非洲爪蟾卵母细胞内源性及外源性ATP和GABA受体介导的膜反应比较

目的 :对非洲爪蟾卵母细胞表达的ATP和GABA激活电流进行比较。方法 :包括mRNA和cDNA的提取、卵母细胞的微量注射及双电极电压钳技术。结果 :①在表达P2X2 或P2X4 的卵母细胞上 ,外加ATP可分别诱导一被Zn2 + 增强的内向电流。②在表达鸡脑mRNA的卵母细胞上 ,可记录到GABA激活电流 ,且此电流可被bicucul line(一种GABAA 受体选择拮抗剂 )所阻断。③在表达了人视网膜 ρ1亚基cRNA的卵母细胞上 ,外加GABA可引起一不被bicuculline阻断的内向电流 ,后者可被I4AA(一种GABAC 受体特异性拮抗剂 )阻断。④在具有滤泡膜的卵母细胞上可记录到 3种形式的ATP激活电流和一外向的慢的GABA激活电流。⑤在除去滤泡膜的卵母细胞上均未记录到ATP和GABA激活电流。结论 :卵母细胞上存在内源性的嘌呤受体、GABAB 和GABAC 受体 ;且此内源性受体存在于滤泡膜上 ;P2X2 、P2X4 嘌呤受体及GABAA 和GABAC 受体均可在卵母细胞上表达 ,表达的受体所介导的激活电流与内源性受体介导的激活电流有明显区别

Comparison between the Responses Mediated by Endogenous and Expressed ATP-and GABA-Receptors in Xenopus Laevis Oocytes

Objective: To sludy the comparison between the responses mediated by endogenous and expressed ATP and GABA receptors in Xenopus laevis oocytes. Methods: The two electrode voltage clamp technique was used. Results: (1) Zn 2+ (10 -5 mol/L) could potentiate the current responses mediated by expressed P2X2 and P2X4 receptors in oocytes; (2) GABA activated current in the oocytes which were injected mRNA of chicken brain could be blocked by bicuculline (10 -5 mol/L), a selective GABA A receptor antagonist; (3) GABA activated current mediated by ρ1 subunit of human retina could not be blocked by bicuculline (10 -5 mol/L), but it could be abolished by picrotoxin (10 -5 mol/L); (4) there were three types ATP activated current in the follicular oocytes, while there was only one type GABA activated current; (5) there were no responses mediated by ATP or GABA receptors in the defollicular oocytes. Conclusion: There exist endogenous GABA A and GABAc receptors and ATP receptors in the follicular oocytes. The current responses mediated by exogenous GABA receptors and P2X2 and P2X4 receptors are different from that mediated by endogenous GABA receptors and ATP receptors.