Glu), Γ-aminobutyric Acid Research Articles

LC-MS/MS-based quantification of tryptophan metabolites and neurotransmitters in the serum and brain of mice

l-Tryptophan (Trp) metabolites and related neurotransmitters play crucial roles in physiological functions, and their imbalances are implicated in the pathology of depression, Alzheimer's disease and other diseases. Measurement of Trp metabolites and related neurotransmitters possesses a great potential to elucidate the disease mechanisms and evaluate the outcomes of therapeutic interventions. A simple, rapid, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for simultaneous determination of Trp, l-kynurenine (Kyn), kynurenic acid (Kyna), 3-hydroxykynurenine (3-HK), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), norepinephrine (NE), l-glutamic acid (Glu), γ-aminobutyric acid (GABA) and acetylcholine (ACh) in mice serum and the brain tissues in a single chromatographic run. Samples were spiked with the internal standard, mixed with trifluoroacetic acid to precipitate protein and analyzed by LC-MS/MS. Chromatographic separation was achieved using a Restek Ultra Aqueous C18 column in combination with a gradient elution within 8 min. Mass spectrometric detection was performed using multiple reaction monitoring with electrospray ionization source in positive mode. The method exhibited good selectivity and correlation coefficient values for the calibration curves of each analyte were >0.99. The limit of detection and quantification ranged from 0.96 to 24.48 nmol/L and 3.42 to 244.82 nmol/L, respectively. The intra- and inter-day precision were ≤13.92%. All analytes were stable in prepared samples at room temperature in the autosampler for 24 h. This method was successfully applied to the analysis of biological samples from control and chronic mild stress (CMS) induced depression mice. It was found that Kyn and 3-HK pathways were enhanced by CMS, while the levels of Trp, Kyna, 5-HIAA, Glu, GABA and ACh were significantly reduced. The changes in 5-HT and NE levels were not uniform in the periphery and the brain. This method can therefore be applied to analyze Trp metabolites and related neurotransmitters levels to monitor disease states, study the mechanisms and outcomes of therapeutic interventions.

Exogenous l-glutamate treatment could induce resistance against Penicillium expansum in pear fruit by activating defense-related proteins and amino acids metabolism

Glutamate is a versatile amino acid and occupies a pivotal position in both mammals and higher plants. Here, we investigated the effects of exogenous l-glutamate (L-Glu) treatment on the inhibition of Penicillium expansum in postharvest pear fruit and possible mechanisms involved. The results showed that application of l-Glu at 1.00 mM induced strong resistance against blue mold rot caused by P. expansum in pear fruit under either 25 °C or 4 °C condition. Meanwhile, l-Glu reduced spore germination of P. expansum both in fruit wounds and in vitro after 24 h of treatment. With the treatment of l-Glu, the activities of five representative defense-related enzymes (β-1,3-glucanase, chitinase, phenylalnine ammonialyase, peroxidase and polyphenol oxidase) and the expression of four pathogenesis-related protein genes (PR1, GLU, CHI3 and CHI4) as well as PAL were all significantly enhanced. More interestingly, our results also revealed the possible involvement of amino acid metabolism, especially the accumulation of Glu, γ-aminobutyric acid (GABA) and arginine, may account for decay inhibition in the postharvest pear fruit to an extent.

Novel cogrinding of donepezil with neurotransmitters and coumarins: characterization, physical properties and in vitro drug release study

