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Background: Interactions between the endocannabinoid system (ECS) and neurotransmitter systems might mediate the risk of developing a schizophrenia spectrum disorder (SSD). Consequently, we investigated in patients with SSD and healthy controls (HC) the relations between (1) plasma concentrations of two prototypical endocannabinoids (N-arachidonoylethanolamine [anandamide] and 2-arachidonoylglycerol [2-AG]) and (2) striatal dopamine synthesis capacity (DSC), and glutamate and y-aminobutyric acid (GABA) levels in the anterior cingulate cortex (ACC). As anandamide and 2-AG might reduce the activity of these neurotransmitters, we hypothesized negative correlations between their plasma levels and the abovementioned neurotransmitters in both groups., Methods: Blood samples were obtained from 18 patients and 16 HC to measure anandamide and 2-AG plasma concentrations. For all subjects, we acquired proton magnetic resonance spectroscopy scans to assess Glx (i.e. glutamate plus glutamine) and GABA + (i.e. GABA plus macromolecules) concentrations in the ACC. Ten patients and 14 HC also underwent [ 18 F]F-DOPA positron emission tomography for assessment of striatal DSC. Multiple linear regression analyses were used to investigate the relations between the outcome measures., Results: A negative association between 2-AG plasma concentration and ACC Glx concentration was found in patients ( p = 0.008). We found no evidence of other significant relationships between 2-AG or anandamide plasma concentrations and dopaminergic, glutamatergic, or GABAergic measures in either group., Conclusions: Our preliminary results suggest an association between peripheral 2-AG and ACC Glx levels in patients.

A high number of non-protein amino acids are chiral compounds that have demonstrated to be relevant in different fields. Their determination enables to obtain valuable information related to food quality and safety and has also a high interest from a biological point of view since many of them are key compounds in metabolic pathways or are related with different pathologies.In the development of analytical methodologies to perform chiral separations, capillary electrophoresis (CE) is well-established and one of the most powerful separation techniques as a consequence of its high efficiency, short analysis time, and versatility.This chapter shows, by means of three interesting examples, the application of different CE methodologies to the chiral analysis of non-protein amino acids. The first example describes different electrokinetic chromatography (EKC)-UV methodologies based on the use of negatively charged cyclodextrins as chiral selectors to carry out the stereoselective separation of ten different non-protein amino acids of relevance from a biological or food analysis point of view. The second method illustrates the EKC-UV analysis of L-citrulline and its enantiomeric impurity in food supplements using sulfated-γ-cyclodextrin as chiral selector. The last example shows the simultaneous enantiomeric separation of 3,4-dihydroxy-DL-phenylalanine and all the other chiral constituents involved in the phenylalanine-tyrosine metabolic pathway by using an EKC-MS methodology.

In this work, we report a fluorescence strategy for detecting dopamine (DA) and sensing tyrosinase (TYR) activity on the basis of the dual-emission carbon dots (DECDs), which contain two emitters: the blue emitters (BE, maximum emission at 385nm) and yellow emitters (YE, maximum emission at 530nm). Gold nanoparticles (AuNPs) can effectively quench the two emissions of DECDs. The addition of DA aggregates AuNPs effectively, leading to the fluorescence recovery of dual emitters gradually. This strategy exhibits a high selectivity toward DA and shows good linear ranges, such as 0.5-3μM for BE and 0.1-3μM for YE. Additionally, the proposed method is successfully applied to the determination of DA in real samples with satisfactory recoveries. Subsequently, this DECDs-AuNPs platform is further taken advantage to assess TYR activity by the aid of TYR's capability for oxidation of DA into dopaquinone, which will not induce the agglomeration of AuNPs, so the fluorescence quenching of DECDs is associated with TYR activity. Finally, the mechanism of the reaction is discussed in detail, and the results suggest that both amine and phenolic hydroxyl groups of DA bring the aggregation of AuNPs., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The Patlak graphical analysis (PGA REF ) for quantification of irreversible tracer binding with a reference tissue model was approximated by a dual time point imaging approach (DTP REF ). The DTP REF was applied to 18 [ 18 F]-FDOPA brain scans using the occipital cortex as reference region (DTP OCC ) and compared to both PGA OCC and striatal-to-occipital ratios (SOR). Pearson correlation analysis and Bland-Altman plots showed an excellent correlation and good agreement between DTP OCC and PGA OCC , while correlations between SOR and PGA OCC were consistently lower. Linear discriminant analysis (LDA) demonstrated a similar performance for all methods in differentiating patients with Parkinson's disease (PD) from healthy controls (HC). Specifically for [ 18 F]-FDOPA brain imaging, these findings validate DTP OCC as an approximation for PGA OCC , providing the same quantitative information while reducing the acquisition time to two short static scans. For PD patients, this approach can greatly improve patient comfort while reducing motion artifacts and increasing image quality. In general, DTP REF can improve the clinical applicability of tracers with irreversible binding characteristics when a reference tissue is available.

Introduction: Homocysteine increase and glutathione derivative cysteinyl-glycine fall are indirect biomarkers for oxidative stress, for instance due to dopamine D 1 receptor stimulation., Objectives: To investigate the influence of the D 1 receptor agonists levodopa and rotigotine compared with placebo on homocysteine and cysteinyl-glycine in plasma of patients with Parkinson's disease., Methods: Patients received 100 mg levodopa, 4 mg rotigotine or placebo. Cysteinyl-glycine and homocysteine were measured every 30 min over three hours., Results: Homocysteine rose during levodopa- and placebo administration. Rotigotine had no effect. Cysteine-glycine only increased after placebo- but not after levodopa- or rotigotine., Discussion: Homocysteine elevation results from hepatic and gastrointestinal methylation processes. Transdermal rotigotine circumvents these methylation locations. Turnover of segregated alkyl residuals from rotigotine serves as methyl group donors, which counteract homocysteine increment. The placebo-related cysteinyl-glycine increase results from reduced free radical exposure. Low levodopa dosing and antioxidants in the rotigotine patch matrix prevented cysteinyl-glycine fall.

The aim of study was to develop a suitable analytical method for simultaneous estimation of levodopa, carbidopa and 3-O-methyl dopa in rat plasma. Chromatographic separation of plasma samples was achieved using a reverse-phase C18 column. The mobile phase used consisted of a mixture of methanol and phosphate buffer (10 mM, pH 3.50) in the ratio of 90:10 v/v. All analytes were estimated by electrochemical detection at +800 mV. The developed method has been validated as per the standard guidelines. Precision study results were found to be satisfactory, with percentage relative standard deviation for repeatability and intermediate precision <3.96 and 6.56%, respectively, for all analytes detected in rat plasma. The developed method in rat plasma was found to be simple, rapid, accurate, precise and specific. The proposed method has been successfully applied for analysis of rat plasma samples obtained during an oral pharmacokinetic study of sustained release pellets of levodopa and carbidopa in rats. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)

