Hechler V, Schmitt M, Bourguignon J J, Maitre M
Centre de Neurochimie du CNRS, Strasbourg, France.
Neurosci Lett. 1990 Mar 2;110(1-2):204-9. doi: 10.1016/0304-3940(90)90812-n.
Trans-gamma-hydroxycrotonate (THCA), a compound naturally present in rat brain, possesses high-affinity binding sites with a heterogeneous distribution which are superimposable with those for gamma-hydroxybutyrate (GHB). Binding studies of THCA on rat brain membranes revealed two binding components, one of high affinity (Kd1, 7 nM, Bmax1 42 fmol/mg protein) and the other of low affinity (Kd2, 2 microM, Bmax2 13 pmol/mg protein). Displacement curves of [3H]THCA by THCA and GHB or of [3H]GHB by THCA are in favour of the existence of a specific high affinity site for THCA. Quantitative autoradiography with image analysis of [3H]THCA binding in rat brain slices indicated that [3H]THCA high affinity binding was displaced at a lower potency by GHB. THCA showed also some selectivity in displacing [3H]GHB from its high affinity binding site (Kd = 95 nM). This mutual overlap favours a subpopulation of GHB receptors, which have THCA as a natural ligand, showing partial agonistic properties compared to GHB. The functional significance of this result remains unknown.
反式-γ-羟基巴豆酸酯（THCA）是一种天然存在于大鼠脑中的化合物，具有分布不均一的高亲和力结合位点，这些位点与γ-羟基丁酸（GHB）的结合位点重叠。THCA与大鼠脑膜的结合研究揭示了两个结合成分，一个具有高亲和力（Kd1，7 nM，Bmax1 42 fmol/mg蛋白质），另一个具有低亲和力（Kd2，2 μM，Bmax2 13 pmol/mg蛋白质）。THCA对[3H]THCA的置换曲线以及THCA对[3H]GHB的置换曲线均支持存在THCA的特异性高亲和力位点。对大鼠脑切片中[3H]THCA结合进行图像分析的定量放射自显影表明，GHB以较低效力置换[3H]THCA的高亲和力结合。THCA在从其高亲和力结合位点（Kd = 95 nM）置换[3H]GHB方面也表现出一定的选择性。这种相互重叠有利于存在一个GHB受体亚群，该亚群以THCA作为天然配体，与GHB相比具有部分激动特性。该结果的功能意义尚不清楚。