Abstract This research aimed to improve the physicochemical properties of the donepezil hydrochloride drug (DH) that is used for the treatment of mild to moderate Alzheimer’s disease. Due to the transformation of DH from the anhydrous to monohydrate state as a function of relative humidity (RH) and side effects from high absorption in the gastrointestinal system, we focused the study on the physicochemical properties of DH. The donepezil free base was prepared by slow evaporation of DH in methanol. The 1:1 molar ratio of DH and donepezil free base (DP-M) was cocrystallized with L-glutamic acid (Glu), γ-aminobutyric acid (GABA), dopamine hydrochloride (DM), and coumarin derivatives (7H4MC, 57DH4MC and 78DH4MC) using the co-grinding method. The drug was loaded into a 1:1 molar ratio of chitosan-gelatin composites sponge. The prepared samples were characterized using FT-IR, NMR, and SEM. The humidity and solubility of all samples were evaluated. All solid cocrystals were stable at room temperature (30±2 °C) with 57-70 % RH over a 2-month period and did not change to the hydrate form. Moreover, improved dissolution profiles were observed in HCl at pH 1.2 and phosphate buffer (PBS) at pH 7.4 and 37 °C. Finally, the cocrystals exhibited a slow and controlled release in vitro from the 1:1 molar ratio of chitosan-gelatin composite sponges in HCl at pH 1.2 and PBS at pH 7.4 after storage for 24 h. These results suggested that cocrystals are very promising for the enhancement of the donepezil drug when compared with DH.

Effect of 17β estradiol on propofol-induced long-term cognitive dysfunction in developing rats: the relationship with hippocampal Glu/GABA

Objective To evaluate the effect of 17β estradiol on propofol-induced long-term cognitive dysfunction in developing rats and the relationship with hippocampal glutamate (Glu)/γ-aminobutyric acid (GABA). Methods Sixty healthy male Sprague-Dawley rats, aged 7 days, weighing 11-18 g, were divided into 5 groups (n=12 each) using a random number table method: dimethyl sulfoxide (DMSO) group, fat emulsion group (group F), 17β estradiol group (group E), propofol group (group P) and propofol plus 17β estradiol group (group P+ E).17β estradiol 600 μg/kg was subcutaneously injected in group E, and the equal volume of DMSO was given instead in group DMSO.Propofol 75 mg/kg was intraperitoneally injected in group P, and the equal volume of fat emulsion was given instead in group F. 17β estradiol 600 μg/kg was subcutaneously injected and 30 min later propofol 75 mg/kg was intraperitoneally injected in group P+ E.Injection was performed once every 24 h for 7 consecutive days in each group.Morris water maze test was performed at 60 days of age.The rats were sacrificed after the end of Morris water maze test and hippocampi were removed for determination of Glu content (by ultraviolet colorimetry method) and GABA content (using enzyme-linked immunosorbent assay) in hippocampal tissues.Glu/GABA ratio was calculated. Results There was no significant difference in the escape latency, the number of crossing the original platform, percentage of time spent in target quadrant, Glu content or Glu/GABA ratio between group DMSO, group F and group E (P>0.05). There was no significant difference in GABA content among the five groups (P>0.05). Compared with group F, the escape latency was significantly prolonged, the number of crossing the original platform was reduced, and the percentage of time spent in target quadrant, Glu content and Glu/GABA ratio were decreased in group P (P<0.05). Compared with group P, the escape latency was significantly shortened, the number of crossing the original platform was increased, and the percentage of time spent in target quadrant, Glu content and Glu/GABA ratio were increased in group P+ E (P<0.05). Conclusion 17β estradiol can improve propofol-induced long-term cognitive dysfunction and the mechanism may be related to maintaining hippocampal Glu/GABA balance in developing rats. Key words: Propofol; Estradiol; Cognition disorders; Glutamic acid; gamma-Aminobutyric acid; Hippocampus

Study on the effect of acupuncture at Sìshéncōng (四神聪 EX-HN 1) and Băihuì (百会 GV 20) on the serum amino acids neurotransmitters of insomnia patients

