Quantification of neurotransmitters in microdialysate samples following quetiapine dosing to schizophrenia phenotyped rats using a validated LC-MS/MS method.

A versatile method was developed and validated for simultaneous determination of the monoamine neurotransmitters (MNT) dopamine (DA), 3-4-dyhydroxyphenilacetic acid (DOPAC), homovanilic acid (HVA), serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) in rat brain microdialysate samples using high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS). The method allowed for small sample volume, using positive and negative ionization mode in a single run analysis without any derivatization or cleanup steps. Analytes were quantified at concentrations ranging from 100 ng/mL to 0.05, 10, 0.5, 0.1 or 1 ng/mL (lower limit of quantification, LLOQ) of DA, DOPAC, HVA, 5-HT and 5-HIAA, respectively, showing linearity (r > 0.98), accuracy, and precision (R.S.D ± 15%) according to validation limits accepted by international guidelines. The method was successfully applied for monitoring the concentration changes of MNT in microdialysate samples from medium prefrontal cortex of Wistar rats in a neurodevelopmental model of schizophrenia before and after quetiapine 5 mg/kg i.v. bolus dose administration. No alterations in MNTs were observed in schizophrenia phenotyped rats (SPR) in comparison to the baseline shading a light on the limited response rate to antipsychotic drugs observed in chronic schizophrenic patients.

Semi-Mechanistic Pharmacokinetic Modeling of Lipid Core Nanocapsules: Understanding Quetiapine Plasma and Brain Disposition in a Neurodevelopmental Animal Model of Schizophrenia.

This study investigated plasma and brain disposition of quetiapine lipid core nanocapsules (QLNC) in naive and schizophrenic (SCZ-like) rats and developed a semimechanistic model to describe changes in both compartments following administration of the drug in solution (FQ) or nanoencapsulated. QLNC (1 mg/ml) presented 166 ± 39 nm, low polydispersity, and high encapsulation (93.0% ± 1.4%). A model was built using experimental data from total and unbound plasma and unbound brain concentrations obtained by microdialysis after administration of single intravenous bolus dose of FQ or QLNC to naive and SCZ-like rats. A two-compartment model was identifiable both in blood and in brain with a bidirectional drug transport across the blood-brain barrier (CLin and CLout). SCZ-like rats' significant decrease in brain exposure with FQ (decrease in CLin) was reverted by QLNC, showing that nanocarriers govern quetiapine tissue distribution. Model simulations allowed exploring the potential of LNC for brain delivery. SIGNIFICANCE STATEMENT: A population approach was used to simultaneously model total and unbound plasma and unbound brain quetiapine concentrations allowing for quantification of the rate and extent of the drug's brain distribution following administration of both free drug in solution or as nanoformulation to naive and SCZ-like rats. The model-based approach is useful to better understand the possibilities and limitations of this nanoformulation for drug delivering to the brain, opening the opportunity to use this approach to improve SCZ-treatment-limited response rates.

Neurometabolic effects of sweetened solution intake during adolescence related to depressive-like phenotype in rats.

OBJECTIVE: Exposure to artificial sweeteners, such as aspartame, during childhood and adolescence has been increasing in recent years. However, the safe use of aspartame has been questioned owing to its potentially harmful effects on the developing brain. The aim of this study was to test whether the chronic consumption of aspartame during adolescence leads to a depressive-like phenotype and to investigate the possible mechanisms underlying these behavioral changes. METHODS: Adolescent male and female rats were given unlimited access to either water, solutions of aspartame, or sucrose in their home cages from postnatal day 21 to 55. RESULTS: Forced swim test revealed that both chronic aspartame and sucrose intake induced depressive-like behaviord, which was more pronounced in males. Additionally, repeated aspartame intake was associated with increased cerebrospinal fluid (CSF) aspartate levels, decreased hippocampal neurogenesis, and reduced activation of the hippocampal leptin signaling pathways in males. In females, we observed a main effect of aspartame: reducing PI3K/AKT one of the brain-derived neurotrophic factor pathways; aspartame also increased CSF aspartate levels and decreased the immunocontent of the GluN2A subunit of the N-methyl-d-aspartic acid receptor. CONCLUSION: The findings revealed that repeated aspartame intake during adolescence is associated with a depressive-like phenotype and changes in brain plasticity. Interestingly, males appear to be more vulnerable to the adverse neurometabolic effects of aspartame than females, demonstrating a sexually dimorphic response. The present results highlighted the importance of understanding the effects caused by the constant use of this artificial sweetener in sensitive periods of development and contribute to regulation of its safe use.