Rinaldi-Carmona M, Pialot F, Congy C, Redon E, Barth F, Bachy A, Brelière J C, Soubrié P, Le Fur G
Sanofi Recherche, Montpellier, France.
Life Sci. 1996;58(15):1239-47. doi: 10.1016/0024-3205(96)00085-9.
SR 141716A belongs to a new class of compounds (diarylpyrazole) that inhibits brain cannabinoid receptors (CB1) in vitro and in vivo. The present study showed that [3H]-SR 141716A binds with high affinity (Kd=0.61 +/- 0.06 nM) to a homogenous population of binding sites (Bmax=0.72 +/- 0.05 pmol/mg of protein) in rate whole brain (minus cerebellum) synaptosomes. This specific binding was displaced by known cannabinoid receptor ligands with the following rank order of potency SR 141716A > CP 55,940 > WIN 55212-2 = delta9-THC > anandamide. Apart from anandamide, all these compounds were found to interact competitively with the binding sites labeled by [3H]-SR 141716A. On the other hand, agents lacking affinity for cannabinoid receptors were unable to displace [3H]-SR 141716A from its binding sites (IC50 > 10 microM). In addition, the binding of [3H]-SR 141716A was insensitive to guanyl nucleotides. Regional rat brain distribution of CB1 cannabinoid receptors detected by [3H]-SR 141716A saturation binding and autoradiographic studies, showed that this distribution was very similar to that found for [3H]-CP 55,940. In vivo, the [3H]-SR 141716A binding was displaced by SR 141716A with ED50 values of 0.39 +/- 0.07 and 1.43 +/- 0.29 mg/kg following intraperitoneal and oral administration, respectively. Finally, the [3H]-SR 141716A binding sites remained significantly occupied for at least 12 hr following oral administration of 3 mg/kg SR 141716A. Taken together, these results suggest that SR 141716A in its tritiated form is a useful research tool for labeling brain cannabinoid receptors (CB1) in vitro and in vivo.
SR 141716A属于一类新型化合物（二芳基吡唑），在体外和体内均可抑制脑大麻素受体（CB1）。本研究表明，[3H]-SR 141716A以高亲和力（Kd = 0.61±0.06 nM）与大鼠全脑（小脑除外）突触体中一组均匀的结合位点（Bmax = 0.72±0.05 pmol/mg蛋白质）结合。这种特异性结合被已知的大麻素受体配体取代，其效力顺序如下：SR 141716A > CP �5,940 > WIN 55212-2 = Δ9-四氢大麻酚 > 花生四烯乙醇胺。除花生四烯乙醇胺外，发现所有这些化合物均与[3H]-SR 141716A标记的结合位点竞争性相互作用。另一方面，对大麻素受体缺乏亲和力的试剂无法将[3H]-SR 141716A从其结合位点上取代（IC₅₀ > 10 μM）。此外，[3H]-SR 141716A的结合对鸟苷酸不敏感。通过[3H]-SR 141716A饱和结合和放射自显影研究检测到的大鼠脑CB1大麻素受体区域分布表明，这种分布与[3H]-CP 55,940的分布非常相似。在体内，腹腔注射和口服SR 141716A后，[3H]-SR 141716A的结合分别被SR 141716A以ED₅₀值0.39±0.07和1.43±0.29 mg/kg取代。最后，口服3 mg/kg SR 141716A后，[3H]-SR 141716A结合位点至少12小时内仍被显著占据。综上所述，这些结果表明，氚化形式的SR 141716A是一种在体外和体内标记脑大麻素受体（CB1）的有用研究工具。