ObjectiveTo explore the efficacy of acupuncture at Sìshéncōng (四神聪 EX-HN 1) and Băihuì (百会 GV 20) as well as the possible mechanism. MethodsEighty cases of insomnia patients treated in our hospital were selected, and randomly divided into a control group and a treatment group according to the random number table method. Conventional treatment was carried out in the control group by giving diazepam tablets, and acupuncture at EX-HN 1 and GV 20 was conducted in the treatment group. The sleep time and quality, PSQI score, and the level changes of blood glutamic acid (GLU), γ-aminobutyric acid (GABA), norepinephrine (NE) and dopamine (DA) were compared in the patients in each group before and after treatment. ResultsCompared with the results before treatment, the time for falling asleep of the patients in the two groups shortened (both P<0.05), the levels of GLU and GABA increased (all P<0.05), the sleep time was longer (both P<0.05), and the levels of NE and DA, as well as the PSQI score reduced (all P<0.05). Compared with the control group, the levels of NE and DA, as well as the PSQI score of patients in the treatment group reduced after treatment (P<0.05), the time for falling asleep shortened (P<0.05), the levels of GLU and GABA increased (P<0.05), and the sleep time was longer (P<0.05). ConclusionAcupuncture at EX-HN 1 and GV 20 can prolong the sleep time, improve the sleep quality, and the clinical efficacy is superior to that of western medicine treatment. The mechanism may be related to the synthesis and release of amino acids neurotransmitters.

Metabolomics of Neurotransmitters and Related Metabolites in Post-Mortem Tissue from the Dorsal and Ventral Striatum of Alcoholic Human Brain.

We report on changes in neurotransmitter metabolome and protein expression in the striatum of humans exposed to heavy long-term consumption of alcohol. Extracts from post mortem striatal tissue (dorsal striatum; DS comprising caudate nucleus; CN and putamen; P and ventral striatum; VS constituted by nucleus accumbens; NAc) were analysed by high performance liquid chromatography coupled with tandem mass spectrometry. Proteomics was studied in CN by two-dimensional gel electrophoresis followed by mass-spectrometry. Proteomics identified 25 unique molecules expressed differently by the alcohol-affected tissue. Two were dopamine-related proteins and one a GABA-synthesizing enzyme GAD65. Two proteins that are related to apoptosis and/or neuronal loss (BiD and amyloid-β A4 precursor protein-binding family B member 3) were increased. There were no differences in the levels of dopamine (DA), 3,4-dihydrophenylacetic acid (DOPAC), serotonin (5HT), homovanillic acid (HVA), 5-hydroxyindoleacetic acid (HIAA), histamine, L-glutamate (Glu), γ-aminobutyric acid (GABA), tyrosine (Tyr) and tryptophan (Tryp) between the DS (CN and P) and VS (NAc) in control brains. Choline (Ch) and acetylcholine (Ach) were higher and norepinephrine (NE) lower, in the VS. Alcoholic striata had lower levels of neurotransmitters except for Glu (30 % higher in the alcoholic ventral striatum). Ratios of DOPAC/DA and HIAA/5HT were higher in alcoholic striatum indicating an increase in the DA and 5HT turnover. Glutathione was significantly reduced in all three regions of alcohol-affected striatum. We conclude that neurotransmitter systems in both the DS (CN and P) and the VS (NAc) were significantly influenced by long-term heavy alcohol intake associated with alcoholism.

Simultaneous determination of 8 neurotransmitters and their metabolite levels in rat brain using liquid chromatography in tandem with mass spectrometry: Application to the murine Nrf2 model of depression

