Dopamine D2 receptors selectively labeled by a benzamide neuroleptic: [3H]-YM-09151-2.
In order to label dopamine D2 receptors selectively we tritiated the potent benzamide neuroleptic, YM-09151-2 (26.7 Ci/mmol). The binding of [3H]-YM-09151-2 to canine striatal membranes was saturable and specific with a KD of 57 pmol/l and Bmax of 36 pmol/g tissue as determined by Scatchard analysis. The KD, but not the Bmax, of [3H]-YM-09151-2 increased 6-fold in the absence of sodium chloride. [3H]-YM-09151-2 labeled 40% more sites than [3H]-spiperone in the same tissue homogenate. [3H]-YM-09151-2 binding was inhibited by dopaminergic drugs in a concentration and stereoselective manner with the appropriate dopamine D2 receptor profile. Thus, dopamine agonists inhibited [3H]-YM-09151-2 binding to canine striatal membranes with the following rank order of potency: (-)-N-n-propylnorapomorphine greater than apomorphine greater than (+/-)-6,7-dihydroxy-2-aminotetralin greater than (+)-N-n-propylnorapomorphine greater than dopamine greater than (-)-noradrenaline greater than serotonin greater than (-)-isoprenaline. Dopaminergic antagonists competed for [3H]-YM-09151-2 binding with the following order of potency: spiperone greater than (+)-butaclamol greater than haloperidol greater than clebopride greater than (-)-sulpiride greater than SCH-23390 greater than (-)-butaclamol. Furthermore, dopamine agonists recognized 2 states of the receptor labeled by [3H]-YM-09151-2, Dhigh2 and Dlow2. The Dhigh2 state of the receptor could be converted to Dlow2 by guanine nucleotides and sodium ions as is the case for [3H]-spiperone binding to D2 receptors. [3H]-YM-09151-2 appears to be a more selective ligand for dopamine D2 receptors than [3H]-spiperone, since YM-09151-2 displays approximately 9-fold lower affinity than spiperone for cortical serotonergic (S2) receptors. [3H]-YM-09151-2 may become a useful tool for the selective characterization of dopamine D2 receptors.
Niznik
H B
HB
Grigoriadis
D E
DE
Pri-Bar
I
I
Buchman
O
O
Seeman
P
P
D000818:Animals; D014150:Antipsychotic Agents / Q000378:metabolism*; D001549:Benzamides / Q000378:metabolism*; D001667:Binding, Competitive; D003342:Corpus Striatum / Q000378:metabolism; D004285:Dogs; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007650:Ketanserin; D007700:Kinetics; D010880:Piperidines / Q000378:metabolism; D011954:Receptors, Dopamine / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D013134:Spiperone / Q000378:metabolism; D013379:Substrate Specificity; D013764:Tetrahydronaphthalenes / Q000378:metabolism
D014150:Antipsychotic Agents; D001549:Benzamides; D010880:Piperidines; D011954:Receptors, Dopamine; D013764:Tetrahydronaphthalenes; D006165:Guanylyl Imidodiphosphate; D013134:Spiperone; C011639:ADTN; D007650:Ketanserin; D012964:Sodium; C030265:nemonapride