Antipsychotics differ in their ability to internalise human dopamine D 2S and human serotonin 5-HT 1A receptors in HEK293 cells

Abstract

Antipsychotic drugs act preferentially via dopamine D 2 receptor blockade, but interaction with serotonin 5-HT 1A receptors has attracted interest as additional target for antipsychotic treatment. As receptor internalisation is considered crucial for drug action, we tested the propensity of antipsychotics to internalise human (h)D 2S receptors and h5-HT 1A receptors. Agonist-induced internalisation of hemaglutinin (HA)-tagged hD 2S and HA-h5-HT 1A receptors expressed in HEK293 cells was increased by coexpression of G-protein coupled receptor kinase 2 and β-arrestin2. At the HA-hD 2S receptor, dopamine, quinpirole and bromocriptine behaved as full agonists, while S(−)-3-(3-hydroxyphenyl)- N- n-propylpiperidine [(−)-3PPP] and sarizotan were partial agonists. The typical antipsychotic, haloperidol, and the atypical compounds, olanzapine, nemonapride, ziprasidone and clozapine did not internalise HA-hD 2S receptors, whereas aripiprazole potently internalised these receptors (> 50% relative efficacy). Among antipsychotics with combined D 2/5-HT 1A properties, bifeprunox and (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 (SSR181507) partially internalised HA-hD 2S receptors, piperazine, 1-(2,3-dihydro-1,4-benzodioxin-5-yl)-4-[[5-(4-fluorophenyl)-3-pyridinyl]methyl (SLV313) and N-[(2,2-dimethyl-2,3-dihydro-benzofuran-7-yloxy)ethyl]-3-(cyclopent-1-enyl)-benzylamine (F15063) were inactive. At the HA-h5-HT 1A receptor, serotonin, (+)-8-hydroxy-2-(di- n-propylamino)tetralin [(+)-8-OH-DPAT] and sarizotan were full agonists, buspirone acted as partial agonist. (−)-Pindolol showed little activity and no internalising properties were manifested for the 5-HT 1A receptor antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]-ethyl]- N-(2-pyridinyl)cyclohexanecarboxamide (WAY100635). Most antipsychotics induced HA-h5-HT 1A receptor internalisation, with an efficacy rank order: nemonapride > F15063 > SSR181507 > bifeprunox ≈ SLV313 ≈ ziprasidone > aripiprazole and potencies: SLV313 > SSR181507 ≈ F15063 > bifeprunox ≈ nemonapride ≈ aripiprazole > ziprasidone. Interestingly, the internalisation induced by clozapine was only minimal, whereas aripirazole and bifeprunox were more potent for internalisation than for G-protein activation. These different profiles of antipsychotics for receptor internalisation may help to evaluate their potential therapeutic impact in the treatment of schizophrenia.