title: Novel systemically active galanin receptor 2 ligands in depression-like behavior.
abstract: Neuropeptide galanin and its three G-protein coupled receptors, galanin receptor type 1-galanin receptor type 3 (GalR1-GalR3), are involved in the regulation of numerous physiological and disease processes, and thus represent tremendous potential in neuroscience research and novel drug lead development. One of the areas where galanin is involved is depression. Previous studies have suggested that activation of GalR2 leads to attenuation of depression-like behavior. Unfortunately, lack of in vivo usable subtype specific ligands hinders testing the role of galanin in depression mechanisms. In this article, we utilize an approach of increasing in vivo usability of peptide-based ligands, acting upon CNS. Thus, we have synthesized a series of novel systemically active galanin analogs, with modest preferential binding toward GalR2. We have shown that specific chemical modifications to the galanin backbone increase brain levels upon i.v. injection of the peptides. Several of the new peptides, similar to a common clinically used antidepressant medication imipramine, exerted antidepressant-like effect in forced swim test, a mouse model of depression, at a surprisingly low dose range (< 0.5 mg/kg). We chose one of the peptides, J18, for more thorough study, and showed its efficacy also in another mouse depression model (tail suspension test), and demonstrated that its antidepressant-like effect upon i.v. administration can be blocked by i.c.v. galanin receptor antagonist M35. The effect of the J18 was also abolished in GalR2KO animals. All this suggests that systemically administered peptide analog J18 exerts its biological effect through activation of GalR2 in the brain. The novel galanin analogs represent potential drug leads and a novel pharmaceutical intervention for depression.
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia; Department of Neurochemistry, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Indrek
authors.initials: I
authors.lastname: Saar
authors.forename: Jaanus
authors.initials: J
authors.lastname: Lahe
authors.forename: Kent
authors.initials: K
authors.lastname: Langel
authors.forename: Johan
authors.initials: J
authors.lastname: Runesson
authors.forename: Kristin
authors.initials: K
authors.lastname: Webling
authors.forename: Jaak
authors.initials: J
authors.lastname: Järv
authors.forename: Jussi
authors.initials: J
authors.lastname: Rytkönen
authors.forename: Ale
authors.initials: A
authors.lastname: Närvänen
authors.forename: Tamas
authors.initials: T
authors.lastname: Bartfai
authors.forename: Kaido
authors.initials: K
authors.lastname: Kurrikoff
authors.forename: Ülo
authors.initials: Ü
authors.lastname: Langel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000929:Antidepressive Agents, Tricyclic / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects*; D001667:Binding, Competitive / Q000187:drug effects; D045744:Cell Line, Tumor; D003863:Depression / Q000523:psychology*; D015195:Drug Design; D005260:Female; D019004:Galanin / Q000378:metabolism; D019417:Hindlimb Suspension; D006801:Humans; D007099:Imipramine / Q000494:pharmacology; D008024:Ligands; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000494:pharmacology; D044092:Receptor, Galanin, Type 2 / Q000187:drug effects*; D013550:Swimming / Q000523:psychology; D014018:Tissue Distribution
chemical_list: D000929:Antidepressive Agents, Tricyclic; D008024:Ligands; D010455:Peptides; D044092:Receptor, Galanin, Type 2; D019004:Galanin; D007099:Imipramine
keywords: animal models of depression; depression; galanin; galanin receptor type 2; neuropeptide; tail suspension test