Determination Of Amino Acid Neurotransmitters Research Articles

Simultaneous determination of amino acid and monoamine neurotransmitters in serum by high performance liquid chromatography coupled with precolumn derivatization

Using o-phthalaldehyde (OPA) as the derivatization reagent, a precolumn derivatized -high performance liquid chromatography (HPLC) method was developed for the simultaneous determination of amino acid neurotransmitters taurine (Tau), glutamic acid (Glu), glycine(Gly), and γ -aminobutyric acid (γ-GABA), as well as the monoamine neurotransmitter dopamine (DA), in serum samples. The samples and ethanol were mixed at a volume ratio of 1:2 (v/v) for protein precipitation. After centrifugation, the supernatant was withdrawn and blown to dryness using nitrogen. The residue was pre-column derivatized with OPA, and the derivatized product was isolated by gradient elution ona Luna 5u C18 column (250 mm×4.6 mm, 5 μm). Under the optimal experimental conditions, the five neurotransmitters showed good linearities (r2 ≥ 0.9866). The limits of detection were between 0.10 and 0.40 μmol/L. The spiked recoveries at different spiked levels were 87.57%-115.31%, and the RSDs were below 7.80%. This method is simple, sensitive, and it can be promised for the simultaneous detection of amino acid and monoamine neurotransmitters.

Analysis of amino acid neurotransmitters from rat and mouse spinal cords by liquid chromatography with fluorescence detection

A RP-LC-FL detection method has been developed to identify and quantitate four amino acid neurotransmitters including glutamic acid, glycine, taurine and γ-aminobutyric acid in rat and mouse spinal cord tissue. 3-(4-carboxybenzoyl)-2-quinolinecarboxaldehyde (CBQCA) was employed for the derivatization of these neurotransmitters prior to RP-LC-FL analysis. Different parameters which influenced separation and derivatization were optimized. Under optimum conditions, linearity was achieved within the concentration ranges of 0.50–50.00μM for all analytes with correlation coefficients from 0.9912 to 0.9997. The LODs ranged from 0.03μM to 0.06μM. The proposed method has been successfully applied to the determination of amino acid neurotransmitters in biological samples such as rat and mouse spinal cord with satisfactory recoveries.

Determination of amino acid neurotransmitters in rat hippocampi by HPLC‐UV using NBD‐F as a derivative

A simple, rapid and accurate high-performance liquid chromatography method with ultraviolet-visible detection was developed for the determination of five amino acid neurotransmitters - aspartate, glutamic acid, glycine, taurine and γ-aminobutyric acid - in rat hippocampi with pre-column derivatization with 4-fluoro-7-nitrobenzofurazan. Several conditions which influenced derivatization and separation, such as pH, temperature, acetonitrile percentage mobile phase and flow rate, were optimized to obtain a suitable protocol for amino acids quantification in samples. The separation of the five neurotransmitter derivatives was performed on a C18 column using a mobile phase consisting of phosphate buffer (0.02 mol/L, pH 6.0)-acetonitrile (84:16, v/v) at a flow rate of 1.0 mL/min with the column temperature at 30°C. The detection wavelength was 472 nm. Without gradient elution, the five neurotransmitter derivatives were completely separated within 15 min. The linear relation was good in the range from 0.50 to 500 µmol/L, and the correlation coefficients were ≥0.999. Intra-day precision was between 1.8 and 3.2%, and inter-day precision was between 2.4 and 4.7%. The limits of detection (signal-to-noise ratio 3) were from 0.02 to 0.15 µmol/L. The established method was used to determine amino acid neurotransmitters in rat hippocampi with satisfactory recoveries varying from 94.9 to 105.2%.

Determination of amino acid neurotransmitters in mouse brain tissue using high-performance liquid chromatography with fluorescence detection

Determination of amino acid neurotransmitters in mouse brain tissue using high-performance liquid chromatography with fluorescence detection

Determination of amino acid neurotransmitters in mouse brain tissue using high-performance liquid chromatography with fluorescence detection

Determination of amino acid neurotransmitters in mouse brain tissue using high-performance liquid chromatography with fluorescence detection

1,3,5,7-Tetramethyl-8-(N-hydroxysuccinimidyl butyric ester)difluoroboradiaza-s-indacene as a new fluorescent labeling reagent for HPLC determination of amino acid neurotransmitters in the cerebral cortex of mice

1,3,5,7-Tetramethyl-8-(N-hydroxysuccinimidyl butyric ester)difluoroboradiaza-s-indacene (TMBB-Su), a new BODIPY-based fluorescent probe, was designed and synthesized for the labeling of amino compounds. It was used as a pre-column derivatizing reagent for determination of amino acid neurotransmitters by high-performance liquid chromatography (HPLC). The fluorescence quantum yield in acetonitrile increased from 0.84 to 0.95 when it reacted with amino acid neurotransmitters. Derivatization of TMBB-Su with seven amino acid neurotransmitters was completed within 30 min at 25 °C in 24.0 mmol L(-1) pH 7.8 boric acid buffer. The separation was performed on a C(18) column with methanol-water-buffer 55:35:10 (v/v) as mobile phase (buffer: 0.10 mol L(-1) H(3)Cit-0.10 mol L(-1) NaOH). Interference from the other concomitant amino acids was eliminated successfully by means of pH gradient elution. With fluorescence detection at 494 and 504 nm for excitation and emission, respectively, the limits of detection (signal-to-noise ratio = 3) were from 2.1 to 12.0 nmol L(-1). The proposed method has been used to determine amino acid neurotransmitters in the cerebral cortex of mice with cerebral ischemia at the convalescence stage with satisfactory recoveries varying from 94.9 to 105.2%.

