Evidence for a role of Hsp70 in the neuroprotection induced by heat shock pre-treatment against 3,4-methylenedioxymethamphetamine toxicity in rat brain

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') produces acute hyperthermia which increases the severity of the selective serotoninergic neurotoxicity produced by the drug in rats. Heat shock protein 70 (Hsp70) is a major inducible cellular protein expressed in stress conditions and which is thought to exert protective functions. MDMA (12.5 mg/kg, i.p.), given to rats housed at 22 degrees C, produced an immediate hyperthermia and increased Hsp70 in frontal cortex between 3 h and 7 days after administration. MDMA, given to rats housed at low ambient temperature (4 degrees C) produced transient hypothermia followed by mild hyperthermia but no increase in Hsp70 expression, while rats treated at elevated room temperature (30 degrees C) showed enhanced hyperthermia and similar expression of Hsp70 to that seen in rats housed at 22 degrees C. Fluoxetine-induced inhibition of 5-HT release and hydroxyl radical formation did not modify MDMA-induced Hsp70 expression 3 h later. Four- or 8-day heat shock (elevation of basal rectal temperature by 1.5 degrees C for 1 h) or geldanamycin pre-treatment induced Hsp70 expression and protected against MDMA-induced serotoninergic neurotoxicity without affecting drug-induced hyperthermia. Thus, MDMA-induced Hsp70 expression depends on the drug-induced hyperthermic response and not on 5-HT release or hydroxyl radical formation and pre-induction of Hsp70 protects against the long-term serotoninergic damage produced by MDMA.     

Protection against 3,4-methylenedioxymethamphetamine-induced neurodegeneration produced by glutathione depletion in rats is mediated by attenuation of hyperthermia

3,4-Methylenedioxymethamphetamine (MDMA) administration produces neurotoxic degeneration of serotonin terminals in rat brain. These effects occur only after systemic administration and not after central injection, suggesting that peripheral metabolism, possibly hepatic, is required for toxicity. Glutathione is one of the principal cellular defence mechanisms, but conjugation with glutathione can, on some occasions, increase the reactivity of certain molecules. Previous studies have shown that central administration of glutathione adducts of a MDMA metabolite produces a neurotoxicity profile similar to that of systemic MDMA. In the present study, depletion of peripheral (hepatic) glutathione by 43% with dl-buthionine-(S,R)-sulfoximine (an inhibitor of glutathione synthesis) did not attenuate MDMA-induced neurotoxicity as indicated by the 34% loss of [(3) H]paroxetine binding to the serotonin uptake sites in Dark Agouti rats treated with the inhibitor. However, a more profound depletion (92%) of glutathione by diethylmaleate (direct conjugation) administration significantly reduced the serotonergic neurotoxicity produced by MDMA. This depletion protocol also attenuated the hyperthermic response to MDMA. A combination protocol utilising both buthionine-(S,R)-sulfoximine and diethylmaleate that did not alter the hyperthermic response of the rats given MDMA also failed to attenuate the neurotoxicity. These findings indicate that glutathione depletion does not offer specific protection against MDMA-induced serotonin neurotoxicity in Dark Agouti rats.     

Augmentation of serotonin release by sustained exposure to MDMA and methamphetamine in rat organotypic mesencephalic slice cultures containing raphe serotonergic neurons

Several lines of evidence suggest the involvement of the raphe-serotonergic neurons in addiction to psychostimulants and some recreational drugs. In this study, we established rat organotypic mesencephalic slice cultures containing the raphe nuclei and examined the effects of sustained exposure to 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine (METH). Immunostaining for tryptophan hydroxylase (TPH) studies revealed that serotonergic neurons were abundant in the slice cultures. Sustained exposure to MDMA and METH (1-1000 microM) for 4 days had little effect on the serotonin tissue content, [(3)H]citalopram binding, or expression/phosphorylation of TPH. Treatment with MDMA or METH for 30 min increased serotonin release in a concentration-dependent manner. Slice cultures were exposed to MDMA for 4 days following a 1-day withdrawal period and then challenged with MDMA (10 microM). Sustained MDMA exposure augmented MDMA-induced serotonin release in a concentration-dependent manner, indicating serotonergic sensitization. Similar serotonergic sensitization was observed for METH. The development of MDMA-induced serotonergic sensitization was attenuated by the NMDA receptor antagonist, MK-801 (10 microM). These results suggest that in mesencephalic slice cultures sustained MDMA or METH exposure induces serotonergic sensitization through activation of NMDA receptors without serotonergic neurotoxicity. The in vitro model system could help to elucidate the mechanisms underlying drug addiction.     

