The D3 dopamine receptor has been proposed as a potential target for the treatment of schizophrenia and drug abuse. This study compares the distribution of D3 sites in mouse, rat, guinea pig, and rabbit brain, and dog and human cerebellum using quantitative autoradiography with the putatively selective D3 receptor radioligand [3H]PD 128907. In the mouse, rat, guinea pig, and rabbit, specific [3H]PD 128907 binding was heterogeneously distributed with highest densities observed in the islands of Calleja, followed by the nucleus accumbens. Moderate densities of [3H]PD 128907 binding were observed in the anteroventral and dorsomedial caudate nucleus. Dense [3H]PD 128907-labelled sites were observed in the dorsal thalamus, posterior mamilliary nucleus, and dorsomedial interpeduncular nucleus of the rabbit that were not detected in the other species studied. Moderately dense PD 128907 binding was also observed in the molecular layer of cerebellar lobule X of the rat but not in the mouse, guinea pig, rabbit, dog, or human. These observations indicate significant inter-species differences in the distribution of D3 receptors.
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