Ca2+ channel inhibition by kappa opioid receptors expressed in Xenopus oocytes.
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.
Kaneko
S
S
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kyoto University, Japan.
Fukuda
K
K
Yada
N
N
Akaike
A
A
Mori
Y
Y
Satoh
M
M
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000818:Animals; D001464:Barium / Q000037:antagonists & inhibitors / Q000502:physiology; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D004553:Electric Conductivity; D019204:GTP-Binding Proteins / Q000502:physiology; D007267:Injections; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism*; D037342:Pertussis Toxin; D011759:Pyrrolidines / Q000494:pharmacology; D012313:RNA; D051381:Rats; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000235:genetics / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D014982:Xenopus laevis / Q000378:metabolism*
D015220:Calcium Channels; D011759:Pyrrolidines; D017473:Receptors, Opioid, kappa; D010566:Virulence Factors, Bordetella; D001464:Barium; C051844:norbinaltorphimine; D009271:Naltrexone; D012313:RNA; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins