Small water soluble molecules migrate through the pores of Ganetespib HSP (e.g. HSP90) inhibitor the microdialysis membrane by passive diffusion, creating a dynamic equilibrium between the extracellular fluid and the perfusion liquid [9]. Typically, 5-50 ��L samples are collected screening library Inhibitors,Modulators,Libraries at a flow rate of 0.5-2.5 ��L/min. Depending on the perfusion rate, location of the probe, the timing of implantation, the composition of the perfusion liquid, dimensions of the membrane and its diffusion properties, acetylcholine concentrations in basal microdialysis samples range between 0.1-3 nM [10-16]. The application of the microdialysis technique for intracerebral acetylcholine monitoring therefore requires a highly sensitive and reliable method for acetylcholine quantification.

Liquid Inhibitors,Modulators,Libraries chromatography with Inhibitors,Modulators,Libraries tandem mass spectrometry was Inhibitors,Modulators,Libraries more recently developed as a sensitive but expensive method for acetylcholine determination in microdialysis samples, reaching a detection limit of 0.02-0.03 nM [16-19]. However, the Inhibitors,Modulators,Libraries most widely used method for acetylcholine quantification in brain microdialysis samples to date remains liquid chromatography with electrochemical Inhibitors,Modulators,Libraries detection. This method is based on the chromatographic separation of acetylcholine from choline and other matrix components, conversion of acetylcholine to hydrogen peroxide by acetylcholine esterase and choline oxidase and amperometric detection of the produced hydrogen peroxide [20]. A detection limit of 0.

2-2 nM was reported for microbore liquid chromatography systems with acetylcholine esterase and choline oxidase chemically bound in an immobilized enzyme reactor (IMER) and hydrogen peroxide detection on a horseradish peroxidase osmium-redox polymer coated glassy carbon or gold ring disc Inhibitors,Modulators,Libraries electrode (Figure 1) [10-15, 21-23].

This assay is sufficiently sensitive to detect acetylcholine in basal microdialysis samples under optimized conditions, but has not been thoroughly validated within the corresponding concentration range. Furthermore, a limited robustness of the chromatographic separation and enzymatic conversions has been reported [22, 24]. Consequently, in most microdialysis studies a Inhibitors,Modulators,Libraries cholinesterase inhibitor, such as neostigmine or physostigmine, is added to the perfusion liquid to augment the concentration of acetylcholine in the extracellular fluid and facilitate reliable quantification [25].

However, artificially increasing acetylcholine concentrations exerts a significant influence on the cholinergic system and may confound the interpretation of drug Anacetrapib effects or mask alterations in acetylcholine transmission in animal models for pathology [25-27]. Further optimization Site URL List 1|]# selleck catalog of the chromatographic parameters may therefore lead to a more reliable determination of acetylcholine in microdialysis samples without the use of cholinesterase inhibitors.Figure 1.Chromatography setup.