title: Characterization of [(3) H]LS-3-134, a novel arylamide phenylpiperazine D3 dopamine receptor selective radioligand.
abstract: LS-3-134 is a substituted N-phenylpiperazine derivative that has been reported to exhibit: (i) high-affinity binding (Ki value 0.2 nM) at human D3 dopamine receptors, (ii) > 100-fold D3 versus D2 dopamine receptor subtype binding selectivity, and (iii) low-affinity binding (Ki  > 5000 nM) at sigma 1 and sigma 2 receptors. Based upon a forskolin-dependent activation of the adenylyl cyclase inhibition assay, LS-3-134 is a weak partial agonist at both D2 and D3 dopamine receptor subtypes (29% and 35% of full agonist activity, respectively). In this study, [(3) H]-labeled LS-3-134 was prepared and evaluated to further characterize its use as a D3 dopamine receptor selective radioligand. Kinetic and equilibrium radioligand binding studies were performed. This radioligand rapidly reaches equilibrium (10-15 min at 37°C) and binds with high affinity to both human (Kd  = 0.06 ± 0.01 nM) and rat (Kd  = 0.2 ± 0.02 nM) D3 receptors expressed in HEK293 cells. Direct and competitive radioligand binding studies using rat caudate and nucleus accumbens tissue indicate that [(3) H]LS-3-134 selectively binds a homogeneous population of binding sites with a dopamine D3 receptor pharmacological profile. Based upon these studies, we propose that [(3) H]LS-3-134 represents a novel D3 dopamine receptor selective radioligand that can be used for studying the expression and regulation of the D3 dopamine receptor subtype.
authors.affiliation: Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, Texas, USA.
authors.forename: Claudia
authors.initials: C
authors.lastname: Rangel-Barajas
authors.forename: Maninder
authors.initials: M
authors.lastname: Malik
authors.forename: Michelle
authors.initials: M
authors.lastname: Taylor
authors.forename: Kim A
authors.initials: KA
authors.lastname: Neve
authors.forename: Robert H
authors.initials: RH
authors.lastname: Mach
authors.forename: Robert R
authors.initials: RR
authors.lastname: Luedtke
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D001667:Binding, Competitive / Q000187:drug effects; D003342:Corpus Striatum / Q000187:drug effects; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D008024:Ligands; D009714:Nucleus Accumbens / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects*; D011869:Radioligand Assay; D051381:Rats; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D050637:Receptors, Dopamine D3 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D014162:Transfection; D014316:Tritium / Q000493:pharmacokinetics
chemical_list: D001549:Benzamides; D018492:Dopamine Antagonists; D008024:Ligands; C000594177:N-((4-(4-(2-(2-fluoroethoxy)phenyl)-1-piperazinyl)butyl)-4-(3-thienyl)benzamide; D010879:Piperazines; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D014316:Tritium; D012965:Sodium Chloride; C031503:phenylpiperazine
keywords: D2-like dopamine receptors; D3 dopamine receptors; dopamine receptors; radioligand binding