CHARACTERIZATION OF A PUTATIVELY VESICULAR BINDING-SITE FOR [H-3] MPP+ IN MOUSE STRIATAL MEMBRANES

[H-3] N-Methyl-4-phenylpyridinium ion (MPP+) binds with a fully reversible, high affinity process to a population of sites mainly localized in the mouse striatum (B(max) = 168 +/- 15 fmol/mg protein, K(D) = 1.4 +/- 0.4 nM). The majority of specifically-bound radioactivity was localized in the synaptosomal fraction. Unilateral, striatal denervation with 6-hydroxydopamine (6-OHDA) markedly (by 65-70%) decreased the number of [H-3]MPP+ sites. Besides dopamine, the vesicular markers tyramine, tetrabenazine and reserpine inhibited [H-3]MPP+, while mazindol was a poor displacer. Adenosine triphosphate (ATP) and Mg2+-ions did not affect [H-3]MPP+ binding. It is concluded that these sites may represent a marker of striatal storage vesicles for dopamine.