Ca2+ channel inhibition by kappa opioid receptors expressed in Xenopus oocytes

Neuroreport. 1994 Dec 20;5(18):2506-8. doi: 10.1097/00001756-199412000-00025.


Functional coupling between kappa opioid receptors and voltage-dependent Ca2+ channels was studied in the Xenopus oocyte translation system, in which specific RNAs encoding rat kappa opioid receptor, rabbit BI-2 alpha 1 subunit, and human beta subunit were co-injected. Perfusion of the oocytes with U50488H inhibited depolarization-evoked Ba2+ current (IBa) in a reversible manner, showing maximal inhibition of 25% at 1 microM (IC50 = 31 nM). The inhibitory effect of U50488H was desensitized by pre-exposure of the oocytes to U50488H and abolished by the kappa opioid antagonist nor-binaltorphimine and by overnight pretreatment with pertussis toxin. Agents affecting the activity of protein kinase A or C did not affect the U50488H-induced inhibition of IBa. These findings suggest that kappa opioid receptors inhibit the activity of neuronal Ca2+ channels via GTP-binding proteins, without the participation of protein kinase A or C.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
  • Animals
  • Barium / antagonists & inhibitors
  • Barium / physiology
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Electric Conductivity
  • GTP-Binding Proteins / physiology
  • Injections
  • Naltrexone / analogs & derivatives
  • Naltrexone / pharmacology
  • Oocytes / metabolism*
  • Pertussis Toxin
  • Pyrrolidines / pharmacology
  • RNA
  • Rats
  • Receptors, Opioid, kappa / agonists
  • Receptors, Opioid, kappa / genetics
  • Receptors, Opioid, kappa / physiology*
  • Virulence Factors, Bordetella / pharmacology
  • Xenopus laevis / metabolism*


  • Calcium Channels
  • Pyrrolidines
  • Receptors, Opioid, kappa
  • Virulence Factors, Bordetella
  • Barium
  • norbinaltorphimine
  • Naltrexone
  • RNA
  • 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
  • Pertussis Toxin
  • GTP-Binding Proteins