Metabotropic responses to acetylcholine and serotonin of Xenopus oocytes injected with rat brain mRNA are transduced by different G-protein subtypes

Abstract

To assign the GTP-binding protein (G-protein) subtype involved in the signal transduction from exogenous receptors to phospholipase C in the Xenopus oocyte translation system, antisense DNA complementary to rat G-protein α-subunit MRNA was designed and injected together with rat brain poly(A) + RNA. Current response of mRNA-injected oocytes to acetylcholine (ACh) was suppressed dose-dependently by a co-injection of G ilα-antisense DNA, but response of the same oocytes to serotonin (5-HT) was not inhibited. In the oocytes co-injected with G oα-antisense DNA, the 5-HT response was more effectively suppressed than the ACh response. These results suggest that G oα but not G ilα intermediates brain 5-HT IC receptor function, and in contrast, muscarinic receptors derived from rat brain utilize G ilα rather than G oα to activate phospholipase C.