Till Örebro universitet

We have analyzed the binding properties of the selective D3 receptor agonist [3H]PD 128907 in 120 days old rats. In tissue sections, we found high numbers of binding sites for [3H]PD 128907 both in the islands of Calleja and the caudate-putamen (Bmax values being 500 and 1000 fmol/mg protein, respectively). The KD values were higher in the caudate-putamen than in the islands of Calleja. Similar regional differences in Bmax and KD values were observed in membranes from the caudate-putamen and the subcortical limbic region. The distribution of [3H]PD 128907 in adult rats is markedly different from that observed in young rats. Taken together, the present results suggest a prominent presence of D3 receptors in the caudate-putamen of adult, but not young, rats. Hence, these findings may have important physiological, pathophysiological, and clinical implications.