Metabolic GHB precursor succinate binds to γ-hydroxybutyrate receptors: Characterization of human basal ganglia areas nucleus accumbens and globus pallidus

• Published in: Journal of neuroscience research 2006-07, Vol.84 (1), p.27-36
• Main Authors: Molnár, Tünde, Fekete, Erzsébet Kútiné, Kardos, Julianna, Simon-Trompler, Edit, Palkovits, Miklós, Emri, Zsuzsa
• Format: Article
• Language: English
• Subjects: Animals; Baclofen - pharmacology; Benzocycloheptenes - pharmacology; carbenoxolone hemisuccinate; Dose-Response Relationship, Drug; drug of abuse; extrasynaptic binding site; GABA Agonists - pharmacology; GABA Antagonists - pharmacology; GABAB receptor subtype; gamma-Aminobutyric Acid - pharmacokinetics; GHB receptor subtype; Globus Pallidus - cytology; Globus Pallidus - drug effects; Globus Pallidus - metabolism; Humans; Male; Models, Biological; Nucleus Accumbens - cytology; Nucleus Accumbens - drug effects; Nucleus Accumbens - metabolism; Postmortem Changes; Protein Binding - drug effects; Protein Binding - physiology; Radioligand Assay - methods; Rats; Rats, Wistar; Receptors, Cell Surface - metabolism; succinate; Succinic Acid - pharmacokinetics; synaptic binding site; Synaptosomes - drug effects; Tritium - pharmacokinetics
• ISSN: 0360-4012; 1097-4547
• DOI: 10.1002/jnr.20867

Binding of the metabolic γ‐hydroxybutyrate (GHB) precursor succinate to NCS‐382‐sensitive [3H]GHB‐labeled sites in crude synaptosomal or purified synaptic membrane fractions prepared from the human nucleus accumbens (NA), globus pallidus (GP) and rat forebrain has been shown. This site can be characterized by binding of ethyl hemisuccinate and gap‐junction blockers, including carbenoxolone hemisuccinate and β‐GRA. There was no significant binding interaction between GABAB receptor ligands (CGP 55845, (R)‐baclofen) and these [3H]GHB‐labeled sites. GHB, NCS‐382 and succinate binding profile of [3H]GHB‐labeled sites in rat forebrain, human NA or GP synaptic membranes were similar. The synaptic fraction isolated from the rat forebrain was characterized by GHB binding inhibition constants: Ki,NCS‐382 = 1.2 ± 0.2 μM, Ki,GHB = 1.6 ± 0.3 μM and Ki,SUCCINATE = 212 ± 66 μM. In crude membranes containing mainly extrasynaptic membranes, distinct GHB and GABAB receptor sites were found in the NA. By contrast, extrasynaptic GABAB receptor sites of rat forebrain and GP were GHB‐ and succinate‐sensitive, respectively. The heterogeneity of GABAB sites found in native membranes indicates GABAB receptor‐dependent differences in GHB action. Based on these findings, we suggest that succinate (and possibly drugs available as succinate salt derivatives) can mimic some of the actions of GHB. © 2006 Wiley‐Liss, Inc.