Objectives: To compare the acute effects of uninterrupted sitting with sitting interrupted by brief bouts of light-intensity walking on self-reported fatigue, cognition, neuroendocrine biomarkers and cardiometabolic risk markers in overweight/obese adults., Design: Randomised two-condition crossover trial., Setting: Laboratory study conducted in Melbourne, Australia., Participants: 19 overweight/obese adults (45-75 years)., Interventions: After an initial 2 h period seated, participants consumed a meal-replacement beverage and completed (on 2 days separated by a 6-day washout period) each condition over the next 5 h: uninterrupted sitting (sedentary condition) or sitting with 3 min bouts of light-intensity walking every 30 min (active condition)., Primary Outcome Measures: Self-reported fatigue, executive function and episodic memory at 0 h, 4 h and 7 h., Secondary Outcome Measures: Neuroendocrine biomarkers and cardiometabolic risk markers (blood collections at 0 h, 4 h and 7 h, blood pressure and heart rate measured hourly and interstitial glucose measured using a continuous glucose monitoring system)., Results: During the active condition, fatigue levels were lower at 4 h (-13.32 (95% CI -23.48 to -3.16)) and at 7 h (-10.73 (95% CI -20.89 to -0.58)) compared to the sedentary condition. Heart rate was higher at 4 h (4.47 (95% CI 8.37 to 0.58)) and at 7 h (4.32 (95% CI 8.21 to 0.42)) during the active condition compared to the sedentary condition. There were no significant differences between conditions by time for other variables. In the sedentary condition, changes in fatigue scores over time correlated with a decrease in heart rate and plasma dihydroxyphenylalanine (DOPA) and an increase in plasma dihydroxyphenylglycol (DHPG)., Conclusions: Interrupting prolonged sitting with light-intensity walking breaks may be an effective fatigue countermeasure acutely. Fatigue levels corresponded with the heart rate and neuroendocrine biomarker changes in uninterrupted sitting in this pilot study. Further research is needed to identify potential implications, particularly for the occupational health context., Trial Registration Number: ACTRN12613000137796; Results., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Aromatic L-amino acid decarboxylase (AADC) deficiency is an inborn error of metabolism affecting the biosynthesis of serotonin, dopamine, and catecholamines. We report a case of AADC deficiency that was detected using the Global MAPS platform. This is a novel platform that allows for parallel clinical testing of hundreds of metabolites in a single plasma specimen. It uses a state-of-the-art mass spectrometry platform, and the resulting spectra are compared against a library of ~2500 metabolites. Our patient is now a 4 year old boy initially seen at 11 months of age for developmental delay and hypotonia. Multiple tests had not yielded a diagnosis until exome sequencing revealed compound heterozygous variants of uncertain significance (VUS), c.286G>A (p.G96R) and c.260C>T (p.P87L) in the DDC gene, causal for AADC deficiency. CSF neurotransmitter analysis confirmed the diagnosis with elevated 3-methoxytyrosine (3-O-methyldopa). Metabolomic profiling was performed on plasma and revealed marked elevation in 3-methoxytyrosine (Z-score +6.1) consistent with the diagnosis of AADC deficiency. These results demonstrate that the Global MAPS platform is able to diagnose AADC deficiency from plasma. In summary, we report a novel and less invasive approach to diagnose AADC deficiency using plasma metabolomic profiling., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background: In this study, we developed and validated a HPLC-MS/MS method capable of simultaneously determining levodopa, carbidopa, entacapone, tolcapone, 3-O-methyldopa and dopamine in human plasma. RESULTS & METHODOLOGY: Chromatographic separation was achieved using a C8 column with a mobile phase consisting of a gradient of water and acetonitrile:methanol (90:10 v/v), both containing 0.1% formic acid. The developed method was selective, sensitive (LD<7.0 ng ml(-1)), linear (r>0.99), precise (RSD<11.3%), accurate (RE<11.8%) and free of residual and matrix effects. The developed method was successfully applied in plasma patients with Parkinson's disease using Stalevo®., Conclusion: The new method can be used for the clinical monitoring of these substances and applied to adjustments in drug dosages.

Background: According to recent investigations, the eradication of Helicobacter pylori (H. pylori) may influence levodopa (LD) pharmacokinetics (PK) and improve the motor function of infected patients with Parkinson disease (PD). The aim of this study was to compare PK of LD and its metabolite 3-O-methyldopa (3-OMD), between H. pylori-positive (HP+) and -negative (HP-) patients with PD and motor fluctuations., Materials and Methods: Patients with the clinical diagnosis of PD, under stable LD therapy, reporting daily motor fluctuations and who had no history of previous eradication treatment were screened for the H. pylori infection with an antigen stool test. Two groups of patients-bacteria-infected and noninfected-matched demographically and clinically, were selected for the examination of PK values. Blood samples were collected after morning oral LD dose. Noncompartmental PK parameters were computed from the LD and 3-OMD plasma concentration-time data., Results: Interindividual variability was seen in LD absorption curve in both groups. There were no clinically significant differences in PK parameters of LD and 3-OMD. Changes of small magnitude but with possible clinical impact were found according to tmax and Cmax that tended to be lower in HP- patients and AUC0-t that was larger in the HP+ group. The Cmax value of 3-OMD was almost identical in both groups. The HP- group had smaller AUC0-∞t of 3-OMD., Conclusions: The H. pylori infection in PD patients with motor fluctuations, despite not significantly influencing PK parameters of LD and 3-OMD, may still have important clinical implications.

Background: Inherited defects that affect the synthesis or metabolism of neurotransmitters cause severe motor dysfunction. The diagnosis of these diseases, including aromatic L-amino-acid decarboxylase (AADC) deficiency, typically requires cerebrospinal fluid (CSF) neurotransmitter analysis. However, 3-O-methyldopa (3-OMD), which is a catabolic product of L-dopa that accumulates in individuals with AADC deficiency, can be detected in blood., Methods: 3-OMD concentrations were measured in dried blood spots (DBSs). One 3.2-mm punch was eluted with 90% methanol containing a deuterated internal standard (3-OMD-d3), and then analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS)., Results: 3-OMD in DBSs was shown to be stable for more than 28 days at 37°C. We measured DBS 3-OMD concentrations in controls and patients with AADC deficiency. 3-OMD concentrations in normal newborns and children decreased with age. Patients with AADC deficiency revealed >15-fold increase of DBS 3-OMD concentrations. Archive newborn screening DBS samples, obtained from 6 patients with AADC deficiency, revealed more than 19-fold increase of 3-OMD concentrations., Conclusions: We demonstrated that DBS 3-OMD concentrations were highly elevated in newborns and children with AADC deficiency. Because 3-OMD is stable in DBS, this method can be used for both high risk and newborn screening of AADC deficiency., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Objectives: This study was conducted to examine (1) the effects of dietary weight loss on indices of norepinephrine (NE) turnover and (2) whether baseline hyperinsulinemia modulates sympathetic neural adaptations., Methods: Obese individuals aged 56 ± 1 year, BMI 32.5 ± 0.4 kg/m(2) , with metabolic syndrome, underwent a 12-week hypocaloric diet (HCD, n = 39) or no treatment (n = 26). Neurochemical measurements comprised arterial dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylglycol (DHPG), and NE concentrations, the steady-state ratio of [3H]-DHPG to [3H]-NE, as an index of neuronal uptake, and calculated whole-body plasma NE clearance and spillover rates., Results: Body weight decreased by -7.4 ± 0.5% in HCD group (P < 0.001) and was accompanied by reductions in DOPA, NE, and DHPG averaging -14 ± 5% (P = 0.001), -23 ± 4% (P <0.001), and -5 ± 4% (P = 0.03), respectively. NE spillover rate decreased by -88 ± 39 ng/min (P = 0.01), whereas neuronal uptake and NE plasma clearance were unchanged. Despite similar weight loss, hyperinsulinemic subjects exhibited greater reductions in NE and NE spillover rate, compared to normoinsulinemic subjects (group by time interaction P < 0.05)., Conclusions: Weight loss is associated with down-regulation of sympathetic nervous activity but no overall alteration in disposition indices. Hyperinsulinemic subjects derive a greater sympathoinhibitory benefit during weight loss., (Copyright © 2013 The Obesity Society.)

