Capillary electrophoresis combined with microdialysis in the human spinal cord: A new tool for monitoring rapid peroperative changes in amino acid neurotransmitters within the dorsal horn

Abstract

A method originally developed for the separation of the three neurotransmitters gamma-aminobutyric acid (GABA), glutamate (Glu) and L-aspartate (L-Asp) in microdialysis samples from rat brain (Sauvinet et al., Electrophoresis 2003, 24, 3187-3196) was applied to human spinal dialysates obtained during peroperative microdialysis from patients undergoing surgery against chronic pain. Molecules were tagged on their primary amine function with the fluorogene agent, naphthalene-2,3-dicarboxaldehyde (NDA), and, after separation by capillary electrophoresis (CE, 75 mmol/L borate buffer, pH 9.2, containing 70 mmol/L sodium dodecyl sulfate and 10 mmol/L hydroxypropyl-beta-cyclodextrin, + 25 kV voltage), were detected by laser-induced fluorescence detection (LIFD) using a 442 nm helium-cadmium laser. The complete method, including microdialysis sampling and analysis by CE-LIFD, has been validated for the analysis of human spinal microdialysates. The analytical detection limits were 1, 3.7 and 17 nmol/L for GABA, Glu and L-Asp respectively. This method allows an accurate measurement of the three amino acid neurotransmitters during an in vivo monitoring performed as rapidly as every minute in the human spinal dorsal horn. In addition, the effect of a brief peroperative electrical stimulation of the dorsal rootlets was investigated. The results obtained illustrate the advantages of combining microdialysis with CE-LIFD for studying neurotransmitters with such a high sampling rate.

Determination of amino acids by micellar EKC: Recent advances in method development and novel applications to different matrices

“…In a series of interesting papers [101][102][103], Sauvinet et al [101] have shown the applicability of MEKC for the simultaneous analysis of GABA, Glu, and L-Asp in submicroliter samples of dialysates from rat striatum [101]. They developed this method using a commercially available instrument and validated the procedure on both analytical and pharmacological basis.…”

“…They developed this method using a commercially available instrument and validated the procedure on both analytical and pharmacological basis. In addition, they also performed the simultaneous analysis of an antiepilectic drug (vigabratin) and the above amino acids in rat brain microdialysates [102] and determined these amino acids in human spinal dialysates obtained during peroperative microdialysis from patients undergoing surgery against chronic pain [103]. They used 75 mM sodium borate buffer, pH 9.2, containing variable concentrations of SDS (from 60 to 70 mM) and variable concentrations (from 5 to 10 mM) of hydroxypropyl-b-CD as BGE.…”

Recent advances in amino acid analysis by capillary electrophoresis

“…and 17 nM for GABA, Glu, and L-Asp, respectively [57]. This method allows an accurate measurement of the three amino acid neurotransmitters during an in vivo monitoring performed as rapidly as one sample per minute in the human spinal dorsal horn.…”

“…Typical electropherograms using CE-LIF of a microdialysate obtained from the spinal dorsal horn in a patient with chronic pain (top), a standard solution (middle) containing 500 nM GABA, 5 mM Glu/L-Asp compared to a brain dialysate obtained from rat striatum (bottom). Cysteic acid is the internal standard ( [57] with permission).…”

Bioanalytical profile of the l-arginine/nitric oxide pathway and its evaluation by capillary electrophoresis

“…Analytical parameters quantified in both of these reports would be sufficient to identify key organic components of the L-arginine/NO pathway. Example of microdialysis systems that can be used in combination with CE-LIF for analysis of human cerebrospinal fluid samples with 1-min sampling have been recently described by Parrot et al [396].…”