Partial agonist properties of the antipsychotics SSR181507, aripiprazole and bifeprunox at dopamine D2 receptors: G protein activation and prolactin release.
Dopamine D2 receptor antagonists induce hyperprolactinemia depending on the extent of D2 receptor blockade. We compared the effects of the new antipsychotic agents SSR181507 ((3-exo)-8-benzoyl-N-[[(2 s)7-chloro-2,3-dihydro-1,4-benzodioxin-1-yl]methyl]-8-azabicyclo[3.2.1]octane-3-methanamine monohydrochloride), bifeprunox (DU127090: 1-(2-Oxo-benzoxazolin-7-yl)-4-(3-biphenyl)methylpiperazinemesylate) and SLV313 (1-(2,3-dihydro-benzo[1,4]dioxin-5-yl)-4-[5-(4-fluorophenyl)-pyridin-3-ylmethyl]-piperazine) with those of aripiprazole (7-{4-[4-(2,3-dichlorophenyl)-1-piperazinyl]-butyloxy)-3,4-dihydro-2(1 H)-quinolinone), clozapine and haloperidol, on functional measures of dopamine D2 receptor activity in vitro and in vivo: [35S]-GTPgammaS binding to membranes from Sf9 insect cells expressing human dopamine D2 Long (hD2 L) receptors, and serum prolactin levels in the rat. All compounds antagonized apomorphine-induced G protein activation at dopamine hD2 L receptors. Antagonist potencies of aripiprazole, bifeprunox and SLV313 were similar to haloperidol (pK(b) = 9.12), whereas SSR181507 (8.16) and clozapine (7.35) were less potent. Haloperidol, SLV313 and clozapine were silent antagonists but SSR181507, bifeprunox and aripiprazole stimulated [35S]-GTPgammaS binding by 17.5%, 26.3% and 25.6%, respectively, relative to 100 microM apomorphine (Emax = 100%). pEC50s were: SSR181507, 8.08; bifeprunox, 8.97; aripiprazole, 8.56. These effects were antagonized by raclopride. Following oral administration in vivo, the drugs increased prolactin release to different extents. SLV313 and haloperidol potently (ED50 0.12 and 0.22 mg/kg p.o., respectively) stimulated prolactin release up to 86 and 83 ng/ml. Aripiprazole potently (ED50 0.66 mg/kg p.o.) but partially (32 ng/ml) induced prolactin release. SSR181507 (ED50 4.9 mg/kg p.o.) also partially (23 ng/ml) enhanced prolactin release. Bifeprunox only weakly increased prolactin at high doses (13 ng/ml at 40 mg/kg) and clozapine only affected prolactin at the highest dose tested (41 ng/ml at 40 mg/kg). Prolactin levels of the corresponding vehicle-treated animals were <4.3 ng/ml. These data show that (1) SSR181507, aripiprazole and bifeprunox, but not SLV313, are partial agonists at dopamine hD2 L receptors in vitro; (2) SSR181507, bifeprunox and aripiprazole exhibit reduced prolactin release in vivo compared with drugs that are neutral antagonists at dopamine D2 receptors.
Division de Neurobiologie I, Centre de Recherche Pierre Fabre, 17 avenue Jean Moulin, 81106 Castres, France.
Cristina
C
Cosi
Elisabeth
E
Carilla-Durand
Marie Bernadette
MB
Assié
Anne Marie
AM
Ormiere
Mireille
M
Maraval
Nathalie
N
Leduc
Adrian
A
Newman-Tancredi
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D000068180:Aripiprazole; D001583:Benzoxazoles / Q000494:pharmacology; D001667:Binding, Competitive / Q000187:drug effects; D002460:Cell Line; D003024:Clozapine / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006220:Haloperidol / Q000494:pharmacology; D006801:Humans; D008297:Male; D010879:Piperazines / Q000494:pharmacology; D011388:Prolactin / Q000097:blood; D015363:Quinolones / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000819:agonists* / Q000378:metabolism; D058825:Serotonin 5-HT1 Receptor Agonists; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D018411:Spodoptera; D013462:Sulfur Radioisotopes; D014326:Tropanes / Q000494:pharmacology
C480819:(3-exo)-8-benzoyl-N-(((2S)7-chloro-2,3-dihydro-1,4-benzodioxin-1-yl)methyl)-8-azabicyclo(3.2.1)octane-3-methanamine monohydrochloride; C504317:1-(2,3-dihydro-1,4-benzodioxin-5-yl)-4-((5-(4-fluorophenyl)-3-pyridinyl)methyl)piperazine; D014150:Antipsychotic Agents; D001583:Benzoxazoles; D004146:Dioxanes; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D010879:Piperazines; D015363:Quinolones; D017448:Receptors, Dopamine D2; D058825:Serotonin 5-HT1 Receptor Agonists; D017366:Serotonin Receptor Agonists; D013462:Sulfur Radioisotopes; D014326:Tropanes; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000068180:Aripiprazole; D011388:Prolactin; C509981:bifeprunox; D019204:GTP-Binding Proteins; D003024:Clozapine; D006220:Haloperidol