Analysis of neurotransmitters and their metabolites is useful for the diagnosis of central nervous system diseases. A liquid chromatography–tandem mass spectrometry (LC–MS/MS) method with protein precipitation was developed to monitor levels of adrenaline (AD), noradrenaline (NA), glutamic acid (Glu), γ-aminobutyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT), 5-hydroxyindole acetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) in rat brain tissue. Isoprenaline was used as an internal standard (IS). Neurotransmitters and metabolites were eluted with a reverse phase column under gradient conditions through a mobile phase consisting of 0.2% formic acid water solution/acetonitrile. The compounds were detected and quantified by LC–MS/MS with positive or negative electrospray ionization, which operates in multiple-reaction monitoring mode. The method was linear or polynomial (R2>0.99) for AD, NA, Glu, GABA, DA, 5-HT, 5-HIAA, and MHPG in the range of 0.25–200, 0.5–200, 250–20,000, 250–20,000, 0.25–200, 10–3000, 1–50, and 1–50ng/mL, respectively. The validation assays for accuracy and precision, matrix effect, extraction recovery, stability and carry-over of the samples for neurotransmitters and metabolites were consistent with the requirements of regulatory agencies. The method enables rapid quantification of neurotransmitters and their metabolites and has been applied in the nuclear factor (erythroid 2-derived)–like 2 (Nrf2) knockout mouse model of depression.

Propofol differentially inhibits the release of glutamate, γ-aminobutyric acid and glycine in the spinal dorsal horn of rats.

Propofol (2, 6-diisopropylphenol) is an intravenous anesthetic that is commonly used for the general anesthesia. It is well known that the spinal cord is one of the working targets of general anesthesia including propofol. However, there is a lack of investigation of the effects of propofol on spinal dorsal horn which is important for the sensory transmission of nociceptive signals. The objective of this study was to investigate the effects of increasing dosage of propofol on the release of glutamate (Glu), γ-aminobutyric acid (GABA) and glycine (Gly) in the spinal dorsal horn. The efflux of Glu, GABA or Gly in the spinal dorsal horn of rats was detected using transverse spinal microdialysis under an awake condition and various depths of propofol anesthesia. The infusion rates of propofol were, in order, 400 µg/(kg·min), 600 µg/(kg·min) and 800 µg/(kg·min), with a 20 min infusion period being maintained at each infusion rate. Propofol decreased the glutamate efflux within spinal dorsal horn in a dose-dependent manner, and the maximum decrease was 56.8 ± 6.0% at high-dose propofol infusion producing immobility. The inhibitory GABA and Gly efflux was also decreased about 15-20% at low-dose propofol infusion only producing sedation, but did not continue to drop with higher doses of propofol. Propofol decreased both excitatory and inhibitory amino acids efflux in spinal dorsal horn, and the preferential suppression of the excitatory amino acid might be associated with the analgesic effect of propofol.

Correlation of maternal abuse during pregnancy with infant temperament and development

ObjectiveTo investigate the effects of domestic violence (DV) against pregnant women on their infant's development in China.Design247 mothers were interviewed using the Chinese version of the Abuse Assessment Screen, and...

Changes in hypothalamic neurotransmitter and prostanoid levels in response to NMDA, CRF, and GLP-1 stimulation.

Determination of neuroactive substances, such as neurotransmitters and prostanoids, in the extracellular space of the living brain is a very important technique in neuroscience. The hypothalamic paraventricular nucleus (PVN) is one of the most important autonomic control centers in the brain. Recently, we demonstrated that thromboxane (Tx) A2 in the PVN may play an important role in adrenomedullary outflow evoked by N-methyl-D-aspartate (NMDA), corticotrophin-releasing factor (CRF), and glucagon-like peptide-1 (GLP-1) stimulation using microdialysis sampling and liquid chromatography-ion trap tandem mass spectrometry (LC-ITMS(n)). In the present study, we investigated whether centrally administered NMDA, CRF, and GLP-1 can release five neurotransmitters, acetylcholine (ACh), histamine, glutamate (Glu), γ-aminobutyric acid (GABA), and serotonin (5-HT), along with six prostanoids, TxB2, prostaglandin (PG) E2, PGD2, 15-deoxy-∆(12,14) (15d)-PGJ2, 6-keto-PGF1α, and PGF2α in rat PVN microdialysates after optimization of LC-ITMS(n) conditions . All stimulations increased the levels of 5-HT, TxB2, PGE2, and PGF2α (except for 5-HT stimulated with GLP-1). Only NMDA increased the levels of ACh, Glu, and GABA. Treatment with dizocilpine maleate (MK-801), a noncompetitive NMDA receptor antagonist, attenuated the NMDA-induced increase in the levels of neuroactive substances except for Glu. This is the first study to use LC-ITMS(n) to analyze neurotransmitters and prostanoids in the same microdialysates from rat PVN.

