Shapiro M S, Wollmuth L P, Hille B
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
Neuron. 1994 Jun;12(6):1319-29. doi: 10.1016/0896-6273(94)90447-2.
We characterized inhibition of N-type Ca2+ and M current K+ channels in rat superior cervical ganglion neurons by angiotensin II (angioII) using the patch clamp. Of 120 neurons, 97 showed inhibition of ICa (mean 32%), which was slow in onset and very slow to reverse under whole-cell recording conditions. This inhibition was blocked by the AT1 receptor antagonist losartan, attenuated by inclusion of 2 mM GDP-beta-S in the pipette, mostly pertussis toxin insensitive, half-sensitive to N-ethylmaleimide, and wholly voltage independent. With 20 mM instead of 0.1 mM BAPTA in the pipette, the inhibition was strongly attenuated; however, we detected no angioII-induced [Ca2+]i signal using the fluorescent indicator indo-1. IBa from cell-attached patches was reduced by bath-applied angioII (mean 33%), suggesting use of a diffusible cytoplasmic messenger. M currents were inhibited by angioII in 8 of 11 neurons (mean 50%) cultured overnight. Hence, a second agonist, angioII, may share the slow, second messenger-utilizing, pertussis toxin-insensitive signaling pathway used by muscarinic agonists.
我们使用膜片钳技术研究了血管紧张素II（angioII）对大鼠颈上神经节神经元中N型Ca2+和M电流K+通道的抑制作用。在120个神经元中，97个表现出ICa抑制（平均32%），在全细胞记录条件下，其起效缓慢且恢复极慢。这种抑制作用被AT1受体拮抗剂氯沙坦阻断，通过在微管中加入2 mM GDP-β-S而减弱，大多对百日咳毒素不敏感，对N-乙基马来酰亚胺半敏感，且完全不依赖电压。当微管中使用20 mM而非0.1 mM BAPTA时，抑制作用显著减弱；然而，我们使用荧光指示剂indo-1未检测到angioII诱导的[Ca2+]i信号。通过浴加angioII可使细胞贴附膜片的IBa降低（平均33%），提示使用了一种可扩散的细胞质信使。在培养过夜的11个神经元中，有8个的M电流被angioII抑制（平均50%）。因此，第二种激动剂angioII可能与毒蕈碱激动剂共享缓慢的、利用第二信使的、对百日咳毒素不敏感的信号通路。
