GABAB receptor activation inhibits Ca2(+)-activated 86Rb-efflux in cultured spinal cord neurons via G-protein mechanism.
86Rb-efflux assay in primary cultured spinal cord neurons was developed to study the effect of GABAB receptor activation on Ca2(+)-activated K(+)-channels. Depolarization of the cultured cells with 100 mM KCl increased the 86Rb-efflux significantly. This efflux was blocked partly by quinine sulfate, tetraethylammonium, and La3+, indicating the involvement of Ca2(+)-activated K(+)-channels. Both (-)-baclofen and GABA inhibited the Ca2(+)-activated 86Rb-efflux. This inhibition seems to be mediated through GABAB receptor activation as it was blocked by GABAB antagonist phaclofen, but not by bicuculline. Moreover, pertussis toxin blocked the ability of (-)-baclofen to inhibit the Ca2(+)-activated 86Rb-efflux, showing that GABAB receptor activation involves G-protein mechanism. Further, forskolin and phorbol ester also attenuated the action of (-)-baclofen. This suggests that the GABAB receptors are negatively coupled to adenylate cyclase. These results show that the action of GABAB receptors involved G-proteins and adenylate cyclase. This assay may provide an ideal model to study GABAB receptor pharmacology.
Kamatchi
G L
GL
Department of Pharmacology, University of Texas Health Science Center, San Antonio 78284-7764.
Ticku
M K
MK
D037361:Adenylate Cyclase Toxin; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D037342:Pertussis Toxin; D011963:Receptors, GABA-A / Q000502:physiology*; D012414:Rubidium Radioisotopes / Q000493:pharmacokinetics*; D013116:Spinal Cord / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D011963:Receptors, GABA-A; D012414:Rubidium Radioisotopes; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D001418:Baclofen; D002118:Calcium