An update of the classical and novel methods used for measuring fast neurotransmitters during normal and brain altered function.

To understand better the cerebral functions, several methods have been developed to study the brain activity, they could be related with morphological, electrophysiological, molecular and neurochemical techniques. Monitoring neurotransmitter concentration is a key role to know better how the brain works during normal or pathological conditions, as well as for studying the changes in neurotransmitter concentration with the use of several drugs that could affect or reestablish the normal brain activity. Immediate response of the brain to environmental conditions is related with the release of the fast acting neurotransmission by glutamate (Glu), γ-aminobutyric acid (GABA) and acetylcholine (ACh) through the opening of ligand-operated ion channels. Neurotransmitter release is mainly determined by the classical microdialysis technique, this is generally coupled to high performance liquid chromatography (HPLC). Detection of neurotransmitters can be done by fluorescence, optical density, electrochemistry or other detection systems more sophisticated. Although the microdialysis method is the golden technique to monitor the brain neurotransmitters, it has a poor temporal resolution. Recently, with the use of biosensor the drawback of temporal resolution has been improved considerably, however other inconveniences have merged, such as stability, reproducibility and the lack of reliable biosensors mainly for GABA. The aim of this review is to show the important advances in the different ways to measure neurotransmitter concentrations; both with the use of classic techniques as well as with the novel methods and alternant approaches to improve the temporal resolution.

Absolute Quantitation of Glutamate, GABA and Glutamine using Localized 2D Constant-time COSY Spectroscopy in Vivo

We propose an absolute quantitation method for metabolites with strongly coupled spin systems using localized 2-dimensional (2D) constant-time correlation spectroscopy (CT-COSY). We also develop two methods for improving the quality of in vivo CT-COSY spectra. We substituted an image selected in vivo spectroscopy (ISIS) pulse for a 180° slice pulse in the CT-COSY module to decrease the slice displacement error caused by the chemical shift difference. We measured the slice displacement error due to the differences in the carrier frequency of slice pulse in a phantom experiment to demonstrate this feature. We also developed an asymmetric sampling scheme along the t1 direction to resolve diagonal peaks even in the magnitude mode of 2D spectra. We collected CT-COSY signals of a human brain for a 14% asymmetric sampling scheme. After reconstruction, we obtained a 2D CT-COSY spectrum in magnitude mode and compared a peak of glutamate (Glu) C4H on that spectrum to a peak displayed in absorption mode. In our proposed absolute quantitation method, we developed T2 correction, curve-fitting for computing peak volume and calibration by an internal water reference. We used the method to measure the Glu concentration in 10-mM glutamate phantom experiments. We also attempted to measure concentrations of Glu, γ-aminobutyric acid (GABA) and glutamine (Gln) in a human brain. Slice displacement error was decreased by a factor of 2.5 using the proposed sequence. Spectra with narrow linewidths could be obtained using the asymmetric sampling scheme in the magnitude mode. Measured Glu concentration in the solution phantom was 9.4 mM. Concentrations of Glu (9.5 mM), GABA (0.61 mM) and Gln (3.6 mM) in a human brain measured by our method agreed well with previously reported values. Concentrations of metabolites with strongly coupled spin systems can be measured using our proposed absolute quantitation method on 2D CT-COSY spectra.

