A sensitive, dependable, simple and rapid method based on capillary electrophoresis with diode array detection (CE-DAD) was developed for identification and determination of eleven flavonoids (apigetrin, naringin, naringenin, catechin, galangin, apigenin, luteolin, quercetin, myricetin, kaempferol, and kaempferide) in chamomile and linden flower extracts. Several parameters which influence the separation were investigated to determine the optimum conditions. At room temperature, the eleven flavonoids could be well separated within 11 min. in a 55 cm length capillary at a separation voltage of 24 kV with 40 mM borate buffer (pH 8.9). Under optimum conditions, linearity was achieved within the concentration ranges of 2.5–100.0 μM for all analytes except myricetin and luteolin (5.0–100.0 μM) with correlation coefficients ≥ 0.999. The method was successfully applied to the determination of flavonoids in plant samples such as chamomile and linden flowers with satisfactory recoveries.

A micellar electrokinetic chromatography and laser-induced fluorescence (MEKC-LIF) method based on derivatization with naphthalene-2,3-dicarboxyaldehyde (NDA) was optimized to separate and detect glutamate (Glu), gamma-aminobutyric acid (GABA), dopamine (DA) and carbamathione in brain microdialysis samples. The background electrolyte (BGE) consisted of 22.5 mmol L−1lithium tetraborate, 25 mmol L−1lithium dodecylsulfate and 10% methanol. The separation was carried out on a 65 cm × 50 μm id fused-silica capillary (50 cm effective) at +15 kV voltage with a run time of 25 min. The detection limits for GABA, Glu, DA and carbamathione were 6, 10, 5 and 10 nmol L−1, respectively. This method was used to monitor GABA, Glu, DA and carbamathione in brain microdialysis samples from the nucleus accumbens after the administration of an intra-peritoneal dose of disulfiram (200 mg kg−1) and revealed a disulfiram-induced change in GABA, Glu and DA levels. This method demonstrates a simple, rapid and accurate measurement of three amino acid neurotransmitters and carbamathione for in vivo monitoring in the brain using microdialysis sampling.

Tissue-targeted metabonomics, or the use of microdialysis sampling with NMR detection, can be used to monitor the metabolic profiles of specific tissues without the need to take tissue biopsies. This allows for sampling from the same animal over the time course of the experiment, reducing animal-to-animal variability and decreasing the number of animals required, however, this approach to metabonomics studies has not been fully characterized. In this work liver microdialysis sampling was performed on male Sprague–Dawley rats and the effects of diurnal rhythms, animal activity and anesthesia on the liver extracellular fluid composition examined. Diurnal rhythms and animal activity caused little change in liver metabolism, but anesthesia caused dramatic effects attributed to the hyperglycemia induced by xylazine and isoflurane. This approach was then applied to the characterization of the hepatotoxicity of doxorubicin, an anticancer agent known to induce oxidative stress. In these studies, two probes were implanted in the liver and doxorubicin was dosed through one of the probes. Comparisons were made between the metabolic profiles from the two probes to distinguish basal metabolic effects from those induced by doxorubicin. Doxorubicin altered hepatic metabolism by different mechanisms in anesthetized and awake rats. These studies also provided important implications for the design of future tissue-targeted metabonomics experiments.

This study investigated the penetration of lidocaine around and through a sutured incision following the application of iontophoretic and passive patches in the CD Hairless rat.Concentrations in localized areas (suture, dermis, subcutaneous, and vascular) were determined using microdialysis sampling followed by analysis using liquid chromatography with UV detection.Iontophoresis significantly enhanced the dermal penetration of lidocaine. In an intact skin model, dermal concentrations were 40 times greater following iontophoretic delivery compared to passive delivery. In a sutured incision model, iontophoresis enhanced localized concentrations in the dermis, suture, and subcutaneous regions by 6-, 15-, and 20-fold, respectively. Iontophoretic delivery to a region containing a sutured incision was focused to the incision resulting in a greater increase in the suture concentration and in the subcutaneous region directly below the incision.The four microdialysis probe design was successful in the determination of localized drug penetration in a sutured incision model. Iontophoresis enhanced skin penetration and allowed for site specific delivery when applied to a sutured incision.

ObjectivesThe goal of this study was to use a status epilepticus steady-state chemical model in rats using the convulsant, 3-mercaptopropionic acid (3-MPA), and to compare the changes in striatal neurotransmission on a slow (5 min) and fast (60 s) timescale. In vivo microdialysis was combined with electrophysiological methods in order to provide a complete evaluation of the dynamics of the results obtained.ObjectiveTo compare the effects of a steady-state chemical model pof status epilepticus on striatal amino-acid and amine neurotransmitters contents, as measured via in vivo microdialysis combined with electrophysiological methods. Measurements were performed on samples collected every 60 s and every 5 min. “Fast” (60 s) and “slow” (5 min) sampling timescales were selected, to gain more insight into the dynamics of GABA synthesis inhibition and of its effects on other neurotransmitters and on cortical electrical activity.Methods3-MPA was administered in the form of an intra-venous load (60 mg/kg) followed by a constant infusion (50 mg/kg/min) for min. Microdialysis samples were collected from the striatum at intervals of 5 min and 60 s and analyzed for biogenic amine and amino acid neurotransmitters. ECoG activity was monitored via screws placed over the cortex.ResultsIn the 5 min samples, glutamate (Glu) increased and γ-aminobutyric acid (GABA) decreased monotonically while changes in dopamine (DA) concentration were bimodal. In the sixty second samples, Glu changes were bimodal, a feature that was not apparent with the 5 min samples. ECoG activity was indicative of status epilepticus.ConclusionsThis study describes the combination of in vivo microdialysis with electrophysiology to monitor the effect of 3-MPA on neurotransmission in the brain. This led to a better understanding of the chemical changes in the striatum due to the applied 3-MPA chemical model of status epilepticus.Download high-res image (189KB)Download full-size image

A sensitive, dependable, simple and rapid method based on capillary electrophoresis with diode array detection (CE-DAD) was developed for identification and determination of eleven flavonoids (apigetrin, naringin, naringenin, catechin, galangin, apigenin, luteolin, quercetin, myricetin, kaempferol, and kaempferide) in chamomile and linden flower extracts. Several parameters which influence the separation were investigated to determine the optimum conditions. At room temperature, the eleven flavonoids could be well separated within 11 min. in a 55 cm length capillary at a separation voltage of 24 kV with 40 mM borate buffer (pH 8.9). Under optimum conditions, linearity was achieved within the concentration ranges of 2.5–100.0 μM for all analytes except myricetin and luteolin (5.0–100.0 μM) with correlation coefficients ≥ 0.999. The method was successfully applied to the determination of flavonoids in plant samples such as chamomile and linden flowers with satisfactory recoveries.