D-3 DOPAMINE-RECEPTOR MESSENGER-RNA IS WIDELY EXPRESSED IN THE HUMAN BRAIN

Considerable attention has been given to the association of the D-3 do pamine receptor subtype and limbic function based on the abundant loca lization of D-3 receptor sites and mRNA expression in the islands of C alleja and nucleus accumbens in experimental animals. Though most huma n anatomical studies have focused on the role of D-3 receptors in limi ted brain structures, detailed information about the overall anatomica l organization of the D-3 receptor in the human brain is still, howeve r, not available. In the current study, we examined the anatomical dis tribution of D-3 receptor mRNA expression at different levels of the h uman brain in whole hemisphere horizontal cryosections using in situ h ybridization. This approach made it possible to establish for the firs t time the wide and heterogenous expression of the D-3 receptor gene t hroughout the human brain. As expected, the most abundant D-3 mRNA exp ression levels were found in the islands of Calleja and discrete cell cluster populations within the ventral striatum/nucleus accumbens regi on. High levels were also evident within the dentate gyrus and striate cortex. Low to moderate D-3 mRNA expression levels were apparent in m ost brain areas including all other cortical regions (highest in the a nterior cingulate/subcallosal gyrus), caudate nucleus, putamen, anteri or and medial thalamic nucleus, mammillary body, amygdala, hippocampal CA region, lateral geniculate body, substantia nigra pars compacta, l ocus coeruleus, and raphe nuclei. While the current anatomical map of D-3 receptor mRNA expression in the human brain does confirm previous reports that D-3 receptors may play important roles in Limbic-related functions such as emotion and cognition, the findings also suggest oth er non-limbic functions for D-3 mRNA-expressing cell populations such as processing of motor and sensory information. (C) 1998 Elsevier Scie nce B.V.