Liquid chromatography–tandem mass spectrometry method for determination of panel of neurotransmitters in cerebrospinal fluid from the rat model for tauopathy

Alzheimer's disease (AD) is still being recognized today as an unmet medical need. Currently, there is no cure and early preclinical diagnostic assay available for AD. Therefore much attention is now being directed at the development of novel methods for quantitative determination of AD biomarkers in the cerebrospinal fluid (CSF). Here, we describe the liquid chromatography-tandem mass spectrometry method for determination of 5-hydroxytryptamine (SER), 5-hydroxyindoleacetic acid (5-HIAA), homovanilic acid (HVA), noradrenaline (NADR), adrenaline (ADR), dopamine (DA), glutamic acid (Glu), γ-aminobutyric acid (GABA), 3,4-dihydroxyphenylacetic acid (DOPAC) and histamine (HIS) in cerebrospinal fluid (CSF) from the rat model for human tauopathy. The benzoyl chloride was used as pre-column derivatization reagents. Neurotransmitters and metabolites were analysed on ultra performance liquid chromatography (UPLC) on C18 column in combination with tandem mass spectrometry. The method is simple, highly sensitive and showed excellent linearity with regression coefficients higher than 0.99. The accuracy was in a range of 93-113% for all analytes. The inter-day precision (n=5 days), expressed as %RSD, was in a range 2-10% for all analytes. Using this method we detected significant changes of CSF levels of two important neurotransmitters/metabolites, ADR and 5-HIAA, which correlates with progression of neurodegeneration in our animal model.

Determination of monoamine and amino acid neurotransmitters and their metabolites in rat brain samples by UFLC–MS/MS for the study of the sedative-hypnotic effects observed during treatment with S. chinensis

Schisandra chinensis (Turcz.) Baill. has been used as a sedative and hypnotic agent in traditional Chinese medicine for centuries. The purpose of this study was to reveal the influence of insomnia on the levels of the neurotransmitters: glutamate (Glu), γ-aminobutyric acid (GABA), noradrenaline (NE), dopamine (DA), serotonin (5-HT) and their metabolites (5-HIAA, DOPAC and HVA), and to study the role of S. chinensis in the treatment of insomnia. To achieve this goal, an efficient, sensitive and selective method was developed and validated for the simultaneous determination of these five neurotransmitters and their metabolites in rat brain samples using ultra fast liquid chromatography/tandem mass spectrometry (UFLC–MS/MS). The analysis was performed on a Synergi Fusion-RP 80A ODS column (150mm×2.0mm, 4.0μm) using gradient elution, with the mobile phase consisting of acetonitrile and 0.05% formic acid in water. The method was validated using rat brain homogenate samples and showed a good linearity over a wide concentration range (r2>0.99) with a lower limit of quantification (LLOQ) at 4–16ngmL−1. The intra and inter-day assay variability was less than 15% for all analytes. The results indicated that the condition of insomnia elevated GABA, NE, DA, DOPAC and HVA, and reduced 5-HT, 5-HIAA levels in rat brain. The oral administration of S. chinensis (7.5gkg−1day−1, eight days) influenced insomnia by significantly increasing or reducing the levels of the neurotransmitters parameters mentioned above. These results suggested that S. chinensis could alter the levels of these brain neurotransmitters and their metabolites through its sedative-hypnotic effects.

Change in plasma levels of amino acid neurotransmitters and its correlation with clinical heterogeneity in early Parkinson's disease patients.