Levodopa (L-DOPA) is widely used for symptomatic management in Parkinson's disease. We recently showed that (-)-epigallocatechin-3-gallate, a tea polyphenol, not only inhibits L-DOPA methylation, but also protects against oxidative hippocampal neurodegeneration. In the present study, we sought to determine several other common dietary phenolics, namely, tea catechins [(+)-catechin and (-)-epicatechin] and a representative flavonoid (quercetin), for their ability to modulate L-DOPA methylation and to protect against oxidative hippocampal injury. A combination of in vitro biochemical assays, cell culture-based mechanistic analyses, and in vivo animal models was used. While both tea catechins and quercetin strongly inhibit human liver catechol-O-methyltransferase (COMT)-mediated O-methylation of L-DOPA in vitro, only (+)-catechin exerts a significant inhibition of L-DOPA methylation in both peripheral compartment and striatum in rats. The stronger in vivo effect of (+)-catechin on L-DOPA methylation compared to the other dietary compounds is due to its better bioavailability in vivo. In addition, (+)-catechin strongly reduces glutamate-induced oxidative cytotoxicity in HT22 mouse hippocampal neurons in vitro through inactivation of the nuclear factor-κB signaling pathway. Administration of (+)-catechin also exerts a strong neuroprotective effect in the kainic acid-induced oxidative hippocampal neurodegeneration model in rats. In conclusion, (+)-catechin is a dietary polyphenolic that may have beneficial effects in L-DOPA-based treatment of Parkinson patients by inhibiting L-DOPA methylation plus reducing oxidative neurodegeneration., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Chronic levodopa (LD)/dopadecarboxylase inhibitor (DDI) increases homocysteine generation as side reaction of O-methylation. Aim was to investigate the impact of the peripheral COMT inhibitor entacapone (EN) on plasma concentrations of homocysteine, LD and 3-O-methyl-dopa (3-OMD). Patients with Parkinson's disease (PD) received on two consecutive days in a standardised fashion one single dose of 200 mg retarded release LD/carbidopa (CD) or of 150 mg LD/CD/EN, since both were shown to have simultaneous pharmacokinetic LD behaviour. Homocysteine increased after retarded release LD/CD application, but not following LD/CD/EN intake. Homocysteine was lower during the LD/CD/EN condition 80 min after baseline when compared with its levels after LD/CD administration. LD levels simultaneously rose on both days. 3-OMD concentrations did not change. Acute LD/CD application caused a rise of homocysteine levels, which was prevented by LD/CD/EN intake. Therefore, peripheral COMT inhibition may have a beneficial effect on putative, controversially debated components of homocysteine-related progression of PD.

Levodopa (L-dopa) administered with a dopadecarboxylase inhibitor (DDI) increases homocysteine plasma levels. This may support the onset of atherosclerosis-related disorders and neuropsychiatric complications in patients with Parkinson's disease (PD). This homocysteine elevation is considered as long-term effect of chronic L-dopa/DDI treatment. Little is known about the acute effects of L-dopa/DDI intake on homocysteine generation. The objective of this trial was to investigate the relations between L-dopa and homocysteine after acute L-dopa/DDI administration in PD patients with different L-dopa metabolism. Thirty PD patients were divided into groups with superior (I) and less (II) L-dopa absorption after standardized intake of 125 mg L-dopa/benserazide with determination of L-dopa, 3-O-methyl-dopa (3-OMD) and homocysteine in plasma at baseline, 30, 60, and 90 minutes. There was a homocysteine increase in Group I (F = 5; P = 0.005) and a moderate decrease in Group II (F = 4.27; P = 0.01). A rise of 3-OMD (F = 10.51; P < 0.0001) appeared in Group I, but not in Group II (F = 0.91; P = 0.44), accordingly L-dopa accumulation was better in Group I than in Group II. Thus, in conclusion, L-dopa metabolism is an important component for homocysteine elevation after one time L-dopa/DDI administration in PD patients., (2009 Movement Disorder Society.)

Activation of sympato-adrenal system plays an important role in the development of chronic cardiac failure (CCF). However, its relation to morpho-functional state of myocardium in CCF patients is virtually unknown. HPLC with electrochemical detection was used to determine plasma noradrenalin, adrenalin, and their precursors, 3,4-dioxyphenylalanine (DOPA) and dopamine, in patients with different morpho-functional changes in myocardium. The study demonstrated enhanced activity of sympato-adrenal system in patients with CCF. It showed for the first time that activity of sympato-adrenal system in CCF patients depends on the morpho-functional status of myocardium.

Background: It is well established that the serotonergic system (SS) plays important roles in the pathogenesis of cardiovascular diseases. However, the impact of serotonin and its inter-relation with the sympathoadrenal system (SAS) in chronic heart failure (CHF) is poorly understood., Methods: Utilizing high-performance liquid chromatography with electrochemical detection, we determined blood plasma levels of serotonin (5-hydroxy-triptamine, [5-HT](p)), 5- hydroxy-indole-acetic acid ([5-HIAA](p)), epinephrine ([E](p)), norepinephrine ([NE](p)), 3,4-dihydroxy-L-phenyl-alanine ([DOPA](p)), dopamine ([DA](p)) and the platelet concentration of serotonin ([5-HT](pt)) in CHF patients with different morphofunctional alterations of myocardium. The morphofunctional alterations included diastolic dysfunction (DD), diastolic dysfunction with left ventricular hypertrophy (DD&LVH), and diastolic and systolic dysfunction (D&SD)., Results: All CHF groups showed significant rises of [5-HT](p) and [5-HT](pt). DD&LVH and D&SD individuals also had increased [5-HIAA](p). Levels of SAS blood biomarkers were also significantly changed. The correlation between SS and SAS was increased in CHF and corresponded with disease severity., Conclusions: These results clearly demonstrate that in CHF patients significant changes in SS and SAS occur, which are thought to relate to the morphofunctional alterations of myocardium. The observed changes in the levels of these biomarkers may serve as potential surrogates to monitor severity of disease, to evaluate response to drug treatment, and as a rational basis for new therapeutic approaches., (Copyright 2009 S. Karger AG, Basel.)

