Neuropharmacology and NeurotoxicologyRegional distribution of dopamine D4 receptors in rat forebrainTarazi, Frank I.1,2,3; Kula, Nora S.1,2; Baldessarini, Ross J.1,2Author Information 1Consolidated Department of Psychiatry and Neuroscience Program, Harvard Medical School, Boston 2Mailman Research Center, McLean Division of Massachusetts General Hospital, 115 Mill St., Belmont, MA 02178, USA 3Corresponding Author: Frank I. Tarazi Received 15 July 1997; accepted 29 August 1997 NeuroReport: November 10th, 1997 - Volume 8 - Issue 16 - p 3423-3426 Buy Abstract 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. © Lippincott-Raven Publishers.