[Studies on the transmembrane signalling mechanism of the brain using Xenopus oocytes]

Xenopus oocytes have been used as an efficient and convenient expression system of messenger ribonucleic acid (mRNA) exogeneously injected. The transmembrane signalling mechanism of acetylcholine (ACh)- and serotonin (5-HT)-evoked inward current and properties of voltage-sensitive Ca channel (VSCC) current were studied using the oocytes injected with rat brain mRNA. M1 ACh or 5-HT1C receptor stimulation causes Cl- current via G-protein activation, inositol phosphate formation, an increase of free Ca2+ and finally gating of Cl channels via Ca2(+)-calmodulin. Protein kinase C seems to modulate the responses negatively. In addition, N type VSCC was also expressed and regulated by both protein kinases A and C. Limitations of the expression system as well as advantages are discussed.