In Vitro Reactivation of Rat Cortical Tryptophan Hydroxylase Following In Vivo Inactivation by Methylenedioxymethamphetamine

The activity of tryptophan hydroxylase (EC 1.14.16.4) from rat brain was significantly decreased 1 h following a single systemic injection of 3,4-methylenedioxymethamphetamine (MDMA) when assessed ex vivo by radioenzymatic assay or in vivo by the quantitation of 5-hydroxytryptophan accumulation following central L-aromatic amino acid decarboxylase inhibition. Recovery of enzymatic activity in vivo, which occurred within 24 h of low-dose MDMA treatment, appeared not to involve synthesis of new enzyme protein, because the return of enzymatic activity was not prevented by prior cycloheximide. Acutely MDMA-depressed cortical tryptophan hydroxylase activity could be completely restored in vitro by a prolonged (20-24 h) anaerobic incubation in the presence of dithiothreitol and Fe2+ at 25 degrees C; partial reconstitution occurred when 2-mercapto-ethanol was substituted for dithiothreitol. Cortical tryptophan hydroxylase acutely inactivated by methamphetamine or p-chloroamphetamine could be similarly reactivated. MDMA-inactivated cortical tryptophan hydroxylase derived from rats killed later than 3 days after drug treatment could not be significantly reactivated under the conditions described above, indicating the development of irreversible enzymatic damage. Kinetic analysis of enzyme reactivation revealed an approximate doubling of enzyme Vmax with no change in enzyme affinity for either substrate, tryptophan, or pterin cofactor. These studies suggest that MDMA and its congeners inactivate central tryptophan hydroxylase by inducing oxidation of key enzyme sulfhydryl groups. The reactivation capacity of drug-inactivated enzyme at various times after MDMA treatment may provide a means of assessing the development of MDMA-induced neurotoxicity.     

Acute effects of 3,4-methylenedioxymethamphetamine on brain serotonin synthesis in the dog studied by positron emission tomography

The influence of an acute dose (2 mg/kg; i.v.; infused over 10 min) of 3,4-methylenedioxymethamphetamine (MDMA; Ecstasy) on the brain serotonin synthesis in the dog was assessed using alpha [11C]methyl-L-tryptophan and positron emission tomography. The rate of serotonin synthesis measured 1 h after injection of MDMA was six times greater than the base line (before MDMA) synthesis. Five hours after the MDMA injection, serotonin synthesis was about one half that at the base line, and about one thirteenth of the synthesis at 1 h after MDMA. A large increase seen 1 h after MDMA probably relates to the large release of serotonin by MDMA and reflects an attempt of the serotonergic system to replenish released serotonin. This probably correlates with the mood changes reported by humans after MDMA intake. Decrease observed 5 h after MDMA, in part, probably relates to the inhibitory effects of the released serotonin, which could act on the activity of tryptophan hydroxylase directly or indirectly via other monoaminergic systems (e.g. dopaminergic).     

Role of the serotonin uptake carrier in the neurochemical response to methamphetamine: Effects of citalopram and chlorimipramine

The role of the serotonin uptake carrier in the methamphetamine-induced depression of serotonin synthesis was examined. In vivo, coadministration of citalopram or chlorimipramine with methamphetamine blocked the irreversible depression of tryptophan hydroxylase activity observed in the neostriatum and cerebral cortex after repeated administration of high doses of methamphetamine. The methamphetamine-induced reduction of neostriatal serotonin and 5-hydroxyindoleacetic acid was also attenuated by the two uptake inhibitors. In contrast, neither drug antagonized the depression of neostriatal tyrosine hydroxylase activity observed after methamphetamine administration. Citalopram also blocked the reversible inhibition of tryptophan hydroxylase activity observed after the acute administration of methamphetamine. In vitro, citalopram significantly inhibited methamphetamine-induced [³H] serotonin release from neostriatal slices. The results demonstrate that inhibitors of the serotonin uptake carrier can antagonize both the in vivo and in vitro effects of methamphetamine on serotonergic neurons. Furthermore, the methamphetamine-induced depression of serotonin synthesis is dependent upon a functional serotonin uptake system.     

