Quantification of rat brain neurotransmitters and metabolites using liquid chromatography/electrospray tandem mass spectrometry and comparison with liquid chromatography/electrochemical detection

Abstract

Analytical methodology based on solid-phase extraction, polar reversed-phase liquid chromatography, and electrospray tandem mass spectrometry (LC/MS/MS) with isotope dilution was developed and validated for quantifying the neurotransmitters, dopamine and serotonin, and their major metabolites in brain tissue. Limits of detection (0.1-20 pg/mg tissue) were sufficient for analysis of multiple neurotransmitters in rat brain regions, including parietal cortex, hypothalamus, pituitary, substantia nigra, and striatum. Method performance was compared with contemporaneous measurements using a well-established procedure based on ion-pairing reversed-phase liquid chromatography and amperometric detection. The principal advantages of the LC/MS/MS method include a more robust sample purification procedure, an optimized chromatographic separation, and the qualitative and quantitative assurance that comes from coeluting isotopically labeled internal standards; however, sensitivity did not consistently improve upon that provided by amperometric detection. This methodology may be particularly useful for applications in which simultaneous determinations are required for drugs and their affected neurotransmitters in specific brain regions.

Analysis of multiple quaternary ammonium compounds in the brain using tandem capillary column separation and high resolution mass spectrometric detection

“…Although LOD was not measured in the present study, we checked the MS signal to noise ratio of each analyte and found all of them were much higher than 10 in the brain samples, a high value allowing differential analysis. Similar to relative quantitative analysis studies commonly conducted in metabolomics and proteomics for endogenous substances [37][38][39], we monitored the CVs of analyte peak area/IS peak area ratios for quality control [40]. Using three technical replicates prepared from homogenized tissues (see Section 2), we were able to demonstrate the high precision of our method as shown by coefficients of variation (CVs) among measurements of under 17% for all the QACs (see Fig.…”

Synthesis of [13C4]Baraclude® (entecavir)

“…Although the proposed sequence contains discouraging problematic transformations, it has been extensively used in the literature to access purine nucleosides and carbocyclic analogs. 6 Fortunately, [ 13 C]guanidine HCl, 1 and diethyl [1,2,[3][4][5][6][7][8][9][10][11][12][13] C 3 ]malonate, 2 are useful labeled reagents and readily available. These reagents provided 2-amino- 4,6-dichloro[2,4,5,6-13 C 4 ]pyrimidine, 3 in a two-step sequence.…”

“…The confirmatory assurance that comes from the co-elution of drug with its stable isotope labeled form is in part accountable for the superior quality of the reference standard. 4 Hence, we became interested in the synthesis of [ 13 C 4 ]entecavir.…”

Effect of Electroacupuncture on Anovulation, Epinephrine and Norepinephrine Levels in Drug Induced Polycystic Ovary Rats

“…To measure plasma EPI and NE levels high-performance liquid chromatography (HPLC) with electrochemical detection method was used (15,16,17) Histological study of ovary The normal control and at the end of all experimental groups were euthanized, ovaries were removed, cleaned of adherent connective fat tissue, and fixed in 4% formaldehyde buffer; tissue samples were prepared wax blocks and sections were taken using microtome. Tissue sections were stained with haematoxylin-eosin (NICE chemicals), the slides were viewed under a light microscope and a well-trained pathologist performed the follicle population, morphological variation and number of the follicle.…”