen at six and 24 hours following Selank administration, reporting the most pronounced mRNA alterations for Bcl6, C3, Casp1, Il2rg, and Xcr1 [13]. A 2008 clinical immunology report by Uchakina and colleagues noted T-helper cytokine profile changes and altered serum leu-enkephalin half-life in subjects with anxiety-asthenic disorders receiving Selank [14], providing a clinical-level parallel to the preclinical immunomodulatory findings.

Clinical Investigation: Comparative Trial

The principal published clinical investigation of Selank is a 2008 parallel-group trial by Zozulia, Neznamov, and colleagues in Zhurnal Nevrologii i Psikhiatrii [10]. The trial enrolled 62 subjects with generalized anxiety disorder or neurasthenia — 30 allocated to Selank and 32 to medazepam — over a 14-day observation period. Outcomes on the Hamilton Anxiety Rating Scale, Zung Self-Rating Anxiety Scale, and Clinical Global Impression were characterized by the authors as comparable between the two groups. The Selank group additionally showed antiasthenic effects not observed in the medazepam arm, and serum leu-enkephalin half-life was reported to rise in the Selank group and to correlate with anxiety score reduction [10]. These findings informed the successful Russian regulatory application filed the following year.

Active Research Frontier

Direct receptor binding data for Selank — including radioligand displacement studies at defined GABA-A subunit combinations or opioid receptor subtypes — represent an active area of characterization in the published literature. Human pharmacokinetic data, including bioavailability and metabolite profiling, are areas where additional investigation would strengthen translational interpretation of the preclinical mechanistic picture. The mechanistic relationships among enkephalinase inhibition, GABAergic gene modulation, and BDNF regulation remain subjects of ongoing structural and pathway-level research, as reviewed by Andreeva and Myasoedov in 2019 [15]. Comparable frontier questions exist in the research literature on Epithalon, another Russian peptide compound with an active academic program but limited human pharmacokinetic data in Western literature.

References

1. Kozlovskii II, Danchev ND. The optimizing action of the synthetic peptide Selank on a conditioned active avoidance reflex in rats. Neuroscience and Behavioral Physiology. 2003;33(7):639–643. https://doi.org/10.1023/A:1024444321191 PMID: 14552529.

2. Semenova TP, Kozlovskaya MM, Zuikov AV, Kozlovskiy II, Myasoedov NF. Selank and short peptides of the tuftsin family in the regulation of adaptive behavior in stress. Neuroscience and Behavioral Physiology. 2003;33(9):853–860. https://doi.org/10.1023/A:1025988519919 PMID: 12154572.

3. Kasian AM, Kolomin TA, Andreeva LA, Bondarenko ON, Myasoedov NF, Slominsky PA, Shadrina MI. Peptide Selank enhances the effect of diazepam in reducing anxiety in unpredictable chronic mild stress conditions in rats. Behavioural Neurology. 2017;2017:5091027. https://doi.org/10.1155/2017/5091027 PMC5322660.

4. Volkova A, Shadrina M, Kolomin T, Andreeva L, Limborska S, Myasoedov N, Slominsky P. Selank administration affects the expression of some genes involved in GABAergic neurotransmission. Frontiers in Pharmacology. 2016;7:31. https://doi.org/10.3389/fphar.2016.00031 PMC4757669.

5. Filatova EV, Kasian AM, Kolomin TA, Rybalkina EY, Alieva AK, Andreeva LA, Limborska SA, Myasoedov NF, Pavlova GV, Slominsky PA, Shadrina MI. GABA, Selank, and olanzapine affect the expression of genes involved in GABAergic neurotransmission in IMR-32 cells. Frontiers in Pharmacology. 2017;8:89. https://doi.org/10.3389/fphar.2017.00089 PMID: 28293190. PMC5328971.

6. Dolotov OV, Sebentsova EA, Sourina MM, Malygina TR, Serebriakova EV, Andreeva LA, Alfeeva LYu, Grivennikov IA, Myasoedov NF. Changes in the transcription profile of the hippocampus in response to administration of the tuftsin analog Selank. Neuroscience and Behavioral Physiology. 2014;44(8):852–861. https://doi.org/10.1007/s11055-014-9992-4 PMID: 24450168.

7. Semenova TP, Kozlovskaya MM, Zakharova NM. The inhibitory effect of Selank on enkephalin-degrading enzymes as a possible mechanism of its anxiolytic activity. Eksperimental'naia i Klinicheskaia Farmakologiia. 2001;64(2):3–6. PMID: 11550013. https://pubmed.ncbi.nlm.nih.gov/11550013/

8. Semenova TP, Kozlovskaya MM, Zakharova NM, Kozlovskiy II. Intranasal administration of the peptide Selank regulates BDNF expression in the rat hippocampus in vivo. Doklady Biological Sciences. 2008;421:241–243. https://doi.org/10.1134/S0012496608040066

9. Laukova M, Alaluf LG, Serova LI, Arango V, Sabban EL. Selank, peptide analogue of tuftsin, protects against ethanol-induced memory impairment by regulating BDNF content in the hippocampus and prefrontal cortex in rats. Bulletin of Experimental Biology and Medicine. 2019;167(5):641–644. https://doi.org/10.1007/s10517-019-04588-9

10. Zozulia AA, Neznamov GG, Syunyakov TS, Kost NV, Gabaeva MV, Sokolov OIu, Sebentsova EA, Akhromeeva SA, Panchenko LF, Andriushenko AV, Teleshova ES, Shadrina MI, Slominsky PA, Miasoedov NF. Efficacy and possible mechanisms of action of a new peptide anxiolytic selank in the therapy of generalized anxiety disorders and neurasthenia. Zhurnal Nevrologii i Psikhiatrii Imeni S.S. Korsakova. 2008;108(4):38–48. PMID: 18454096.

11. Konstantinopolsky MA, Chernyakova IV, Poletaeva II, Zhukova II, Andreeva LA, Myasoedov NF. Selank, a peptide analog of tuftsin, attenuates aversive signs of morphine withdrawal in rats. Bulletin of Experimental Biology and Medicine. 2022;173(5):581–584. https://doi.org/10.1007/s10517-022-05624-x PMID: 36322304.

12. Narkevich VB, Klodt PM, Kudrin VS, Volkova AB, Kolomin TA, Andreeva LA, Myasoedov NF, Raevsky KS. Effect of selank on the main carboxypeptidases in the rat nervous tissue. Journal of Evolutionary Biochemistry and Physiology. 2012;48(3):302–308. https://doi.org/10.1134/S0022093012030073 PMID: 22827026.

13. Ershov FI, Mezentseva MV, Baidakova GV, Suetina IA, Troitskaia NN, Andreeva LA, Myasoedov NF. Expression of inflammation-related genes in mouse spleen under tuftsin analog Selank. Peptides. 2011;32(7):1553–1558. https://doi.org/10.1016/j.peptides.2011.03.024

14. Uchakina ON, Uchakin PN, Miasoedov NF, Andreeva LA, Shcherbenko VE, Mezentseva MV, Gabaeva MV, Sokolov OIu, Zozulia AA, Ershov FI. Immunomodulatory effects of selank in patients with anxiety-asthenic disorders. Zhurnal Nevrologii i Psikhiatrii Imeni S.S. Korsakova. 2008;108(5):71–75. PMID: 18577961.

15. Andreeva LA, Myasoedov NF. Physiological effects of Selank and its fragments. Biology Bulletin. 2019;46(4):390–400. https://doi.org/10.1134/S1062359019040071