Using Single-Walled Carbon Nanotubes as Solid-Phase Extraction Adsorbent for the Sensitive Determination of Amino Acid Neurotransmitters in Human Cerebrospinal Fluids

Carbon nanotubes are a kind of new carbon-based nanomaterials, which have drawn great attention in many application fields including the biomarker analysis in biomedical and clinical research. In the present study, the feasibility of single-walled carbon nanotubes (SWCNTs) as solid-phase extraction (SPE) adsorbent for the determination of amino acid neurotransmitters (AANs) (glutamic, dopamine and γ-amino-n-butyric acid) in human cerebrospinal fluids (CSFs) was investigated. Various parameters affecting SPE efficiency including the eluent and its volume, adsorbent amount and sample volume were systematically studied. The acquired calibration curves were linear (r2 > 0.999) over the concentration range 10 to 500 ng per injection. By using SWCNTs as the SPE adsorbent, the detection limit of 12.9-42.5 fmol (at S/N of 3) were achieved with the preconcentration efficiency of more than 500-folds. The feasibility of the proposed method was validated by successfully applied to the measurements of ANNs in human CSFs sampled from healthy subjects and the patients with human immunodeficiency virus (HIV) infection, malignant melanoma and hypertension. This original application represents a powerful tool to study the kinetics of ANNs release by neuronal cells during neurotransmission, as well as for the understanding of the pathobiological and therapeutic basis of these remarkable molecular for diverse diseases.

Determination of amino acid neurotransmitters in human cerebrospinal fluid and saliva by capillary electrophoresis with laser‐induced fluorescence detection

A CE-LIF detection method has been developed to identify and quantitate six amino acid neurotransmitters including glutamic acid, aspartic acid, gamma-aminobutyric acid, glycine, taurine, and glutamine. N-hydroxysuccinimidyl fluorescein-O-acetate, a fluorescein-based dye, was employed for the derivatization of these neurotransmitters prior to CE-LIF analysis. Different parameters which influenced separation and derivatization were optimized in detail. Under optimum conditions, linearity was achieved within concentration ranges of up to three orders of magnitudes for those analytes with correlation coefficients from 0.9989 to 0.9998. The LODs ranged from 0.06 nM to 0.1 nM, and are thus superior or equivalent to those previously reported in the literature using CE-LIF detection. The proposed method has been successfully applied to the determination of amino acid neurotransmitters in biological samples such as human cerebrospinal fluid and saliva with satisfactory recoveries.

Determination of amino acid neurotransmitters in cerebral cortex of rats administered with baicalin prior to cerebral ischemia by capillary electrophoresis–laser-induced fluorescence detection

An efficient, sensitive and rapid analysis of the amino acid neurotransmitters in the cerebral cortex of rats was developed by capillary electrophoresis with laser-induced fluorescence detection and fluorescein isothiocyanate (FITC) derivatization. This method was used to investigate the pharmacological effect of baicalin during cerebral ischemia. Different parameters which influenced derivatization and separation were optimized. The separation of amino acids was carried out in an uncoated fused-silica capillary (57 cm×75 μm I.D.) with a buffer of 15 m M borate at pH 9.2 and an applied voltage of 17.5 kV. The detection limits for six amino acids were in the range of 2.1×10 −11–6.3×10 −10 M. The changes in the level of amino acid neurotransmitters in brain cortex of three experimental rat groups were studied by this capillary electrophoresis–laser-induced fluorescence detection method. The results show that cerebral ischemia can cause a significant elevation in the concentrations of Glu, Asp, GABA, and Gly in cerebral cortex. Baicalin administration can attenuate the elevations of Glu and Asp induced by cerebral ischemia. This research demonstrates that baicalin may act as a neuroprotectant during cerebral ischemia.

Central Amino Acids Mediate Cardiovascular Response to Angiotensin II in the Rat

To elucidate the role of the rostral ventrolateral medulla (RVLM) in cardiovascular control through the release of central amino acid neurotransmitters, experiments were performed in Sprague–Dawley (normotensive) rats and spontaneously hypertensive rats (SHR) anesthetized with urethane by using microdialysis sampling from the RVLM for determination of amino acid neurotransmitters. The baseline release of the excitatory amino acid neurotransmitter, glutamate (GLU) from the RVLM in SHR was higher and those of the inhibitory amino acid neurotransmitters, glycine (GLY), taurine (TAU), and γ-aminobutyric acid (GABA), were lower than in normotensive rats. Microinjection of angiotensin II (ANG II) into the RVLM caused a dose-dependent increase in mean arterial pressure (MAP) and heart rate (HR), accompanied by increased release of GLU in the RVLM. In contrast, microinjection of the ANG II type 1 receptor (AT 1) antagonist CV 11974 into the RVLM reduced MAP and HR, accompanied by increased release of GLY, TAU and GABA. These changes in MAP and HR after administration of ANG II or AT 1 antagonist were partially blocked by the use of the corresponding antagonist of each amino acid neurotransmitter. Furthermore, these effects were more prominently seen in SHR than in normotensive rats. These results suggest that the release of amino acid neurotransmitters mediate the cardiovascular effects of the angiotensin system in the RVLM, which may be involved in the generation of hypertension in SHR.