Embryonic exposure to corticosterone modifies aggressive behavior through alterations of the hypothalamic pituitary adrenal axis and the serotonergic system in the chicken

Exposure to excess glucocorticoids (GCs) during embryonic development influences offspring phenotypes and behaviors and induces epigenetic modifications of the genes in the hypothalamic–pituitary–adrenal (HPA) axis and in the serotonergic system in mammals. Whether prenatal corticosterone (CORT) exposure causes similar effects in avian species is less clear. In this study, we injected low (0.2 μg) and high (1 μg) doses of CORT into developing embryos on day 11 of incubation (E11) and tested the changes in aggressive behavior and hypothalamic gene expression on posthatch chickens of different ages. In ovo administration of high dose CORT significantly suppressed the growth rate from 3 weeks of age and increased the frequency of aggressive behaviors, and the dosage was associated with elevated plasma CORT concentrations and significantly downregulated hypothalamic expression of arginine vasotocin (AVT) and corticotropin-releasing hormone (CRH). The hypothalamic content of glucocorticoid receptor (GR) protein was significantly decreased in the high dose group (p < 0.05), whereas no changes were observed for GR mRNA. High dose CORT exposure significantly increased platelet serotonin (5-HT) uptake, decreased whole blood 5-HT concentration (p < 0.05), downregulated hypothalamic tryptophan hydroxylase 1 (TPH1) mRNA and upregulated 5-HT receptor 1A (5-HTR1A) and monoamine oxidase A (MAO-A) mRNA, but not monoamine oxidase B (MAO-B). High dose CORT also significantly increased DNA methylation of the hypothalamic GR and CRH gene promoters (p < 0.05). Our findings suggest that embryonic exposure to CORT programs aggressive behavior in the chicken through alterations of the HPA axis and the serotonergic system, which may involve modifications in DNA methylation.     

Determination of 3,4-methylenedioxymethamphetamine and its five main metabolites in rat urine by solid-phase extraction and high performance liquid chromatography with on line mass spectrometry

The consumption of psychostimulant amphetamine-like drugs has increased significantly in recent years. Some MDMA metabolites are probably involved in the neurotoxicity and neurodegeneration caused by prolonged use rather than MDMA itself. We recently developed a method to analyze MDMA and its five main metabolites in rat plasma [7]. We have now fully validated this method to the quantification of these drugs in rat urine. We extracted MDMA and its metabolites with Oasis WCX cartridges, separated them on a Nucleodur C18 analytical column and quantified them by ion-trap mass spectrometry. Linearity was excellent: 12.5–1250 ng/mL urine for HMA, HMMA, MDA and MDMA, 25–2500 ng/mL for HHMA, and 150–7500 ng/mL for HHA (r² > 0.993 for all analytes). The lower limits of quantification were 12.5 ng/mL urine for MDMA, MDA, HMA and HMMA, 25 ng/mL for HHMA and 150 ng/mL for HHA. Reproducibility was good (intra-assay precision = 1.7–6.1%; inter-assay precision = 0.6–5.7%), as was accuracy (intra-assay deviation = 0.1–4.8%; inter-assay deviation = 0.7–7.9%). Average recoveries were around 85.0%, except for HHMA (66.2%) and HHA (53.0%) (CV < 8.3%). We also checked the stability of stock solutions and the internal standards after freeze-thawing and in the autosampler. Lastly, we measured the MDMA, MDA, HHMA, HHA, HMMA and HMA in urine samples taken over 24 h from rats given subcutaneous MDMA.     