This study tested whether familial dysautonomia (FD) involves progressive loss of noradrenergic nerves. Plasma levels of catechols, including dihydroxyphenylglycol (DHPG), norepinephrine (NE), dopamine (DA), and DOPA, were measured in 7 adult patients with FD and 50 healthy control subjects. FD patients were re-tested after a mean follow-up period of 13 years. Compared to controls, FD patients had low plasma levels of DHPG (P < 0.001), high DOPA and DA levels (P = 0.01, P = 0.0002), and high NE:DHPG (P < 0.0001), DA:NE (P = 0.0003), and DOPA:DHPG (P < 0.0001) ratios. At follow-up there were no changes in plasma levels of individual catechols; however, there were further increases in DOPA:DHPG ratios (mean 24 +/- 7%, P = 0.01). In FD, plasma catechol profiles are sufficiently stable, at least over a decade, to be used as a biomarker of disease involvement. An increasing DOPA:DHPG ratio suggests slight but consistent, progressive loss of noradrenergic neurons.

A home-made nano-desorption electrospray ionization (nano-DESI) device and the kinetic method were tested in chiral analysis of model clinical samples containing enantiomers of one of three pharmaceutically important compounds: dihydroxyphenylalanine (DOPA), ephedrine and ibuprofen. The initial evaluation of chiral systems was carried out by direct infusion of solution mixtures (analyte/central metal/chiral reference ligand) to a standard electrospray ionization (ESI) source. Cu(II) was used as a central metal for all analytes, L-phenylalanine was applied as a chiral reference ligand for DOPA, whereas L-tryptophan was used for the other two analytes. Then, the ESI source was substituted by a nano-DESI source and dried spots of 1 microL samples of whole human blood spiked with individual drugs were successfully analyzed without any pre-treatment. Irrespective of a laborious initial nano-DESI set-up, the combination of the kinetic method with nano-desorption electrospray has, for the first time, been demonstrated as a promising tool for chiral analysis of drugs in blood samples.

The clinical importance of simultaneous analysis of 3,4-dihydroxyphenylglycol with other human plasma catecholamines has been investigated to better understand the sympathetic nervous system. However, previous reports have had analytical difficulties with both resolution and extraction. The current study uses a reversed-phase triacontylsilyl silica (C30) column under the mobile phase condition without ion-pair reagents to separate catecholamines and their metabolites, with above 91% recoveries for intra-assay, above 85% for inter-assay, and less than 10% (n=5) coefficient of variation. Lower detection limits (S/N=4) and quantification limits (S/N=6) were 40 and 100 pg/mL for norepinephrine, 3,4-dihydroxyphenylglycol, and 3,4-dihydroxyphenylalanine, 10 and 20 pg/mL for epinephrine, 10 and 40 pg/mL for dopamine. Linear ranges were from 40 to 5000 pg/mL for norepinephrine and 3,4-dihydroxyphenylalanine, from 100 to 5000 pg/mL for 3,4-dihydroxyphenylglycol, and from 10 to 2000 pg/mL for epinephrine and dopamine. The C30 column may prove clinically useful, as it provides a convenient and simultaneous method of evaluation of human plasma catecholamines.

Cushing's syndrome is associated with typical central redistribution of adipose tissue. The aim of the study was to assess lipolysis and catecholamines and their metabolites in subcutaneous abdominal adipose tissue using an in-vivo microdialysis technique. Nine patients with Cushing's syndrome and nine age-, gender- and body mass index (BMI)-matched control subjects were included in the study. Local glycerol concentrations were significantly increased in subcutaneous adipose tissue of patients with Cushing's syndrome (p<0.001). Plasma noradrenaline, dihydroxyphenylglycol and dihydroxyphenylalanine were decreased in patients with Cushing's syndrome (p<0.02, p<0.05, and p<0.02, respectively). Adrenaline, noradrenaline, dihydroxyphenylglycol and dihydroxyphenylalanine concentrations in subcutaneous abdominal adipose were non-significantly higher in patients with Cushing's syndrome. In conclusion, we showed that lipolysis in subcutaneous adipose tissue of patients with Cushing's syndrome is significantly increased as compared to healthy subjects. This finding together with non-significantly increased local catecholamine concentrations in these patients suggests a possible link between increased lipolysis and catecholaminergic activity in subcutaneous adipose tissue.

Objective: Proteins are the major effectors of biological structure and function. Oxidation-induced changes to protein structure can critically impair protein function, with important pathologic consequences. This study was undertaken to examine whether oxidation-induced changes to protein structure occur during pediatric cardiopulmonary bypass and to examine the association with postoperative outcome., Methods: Elevation of the 3,4-dihydroxyphenylalanine content of a protein relative to its native tyrosine content indicates structural damage due to oxidation. Protein 3,4-dihydroxyphenylalanine/native tyrosine ratios were measured before surgery and up to 6 hours after institution of cardiopulmonary bypass in 24 children undergoing repair of congenital heart disease, who were prospectively selected to form a cyanotic and comparable acyanotic control group. Results were correlated with perioperative variables and postoperative outcomes., Results: Elevation of protein 3,4-dihydroxyphenylalanine/tyrosine ratios above baseline (0.48 mmol/mol [SD, 0.11 mmol/mol] vs 0.36 mmol/mol [SD, 0.13 mmol/mol]; P = .001) occurred within 30 minutes of initiating cardiopulmonary bypass in cyanotic but not in acyanotic children and correlated inversely with preoperative arterial oxygen saturation (R = -0.52; P = .03). Protein 3,4-dihydroxyphenylalanine/tyrosine ratios were also increased above baseline at 120 minutes (0.44 mmol/mol [SD, 0.12 mmol/mol]; P = .007) and 180 minutes (0.40 mmol/mol [SD, 0.14 mmol/mol]; P = .01) after the institution of cardiopulmonary bypass in children who underwent prolonged procedures. Elevation of 3,4-dihydroxyphenylalanine/tyrosine during prolonged procedures was associated with postoperative arrhythmias and the need for increased inotropic support (P = .001)., Conclusions: Oxidative injury to proteins occurs during pediatric cardiopulmonary bypass. Cyanotic children are most at risk, particularly those undergoing prolonged procedures, in whom elevation of the protein 3,4-dihydroxyphenylalanine/tyrosine ratio is associated with increased postoperative morbidity.

Measurements of plasma-free normetanephrine and metanephrine provide a sensitive test for diagnosis of pheochromocytoma but may fail to detect tumors that produce predominantly dopamine. Such tumors are extremely rare, usually found as extraadrenal paragangliomas. This report describes measurements of plasma concentrations of free methoxytyramine, the O-methylated metabolite of dopamine, in 120 patients with catecholamine-producing tumors, including nine with extraadrenal paragangliomas secreting predominantly dopamine. In seven of these nine patients, tumors were found incidentally or secondary to the space-occupying complications of the lesions. Plasma concentrations of free methoxytyramine and dopamine were increased in all nine patients, including two with normal plasma and urinary normetanephrine and metanephrine and normal urinary outputs of dopamine. Relative increases above normal for plasma methoxytyramine (104-fold) and dopamine (56-fold) were much greater (P < 0.001) than those for urinary dopamine (3-fold). Insensitivity of the latter for identification of dopamine-secreting tumors was due to dependence of the urinary amine on renal extraction and decarboxylation of circulating 3,4-dihydroxyphenylalanine. Measurements of plasma-free methoxytyramine, in addition to normetanephrine and metanephrine, are unlikely to improve diagnosis of pheochromocytomas in hypertensive patients with symptoms of catecholamine excess but may be useful in selected patients for identification of tumors that produce predominantly dopamine.

