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Eur J Pharmacol. 1994 Jul 15;268(2):187-97.

Cocaine and GBR 12783 recognize nonidentical, overlapping binding domains on the dopamine neuronal carrier.

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  • 1EP 076 du C.N.R.S., U.F.R. de M├ędecine & Pharmacie de Rouen, Saint Etienne du Rouvray, France.

Abstract

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.

PMID:
7957640
[PubMed - indexed for MEDLINE]
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