Comparative neurochemical profile of 3,4-methylenedioxymethamphetamine and its metabolite alpha-methyldopamine on key targets of MDMA neurotoxicity

The neurotoxicity of MDMA or "Ecstasy" in rats is selectively serotonergic, while in mice it is both dopaminergic and serotonergic. MDMA metabolism may play a key role in this neurotoxicity. The function of serotonin and dopamine transporter and the effect of MDMA and its metabolites on them are essential to understand MDMA neurotoxicity. The aim of the present study was to investigate and compare the effects of MDMA and its metabolite alpha-methyldopamine (MeDA) on several molecular targets, mainly the dopamine and serotonin transporter functionality, to provide evidence for the role of this metabolite in the neurotoxicity of MDMA in rodents. MeDA had no affinity for the serotonin transporter but competed with serotonin for its uptake. It had no persistent effects on the functionalism of the serotonin transporter, in contrast to the effect of MDMA. Moreover, MeDA inhibited the uptake of dopamine into the serotonergic terminal and also MAO(B) activity. MeDA inhibited dopamine uptake with a lower IC(50) value than MDMA. After drug washout, the inhibition by MeDA persisted while that of MDMA was significantly reduced. The effect of MDMA on the dopamine transporter is related with dopamine release from vesicular stores, as this inhibition disappeared in reserpine-treated animals. However, the effect of MeDA seems to be a persistent conformational change of this transporter. Moreover, in contrast with MDMA, MeDA did not show affinity for nicotinic receptors, so no effects of MeDA derived from these interactions can be expected. The metabolite reduced cell viability at lower concentrations than MDMA. Apoptosis plays a key role in MDMA induced cellular toxicity but necrosis is the major process involved in MeDA cytotoxicity. We conclude that MeDA could protect against the serotonergic lesion induced by MDMA but potentiate the dopaminergic lesion as a result of the persistent blockade of the dopamine transporter induced this metabolite.     

Initial synthesis and characterization of an immobilized heat shock protein 90 column for online determination of binding affinities

Heat shock protein 90α (Hsp90α) was immobilized on aminopropyl silica via the N terminus to create the Hsp90α(NT) column or via the C terminus to create the Hsp90α(CT) column. Binding to the exposed C terminus on the Hsp90α(NT) column was characterized using frontal chromatography and the C-terminus ligands coumermycin A₁ (CA1) and novobiocin (NOVO). The calculated K_d values were 220 ± 110 nM (CA1) and 100 ± 20 nM (NOVO). Nonlinear chromatography was used to determine the association and dissociation rate constants associated with the NOVO-Hsp90α complex: 22.2 ± 8.8 μM⁻¹ s⁻¹ and 2.7 ± 0.6 s⁻¹, respectively. Binding to the exposed N terminus on the Hsp90α(CT) column was characterized using frontal chromatography. The K_d values of the N-terminus ligands geldanamycin (GM, 90 ± 50 nM), 17-allylamino-17-demethoxygeldanamycin (17-AAG, 210 ± 50 nM), and radicicol (RAD, 20 ± 9 nM) were consistent with previously reported values. The effect of the immobilization on ATPase activity was investigated through the determination of IC₅₀ values for inhibition of ATPase activity on the Hsp90α(CT) column. The IC₅₀ for GM was 2.80 ± 0.18 μM, and the relative IC₅₀ values were 17-AAG > GM > RAD, in agreement with previously reported values and indicating that immobilization had not affected ATPase activity or sensitivity to inhibition.     

Hydrolysis of phosphatidylcholine by cerium(IV) releases significant amounts of choline and inorganic phosphate at lysosomal pH

Niemann-Pick disease and drug-induced phospholipidosis are examples of lysosomal storage disorders in which serious respiratory infections are brought on by high levels of the phospholipid phosphatidylcholine in the acidic lamellar bodies and lysosomes of pulmonary cells. One approach to developing an effective therapeutic agent could involve the use of a metal to preferentially hydrolyze phospholipid phosphate ester bonds at mildly acidic, lysosomal pH values (~ pH 4.8). Towards this end, here we have investigated phosphatidylcholine hydrolysis by twelve metal ion salts at 60 °C. Using a malachite green/molybdate-based colorimetric assay to detect inorganic phosphate released upon metal-assisted phosphate ester bond hydrolysis, Ce(IV) was shown to possess outstanding reactivity in comparison to the eleven other metals. We then utilized cerium(IV) to hydrolyze phosphatidylcholine at normal, core body temperature (37 °C). The malachite green/molybdate assay was used to quantitate free phosphate and an Amplex® Red-based colorimetric assay and matrix-assisted laser desorption ionization time-of-flight mass spectrometry were employed to detect choline. Ce(IV) hydrolyzed phosphatidylcholine more efficiently at lysosomal pH: i.e., at a Triton X-100:phosphatidylcholine molar mixing ratio of 1.57, yields of choline and phosphate were 51 ± 4% and 40 ± 4% at ~ pH 4.8, compared to 28 ± 4% and 27 ± 5% at ~ pH 7.2.     

