Sodium‐Sensitive Cocaine Binding to Rat Striatal Membrane: Possible Relationship to Dopamine Uptake Sites

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Abstract
In rat striatal membranes, NaCl induced a 2-fold increase in the maximal number of cocaine binding sites [Bmax] but did not alter the affinity of these sites for cocaine. This effect was concentration-dependent, specific to Na+, and occurred in membranes prepared from corpus striatum but not from other brain regions. Lesions with 6-hydroxydopamine but not with kainic acid eliminated the Na-induced increase in binding and produced a decrease in the Bmax of binding measured in the presence of NaCl. The capacity of a series of drugs [amphetamine, demethylimipramine buproprion, nomifensine, fluoxetine and nortriptyline] to interfere with Na+-dependent cocaine binding correlated well with their capacity to inhibit [3H]dopamine uptake into rat striatal synaptosomes. Apparently, Na+-dependent cocaine binding sites are localized presynaptically on dopaminergic nerve terminals in corpus striatum and may be related to dopamine uptake sites.