Novel Radioiodinated γ-Hydroxybutyric Acid Analogues for Radiolabeling and Photolinking of High-Affinity γ-Hydroxybutyric Acid Binding Sites

Petrine Wellendorph, Signe Høg, Paola Sabbatini, Martin Holst Friborg Pedersen, Lars Martiny, Gitte M. Knudsen, Bente Frølund, Rasmus P. Clausen, Hans Bräuner-Osborne

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    γ-Hydroxybutyric acid (GHB) is a therapeutic drug, a drug of abuse, and an endogenous substance that binds to low- and high-affinity sites in the mammalian brain. To target the specific GHB binding sites, we have developed a 125I-labeled GHB analog and characterized its binding in rat brain homogenate and slices. Our data show that [125I]4-hydroxy-4-[4-(2-iodobenzyloxy)phenyl]butanoate ([125I]BnOPh-GHB) binds to one site in rat brain cortical membranes with low nanomolar affinity (Kd, 7 nM; Bmax, 61 pmol/mg protein). The binding is inhibited by GHB and selected analogs, but not by γ-aminobutyric acid. Autoradiography using horizontal slices from rat brain demonstrates the highest density of binding in hippocampus and cortical regions and the lowest density in the cerebellum. Altogether, the findings correlate with the labeling and brain regional distribution of high-affinity GHB sites or [3H](E,RS)-(6,7,8,9-tetrahydro-5-hydroxy-5H-benzocyclohept-6-ylidene)acetic acid ([3H]NCS-382) binding sites. Using a 125I-labeled photoaffinity derivative of the new GHB ligand, we have performed denaturing protein electrophoresis and detected one major protein band with an apparent mass of 50 kDa from cortical and hippocampal membranes. [125I]BnOPh-GHB is the first reported 125I-labeled GHB radioligand and is a useful tool for in vitro studies of the specific high-affinity GHB binding sites. The related photoaffinity linker [125I]4-hydroxy-4-[4-(2-azido-5-iodobenzyloxy)phenyl]butanoate can be used as a probe for isolation of the elusive GHB binding protein.
    Original languageEnglish
    JournalJournal of Pharmacology and Experimental Therapeutics
    Volume335
    Issue number2
    Pages (from-to)458-464
    ISSN0022-3565
    DOIs
    Publication statusPublished - 2010

    Keywords

    • Hevesy laboratory
    • Radiation research and nuclear technologies

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