SOLUBILIZATION AND CHARACTERIZATION OF [H-3] IMIPRAMINE AND [H-3] PAROXETINE BINDING-SITES FROM CALF STRIATUM

The serotonin (5-HT) transporter from calf striatum cerebral membranes was solubilized with digitonin and characterized by gel exclusion chr omatography. [H-3]Imipramine and [H-3]paroxetine were utilized as mark ers for labeling it. H-3-imipramine labels a high- and a low-affinity site on striatum membranes, whereas it binds to a single high-affinity site on the solubilized fraction. [H-3]Paroxetine binds with the same affinity to a single site on both membranes and solubilized preparati ons. After gel exclusion chromatography of the solubilizate both [H-3] imipramine rind [H-3]paroxetine bind on an identical fraction of 205 k Da molecular weight, with a similar maximum number of binding sites (B max). Our results suggest that both H-3-imipramine and [H-3]paroxetine bind to a common site on the 5-HT transporter.