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Keywords:

  • Dopamine transporter;
  • Cocaine receptors;
  • GBR 12909;
  • Dopamine distribution;
  • Uptake inhibitors

Abstract

The cocaine analog [3H]CFT ([3H]WIN 35,428) was used to map and characterize cocaine recognition sites in the squirrel monkey brain by quantitative autoradiography. Coronal tissue sections were incubated with 5 nM [3H]CFT to measure total binding or with [3H]CFT in the presence of 30 μM (−)-cocaine to measure nonspecific binding. High densities of [3H]CFT binding sites were present in dopamine-rich brain regions, including the caudate nucleus, putamen, nucleus accumbens, and olfactory tubercle. In each of these regions specific binding was greater than 90% of total binding. Several additional brain regions exhibited intermediate densities of [3H]CFT binding, including the substantia nigra, the zona incerta, the amygdala, and the hypothalamus. Low, though measurable levels of binding were observed in the bed nucleus of the stria terminalis, the ventral tegmental area, the medial preoptic area, the pineal, the hippocampus, and thalamic central nuclei. Near-background levels of binding were found in white matter, cortical regions, globus pallidus, and cerebellum. The pharmacological specificity of [3H]CFT binding in various brain regions was determined in competition studies using [3H]CFT and a range of concentrations of selected monoamine uptake inhibitors. In all brain regions examined, stereoselective inhibition of [3H]CFT binding was observed for the (−) over the (+) isomer of cocaine. For other drugs tested, competition experiments indicated a rank order of potency of GBR 12909 ≥ CFT ≥ bupropion, suggestive of binding of [3H]CFT to elements of the dopamine transport system. The results demonstrate that although densities of [3H]CFT binding sites are highest in the caudate nucleus, putamen, and nucleus accumbens/olfactory tubercle, significant levels of binding can be detected in other brain regions that may contribute to the behavioral and physiological effects of cocaine.