Visualization of dopamine D 1, D 2 and D 3 receptor mRNA's in human and rat brain

Abstract

Using 32P-labelled oligonucleotides derived from the coding regions of dopamine D 1, D 2 and D 3 receptor mRNAs we localized cells containing transcripts for these receptors in the human (hD 1, hD 2) and rat brain (rD 1, rD 2, rD 3). Dopamine D 1 receptor mRNA was detected at high levels in neurons of the caudate and putamen as well as in the nucleus accumbens in both human and rat brain. In the rat brain D 1 receptor mRNA was also abundant in the olfactory tubercles and several thalamic nuclei. In both species D 1 mRNA was absent from the neurons of the substantia nigra and the ventral tegmental area as well as from the globus pallidus medialis in humans and entopeduncular nucleus in rats. In contrast, dopamine D 2 receptor mRNA was found in dopaminergic neurons of the substantia nigra pars compacta and of the ventral tegmental area. In addition high levels of D 2 mRNA were detected in neurons of the caudate, putamen and accumbens nuclei, the olfactory tubercle and the anterior lobe of pituitary gland. In the rat the highest level of hybridization was found in the intermediate lobe of the pituitary gland. In the rat brain dopamine D 3 mRNA was mainly detected in the Islands of Calleja and at lower levels in the anterior nucleus accumbens, the medial mammillary nucleus as well as in the bed nucleus of the stria terminalis. In general, a good agreement was found between the distribution of transcripts and binding sites labelled with the D 1 antagonist SCH 23390 or with the D 2 ligand SDZ 205–502. For D 1 receptors, the main exceptions were the absence of mRNA in the globus pallidus and the substantia nigra despite the high densities of binding sites in these regions. For D 2 receptors, regions where binding sites but not mRNA were detected include the olfactory bulb, neocortex, hippocampus and superior colliculus.