Regional distribution of monoamines and dopamine D1-and D2-receptors in the striatum of the rat

Dopamine (DA) D₁-and D₂-receptor densities were determined in 18 discrete areas of the caudate-putamen-globus pallidus of male Wistar rats and compared to local DA concentrations. All three parameters were found to decrease caudally. The globus pallidus was distinguished by the low concentration of DA and its receptors and high noradrenaline, (NA) content. While there were no mediolateral differences in DA or DA D₁-receptors, a clear mediolateral gradient was observed for DA D₂-receptors which extended over several sections of the brain. The ratio of DA D₁-to D₂-receptors was significantly higher in the dorsal than in the ventral areas of the mediolateral and caudal striatum. This is the first report of clear dorsoventral differences in parameters relating to DA activity in the striatum. These findings may be of particular significance in understanding the functional dichotomy between the dorsal and ventral striatum.