Related Experiment Video
Updated: Aug 19, 2026

A Fluorescent Screening Assay for Identifying Modulators of GIRK Channels
Published on: April 24, 2012
The dual modulation of GIRK1/GIRK2 channels by opioid receptor ligands
1Faculty of Pharmaceutical Sciences, Laboratory of Toxicology, Van Evenstraat 4, 3000, Leuven, Belgium.
Abstract:
It is well known that activation of the cloned kappa-opioid receptor by nanomolar concentrations of U50488H (trans-(+/-)-3, 4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl-benzeneacetamide) , a selective kappa-opioid receptor agonist, leads to the opening of GIRK1 channels. In this study, we demonstrate that the cloned kappa-opioid receptor functionally couples to GIRK1/GIRK2 channels (G-protein-coupled inwardly rectifying K(+) channels), mimicking the probable heteromultimeric state of neuronal GIRK channels. We also show that micromolar concentrations of U50488H reduce GIRK1/GIRK2 current through direct GIRK1/GIRK2 channel block in a voltage-independent manner (IC(50)=70.28+/-3.68 microM). Similarly, it was found that propoxyphene, methadone, and naloxone also can block GIRK1/GIRK2 current. In contrast, elevated concentrations of morphine (up to 1 mM) did not cause channel block. The related inwardly rectifying K(+) channel, IRK1, was not affected by elevated concentrations of these drugs. We conclude that nanomolar concentrations of opioid receptor ligands activate GIRK1/GIRK2 channels through a receptor-mediated pathway, while micromolar concentrations of some opioid receptor ligands inhibit GIRK1/GIRK2 channels by direct channel block.
Related Concept Videos
G-Protein Gated Ion Channels
Sensory organs,...
GPCRs Regulate Adenylyl Cylase Activity
Two...
Ligand-Gated Ion Channel Receptor: Gating Mechanism
The Two-State Receptor Model
The binding affinity of a drug determines its interaction with one...
Opioid Receptors: Overview
Analgesia and Pain Management