The correlation between plasma amino acid (AA) neurotransmitters and clinical heterogeneity in early patients with Parkinson's disease (PD) is still poorly understood. To examine the plasma levels of AA neurotransmitters in early patients with PD and to evaluate their correlation with PD subtypes. Based on the predominant symptoms, fifty-one patients with PD were enrolled and divided into four subgroups: (1) akinetic-rigid type (ART), (2) tremor-dominant type (TDT), (3) postural instability/gait difficulty type (PIGD), and (4) mixed type (MT). Plasma levels of AA were measured by HPLC-RF, and their potential diagnostic practicality and their association with PD subtypes were evaluated by the receiver operating characteristic (ROC) and correlation analysis, respectively. Patients with PD exhibited markedly lower levels of Asp, Glu, Tau, L-ser, and lower values of Glu/GABA ratio than healthy controls. The ROC analysis revealed their high sensitivity (77.1-87.5%) and specificity (58.8-88.2%). Furthermore, the glutamic acid (Glu), γ-aminobutyric acid (GABA) level in the PIGD subtype was increased as compared with other subtypes and was negatively correlated with the ART/PIGD ratio. The decrease in plasma Asp, Glu, Tau, L-ser levels, and the value of Glu/GABA ratio may be helpful for early PD diagnosis. The elevated GABA level may be the biochemical basis for the specific symptoms of PIGD PD.

Regulatory Mechanisms of Skeletal Tissues by Amino Acid Signaling

In this review, we would outline the possible signaling system for three types of amino acids including glutamate (Glu), γ-aminobutyric acid (GABA) and D-serine (D-Ser) to play a role as an extracellular signal mediator in mechanisms underlying maintenance of the cellular homeostasis in skeletal tissues. Although Glu and GABA has been thought to be an excitatory/inhibitory amino acid neurotransmitter in the mammalian central nervous system, our molecular biological analyses give rise to a novel function for Glu and GABA as an autocrine and/or paracrine factor in three types of distinct cell types including osteoblasts, osteoclasts and chondrocytes in bone tissues. Moreover, D-Ser plays a pivotal role in osteoclastogenesis through a mechanism related to the incorporation of serine enantiomers in osteoclasts after the synthesis and subsequent release from adjacent osteoblasts. Accordingly, bone formation and maintenance seems to be under control by amino acid signaling in skeletal tissues as seen with neurotransmission in the brain.

Mechanisms of neurotoxicity and implications for neurological disorders

Keywords: chemical contaminants, neurodegeneration, neurodevelopment, neuroinflammation, neurotoxicty.On 13 July 2012, in conjunction with the 8th FENSForum of Neuroscience in Barcelona, Dr. JordiLlorens and I organized a Satellite Event in theform of a 1-day symposium. The main focus of thesymposium was on the mechanisms of neurotox-icity potentially involved in neurodegenerative dis-eases or neurodevelopmental disorders. Aspectsincluding gene–environment interactions, specificcellular alterations and neurodevelopmental impli-cations were covered by internationally recognizedexperts in their respective field. Reviews based onsix of the oral presentations from invited speakersare included in this issue of the Journal of InternalMedicine.The review by Dr. Julie Andersen, Buck Institutefor Age Research, Novato CA, USA, discusses thepossible link between environmental stress,aging, glial cell senescence and Parkinson’s dis-ease [1]. Certain chronic environmental expo-sures have been linked to the age-relateddevelopment of Parkinson’s disease neuropathol-ogy. Neuronal damage is believed to involve theinduction of neuroinflammatory events mediatedby glial cell activation. Senescent cells accumu-late with age, and they express a senescence-associated secretory phenotype (SASP) connectedto the secretion of many inflammatory cytokines,growth factors and proteases. Andersen proposesthat senescent glia could contribute to age-related neurodegeneration by creating a chroni-cally inflamed milieu. If correct, this novelpotential link between glial senescence and Par-kinson’s disease could change the current under-standing on the role of glial cells in age-relatedneurodegenerative diseases. In particular envi-ronmental stressors associated with Parkinson’sdisease, such as paraquat and MPTP, may act inpart by eliciting senescence and SASP expressionby glial cells in the aging brain, thereby contrib-uting to the characteristic decline in neuronalintegrity that occurs in the disorder.Dr. Rosario Moratalla, Instituto Cajal, CSIC,Madrid,describesinherreviewtheroleofdopaminereceptors in the neurotoxicity of the synthetic drugmethamphetamine [2]. Despite its neurotoxiceffects including loss of dopaminergic fibres andcell bodies, methamphetamine is consumed bymillions of users. There is evidence from clinicalreports suggesting that methamphetamine abusersare predisposed to Parkinson’s disease. The mech-anism of methamphetamine neurotoxicity involvesdopamine receptors. In fact, genetic inactivation ofD1orD2receptorsubtypesprotectsagainstthelossof dopaminergic fibres in the striatum and loss ofdopaminergic neurons in the substantia nigrainduced by methamphetamine. The protectiongiven by D1 receptor inactivation is due to blockadeof hyperthermia, lower dopamine content and turn-over,andhigherlevelsofstoredvesiculardopaminein D1 receptor

