Evidence for Neuronal Origin and Metabotropic Receptor‐Mediated Regulation of Extracellular Glutamate and Aspartate in Rat Striatum In Vivo Following Electrical Stimulation of the Prefrontal Cortex

Abstract

Extracellular levels of glutamate (Glu) and aspartate (Asp) were measured at 5-s intervals in the striatum of chloral hydrate-anesthetized rats by using microdialysis coupled to an automated assay system based on capillary electrophoresis with laser-induced fluorescence

Column Coupling Electrophoresis in Biomedical Analysis

“…This is the sample cleanup provided by the microdialysis. On-line microdialysis-CE assays for neurotransmitters to date have been most successful for easily resolved analytes such as glutamate and aspartate (Thompson et al, 1999;Lada et al, 1997Lada et al, , 1998. However, the efficiency and peak capacity of high-speed CE separations are often not high enough to resolve complex mixtures.…”

“…The separation capillary was coupled to the reactor capillary via a flow-gated interface which allowed dialysate samples to be automatically injected onto the separation capillary. This elimination of fraction collection, combined with the high mass sensitivity of LIF or electrochemical detectors, makes sampling rates on the order of seconds possible (Thompson et al, 1999;Lada et al, 1997Lada et al, , 1998. The microdialysis-CZE-LIF system with on-line derivatization has the advantage of simultaneously obtained high relative recoveries and good temporal resolution with (in-vivo) microdialysis sampling for the real biological system (brain) (Lada et al, 1997).…”

Microdialysis as a tool in local pharmacodynamics

“…30 , 117 This technique enables detection of transient increases in these substances shown to be derived almost exclusively from neurogenic release. 118 Thus, by using this methodology, changes in these amino acids associated with neuronal signaling can be distinguished from metabolic or osmotic events. Using stable isotope tracers in combination with microdialysis is expected to be useful for studying those issues in the human brain, helping to reveal more about the cause of the increased glutamate levels and about glutamate (in combination with glutamine) metabolism in the human brain in general.…”

Biomedical applications of capillary electrophoresis with laser‐induced fluorescence detection

“…This technical improvement of the microdialysis and CE coupling requires very short derivatization periods. Therefore, it is critical to use derivatizing agents such as OPA [52][53][54] or NAD [39,55,56] to produce the fluorescent derivatives in reaction times as short as a minute. This it is not possible using FITC.…”

“…In these conditions, Glu has been measured in 100 nl brain dialysates collected every 6 s from anesthetized rat [30]. Lada et al measured Glu and Asp changes in rat brain microdialysates collected every 5 s after electrical stimulation, or tetrodotoxin [54]. This improvement of time resolution of brain microdialysis might be necessary to enhance the comprehension of the mechanisms of neurotransmitter release when in vivo monitoring techniques are used.…”