The Benzazepine, SCH 23390, Inhibits 3H‐NPA Binding in Mouse Brain In Vivo

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Abstract
The fact that SCH 23390, a selective dopamine (DA) D1 antagonist, blocks the effects of D2 agonist suggests a functional coupling of D1 and D2 receptors. Therefore, the binding of SCH 23390 to D2 receptors was investigated in vivo using 3H-N-n-propylnorapomorphine (NPA), a D2 agonist, and 3-spiperone and 3-raclopride, both D2 antagonists. SCH 23390 failed to inhibit 3-spiperone or 3H-raclopride binding; however, SCH 23390 was relatively potent in inhibiting 3H-NPA binding. These results suggest that (some) antidopaminergic effects of SCH 23390 may results from antagonism of a D2 agonist conformation of the D2 receptor.