Mourre C, Chernova M N, Martin-Eauclaire M F, Bessone R, Jacquet G, Gola M, Alper S L, Crest M
Laboratoire de Neurobiologie Intégrative et Adaptative, Centre National de la Recherche Scientifique-Université de Provence, Marseille, France.
J Pharmacol Exp Ther. 1999 Dec;291(3):943-52.
The distribution of the binding sites for kaliotoxin (KTX), a blocker of voltage-dependent K(+) channels, was studied with quantitative autoradiography in adult rat brain and during postnatal brain maturation. Iodinated KTX bound specifically to tissue sections with a high affinity (K(d) = 82 pM) and a maximal binding capacity of 13.4 fmol/mg protein. The distribution of KTX binding sites within the central nervous system was heterogeneous. The highest densities were found in the neocortex, hypothalamus, dentate gyrus, bed nucleus of the stria terminalis, and parabrachial nuclei. The lowest level was observed in the white matter. From postnatal day 5 onward, KTX binding sites were detectable only in the hindbrain. The density of KTX binding sites in whole brain drastically increased after postnatal day 15 to achieve adult levels at postnatal day 60 in the whole brain. Bath application of KTX to Xenopus laevis oocytes blocked recombinant Kv1.3 and Kv1.1 channels potently and Kv1.2 channels less potently, with respective K(d) values of 0.1, 1.5, and 25 nM. KTX affinities for each of these channels expressed in mammalian cells were about 10-fold lower. A comparison of the distribution of KTX binding sites with that of Kv1 channel polypeptides, together with the pharmacology of KTX block, suggests that the principal targets for KTX in rat brain are K(+) channels containing Kv1.1 and Kv1.3 alpha-subunits.
利用定量放射自显影技术，研究了电压依赖性钾离子通道阻滞剂卡利毒素（KTX）在成年大鼠脑及出生后脑成熟过程中的结合位点分布。碘化KTX以高亲和力（K(d)=82 pM）和13.4 fmol/mg蛋白质的最大结合容量特异性结合组织切片。KTX结合位点在中枢神经系统内的分布是不均匀的。在新皮层、下丘脑、齿状回、终纹床核和臂旁核中发现最高密度。在白质中观察到最低水平。从出生后第5天起，仅在后脑中可检测到KTX结合位点。全脑中KTX结合位点的密度在出生后第15天急剧增加，在出生后第60天达到成年水平。将KTX浴应用于非洲爪蟾卵母细胞可有效阻断重组Kv1.3和Kv1.1通道，对Kv1.2通道的阻断作用较弱，其各自的K(d)值分别为0.1、1.5和25 nM。KTX对在哺乳动物细胞中表达的这些通道的亲和力约低10倍。将KTX结合位点的分布与Kv1通道多肽的分布进行比较，以及KTX阻断的药理学研究表明，大鼠脑中KTX的主要靶点是含有Kv1.1和Kv1.3α亚基的钾离子通道。
