Functional coupling of the nociceptin/orphanin FQ receptor with the G-protein-activated K+ (GIRK) channel.
Nociceptin/orphanin FQ is a heptadecapeptide which was recently isolated from brains. It induces hyperalgesia, in contrast to the analgesic effects of opioid ligands, although it and its receptor structurally resemble opioid peptides and opioid receptors, respectively. To investigate the molecular mechanism underlying nociceptin/orphanin FQ actions, we performed Xenopus oocyte expression assays, in situ hybridization histochemistry and electrophysiological analyses of neurons. We found that the nociceptin/orphanin FQ receptor is functionally coupled with the G-protein-activated K+ (GIRK) channel in Xenopus oocytes, and that the receptor mRNA and GIRK1 mRNA co-exist in various neurons, including hippocampal pyramidal cells. Furthermore, we found that nociceptin/orphanin FQ induces hyperpolarizing currents via inward-rectifier K+ channels in hippocampal pyramidal cells, suggesting that the nociceptin/orphanin FQ receptor couples with the GIRK channel in this region. We conclude that the nociceptin/orphanin FQ receptor couples with the GIRK channel in various neurons, including hippocampal pyramidal cells, thereby modulating neuronal excitability.
Ikeda
K
K
Laboratory for Cellular Information Processing, Institute of Physical and Chemical Research (RIKEN), Saitama, Japan. ikedak@postman.riken.go.jp
Kobayashi
K
K
Kobayashi
T
T
Ichikawa
T
T
Kumanishi
T
T
Kishida
H
H
Yano
R
R
Manabe
T
T
D000818:Animals; D017931:DNA Primers; D004723:Endorphins / Q000494:pharmacology*; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000502:physiology; D009865:Oocytes / Q000502:physiology; D018847:Opioid Peptides / Q000378:metabolism / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000096:biosynthesis / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D017966:Pyramidal Cells / Q000502:physiology; D051381:Rats; D011957:Receptors, Opioid / Q000096:biosynthesis / Q000502:physiology*; D011994:Recombinant Proteins / Q000096:biosynthesis; D014982:Xenopus laevis; D000094942:Nociceptin Receptor; D000097629:Nociceptin
D017931:DNA Primers; D004723:Endorphins; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D018847:Opioid Peptides; D011188:Potassium; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011957:Receptors, Opioid; D011994:Recombinant Proteins; D000094942:Nociceptin Receptor; D000097629:Nociceptin