Background: Volumetric absorptive microsampling (VAMS) is a novel sampling technique for the collection of fixed-volume capillary blood. In this study, a new analytical method was developed and used to quantify 14 different antiepileptic drugs (AEDs) and 2 active metabolites in samples collected by VAMS. These data were compared with concentration measurements in plasma. Methods: The authors developed a selective and sensitive liquid chromatography–mass spectrometry (LC-MS/MS) assay to measure the concentrations of several AEDs in whole blood collected by VAMS, which were compared with a commercially available LC-MS/MS kit for AED monitoring in plasma. Drugs and internal standards were extracted from whole blood/plasma samples by a simple protein precipitation. Results: An LC-MS/MS method analyzing VAMS samples was successfully developed and validated for the determination of various AED concentrations in whole blood according to EMA guidelines for bioanalytical method validation. Extraction recovery was between 91% and 110%. No matrix effect was found. The method was linear for all drugs with R2 ≥0.989 in all cases. Intra-assay and inter-assay reproducibility analyses demonstrated accuracy and precision within acceptance criteria. Carry over and interferences were negligible. No volumetric HCT% bias was found at 3 different HCT values (35%–55%) with recovery being consistently above 87%. Samples are very stable at temperatures ranging from −20°C to 37°C and for a 4-month period. Leftover EDTA samples from 133 patients were tested to determine concentration differences between plasma and whole blood sampled by VAMS. The resulting difference varied less than 15% apart from those drugs with a blood/plasma ratio (R) different from 1. Conclusions: The assay allows for highly sensitive and selective quantification of several AEDs in whole blood samples collected by VAMS. The developed method is accurate and precise and free from matrix effects and volumetric HCT% bias.

Huntington's disease (HD) is notably difficult to diagnose in the early stages. One reason is that the early clinical manifestations of HD vary widely and sometimes have an atypical onset. In this paper we primarily sought information on affected patients who initially presented with movement disorders other than chorea. We also investigated atypical motor presentations in relation to triplet CAG expansions. After reviewing the clinical records of two neurological centres, we identified patients with a final, documented diagnosis of HD and selected for study 205 patients according to their onset of motor manifestations. CAG repeats were analysed. Of the 205 patients studied, 15 had atypical motor symptoms at onset. In this group we identified three types of initial clinical manifestations other than chorea: parkinsonism, ataxia and dystonia. We conclude that HD patients may have different motor manifestations at the initiation of the illness. Patients with atypical movement disorders in the early stages have larger CAG expansions and an earlier age at onset than HD patients with typical onset chorea.

Western blot analysis of protein extracts from rat liver revealed the presence of the mGlu5 receptor, one of the G-protein-coupled receptors activated by glutamate (named ''metabotropic glutamate receptors'' or mGlu receptors). mGlu5 expression was particularly high in extracts from isolated hepatocytes, where levels were comparable with those seen in the rat cerebral cortex. The presence of mGlu5 receptors in hepatocytes was confirmed by reversetranscription polymerase chain reaction (RT-PCR) analysis, immunohistochemistry in neonate or adult rat liver, as well as by immunocytochemical analysis in HepG2 hepatoma cells, where the receptor appeared to be preferentially distributed in cell membranes. Interestingly, mGlu1 receptors (which are structurally and functionally homologous to mGlu5 receptors) were never found in rat liver or hepatocytes. In hepatocytes exposed to anoxic conditions for 90 minutes, glutamate, (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) and quisqualate, which all activate mGlu5 receptors, accelerated the onset and increased the extent of cell damage, while 4-carboxy-3-hydroxyphenylglycine (4C3HPG), an agonist of mGlu2/3 receptors, was inactive. 2-Methyl-6-(2-phenyl-1-ethynyl)-pyridine (MPEP), a novel, noncompetitive, highly selective mGlu5 receptor antagonist, not only abolished the toxic effect of 1S,3R-ACPD, but, unexpectedly, was protective by itself against anoxic damage. This suggests that hepatocytes express mGlu5 receptors and that activation of these receptors by endogenous glutamate facilitates the development of anoxic damage in hepatocytes. (HEPATOLOGY 2000; 31:649-655.)Glutamate is the major excitatory neurotransmitter in the central nervous system (CNS), and evidence for peripheral glutamatergic fibers in mammals is still lacking. However, glutamate receptors have been identified in peripheral organs, including taste buds, 1 myenteric plexus, 2 and pancreatic islet cells. 3 Glutamate receptors may either form membrane ion channels (ionotropic glutamate receptors) or couple to guanosine triphosphate-binding proteins (''metabotropic'' glutamate [mGlu] receptors). mGlu receptors form a family of 8 subtypes, which are subdivided into 3 groups on the basis of their structural homology, pharmacological profile, and transduction pathways. Group I includes mGlu1 and -5 receptors, which are coupled to polyphosphoinositide (PI) hydrolysis and activated by 3,5-dihydroxyphenylglycine (DHPG) and quisqualate; group II (mGlu2 and -3) and -III (mGlu4, -6, -7, and -8) mGlu receptors are instead negatively coupled to adenylyl cyclase activity. 4,5 1S,3R-ACPD behaves as a non-subtype-selective agonist, with a preferential activity on group I and -II mGlu receptors. 4 We were intrigued by the finding that 1S,3R-ACPD and quisqualate stimulate PI hydrolysis in cultured hepatocytes, and this effect is reduced by the mixed mGlu receptor antagonist, ␣-methyl-4-carboxyphenylglycine (MCPG). 6 This suggests that either mGlu1 or -5 (or a related unknown receptor subtype) are expressed and...

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