Regional distribution of dopamine D4 receptors in rat forebrain.
Binding of the D2-like (D2/D3/D4) radioligand [3H]nemonapride under selective conditions (with 300 nM S[-]-raclopride and other masking agents to occlude D2/D3 receptors and non-specific binding sites) revealed a subset of raclopride-insensitive binding sites considered D4-like receptors. These sites were stereoselective to R(-)-N-n-propylnorapomorphine (NPA) over its S(+)-NPA in a similar fashion to cloned D4 receptors expressed in cell lines. In addition, the highly D4-selective agent L-745,870 displaced 74-83% of these sites in rat brain regions, suggesting that most were D4 receptors. These apparent D4 receptors represented a relatively high proportion of D2-like receptors in hippocampus, dorsolateral frontal, medial prefrontal and entorhinal cortex, but fewer in caudate-putamen and nucleus accumbens.
Tarazi
F I
FI
Consolidated Department of Psychiatry and Neuroscience Program, Harvard Medical School, Boston, MA 02178, USA.
Kula
N S
NS
Baldessarini
R J
RJ
D000818:Animals; D001345:Autoradiography; D001549:Benzamides / Q000378:metabolism; D018492:Dopamine Antagonists / Q000378:metabolism; D008297:Male; D009928:Organ Specificity; D016548:Prosencephalon / Q000737:chemistry / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000032:analysis* / Q000378:metabolism; D050638:Receptors, Dopamine D4; D014316:Tritium
D001549:Benzamides; D018492:Dopamine Antagonists; C493601:Drd4 protein, rat; D017448:Receptors, Dopamine D2; D014316:Tritium; D050638:Receptors, Dopamine D4; C030265:nemonapride