Dascal N, Ifune C, Hopkins R, Snutch T P, Lübbert H, Davidson N, Simon M I, Lester H A
Brain Res. 1986 Dec;387(3):201-9. doi: 10.1016/0169-328x(86)90026-4.
Injection of poly(A)+ RNA from rat brain into Xenopus oocytes caused the appearance of Cl currents in response to serotonin (5-HT) and acetylcholine (ACh). Both neurotransmitters evoked two-component currents similar in their time course to the oocyte's endogenous cholinergic muscarinic response, which was shown in previous studies to be mediated by IP3 synthesis leading to Ca release from intracellular stores. The responses to ACh and 5-HT exhibited self- and cross-desensitization, i.e., application of either ACh or 5-HT inhibited the subsequent response to either one of the two transmitters. Intracellular injection of guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) mimicked the 5-HT and ACh response, and also completely suppressed the response to the subsequent application of either ACh or 5-HT. Treatment of the oocytes with pertussis toxin (PTX) caused a 50% attenuation of ACh and 5-HT responses. In the membranes of both control and mRNA-injected oocytes, PTX catalyzed the ADP-ribosylation of a single Mr = approximately 40,000 protein. Injection of the purified beta gamma-subunits of transducin enhanced the 5-HT response. The 5-HT and GTP-gamma-S responses were inhibited by intracellular injection of the Ca2+ chelator, EGTA, as previously shown for the ACh response. These data suggest that ACh and 5-HT receptors, synthesized in the oocytes on the template of brain mRNA, act through a common pathway that involves (a) a guanine nucleotide binding protein and (b) IP3 production leading to Ca mobilization.
将大鼠脑内的多聚腺苷酸（poly(A)+）RNA注射到非洲爪蟾卵母细胞中，会使卵母细胞在受到血清素（5-羟色胺，5-HT）和乙酰胆碱（ACh）刺激时出现氯离子电流。这两种神经递质均诱发了双成分电流，其时间进程与卵母细胞内源性胆碱能毒蕈碱反应相似，先前的研究表明该反应由肌醇三磷酸（IP3）合成介导，导致细胞内储存的钙离子释放。对ACh和5-HT的反应表现出自身脱敏和交叉脱敏，即施加ACh或5-HT会抑制随后对这两种递质中任何一种的反应。细胞内注射鸟苷5'-O-(3-硫代三磷酸)（GTP-γ-S）模拟了5-HT和ACh的反应，并且也完全抑制了随后施加ACh或5-HT时的反应。用百日咳毒素（PTX）处理卵母细胞会使ACh和5-HT反应减弱50%。在对照卵母细胞和注射了mRNA的卵母细胞膜中，PTX均催化了一种分子量约为40,000的单一蛋白质的ADP核糖基化。注射转导素的纯化βγ亚基增强了5-HT反应。如先前对ACh反应所显示的那样，细胞内注射钙离子螯合剂乙二醇双四乙酸（EGTA）可抑制5-HT和GTP-γ-S反应。这些数据表明，在脑mRNA模板上于卵母细胞中合成的ACh和5-HT受体，通过一条共同途径发挥作用，该途径涉及（a）一种鸟嘌呤核苷酸结合蛋白和（b）导致钙离子动员的IP3产生。
