Saadouni S, Refahi-Lyamani F, Costentin J, Bonnet J J
EP 076 du C.N.R.S., U.F.R. de Médecine & Pharmacie de Rouen, Saint Etienne du Rouvray, France.
Eur J Pharmacol. 1994 Jul 15;268(2):187-97. doi: 10.1016/0922-4106(94)90188-0.
In incubation medium containing Na+ as the only cation, the specific binding of [3H]cocaine to a membrane preparation obtained from rat striatum reached a maximal level for 10 mM Na+, whereas higher concentrations decreased its affinity. The specific binding of [3H]cocaine was inhibited monophasically by GBR 12783, mazindol, nomifensine and substrates of the transporter; in saturation experiments, GBR 12783 competitively blocked the [3H]cocaine specific binding and vice versa. Treatment of the striatal membranes with N-ethylmaleimide resulted in a concentration-dependent reduction of the specific binding of [3H]GBR 12783 (1-[2-(diphenylmethoxy)ethyl]4-(3-phenyl-2-[1-3H]propenyl)-piperaz ine) which was significantly more marked than that of the specific binding of [3H]cocaine, the nonspecific binding of [3H]cocaine being measured with either cocaine or dopamine. Addition of substrates or pure uptake inhibitors to the treatment medium afforded protection against the N-ethylmaleimide-induced reduction in both bindings. In particular, cocaine offered protection for [3H]GBR 12783 binding and vice versa. All results are consistent with a model in which pure uptake blockers and substrates recognize nonidentical but overlapping binding domains on the neuronal carrier of dopamine.
在仅以Na⁺作为唯一阳离子的孵育培养基中，[³H]可卡因与从大鼠纹状体获得的膜制剂的特异性结合在Na⁺浓度为10 mM时达到最高水平，而更高的浓度会降低其亲和力。[³H]可卡因的特异性结合受到GBR 12783、吗吲哚、诺米芬辛和转运体底物的单相抑制；在饱和实验中，GBR 12783竞争性地阻断[³H]可卡因的特异性结合，反之亦然。用N-乙基马来酰亚胺处理纹状体膜导致[³H]GBR 12783（1-[2-(二苯基甲氧基)乙基]-4-(3-苯基-2-[1-³H]丙烯基)-哌嗪）的特异性结合呈浓度依赖性降低，这比[³H]可卡因的特异性结合降低更为显著，[³H]可卡因的非特异性结合用可卡因或多巴胺进行测定。向处理培养基中添加底物或纯摄取抑制剂可防止N-乙基马来酰亚胺诱导的两种结合的降低。特别是，可卡因对[³H]GBR 12783的结合具有保护作用，反之亦然。所有结果都与一个模型一致，在该模型中，纯摄取阻断剂和底物识别多巴胺神经元载体上不相同但重叠的结合域。
