Microdialysis sampling glutamate

Piepponen TP, Skujins A. 2001. Rapid and sensitive step gradient assays of glutamate, glycine, taurine and y-amino-butyric acid by high-performance liquid chromatography-fluorescence detection with o-phthalaldehyde-mercap-toethanol derivatization with emphasis on microdialysis samples. J Chromatogr B 757 277-283. 

In the field of food analysis, milk was the real matrix in which several metabolites have been analysed by the use of the microdialysis sampling technique. Acetylcholine, glucose and glutamate were analysed by Yao et al. [189], coupling a microdialysis probe with an on-hne enzymatic reactor and a Pt electrode coated with a 1,2-diaminobenzene polymer. 

Microdialysis sampling has also been coupled to separation-based microchip devices. External probes have been used in microchip electrophoresis for the monitoring of enzyme reactions [32] and have been applied to the in vivo analysis of glutamate in the striatum of an anesthetized rat [33]. Considerations for coupling microdialysis sampling to flow-through and separation-based microchip devices are similar and will now be discussed in more detail, with reference to specific examples from the literature. 

Kaul S, Faiman MD, Lunte CE. Determination of GABA, glutamate and carbama-thione in brain microdialysis samples by capillary electrophoresis with fluorescence detection. Electrophoresis 2011 32 284—91. 

Yao T, Okano G (2008) Simultaneous determination of L-glutamate, acetylcholine and dopamine in rat brain by a flow-injection biosensor system with microdialysis sampling. Anal Sci 24 1469-1473... 

Fig. 2. Transient retinal ischemia increases intravitreal glutamate in rat. Neurochemical data from microdialysis experiments carried out in anesthetized rats to demonstrate that ischemia/reperfusion insult increases intravitreal glutamate. The extracellular level of glutamate shows a moderate increase during the first 10 min of ischemia, more evident toward the end of the ischemic period, to reach statistical significance at 10 and 150 min of reperfusion. Baseline glutamate concentrations (basal values) are the mean concentrations obtained by averaging six samples collected consecutively at 10 min intervals immediately before the onset of ischemia (n — 6 rats). Glutamate values (pM) are expressed as mean S.E.M. Statistical significance was assessed by ANOVA followed by Dunnett s test for multiple comparisons. P < 0.05 and P < 0.001 versus basal values.

Fig. 3. Extracellular levels of GABA and glutamate in rat hippocampus in vivo, as determined by microdialysis and HPLC. Basal and K -evoked levels of GABA (top) and glutamate (bottom) and the effects of SK F 89976-A and L trau5-PDC on the respective transmitter levels are shown. Dialysates were collected over 20 mm in each case. Basal values represent means SEM of six dialysates collected prior to elevation. Because addition induced a transient rise m extracellular ammo acid levels, K -elevated levels represent peak transmitter concentrations measured during 1 h perfusion (i.e., the highest of three 20 min samples) with 100 mMKCl See Section 3.3. for details of the microdialysis procedure and Note 11 for further discussion.

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