Binding Sites for [3H]Cocaine in Mouse Striatum and Cerebral Cortex Have Different Dissociation Kinetics

Abstract: [ 3 H]Cocaine dissociates from its binding sites in the mouse cerebral cortex with a half‐time of 25 s. The dissociation kinetics in the striatum is consonant with the presence of two populations of sites with dissociation half times of 2 s and 27 s, comprising 88% and 12%, respectively, of the total binding sites. On the basis of previous pharmacological characterization of [ 3 H]cocaine binding, we propose that the slowly dissociating component represents the sites associated with 5‐hydroxytryptamine (serotonin) uptake, and the rapidly dissociating component the 3,4 dihydroxyphenylethylamine (dopamine)‐related sites. Evidence is presented that the extremely high dissociation rates do not preclude the measurement of [ 3 H]cocaine binding by rapid filtration. The dissociation of [ 3 H]cocaine from cerebrocortical membranes is slowed to a small but statistically significant extent by serotonin.