Manganese toxicity in the central nervous system: the glutamine/glutamate‐γ‐aminobutyric acid cycle

Manganese (Mn) is an essential trace element that is required for maintaining proper function and regulation of numerous biochemical and cellular reactions. Despite its essentiality, at excessive levels Mn is toxic to the central nervous system (CNS). Increased accumulation of Mn in specific brain regions, such as the substantia nigra, globus pallidus and striatum, triggers neurotoxicity resulting in a neurological brain disorder, termed manganism. Mn has been also implicated in the pathophysiology of several other neurodegenerative diseases. Its toxicity is associated with disruption of the glutamine (Gln)/glutamate (Glu)-γ-aminobutyric acid (GABA) cycle (GGC) between astrocytes and neurons, thus leading to changes in Glu-ergic and/or GABAergic transmission and Gln metabolism. Here we discuss the common mechanisms underlying Mn-induced neurotoxicity and their relationship to CNS pathology and GGC impairment.

Role of astrocytes in manganese mediated neurotoxicity

Astrocytes are responsible for numerous aspects of metabolic support, nutrition, control of the ion and neurotransmitter environment in central nervous system (CNS). Failure by astrocytes to support essential neuronal metabolic requirements plays a fundamental role in the pathogenesis of brain injury and the ensuing neuronal death. Astrocyte-neuron interactions play a central role in brain homeostasis, in particular via neurotransmitter recycling functions. Disruption of the glutamine (Gln)/glutamate (Glu) -γ-aminobutyric acid (GABA) cycle (GGC) between astrocytes and neurons contributes to changes in Glu-ergic and/or GABA-ergic transmission, and is associated with several neuropathological conditions, including manganese (Mn) toxicity. In this review, we discuss recent advances in support of the important roles for astrocytes in normal as well as neuropathological conditions primarily those caused by exposure to Mn.

RP-LC with Fluorescence Detection of Amino Acids in Rat Brain Synaptosomes

For the first time, a simple and validated reversed-phase liquid chromatography (RP-LC) with fluorescence detection has been developed for the simultaneous analysis of glutamate (Glu), γ-aminobutyric acid (GABA), glycine (Gly) and taurine (Tau) in Wistar and tremor rats brain synaptosomes. The samples were separated on a C18 analytical column with gradient elution of methanol and 0.1 mol L−1 potassium acetate at a flow rate of 1 mL min−1. Total run time was approximately 25 min. All calibration curves exhibited good linearity (r 2 > 0.999) within test ranges. The reproducibility was estimated by intra-and inter-day assays and RSD values were less than 2.48%. The recoveries were between 96.32 and 105.21%. The method was successfully applied to the quantification of amino acids in Wistar and tremor rats brain synaptosomes. Through this developed protocol, the levels of Glu in hippocampal and prefrontal cortical synaptosomes of tremor rats were both significantly elevated than those of adult Wistar rats whereas significantly decreased concentrations of GABA and Gly were observed in the hippocampal region of tremor rats without evident difference in the prefrontal cortex between experimental and control groups. In addition, our studies also showed a marked elevation of Tau in tremor rats hippocampal synaptosomes although there was no pronounced difference in the prefrontal cortical region of Wistar and tremor rats.