Hsp60 protein pattern in coral is altered by environmental changes in light and temperature

The heat shock protein Hsp60 exhibited marked oscillation during a 12-hour day period when the coral Turbinaria reniformis was maintained in the laboratory under constant conditions of light (200 μE) and temperature (27 °C). A biphasic pattern of Hsp60 was apparent, punctuated by a low protein level at the midpoint of the 12-hour day period. Oscillation of Hsp60 was also apparent when coral was kept in darkness in lieu of a scheduled light period. The pattern of Hsp60 was altered when coral was exposed to increased light intensity (400 μE) or temperature elevation (32 °C). These observations suggest that Hsp60 in coral exhibits oscillation that is altered by increased light and temperature elevation.     

Temperature-sensitive paramagnetic liposomes for image-guided drug delivery: Mn versus [Gd(HPDO3A)(H2O)]

Temperature-sensitive liposomes (TSLs) loaded with doxorubicin (Dox), and Magnetic Resonance Imaging contrast agents (CAs), either manganese (Mn^2 +) or [Gd(HPDO3A)(H₂O)], provide the advantage of drug delivery under MR image guidance. Encapsulated MRI CAs have low longitudinal relaxivity (r₁) due to limited transmembrane water exchange. Upon triggered release at hyperthermic temperature, the r₁ will increase and hence, provides a means to monitor drug distribution in situ. Here, the effects of encapsulated CAs on the phospholipid bilayer and the resulting change in r₁ were investigated using MR titration studies and ¹H Nuclear Magnetic Relaxation Dispersion (NMRD) profiles. Our results show that Mn^2 + interacted with the phospholipid bilayer of TSLs and consequently, reduced doxorubicin retention capability at 37 °C within the interior of the liposomes over time. Despite that, Mn^2 +-phospholipid interaction resulted in higher r₁ increase, from 5.1 ± 1.3 mM^− 1 s^− 1 before heating to 32.2 ± 3 mM^− 1 s^− 1 after heating at 60 MHz and 37 °C as compared to TSL(Gd,Dox) where the longitudinal relaxivities before and after heating were 1.2 ± 0.3 mM^− 1 s^− 1 and 4.4 ± 0.3 mM^− 1 s^− 1, respectively. Upon heating, Dox was released from TSL(Mn,Dox) and complexation of Mn^2 + to Dox resulted in a similar Mn^2 + release profile. From 25 to 38 °C, r₁ of [Gd(HPDO3A)(H₂O)] gradually increased due to increase transmembrane water exchange, while no Dox release was observed. From 38 °C, the release of [Gd(HPDO3A)(H₂O)] and Dox was irreversible and the release profiles coincided. By understanding the non-covalent interactions between the MRI CAs and phospholipid bilayer, the properties of the paramagnetic TSLs can be tailored for MR guided drug delivery.     

Effect of MDMA-Induced Axotomy on the Dorsal Raphe Forebrain Tract in Rats: An In Vivo Manganese-Enhanced Magnetic Resonance Imaging Study

3,4-Methylenedioxymethamphetamine (MDMA), also known as “Ecstasy”, is a common recreational drug of abuse. Several previous studies have attributed the central serotonergic neurotoxicity of MDMA to distal axotomy, since only fine serotonergic axons ascending from the raphe nucleus are lost without apparent damage to their cell bodies. However, this axotomy has never been visualized directly in vivo. The present study examined the axonal integrity of the efferent projections from the midbrain raphe nucleus after MDMA exposure using in vivo manganese-enhanced magnetic resonance imaging (MEMRI). Rats were injected subcutaneously six times with MDMA (5 mg/kg) or saline once daily. Eight days after the last injection, manganese ions (Mn²⁺) were injected stereotactically into the raphe nucleus, and a series of MEMRI images was acquired over a period of 38 h to monitor the evolution of Mn²⁺-induced signal enhancement across the ventral tegmental area, the medial forebrain bundle (MFB), and the striatum. The MDMA-induced loss of serotonin transporters was clearly evidenced by immunohistological staining consistent with the Mn²⁺-induced signal enhancement observed across the MFB and striatum. MEMRI successfully revealed the disruption of the serotonergic raphe-striatal projections and the variable effect of MDMA on the kinetics of Mn²⁺ accumulation in the MFB and striatum.     