Previous pharmacokinetic trials with standard levodopa formulations showed a different behavior of levodopa degradation in plasma of patients with Parkinson's disease (PD) in various advanced stages. The objective of this trial was to compare levodopa plasma metabolism in PD patients with and without previous long-term levodopa intake after oral intake of a dispensable levodopa/benserazide formulation (DLB). The over a 150 min interval computed area under the curve values of levodopa plasma levels after DLB administration were significantly (ANCOVA: F(1,19) = 7.88, P = 0.01) higher in PD patients with chronic levodopa treatment compared to patients without prior levodopa treatment. The maximum plasma levodopa concentration did not differ (ANCOVA: F(1.19) = 1.17, P = 0.29). Long-term levodopa administration results in an increased levodopa plasma bioavailability in PD patients.

Background: The sympathetic nervous system plays an important role in the regulation of adipose tissue (AT) lipolysis, which is a key step in the metabolic processes leading to the decrease of fat mass. The present study was designed to determine in vivo basal and exercise-stimulated lipolysis and concentrations of catecholamines, the major hormones controlling lipolysis, in subcutaneous abdominal AT in patients with anorexia nervosa (AN), characterized by self-induced starvation and excessive exercises resulting in severe malnutrition and fat store loss. The results of local catecholamines and glycerol levels were compared with those in plasma in both experimental groups., Material and Methods: An in vivo microdialysis technique was used for the assessment of norepinephrine, dihydroxyphenylalanine, dihydroxyphenylacetic acid and glycerol concentrations in subcutaneous AT of 10 women with AN (body mass index: 15.57 +/- 0.55 kg m(-2)) and 10 age-matched controls (body mass index: 21.56 +/- 0.41 kg m(-2)). Both the AN patients and the control subjects underwent a 1.5 W kg(-1) exercise test., Results: Basal AT norepinephrine concentrations were increased in the AN patients in comparison with the controls. Basal AT glycerol concentrations were similar in both groups. During exercise, a local increase in the AT norepinephrine and glycerol concentrations was observed in the AN patients only. In contrast to the controls, the basal AT dihydroxyphenylalanine and dihydroxyphenylacetic acid levels in the AN patients were high and remained unchanged during exercise. Basal and exercise-stimulated plasma norepinephrine, dihydroxyphenylalanine, dihydroxyphenylacetic acid and glycerol levels were not different in the AN patients and healthy controls., Conclusion: Our study provides evidence of elevated baseline and exercise-induced sympathetic nervous activity and exercise-induced lipolysis in abdominal AT of AN patients.

Background: Water ingestion raises blood pressure substantially in patients with perturbed autonomic control and more modestly in older subjects. It is unclear whether prophylactic water drinking improves orthostatic tolerance in normal healthy adults., Methods and Results: Twenty-two healthy subjects, 18 to 42 years of age, with no history of syncope underwent head-up tilt-table testing at 60 degrees for 45 minutes or until presyncope or syncope occurred. In their initial test, participants were randomized to either 16 oz (473 mL) of water drinking 5 minutes before tilt-table testing or tilt-table testing alone, with the alternative in a second test on a different day. During the first 30 minutes of tilt, 8 of 22 subjects without water experienced presyncope but only 1 of 22 who had ingested water (P=0.016). Water drinking attenuated the heart rate increase associated with tilt (P<0.001) while accentuating the increase in total peripheral resistance (P=0.012). The average time study participants tolerated head-up tilt was 26% longer after water (41.1+/-8.1 versus 32.6+/-14.3 minutes, mean+/-SD), with a pairwise mean difference of 8.5+/-14.0 minutes (95% CI, 2.3 to 14.7 minutes; P=0.011)., Conclusions: Water enhances tolerance of upright posture. The effect of water is mediated by increased peripheral vascular resistance. Water ingestion may constitute a simple and effective prophylaxis against vasovagal reactions in healthy subjects, such as those associated with blood donation.

BIA 3-202 is a novel catechol-O-methyltransferase (COMT) inhibitor being developed for use as a levodopa-sparing agent in Parkinson's disease. This study investigated the effect of four single oral doses of BIA 3-202 (50 mg, 100 mg, 200 mg, and 400 mg) compared with placebo on plasma concentrations of levodopa and its metabolite 3- O-methyl-levodopa (3-OMD) and on inhibition of erythrocyte COMT in healthy subjects receiving 100 mg of levodopa and 25 mg of benserazide (Madopar 125). This was a single-centre, double-blind, placebo-controlled, randomised, crossover study with five single-dose treatment periods. The washout period between doses was 2 weeks. On each treatment period, a different dose of BIA 3-202 or placebo was administered concomitantly with Madopar 125. Tolerability was assessed by recording adverse events, vital signs, continuous electrocardiogram and clinical laboratory parameters. In the study, 18 subjects (12 male and 6 female) participated. The drug combination was well tolerated. All doses of BIA 3-202 significantly increased the area under the concentration-time curve (AUC) versus placebo, ranging from 39% (95% confidence intervals, 1.06-1.69) with 50 mg to 80% (95% confidence intervals, 1.42-2.22) with 400 mg. No significant change in mean maximum plasma concentrations (C(max)) of levodopa was found. Mean C(max) and AUC of 3-OMD significantly decreased for all doses tested. BIA 3-202 caused a rapid and reversible inhibition of S-COMT activity, ranging from 57% (50 mg) to 84% (400 mg). In conclusion, the novel COMT inhibitor BIA 3-202 was well tolerated and significantly increased the bioavailability of levodopa and reduced the formation of 3-OMD when administered with standard release levodopa/benserazide.

Human plasma contains several catechols, including the catecholamines norepinephrine, epinephrine, and dopamine, their precursor, L-3,4-dihydroxyphenylalanine (L-DOPA), and their deaminated metabolites, dihydroxyphenylglycol, the main neuronal metabolite of norepinephrine, and dihydroxyphenylacetic acid, a deaminated metabolite of dopamine. Products of metabolism of catechols include 3-methoxytyrosine (from L-DOPA), homovanillic acid and dopamine sulfate (from dopamine), normetanephrine, vanillylmandelic acid, and methoxyhydroxyphenylglycol (from norepinephrine), and metanephrine (from epinephrine). Plasma levels of catechols and their metabolites have related but distinct sources and therefore reflect different functions of catecholamine systems. This article provides an update about plasma levels of catechols and their metabolites and the relevance of those levels to some issues in human health and disease.

