Strøbaek D, Jørgensen T D, Christophersen P, Ahring P K, Olesen S P
NeuroSearch A/S, 93 Pederstrupvej, DK-2750 Ballerup, Denmark.
Br J Pharmacol. 2000 Mar;129(5):991-9. doi: 10.1038/sj.bjp.0703120.
Three genes encode the small-conductance Ca(2+)-activated K(+) channels (SK channels). We have stably expressed hSK1 and rSK2 in HEK 293 cells and addressed the pharmacology of these subtypes using whole-cell patch clamp recordings. The bee venom peptide apamin blocked hSK1 as well as rSK2 with IC(50) values of 3.3 nM and 83 pM, respectively. The pharmacological separation between the subtypes was even more prominent when applying the scorpion peptide blocker scyllatoxin, which blocked hSK1 with an IC(50) value of 80 nM and rSK2 at 287 pM. The potent small molecule blockers showed little differentiation between the channel subtypes. The bis-quinolinium cyclophane UCL 1684 blocked hSK1 with an IC(50) value of 762 pM and rSK2 at 364 pM. The antiseptic compound dequalinium chloride blocked hSK1 and rSK2 with IC(50) values of 444 nM and 162 nM, respectively. The nicotinic acetylcholine receptor antagonist d-tubocurarine was found to block hSK1 and rSK2 with IC(50) values of 27 microM and 17 microM when measured at +80 mV. The inhibition by d-tubocurarine was voltage-dependent with increasing affinities at more hyperpolarized potentials. The GABA(A) receptor antagonist bicuculline methiodide also blocked hSK1 and rSK2 in a voltage-dependent manner with IC(50) values of 15 and 25 microM when measured at +80 mV. In conclusion, the pharmacological separation between SK channel subtypes expressed in mammalian cells is too small to support the notion that the apamin-insensitive afterhyperpolarization of neurones is mediated by hSK1.
有三个基因编码小电导钙激活钾通道（SK通道）。我们已在HEK 293细胞中稳定表达了hSK1和rSK2，并使用全细胞膜片钳记录研究了这些亚型的药理学特性。蜂毒肽蜂毒明肽分别以3.3 nM和83 pM的IC50值阻断hSK1和rSK2。当应用蝎毒肽阻断剂海葵毒素时，亚型之间的药理学差异更为显著，其以80 nM的IC50值阻断hSK1，以287 pM的IC50值阻断rSK2。强效小分子阻断剂对通道亚型的区分作用很小。双喹啉环番UCL 1684以762 pM的IC50值阻断hSK1，以364 pM的IC50值阻断rSK2。抗菌化合物氯化喹啉铵分别以444 nM和162 nM的IC50值阻断hSK1和rSK2。烟碱型乙酰胆碱受体拮抗剂d -筒箭毒碱在+80 mV测量时，以27 μM和17 μM的IC50值阻断hSK1和rSK2。d -筒箭毒碱的抑制作用具有电压依赖性，在更超极化电位下亲和力增加。GABA(A)受体拮抗剂甲磺酸荷包牡丹碱也以电压依赖性方式阻断hSK1和rSK2，在+80 mV测量时IC50值分别为15和25 μM。总之，在哺乳动物细胞中表达的SK通道亚型之间的药理学差异太小，无法支持神经元中蜂毒明肽不敏感的后超极化由hSK1介导这一观点。
