Quamme G A
Department of Medicine, University of British Columbia, Vancouver Hospital, BC, Canada.
Biochim Biophys Acta. 1997 Feb 21;1324(1):18-26. doi: 10.1016/s0005-2736(96)00205-2.
Xenopus oocytes are frequently used for in vivo expression of DNA and RNA, especially those encoding ion channel proteins. Accordingly, it is important to understand the expression and control of endogenous conductances. Ionic currents were studied in native Xenopus oocytes with two-microelectrode voltage-clamp technique to characterize the actions of chlorpromazine (CPZ) and trifluroperazine (TFP), two widely used antipsychotic drugs. External application of CPZ or TFP markedly stimulated endogenous conductances in a dose-dependent and reversible fashion. The current-voltage (I-V) relationship was non linear and dependent on the presence of external chloride. The CPZ-activated currents were inhibited by Cl- channel blockers. Although the removal of external Ca2+ had no effect on CPZ-induced conductances, the injection of BAPTA, a Ca2+ chelator, abolished endogenous activity. Thapsigargin also inhibited channel activity suggesting that CPZ acts through intraoocyte Ca2+ release. The calmodulin inhibitors, calmidazolium and W-7, failed to mimic the action of CPZ. These data provide evidence for external or internal phenothiazine receptors which when activated by CPZ induces Ca(2+)-dependent Cl- channel activity in endogenous native oocytes.
非洲爪蟾卵母细胞常用于DNA和RNA的体内表达，尤其是那些编码离子通道蛋白的DNA和RNA。因此，了解内源性电导的表达和控制很重要。采用双微电极电压钳技术研究了非洲爪蟾天然卵母细胞中的离子电流，以表征两种广泛使用的抗精神病药物氯丙嗪（CPZ）和三氟拉嗪（TFP）的作用。CPZ或TFP的外部应用以剂量依赖性和可逆方式显著刺激内源性电导。电流-电压（I-V）关系是非线性的，并且依赖于外部氯离子的存在。CPZ激活的电流被Cl-通道阻滞剂抑制。虽然去除外部Ca2+对CPZ诱导的电导没有影响，但注射Ca2+螯合剂BAPTA可消除内源性活性。毒胡萝卜素也抑制通道活性，表明CPZ通过卵母细胞内Ca2+释放起作用。钙调蛋白抑制剂氯咪唑和W-7未能模拟CPZ的作用。这些数据为外部或内部吩噻嗪受体提供了证据，当被CPZ激活时，这些受体会在内源性天然卵母细胞中诱导Ca(2+)-依赖性Cl-通道活性。