ATG5 expression induced by MDMA (ecstasy), interferes with neuronal differentiation of neuroblastoma cells

The amphetamine derivative 3, 4-methylenedioxymethamphetamine (MDMA) has become a popular recreational drug, and has also been shown to cause serotonergic neurotoxicity. This report shows that MDMA impairs brain development in a whole mouse embryo culture. The results of quantitative real-time PCR analysis showed that autophagy-related protein 5 (Atg5) expression is elevated in mouse embryo and neuroblastoma cells after MDMA treatment. This elevated Atg5 expression interferes with the neuronal differentiation of neuroblastoma cells such as SH-SY5Y and PC12 cells. Thus, our results suggest that the use of MDMA during pregnancy may impair neuronal development via an induction of Atg5 expression.     

Ovarian follicular dynamics and plasma steroid concentrations are not significantly different in ewes given intravaginal sponges containing either 20 or 40 mg of fluorogestone acetate

Although various progestagens are often used to induce and synchronize estrus and ovulation in ruminants, concerns regarding residues are the impetus to develop alternative approaches, including reduced doses of progestagens. Therefore, the objective was to determine whether ovarian function was affected by halving the dose of fluorogestone acetate in intravaginal sponges for synchronizing ovulation in sheep during the physiologic breeding season. Twenty Manchega ewes, 4-6-year-old, were randomly allocated to receive an intravaginal sponge containing either 20 mg (P20, n = 10) or 40 mg of fluorogestone acetate (P40, n = 10). Cloprostenol (125 μg) was given at sponge insertion, and all sponges were removed after 6 d. Ovarian follicular dynamics (monitored by daily ultrasonography) and other aspects of ovarian function did not differ significantly between the two groups. Ovulatory follicles (OF) grew at a similar growth rate (r = 0.62; P < 0.001), with comparable initial and maximum diameters (4.2 ± 0.4 to 6.0 ± 0.3 mm in P20 vs. 4.6 ± 0.6 to 5.7 ± 0.2 mm in P40, mean ± S.E.M.). Plasma estradiol concentrations (determined once daily) increased linearly during the 72 h interval after sponge removal (1.3 ± 0.1 to 3.3 ± 0.1 pg/mL for P20, P < 0.005 and 1.4 ± 0.1 to 3.1 ± 0.2 pg/mL for P40, P < 0.005). Ten days after sponge removal, ovulation rates (1.2 ± 0.2 for P20 and 1.4 ± 0.3 for P40), and plasma progesterone concentrations (3.8 ± 0.35 ng/mL for P20 and 3.9 ± 0.38 ng/mL for P40) were similar. In conclusion, reducing the dose of fluorogestone acetate from 40 to 20 mg did not affect significantly ovarian follicular dynamics or other aspects of ovarian function.     

Complexation study of europium(III) and curium(III) with urea in aqueous solution investigated by time-resolved laser-induced fluorescence spectroscopy

The complex formation of europium(III) and curium(III) with urea in aqueous solution has been studied at I = 0.1 M (NaClO₄), room temperature and trace metal concentrations in the pH-range of 1-8 at various ligand concentrations using time-resolved laser-fluorescence spectroscopy. While for curium(III) the luminescence maximum is red shifted upon complexation, in case of europium(III) emission wavelengths remain unaltered but a significant change in peak splitting occurs. Both heavy metals form weak complexes of the formulae ML³⁺ and MLOH²⁺ with urea. Stability constants were determined to be log β₁₁₀ = −0.12 ± 0.05 and log β_11-1 = −6.86 ± 0.15 for europium(III) and log β₁₁₀ = −0.28 ± 0.12 and log β_11-1 = −7.01 ± 0.15 for curium(III).     

