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 Gilα‐antisense DNA, but response of the same oocytes to serotonin (5‐HT) was not inhibited. In the oocytes co‐injected with Goα‐antisense DNA, the 5‐HT response was more effectively suppressed than the ACh response. These results suggest that Goα but not Gilα intermediates brain 5‐HTIC receptor function, and in contrast, muscarinic receptors derived from rat brain utilize Gilα rather than Goα to activate phospholipase C.