Suzdak P D, Foged C, Andersen K E
Department of Receptor Neurochemistry, Novo Nordisk A/S, Pharmaceuticals Research, Måløv, Denmark.
Brain Res. 1994 Jun 6;647(2):231-41. doi: 10.1016/0006-8993(94)91322-6.
The kinetic properties and regional distribution of [3H]tiagabine ([3,4-3H]N-[4,4-bis(3-methyl-2-thienyl)but-3-en-1-yl]nipecotic acid) binding to the central GABA uptake carrier was examined in the rat brain using quantitative receptor autoradiography. In slide mounted sections of frontal cortex, the binding of [3H]tiagabine was saturable, reversible and sodium dependent. The kinetics of association and dissociation of [3H]tiagabine were monophasic, and Scatchard transformation of saturation isotherms resulted in a linear plot with a Kd = 58 +/- 7 nM and a Bmax = 58.9 +/- 0.9 pmol/mg protein. The autoradiographic distribution of [3H]tiagabine binding sites in rat brain was heterogeneously distributed. The highest density of [3H]tiagabine binding sites was present in the cerebral cortex, mammillary body, globus pallidus, substantia nigra pars reticulata, hippocampus, dorsal raphé, superior colliculus (outer layer), and cerebellum. The distribution of GABA uptake sites, as measured by [3H]tiagabine binding, in the rat brain is highly consistent with the organization of GABAergic terminals and cell bodies. The present investigation characterized the use of [3H]tiagabine as a novel radioligand for the GABA uptake carrier using quantitative receptor autoradiography. [3H]Tiagabine has several major advantages over the currently utilized radioligand for the GABA uptake carrier [3H]nipecotic acid, in that [3H]tiagabine has an increased affinity, specificity, and is not transported intracellularly via the GABA uptake carrier. These data suggest that [3H]tiagabine represents a novel and highly useful ligand for studying the GABA uptake carrier using quantitative receptor autoradiography.
利用定量受体放射自显影技术，在大鼠脑中检测了[3H]噻加宾（[3,4-3H]N-[4,4-双(3-甲基-2-噻吩基)丁-3-烯-1-基]哌啶酸）与中枢γ-氨基丁酸（GABA）摄取载体结合的动力学特性及区域分布。在额叶皮质的载玻片切片中，[3H]噻加宾的结合具有饱和性、可逆性且依赖于钠离子。[3H]噻加宾的结合和解离动力学呈单相性，饱和等温线的Scatchard转换得到一条线性曲线，解离常数（Kd） = 58 ± 7 nM，最大结合容量（Bmax） = 58.9 ± 0.9 pmol/mg蛋白质。[3H]噻加宾结合位点在大鼠脑中的放射自显影分布是不均匀的。[3H]噻加宾结合位点密度最高的区域存在于大脑皮质、乳头体、苍白球、黑质网状部、海马、背侧中缝核、上丘（外层）和小脑。通过[3H]噻加宾结合测定的大鼠脑中GABA摄取位点的分布与GABA能终末和细胞体的组织结构高度一致。本研究利用定量受体放射自显影技术，将[3H]噻加宾作为一种新型放射性配体用于GABA摄取载体的研究。与目前用于GABA摄取载体的放射性配体[3H]哌啶酸相比，[3H]噻加宾具有几个主要优点，即[3H]噻加宾具有更高的亲和力、特异性，且不会通过GABA摄取载体转运到细胞内。这些数据表明，[3H]噻加宾是一种用于利用定量受体放射自显影技术研究GABA摄取载体的新型且非常有用的配体。
