Topographical distribution of dopaminergic innervation and dopaminergic receptors of the anterior cerebral cortex of the rat

Abstract

The quantitative topographical distribution of the dopaminergic innervation and the DA-sensitive adenylate cyclase were estimated in the anterior cerebral cortex of the rat. The high affinity uptake of [3H]DA and endogenous levels of DA were used as markers of the dopaminergic innervation. [3H]DA uptake, DA levels and DA-sensitive adenylate cyclase were estimated in microdiscs of tissues punched out from frozen serial frontal slices. The uptake of [3H]DA was measured on sucrose homogenates prepared from such microdiscs. The ventral part of the frontal cortex contained the highest DA concentration and DA-sensitive adenylate cyclase activity; the other structures rich in DA and in DA receptors were the cingular (close to the corpus callsoum) and the rhinal cortices. All of these cortical areas were rich in [3H]DA uptake sites. However, curiously, the dorsal part of the frontal cortex, which contained only moderate amounts of DA and of DA-sensitive adenylate cyclase, presented the highest number of [3H]DA uptake sites. Nevertheless, the uptake of [3H]DA in this region decreased by 60% after bilateral electrolytical lesions of the ventral tegmental area (A10 group). The parietal cortex was practically devoid of dopaminergic innervation and of DA-sensitive adenylate cyclase. The activity of the DA-sensitive adenylate cyclase in the frontal, cingular and rhinal cortices was 10-fold higher than that found in the striatum when compared to their respective DA levels.