Akunne H C, de Costa B R, Jacobson A E, Rice K C, Rothman R B
Laboratory of Clinical Psychopharmacology, NIDA Addiction Research Center, Baltimore, MD 21224.
Neurochem Res. 1992 Dec;17(12):1275-83. doi: 10.1007/BF00968412.
We studied the characteristics of [3H]cocaine binding to membranes prepared from whole guinea pig brain. Cocaine binding was specific and saturable. A one-site binding model fit the data adequately: the Kd value of [3H]cocaine was 44 nM with a Bmax value of 280 fmol/mg protein. The rank order of potency for the [3H]cocaine binding site was paroxetine > clomipramine > (-)-cocaine > fluoxetine > mazindol > desipramine > GBR12909 > phencyclidine > benztropine > GBR12935 > (+)-cocaine. The IC50 values of these drugs for inhibition of [3H]cocaine binding were highly correlated with their IC50 values for inhibition of [3H]5-HT uptake into synaptosomes prepared from whole guinea pig brain. High affinity 5-HT uptake inhibitors produced dose-dependent wash-resistant (pseudoirreversible) inhibition of [3H]cocaine binding. The wash-resistant inhibition produced by paroxetine was due to an increase in the Kd of [3H]cocaine binding sites, and was accompanied by an increase in the dissociation rate, consistent with an allosteric mechanism. These studies suggest that, using membranes prepared from whole guinea pig brain, [3H]cocaine labels a binding site associated with serotonin transporter and that paroxetine and cocaine bind to different sites on the serotonin transporter.
我们研究了[3H]可卡因与从豚鼠全脑制备的膜的结合特性。可卡因结合具有特异性且可饱和。单位点结合模型能很好地拟合数据：[3H]可卡因的Kd值为44 nM，Bmax值为280 fmol/mg蛋白质。[3H]可卡因结合位点的效力排序为：帕罗西汀＞氯米帕明＞（-）-可卡因＞氟西汀＞马吲哚＞地昔帕明＞GBR12909＞苯环己哌啶＞苯海索＞GBR12935＞（+）-可卡因。这些药物抑制[3H]可卡因结合的IC50值与其抑制从豚鼠全脑制备的突触体摄取[3H]5-羟色胺（5-HT）的IC50值高度相关。高亲和力5-HT摄取抑制剂对[3H]可卡因结合产生剂量依赖性的耐洗脱（假不可逆）抑制。帕罗西汀产生的耐洗脱抑制是由于[3H]可卡因结合位点的Kd增加，并伴随着解离速率增加，这与变构机制一致。这些研究表明，使用从豚鼠全脑制备的膜，[3H]可卡因标记了一个与5-羟色胺转运体相关的结合位点，并且帕罗西汀和可卡因结合到5-羟色胺转运体的不同位点上。
