In vivo neurochemical and anatomical heterogeneity of the dopamine uptake system in the rat caudate putamen.

The neurochemical and anatomical heterogeneity of dopamine uptake blockade was studied at a medial and lateral position in each of 3 rostrocaudal areas of the rat caudate-putamen. In vivo voltammetric measures of extracellular dopamine indicated a lateral-to-medial and rostral-to-caudal gradient in the effect of uptake blockade. The percentage increase in dopamine was greatest in the rostrolateral area (300%) and least in the caudomedial area (10%). The existence of these lateromedial and rostrocaudal gradients was confirmed by tissue content measures of DOPAC and dopamine to DOPAC ratios in each area. The rostrocaudal gradient in the effect of uptake blockade was independent of the rostrocaudal gradient in dopamine tissue content. The regional gradients detected in dopamine uptake blockade may indicate a heterogeneous distribution in the number of uptake sites, a regional variation in the affinity of the uptake site for the blocker and/or altered neuronal activity mediated by an action of the blocker on dopaminergic cell bodies.