Parkinson disease is characterized by the loss of dopaminergic neurons, thus decreasing the system's ability to produce and store dopamine (DA). Such ability is often investigated using 18F-fluorodopa (FD) positron emission tomography. A commonly used model to investigate the DA synthesis and storage rate is the modified Patlak graphical approach. This approach allows for both plasma and tissue input functions, yielding the respective uptake rate constants K(i) and K(occ). This method requires the presence of an irreversible compartment and the absence of any nontrapped tracer metabolite. In the case of K(occ), this last assumption is violated by the presence of the FD metabolite 3-O-methyl-[18F]fluoro-dopa (3OMFD), which makes the K(occ) evaluation susceptible to a downward bias. It was found that both K(i) and K(occ) are influenced by DA loss and thus are not pure measures of DA synthesis and storage. In the case of K(occ), the presence of 3OMFD exacerbates the effect of DA egress, thus introducing a disease-dependent bias in the K(occ) determination. These findings imply that K(i) and K(occ) provide different assessments of disease severity and that, as disease progresses, K(i) and especially K(occ) become more related to DA storage capacity and less to the DA synthesis rate.

Reasons for Performing Study: The aetiopathogenesis of equine grass sickness (EGS) is unknown. The role of free radical-mediated neuronal damage has not previously been investigated in this condition., Objectives: To investigate the potential contribution of oxidative damage and antioxidant status to neurodegeneration in EGS., Methods: Systemic levels of surrogate biomarkers were determined in 10 horses with acute EGS and in 2 control populations; 10 healthy horses co-grazing with the 10 EGS horses at the onset of clinical disease, and 10 healthy mares grazing where EGS has not been reported., Results: EGS horses had alterations in levels of several antioxidants, consistent with oxidative stress, the acute phase response and/or the secondary metabolic complications of EGS. EGS horses had elevated plasma dihydroxyphenylalanine (DOPA) levels., Conclusions: The elevated DOPA levels probably reflected a generalised disturbance of catecholamine metabolism rather than increased DOPA production via free radical-mediated oxidation of tyrosine. However, there was no evidence of systemic macromolecular oxidative damage., Potential Clinical Relevance: Further work is required to determine whether macromolecular oxidative damage occurring at the neuronal level contributes to EGS.

Malignant melanoma in the anorectal region is a rare disease associated with a very poor prognosis. Taking a biopsy of malignant melanoma is generally contraindicated because of the high risk of inducing metastasis. Although clinical examination and imaging findings are important for the preoperative diagnosis, conventional imaging techniques sometimes fail to provide information from which an accurate diagnosis can be made. We recently treated an 84-year-old woman with rectal malignant melanoma, in whom magnetic resonance imaging showed atypical findings. On the other hand, N-isopropyl- p-(123)I-iodoamphetamine single photon emission computed tomography and 5- S-cysteinyl dopa in blood serum, as a tumor marker of malignant melanoma, proved very effective for establishing the preoperative diagnosis. Despite radical abdominoperineal resection, the patient died of multiple liver and lung metastases about 5 months after surgery.

This study examined whether serotonin transporter (5-HTT) gene knockout influences adrenomedullary, sympathoneural, or hypothalamo-pituitary-adrenal responses to acute immobilization. In conscious, cannulated mice, arterial plasma concentrations of catecholamines, ACTH, and corticosterone were measured at baseline and after 15 min of immobilization. Tissue levels of serotonin (5-HT), catecholamines, and hormones were also measured in pituitary and adrenal glands. At baseline, adrenal and pituitary 5-HT concentrations in knockout (5-HTT(-/-)) mice were markedly lower than those in littermate control (5-HTT(+/+)) mice, whereas the groups did not differ in levels of catecholamines or hormones in plasma or tissue. Immobilization increased plasma levels of catecholamines, ACTH, and corticosterone in all genotypes. 5-HTT(-/-) mice had exaggerated responses of plasma epinephrine to immobilization and significant reductions in adrenal epinephrine, norepinephrine, and 5-HT contents compared with values in littermate controls. Pituitary ACTH was significantly reduced after immobilization in 5-HTT(-/-) mice only, but increases in plasma ACTH and corticosterone levels did not differ between genotypes. The results suggest that one 5-HTT function is to restrain adrenomedullary activation in response to immobilization. Exaggerated adrenomedullary responses seem to be an autonomic correlate of the anxiety-like behaviors in 5-HTT knockout mice.

Subarachnoid haemorrhage is a serious condition, often accompanied by cerebral vasospasm and hydrocephalus, which may result in delayed cerebral ischaemia and neurological deterioration. While the mechanisms responsible remain unknown, activation of the sympathetic nervous system, leading to elevated levels of circulating catecholamines is, at least in part, implicated. In this study, we sought to examine the importance of sympathetic nervous activation and its relation to brain monoaminergic neurotransmission in 25 patients following subarachnoid haemorrhage by examining plasma and cerebrospinal fluid levels of the catecholamines noradrenaline, adrenaline and dopamine, and their metabolites. Total body sympathetic activity was concurrently assessed using isotope dilution methodology. In the early phase following subarachnoid haemorrhage patients exhibited markedly elevated rates of spillover of noradrenaline to plasma (9.11 +/- 1.12 vs. 3.39 +/- 0.26 nmol/min, p < 0.01), with rates being higher in those patients in whom hydrocephalus developed (11.15 +/- 1.40 vs. 7.90 +/- 1.41 nmol/min, p = 0.05). The degree of sympathetic nervous activation tended to be higher in females compared with males. Lower cerebral perfusion pressures were observed in those patients in whom cerebrospinal fluid concentrations of noradrenaline and dopamine metabolites were high. A marked sympathetic nervous activation, more pronounced in women and in those with hydrocephalus, occurs following subarachnoid haemorrhage. The diminished cerebral perfusion seen following subarachnoid bleeding may occur as a result of activation of central catecholaminergic neurones., (Copyright 2002 Elsevier Science Inc.)

One main metabolizing pathway of levodopa is O-methylation to 3-O-methyldopa (3-OMD) by catechol-O-methyltransferase (COMT). Since COMT requires Mg2+ and S-adenosylmethionine as methyl donor for this transmethylating process, COMT converts S-adenosylmethionine to S-adenosylhomocysteine and subsequent homocysteine. Objective of this study was to demonstrate relations between plasma levodopa, 3-OMD and total homocysteine in treated parkinsonian subjects. We measured homocysteine, levodopa and 3-OMD by HPLC. We compared plasma homocysteine in two groups of treated parkinsonian subjects subdivided according to their 3-OMD level. Homocysteine was significantly (p = 0.002) elevated in the group with higher 3-OMD concentrations and positively (r = 0.52, p = 0.0006) correlated to 3-OMD. Homocysteine induces vascular disease. Previous studies showed an increase of ischaemic heart- and cerebrovascular disease in treated parkinsonian patients.

Unlabelled: Inhibition of the catechol-O-methyltransferase (COMT) is an effective treatment for end-of-dose fluctuations in advanced Parkinson's disease. The aim of the present investigation was to analyse the consequences of subsequent alterations in levodopa metabolism under common treatment conditions when the levodopa dose is adjusted due to the occurrence of dyskinesias after initiation of the COMT-inhibitor. Ten patients with advanced Parkinson's disease (Hoehn & Yahr stage IV) were medicated with tolcapone. Prior to and five to ten days after the initiation of tolcapone 300 mg/d, serum level profiles of levodopa and its metabolites (3-O-methyldopa (3-OMD), dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA)) were performed. The mean daily levodopa dose was reduced from 894 +/- 248 mg to 646 +/- 252 mg (p = 0.003). There was a significant increase in the area under the curve (AUC) of DOPAC during COMT-inhibition compared to the baseline profile (p = 0.009). There were significant decreases of the AUC of HAV (p = 0.001) and the ratios of the AUC HVA / AUC DOPAC (p = 0.0001) and AUC 3-OMD / AUC levodopa (p = 0.0001)., Conclusion: The elevation of DOPAC and the decrease of HVA and HVA / DOPAC reflect a shift of the levodopa metabolism towards the MAO-B dependent oxidative pathway. This might contribute to production of hydroxyl radicals and induction of oxidative stress.

