The main objectives of the project are: • to develop miniaturized atmospheric pressure chemical ionization (micro-APCI) and atmospheric pressure photoionization (micro-APPI) interfaces to combine micro-liquid chromatography and time-of-flight mass spectrometry. • to develop a novel sampling method for the selective microdialysis of neutral neurosteroids based on liquid-phase microextraction • to apply the new methods in the pharmacological studies of neuronal nicotinic acetylcholine receptors and in the neurobiological and mechanistical studies of the glial cell line-derived neurotrophic factor by determining acetylcholine, catecholamines, amino acids, neurosteroids, neuropeptides and their metabolites in brain tissue and microdialysis • education of graduate and postgraduate students Neurotransmitters are a class of compounds, which are involved in brain function. Neurotransmitters mod ulate neurotransmission by binding to neurotransmitter receptors, exert physiolo gical functio ns and regulate brain activity. The concentrations of neurotransmitters in brain have been shown to be at close relation with brain activity. Therefore, the analytical methods of neurotransmitters are at focal point in brain research. However, the sensitivity and specificity of the present and most used method, liquid chromatography (LC) using electrochemical (EC) or mass spectrometric (MS) detection, are often not enough, especially to detect metabolites of the neurotransmitters. The most potential method LC/MS using electrospray ionization does not provide good enough sensitivity for neutral compounds such as neurosteroids. Furthemore, the sensitivity of highly hydrophilic and relatively small compounds, such as amino acids, some catecholamines and especially their phase II metabolites (glucuronides and sulphates) do not often suffice with ESI. The aim of this research is to develop ultra sensitive and specific methods for the determination of neurotransmitters and th eir metabolit es in brain tissue and microdialysis samples by developing a miniaturized atmospheric pressure chemical ionization (micro-APCI) and photo ionization (micro-APPI) methods. The ionization methods will be used as interfaces in micro-liquid chromatography–quadrupole time of flight mass spectrometry (micro-LC–Q-TOF). The usability of micro-APCI and -APPI will be compared with ESI. It is strongly expected that APCI and APPI provide better sensisitivity for neutrals and hydrophilic neurotransmitters, since they are ionized after vaporization of the compounds in the gas phase by corona dicharge needle or by photoionization lamp. Due to ion evaporation process by which the ions are formed in ESI, the neutral compounds and highly hyrophilic small compounds are not ionized efficiently. The excellent specificity and sensitivity of the micro-LC–micro-APCI/APPI-Q-TOF may open new possibilities in analy s is of neutral neurosteroids, hydrophilic amino acids, catecholamines and especiall y their metabo lites in the microdialysis brain samples of genetically modified mice.
Vastaava tutkija
Kostiainen Risto, Helsingin yliopisto, Farmasian tiedekunta Hankkeen kesto 2004 -
Asiasanat
Neurotransmitters, Mass spectrometry
Hankkeen vaihe: päättynyt
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