Micromolar concentrations of rimonabant directly inhibits delta opioid receptor specific ligand binding and agonist-induced G-protein activity

Ferenc Zádor, Dóra Kocsis, Anna Borsodi, Sándor Benyhe

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

What is known There is a growing number of evidence showing, that the cannabinoid receptor 1 (CB1) antagonist rimonabant has many non-cannabimimetic actions, such as affecting the opioid system. The direct effect of rimonabant on opioid receptors has been studied so far mainly on μ-opioid receptors. However recently the δ-opioid receptor (DOR) receives much more attention as before, due to its potential therapeutic applications, such as nociception or treatment for psychiatric disorders. Objectives To investigate the direct effect of rimonabant on DOR specific ligand binding and on the DOR mediated G-protein activation. Results Micromolar concentrations of rimonabant directly inhibited the DOR specific agonist binding in radioligand competition binding experiments using Chinese hamster ovary cells stably transfected with mouse DOR (CHO-mDOR). However the inhibition occurred also in the subnanomolar range during DOR specific antagonist binding in similar experimental conditions. In functional [35S]GTPγS binding assays rimonabant significantly decreased the basal receptor activity in CHO-mDOR but also in parental CHO cell membranes. During DOR agonist stimulation, micromolar concentration of rimonabant attenuated the DOR G-protein activation and the potency of the activator ligand in [35S] GTPγS binding assays performed in CHO-mDOR, in wild type and also in CB1/CB2 double knock-out mouse forebrain membranes. Yet again this inhibitory action was DOR specific, since it did not occur during other specific GPCR agonist mediated G-protein activation. Conclusion Rimonabant directly inhibited DOR function in the micromolar concentrations. The inhibitory actions indicate an antagonistic behavior towards DOR which was established by the followings: (i) rimonabant inhibited DOR antagonist binding more effectively than agonist binding, (ii) the inverse agonistic, agonistic effect of the compound can be excluded, and (iii) additionally according to previous findings the allosteric mechanism can also be foreclosed.

Original languageEnglish
Pages (from-to)14-22
Number of pages9
JournalNeurochemistry international
Volume67
Issue number1
DOIs
Publication statusPublished - Feb 1 2014

Keywords

  • Cannabinoid receptor
  • Delta opioid receptor
  • G-protein
  • Radioligand binding
  • Rimonabant
  • [ S]GTPγS binding

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Cell Biology

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