Topographical distribution of dopaminergic innervation and of dopaminergic receptors in the rat striatum. I. Microestimation of [3H]dopamine uptake and dopamine content in microdiscs

Topographical variations in the uptake of [3H]dopamine (DA) and in the endogenous content of DA were estimated in the striatum of the rat. For this purpose, microdiscs were punched out in serial 500 μm sections. [3H]DA uptake was measured in 0.25 M sucrose homogenates prepared from microdiscs punched out from frozen slices (−7 °C). This uptake was similar to that observed in fresh tissues. It was unaffected by desmethylimipramine (5 × 10−7M), inhibited by benztropine (10−6M) and no longer detectable after 6-hydroxydopamine-induced degeneration of the nigrostriatal dopaminergic pathway. Both [3H]DA uptake and DA content decreased regularly from the rostral to the caudal part of the structure. In contrast, no important differences could be found in the dorso-ventral plane. These results suggest that the extent of dopaminergic innervation is heterogenous within the structure.