D1 and D2 dopamine receptor mRNA expression in whole hemisphere sections of the human brain

Understanding dopamine signaling in human behavior requires knowledge of th e distribution of all molecular components involved in dopamine pathways th roughout the human brain. In the present study, the relative distributions of D1 and D2 dopamine receptor mRNAs were determined by in situ hybridizati on histochemistry in whole hemisphere sections from normal human post morte m brains. The findings confirmed information documented from single structu re examination that the highest expression of both the D1 and D2 mRNAs were localized to the striatum. The cerebral cortex expressed moderate D1 mRNA in all regions with the highest signal in the medial orbital frontal area ( Brodmann areas 11, 14), the paraterminal gyrus (Brodmann area 32) and the i nsular cortex (Brodmann areas 13-16), whereas the D2 mRNA expression had ve ry low cortical expression. The bed nucleus of the stria terminalis and isl ands of Calleja had high expression of the D1 mRNA and moderate D2 mRNA lev els. Moderate to high expression of the D2 mRNA was evident in the hippocam pal formation, parafascicular and paraventricular thalamic nuclei, genicula te bodies, subthalamic nucleus, and pineal gland, all of which were devoid of, or showed only faint, D1 mRNA expression. Brainstem regions, e.g. subst antia nigra, red nucleus, inferior colliculus, medial lemniscus, and pontin e nuclei expressed D2, but not D1, mRNA. These results emphasize the differ ential anatomical localization or D1 and D2 dopamine receptor mRNA neuronal populations in the human brain. The restricted expression of the D1 mRNA t o the cortical mantle and to a few forebrain structures indicates a strong involvement of the DI system in cognitive function. (C) 2001 Elsevier Scien ce B.V. All rights reserved.