Purpose: To evaluate the clinical significance of 5-S-cysteinyldopa (5-S-CD), a major intermediate in melanin synthesis, as a potential diagnostic tumor marker for uveal malignant melanoma., Methods: The levels of 5-S-CD in the serum were measured by high-performance liquid chromatography in 16 patients with primary uveal melanoma. The levels of 5-S-CD were also measured in both aqueous and vitreous humor in 10 patients with uveal melanoma. The serum of healthy volunteers and patients with skin diseases other than melanoma, and the intraocular fluids of patients with cataract and vitreoretinal diseases were used as controls., Results: Serum concentrations of 5-S-CD in patients with uveal melanoma in the absence of extraocular metastases were close to those of controls; however, serum concentrations of 5-S-CD were significantly elevated in patients with extraocular metastases of melanoma. Concentrations of 5-S-CD in the intraocular fluids, especially vitreous humor, were higher in patients with uveal melanoma than in controls., Conclusions: 5-S-CD in intraocular fluids may serve as a useful biochemical marker for the diagnosis of uveal melanoma. Serum 5-S-CD may contribute to the assessment of the presence and progression of extraocular metastases in patients with uveal melanoma.

1-[3,4-Dihydroxy-5-nitrophenyl]-2-phenyl-ethanone (BIA 3-202) is a new long-acting catechol-O-methyltransferase (COMT) inhibitor with limited access to the brain. The present study evaluated the interference of BIA 3-202 upon levels of L-3,4-dihydroxyphenylalanine (L-DOPA) and metabolites in plasma (3-O-methyl-L-DOPA) and brain [3-O-methyl-L-DOPA, dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA)] in rats orally treated with L-DOPA (20 mg/kg) plus benserazide (30 mg/kg). At different time points (1, 3 and 6 h) after the administration of BIA 3-202 (0, 3, 10 and 30 mg/kg) or L-DOPA plus benserazide, rats were sacrificed and the right striatum was quickly dissected out and stored for the assay of L-DOPA, 3-O-methyl-L-DOPA, dopamine and amine metabolites. Levels of L-DOPA, 3-O-methyl-L-DOPA, dopamine, DOPAC and HVA in the striatum in L-DOPA plus benserazide-treated rats were higher than in vehicle-treated rats. However, this increase in striatal L-DOPA, dopamine, DOPAC and HVA was, in a dose- and time-dependent manner, even higher (P<0.05) in rats given BIA 3-202 (3, 10 and 30 mg/kg). This effect was accompanied by a marked decrease in 3-O-methyl-L-DOPA levels in the striatum of L-DOPA plus benserazide-treated rats. Increases in levels of L-DOPA and decreases in 3-O-methyl-L-DOPA levels in plasma also accompanied the administration of BIA 3-202. BIA 3-202 did not significantly affect levels of DOPAC and HVA in the striatum in vehicle-treated rats. It is concluded that administration of BIA 3-202 enhances the availability of L-DOPA to the brain by reducing its O-methylation in the periphery, which may prove beneficial in parkinsonian patients treated with L-DOPA plus an aromatic amino acid decarboxylase inhibitor.

The hormonal status was studied in the dynamics of postpartum stress in the puerperas who lived in the town of Balkhash under the influence of an industrial complex. The puerperas were found to show no pronounced adrenal cortical response to postpartum stress; there was monotony of changes in the content of dopa and dophamine and the levels of adrenaline and noradrenaline remained high on day 5 after delivery as compared with the controls. There were high levels of prolactin and cortisole, which suggests different stress levels in Balkhash females and in the controls. It can be assumed that chronic exposure to industrial noxious agents results in so-called cross resistance caused by one stressor (delivery) in relation to the effect of other-order (ecological) stressors rather than in depletion of the hormonal system.

In healthy men, a decrease in plasma testosterone levels was observed in the context of metabolic stress. While physiological mechanisms underlying this response are unclear, there are several lines of evidence suggesting circulating epinephrine's influence on plasma testosterone levels. The purpose of this study was to directly relate stress-induced changes in plasma testosterone and epinephrine. The stressor used was blockade of glucose metabolism with pharmacological doses (40 mg/kg) of 2 deoxyglucose (2DG). Arterial plasma samples from 10 healthy males were assayed at 20 minutes intervals for 60 minutes for the concentrations of testosterone, epinephrine and related biochemicals. Bolus administration of 2DG resulted in progressive decline in testosterone and increases in epinephrine and norepinephrine plasma levels (mean change from baseline: 29, 2530 and 186%, respectively). Inverse correlation was detected between both absolute (r(s)=-0.72; df=8; p=0.017) and baseline-corrected testosterone concentrations at the 60 minute time point and epinephrine area under the curve values. Our results suggest that adrenomedullary activation may be involved in stress-induced testosterone effects. The implications of these data for the understanding of the role of catecholamines in glucoprivic stress response are discussed.

Catecholamines and their metabolites are important in the diagnosis of neuroblastoma (NB). Plasma (p-) levels of 3,4-dihydroxyphenylalanine (DOPA) are increased in most NB, probably reflecting decreased DOPA decarboxylase activity. Urine (u-) homovanillic acid (HVA), a DOPA and dopamine (DA) metabolite. is also increased in most NB. DOPAC (3,4-dihydroxyphenylacetic acid) is an important metabolite of DA in tissues with monoamine oxidase (MAO) activity. Because MAO is expressed in NB tumor cells, we studied the importance of measuring p-DOPAC and p-DOPA as compared to u-HVA and u-vanillylmandelic acid (VMA) in the diagnosis and follow-up of NB. DOPAC, DOPA, dopamine, noradrenaline, adrenaline, VMA and HVA were measured by reverse-phase HPLC with electrochemical detection in 106 children (28 with NB (13 newly diagnosed), 25 with other solid tumors, 28 hospitalized for nonneoplastic diseases, and 25 healthy children). P-DOPAC or p-DOPA concentrations were above the upper normal range in 92% of untreated NB patients, as were u-HVA or u-VMA levels. None of these tumor markers was correlated to tumor stage or survival. P-DOPA but not p-DOPAC was correlated to age in NB children. Increased values of p-DOPAC and p-DOPA were found in one patient surviving NB for 10 years. Plasma DOPAC concentrations were decreased in children hospitalized for non-NB diseases, probably reflecting reduced food intake. Plasma analyses of DOPA and DOPAC seem to be useful alternatives in the diagnosis and follow-up of NB if urine sampling is to be avoided. Plasma DOPAC may be an index of nutritional status in various diseases.