Development of high performance liquid chromatography/electrospray ionization mass spectrometry for assay of ginkgolic acid (15:1) in rat plasma and its application to pharmacokinetics study

A highly sensitive HPLC–ESI-MS method has been developed and validated for the quantification of ginkgolic acid (15:1) in a small quantity of rat plasma (50 μL) using its homologous compound ginkgolic acid (17:1) as an internal standard. GA (15:1) and GA (17:1) were extracted from biological matrix by direct protein precipitation with 5-fold volume of methanol and separated on an Elite hypersil BDS C₁₈ column (2.1 × 100 mm, 3 μm), eluted with acetonitrile:water (92:8, v/v, containing 0.3% glacial acetic acid). Linear range was 8–1000 ng/mL with the square regression coefficient (r²) of 0.996. The lowest concentration (8 ng/mL) in the calibration curve was estimated as LLOQ with both deviation of accuracy and RSD of precision <20% (n = 6). The intra- and inter-day precision ranged from 3.6% to 9.9%, and the intra- and inter-day accuracy was between 89.9% and 101.3%. This method was successfully applied to study pharmacokinetics of GA (15:1) in rats after oral administration at a dose of 10 mg/kg. GA (15:1) pharmacokinetic parameters C_max, T_max, t_1/2, AUC_0–12h are 1552.9 ± 241.0 ng/mL, 0.9 ± 0.7 h, 5.5 ± 2.6 h, 3356.0 ± 795.3 ng h/mL, respectively.     

Extended periods of neural induction and propagation of embryonic stem cell-derived neural progenitors with EGF and FGF2 enhances Lmx1a expression and neurogenic potential

Neural stem (NS) cells are multipotent cells defined by their capacity to proliferate and differentiate into all neuronal and glial phenotypes. NS cells can be obtained from specific regions of the adult brain, or generated from embryonic stem cells (ESCs). NS cells differentiate into neural progenitor (NP) cells and subsequently neural precursors, as transient steps towards terminal differentiation into specific mature neuronal or glial phenotypes. When cultured in EGF and FGF2, ESC-derived NS cells have been reported to be stable and multipotent. Conditions that enable differentiation of NS cells through the committed progenitor and precursor stages to specific neuronal subtypes have not been fully established. In this study we investigated, using Lmx1a reporter ESCs, whether the length of neural induction (NI) dictated the phenotypic potential of cultures of ESC-derived NS cells or NP cells. Following 4, 7 or 10 day periods of NI, ESCs in monolayer culture were harvested and cultured as neurospheres, prior to replating as monolayer cultures for several passages in EGF and FGF2. The NS/NP cultures were then directed towards mature neuronal fates over 16-17 days. 4 and 7-day NS cell cultures could not be differentiated towards dopaminergic, serotonergic or cholinergic fates as determined by the absence of tyrosine hydroxylase, 5-HT or choline acetyltransferase (ChAT) immunolabelling. In contrast NS/NP cultures derived after 10 days of NI were able to generate tyrosine hydroxylase and 5-HT positive neurons (24 ± 6 and 13 ± 1% of the βIII-tubulin positive population, respectively, n = 3). Our data suggest that extended periods of neural induction enhanced the potential of mouse ESC-derived NS/NP cells to generate specific subtypes of neurons. NS/NP cells derived after shorter periods of NI appeared to be lineage-restricted in relation to the neuronal subtypes observed after removal of EGF.     

Short- and long-term effects of MDMA ("ecstasy") on synaptosomal and vesicular uptake of neurotransmitters in vitro and ex vivo

3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") is a commonly abused drug which has been shown to be neurotoxic to serotonergic neurons in many species. The exact mechanism responsible for the neurotoxicity of MDMA is, however, poorly understood. In this study, the effects of MDMA on the synaptosomal and vesicular uptake of neurotransmitters were investigated. Our results show that MDMA (0.5-20 microM) reduces both synaptosomal and vesicular uptake of serotonin and dopamine in a dose dependent manner in vitro, while the uptake of glutamate and gamma-aminobutyric acid (GABA) remains unaffected. Ex vivo experiments support the importance of the monoamines, with predominant dopaminergic inhibition at short-term exposure (3 x 15 mg/kg; 2-h intervals), and exclusively serotonergic inhibition at long-term exposure (2 x 10 mg/kg per day; 4 days). This study also compares MDMA and the structurally related antidepressant paroxetine, in an attempt to reveal possible cellular mechanisms for the serotonergic toxicity of MDMA. One important difference between paroxetine and MDMA is that only MDMA has the capability of inhibiting vesicular uptake of monoamines at doses used. We suggest that inhibition of the vesicular monoamine transporter-2, and a following increase in cytoplasmatic monoamine concentrations, might be crucial for the neurotoxic effect of MDMA.