Effect of typical and atypical antipsychotics on DOPA transport in dopaminergic neurons

E. Moura1,2, E. Silva3,4, E. Magalhães-Ribeiro1, M.P. Serrão1, M.A. Vieira-Coelho1,2. 1Faculdade de Medicina da Universidade do Porto, Departamento de Farmacologia & Terapêutica, Portugal, 2Instituto de Biologia Molecular e Celular, Departamento de Neurofarmacologia, Portugal, 3Faculdade de Medicina da Universidade do Porto, Departamento de Biologia Experimental, Portugal, 4Instituto de Biologia Molecular e Celular, Departamento de Stress in Animals, Portugal

Introduction The antipsychotic drugs constitute a large class of chemically diverse drugs that possess the ability to suppress the positive symptoms of schizophrenia (Strange, 2008). Most antipsychotic drugs also cause a broad range of side effects, including motor (extrapyramidal) side effects. In this study we investigated the effect of antipsychotics on L-DOPA transport in a neuronal cell line, the SH-SY5Y cells.

Methods and Statistics SH-SY5Y cells were differentiated by treatment with retinoic acid (10 µM) for 3 days followed by treatment with TPA (80 nM) for another 3 days. Differentiated SH-SY-5Y cells were pre-incubated (30 minutes) with 10 µM of the antipsychotic drugs chloropromazine (CHL), haloperidol (HAL), ziprazidone (ZIP), risperidone (RIS), quetiapine (QUE), olanzapine (OLA) or clozapine (CLO), and incubated a further 6 minutes with L-DOPA (2.5-2500 µM). L-DOPA levels in cells were evaluated by high performance liquid chromatography with electrochemical detection. Results are presented as arithmetic mean ± standard error mean. Statistical analysis was done by one-way ANOVA. Differences were considered significant at P<0.05.

Results SH-SY5Y cells take up L-DOPA in a time dependent (linear until 6 minutes) and concentration dependent (2.5-2500 µM) manner. Non-linear analysis of the saturation curves revealed for L-DOPA a KM (in µM) of 1417±458 and a Vmax (in nmol/mg protein/6 min) of 286±42. Pre-incubation with OLA, HAL or ZIP did not produce a significant effect on the Vmax values (OLA: 279±48; HAL: 276±55; ZIP: 290±50 nmol/mg protein/6 min, n=6) or the KM values (OLA: 1309±501; HAL: 1205±577; ZIP: 1710±576 µM, n=6) for the accumulation of increasing concentrations L-DOPA (2.5–2500 µM). Pre-incubation with QUE, CLO or RIS produced an increase in the Vmax values (QUE: 390±46*; CLO: 366±140; RIS: 333±84 nmol/mg protein/6 min, n=6, *P<0.05 compared to control values) without changes in the KM values (QUE: 1406±386; CLO: 2726±1764; RIS: 1578±814 µM, n=6) for the accumulation of increasing concentrations L-DOPA (2.5–2500 µM). Pre-incubation with CHL produced a significant decrease in the Vmax values (CHL: 215±50 nmol/mg protein/6 min, n=6, *P<0.05 compared to control values) without changes in the KM values (QUE: 1406±386; CLO: 2726±1764; RIS: 1578±814 µM, n=6) for the accumulation of increasing concentrations L-DOPA (2.5–2500 µM).

Conclusions In differentiated SH-SY5Y cells DOPA uptake is decreased by pre-incubation with chlopromazine and increased by pre-incubation with the atypical antipsychotics quetiapine, clozapine and risperidone.

Strange PG (2008) TIPS 29(6): 314-321