Palma A L, Wang H H
Department of Biology, University of California, Santa Cruz 95064.
J Membr Biol. 1991 Jun;122(2):143-53. doi: 10.1007/BF01872637.
Phencyclidine is a highly specific noncompetitive inhibitor of the nicotinic acetylcholine receptor. In a novel approach to study this site, a spin-labeled analogue of phencyclidine, 4-phenyl-4-(1-piperidinyl)-2,2,6,6-tetramethylpiperidinoxyl (PPT) was synthesized. The binding of PPT inhibits 86Rb flux (IC50 = 6.6 microM), and [3H]phencyclidine binding to both resting and desensitized acetylcholine receptor (IC50 = 17 microM and 0.22 microM, respectively). From an indirect Hill plot of the inhibition of [3H]phencyclidine binding by PPT, a Hill coefficient of approximately one was obtained in the presence of carbamylcholine and 0.8 in alpha-bungarotoxin-treated preparations. Taken together, these results indicate that PPT mimics phencyclidine in its ability to bind to the noncompetitive inhibitor site and is functionally active in blocking ion flux across the acetylcholine receptor channel. Analysis of the electron spin resonance signal of the bound PPT suggests that the environment surrounding the probe within the ion channel is hydrophobic, with a hydrophobicity parameter of 1.09. A dielectric constant for the binding site was estimated to be in the range of 2-3 units.
苯环己哌啶是烟碱型乙酰胆碱受体的一种高度特异性非竞争性抑制剂。在一种研究该位点的新方法中，合成了苯环己哌啶的自旋标记类似物4-苯基-4-(1-哌啶基)-2,2,6,6-四甲基哌啶氮氧自由基(PPT)。PPT的结合抑制了86Rb通量(IC50 = 6.6微摩尔)，以及[3H]苯环己哌啶与静息和脱敏乙酰胆碱受体的结合(IC50分别为17微摩尔和0.22微摩尔)。从PPT对[3H]苯环己哌啶结合抑制作用的间接希尔图来看，在氨甲酰胆碱存在的情况下，希尔系数约为1，在α-银环蛇毒素处理的制剂中为0.8。综上所述，这些结果表明，PPT在与非竞争性抑制剂位点结合的能力上模拟了苯环己哌啶，并且在阻断离子通过乙酰胆碱受体通道的通量方面具有功能活性。对结合的PPT的电子自旋共振信号分析表明，离子通道内探针周围的环境是疏水的，疏水参数为1.09。结合位点的介电常数估计在2 - 3个单位范围内。