6-[18F]Fluoro-L-DOPA (FDOPA) is an imaging agent used in the study of dopamine terminals in the living brain using positron emission tomography (PET). To better understand the role of tracer metabolism in dynamic FDOPA PET studies, the pharmacokinetics of individual FDOPA metabolites in extracellular space in the striata of anesthetized rats was investigated using in vivo microdialysis. Brain tissues were also analysed to obtain FDOPA metabolite distribution in the combined intracellular and extracellular spaces. Total extracellular [18F] radioactivity in rat striata was observed to rise and peak at 30 min post-injection (p.i.) and declined with clearance half-life of 2 h. In the extracellular space, the dominant FDOPA metabolite at early times was FDOPAC, followed by FHVA at 50 min, then F-sulfoconjugates at 70 min and finally 3-O-methyl-6-Fluoro-L-DOPA (3OMFD) at later times. These results are consistent with the sequential metabolism and brain clearance of L-DOPA and its metabolites. Analysis of whole striatal tissue confirmed the intraneuronal localization of fluorodopamine most likely stored in vesicles. A new but not unexpected finding was the enrichment of 3OMFD in intraneuronal striatal space which is perhaps a factor in its slow cerebral clearance. Since FDOPA PET data reflects the overall pharmacokinetics of several [18F]-metabolites, the observed different rates of formation and clearance and also different neuronal localization of each metabolite contribute to the measures obtained in dynamic FDOPA PET studies. These metabolic steps and their role in tracer kinetics are, thus, important factors to consider in ascribing physiologic significance to PET-derived measures.

Objective: Neuroleptic malignant syndrome (NMS) may be associated with a dysregulation of the catecholaminergic and serotonergic systems. The objective of the present study was to evaluate prospectively the circulatory levels of serotonin (5-HT), epinephrine (E) and dopa in patients suffering from NMS., Method: Platelet-poor plasma (PPP) levels of serotonin, epinephrine and dopa in eight NMS patients were measured twice: in the acute state and in the state of remission., Results: PPP dopa concentration was significantly lower in acute NMS state compared to the remission state (P = 0.023). In contrast, PPP E level was significantly higher (P = 0.019) in the acute NMS state and PPP 5-HT concentrations in the acute state tended to be higher than those at remission (P = 0.078). 5-HT/dopa ratio was significantly higher in the acute NMS (P = 0.015)., Conclusion: These results may reflect reduction in dopaminergic function and increase in adrenergic and serotonergic activity in the acute NMS state.

The etiology of vitiligo is still being debated, although neural factors seem to play a pivotal role in its pathogenesis. In our search for a link between vitiligo and the activity of monoaminergic systems, we used high-pressure liquid chromatography and electrochemical detector (HPLC-ED) methods to measure the plasma levels of the following substances in 35 healthy subjects and in 70 patients suffering from nonsegmental vitiligo at the different stages of the disease: catecholamines [norepinephrine (NE), epinephrine (E), and dopamine (DA)], their precursor 3,4-dihydroxyphenylalanine (DOPA), their metabolites [3-methoxy-4-hydroxyphenylglycol (MHPG), normetanephrine (NMN), metanephrine (MN), and homovanillic acid (HVA)], and 5-hydroxyindolacetic acid (5-HIAA) as the major metabolite of serotonin. We found that the levels of NE, E, NMN, MN, HVA, and 5-HIAA were significantly higher in patients compared to controls. The patients at an active phase of the disease (n = 49/70) showed significantly higher levels of NE, NMN, MHPG, and HVA than ones at a stable phase. The patients with progressive vitiligo and at its more recent onset (< 1 year) showed significantly increased levels of E, NE, and MN in comparison with longer-term sufferers. No significant differences were observed when the patients were subdivided according to the type of vitiligo or their age at its onset. The higher catecholamine and metabolite levels in the early phase of the disease may reflect increased activity by monoaminergic systems, probably due to stressful events, including the onset of vitiligo itself.

Background: Short-term exposure to high-altitude hypoxia increases hypoxic ventilatory sensitivity (HVS) in healthy humans. Dopamine (DA) is the implicated neurotransmitter in carotid body (CB) chemoreceptor response, and the microenvironmental conditions in CB tissue are comparable to blood. Continuous DA infusion affected ventilation in animals and humans. Age-related oscillations in blood DA levels may influence peripheral chemoreflexes., Objective: Hypoxic ventilatory responses (HVR) relative to blood DA concentration and its precursor, dihydroxyphenylalanine (DOPA) was measured in young and elderly men during short-term altitude adaptation., Methods: Nine elderly climbers (group 1:61+/-1.4 years) and 7 young healthy subjects (group 2: 23+/-2 years) were tested at sea level on day 0, on day 3 after passive transport to 2,200 m, and on day 14 after climbing to 4,200 and 5,642 m., Results: Sea level HVR in group 1 was 47% lower than in group 2, accompanied by higher blood DOPA (300%) and DA (37%) content. Initial DA and DOPA concentrations showed a negative correlation with initial HVR but a positive correlation with age. Passive transport to middle altitude (2,200 m) increased HVS, doubling HVR slopes in groups 1 and 2 and producing increased maximum expired minute ventilation during isocapnic rebreathing (29 and 28%, respectively). Day 3 2,200-meter blood DOPA content decreased by 22% in group 1 and increased by 300% in group 2. DA increased in both groups., Conclusion: The relationship between HVR and the reciprocal DA and DOPA values seen in both groups is associated with age, producing decreased DA receptor sensitivity and enhanced DA reuptake during adaptation to high altitude., (Copyright 2000 S. Karger AG, Basel.)

Adaptation to intermittent hypoxia can enhance a hypoxic ventilatory response (HVR) in healthy humans. Naturally occurring oscillations in blood dopamine (DA) level may modulate these responses. We have measured ventilatory response to hypoxia relative to blood DA concentration and its precursor DOPA before and after a 2-week course of intermittent hypoxic training (IHT). Eighteen healthy male subjects (mean 22.8+/-2.1 years old) participated in the study. HVRs to isocapnic, progressive, hypoxic rebreathing were recorded and analyzed using piecewise linear approximation. Rebreathing lasted for 5-6 min until inspired O2 reached 8 to 7%. IHT consisted of three identical daily rebreathing sessions separated by 5-min breaks for 14 consecutive days. Before and after the 2-week course of IHT, blood was sampled from the antecubital vein to measure DA and DOPA content. The investigation associated pretraining high blood DA and DOPA values with low HVR (r = -0.66 and -0.75, respectively), elevated tidal volume (r = 0.58 and 0.37) and vital capacity (r = 0.69 and 0.58), and reduced respiratory frequency (r = -0.89 and -0.82). IHT produced no significant change in ventilatory responses to mild hypoxic challenge (Peto2 from 110 to 70-80 mm Hg; 1 mm Hg = 133.3 Pa) but elicited a 96% increase in ventilatory response to severe hypoxia (from 70-80 to 45 mm Hg). Changes in HVRs were not accompanied by statistically significant shifts in blood DA content (24% change), although a twofold increase in DOPA concentration was observed. Individual subject's changes in DA and DOPA content were not correlated with HVR changes when these two parameters were evaluated in relation to the IHT. We hypothesize that DA flowing to the carotid body through the blood may provoke DA autoreceptor-mediated inhibition of endogenous DA synthesis-release, as shown in our baseline data.