Regional in vivo binding of [3H]N-propylnorapomorphine in the mouse brain. Evidence for labelling of central dopamine receptors.

Tail vein injections of [3H]N-propylnorapomorphine ([3H]NPA) in male mice resulted in a dose-related accumulaton of radioactivity in the following brain regions: striatum (max), olfactory tubercle and cerebellum (min). The specific binding was saturable with increasing concentrations of the drug and stereospecifically displaced by (+) butaclamol. Dopamine agonist (apomorphine, NPA and bromocriptine) and antagonists (spiperone, haloperidol, (+) butaclamol and I-sulpiride) all caused dose-dependent prevention of [3H]NPA binding. Mianserin, phenoxybenzamine and propranolol did not prevent the in vivo [3H]NPA binding suggesting that [3H]NPA binds specifically to dopamine receptors in the striatum and the olfactory tubercle of the mouse.