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

Abstract: In rat striatal membranes, NaCl induced a twofold increase in the maximal number of cocaine binding sites but did not alter the affinity of these sites for cocaine. This effect was concentration‐dependent, specific to sodium ions, 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 sodium‐induced increase in binding and produced a decrease in the B max of binding measured in the presence of NaCl. The capacity of a series of drugs to interfere with Na + –dependent cocaine binding correlated well with their capacity to inhibit [ 3 H]dopamine uptake into rat striatal synaptosomes. The present results suggest that Na + –dependent cocaine binding sites are localized presynaptically on dopaminergic nerve terminals in corpus striatum, and may be related to dopamine uptake sites.