Simultaneous liquid chromatographic determination of seventeen of the major monoamine neurotransmitters, precursors and metabolites. I. Optimization of the mobile phase using factorial designs and a computer program to predict chromatograms

Executive (dys)function after stroke: special considerations for behavioral pharmacology

Stroke is a worldwide leading cause of death and long-term disability with concurrent secondary consequences that are largely comprised of mood dysfunction, as well as sensory, motor, and cognitive deficits. This review focuses on the cognitive deficits associated with stroke specific to executive dysfunction (including decision making, working memory, and cognitive flexibility) in humans, nonhuman primates, and additional animal models. Further, we review some of the cellular and molecular underpinnings of the individual components of executive dysfunction and their neuroanatomical substrates after stroke, with an emphasis on the changes that occur during biogenic monoamine neurotransmission. We concentrate primarily on changes in the catecholaminergic (dopaminergic and noradrenergic) and serotonergic systems at the levels of neurotransmitter synthesis, distribution, reuptake, and degradation. We also discuss potential secondary stroke-related behavioral deficits (specifically, poststroke depression as well as drug-abuse potential and addiction) and their relationship with stroke-induced deficits in executive function, an especially important consideration given that the average age of the human stroke population is decreasing. In the final sections, we address pharmacological considerations for the treatment of ischemia and the subsequent functional impairment, as well as current limitations in the field of stroke and executive function research.

Oxidative stress induced by morphine in brain of rats fed with a protein deficient diet

The objective of the study is to determine the damage by oxidative stress induced by morphine in brain of rats fed with a protein-deficient diet. Twenty-eight malnourished male Wistar rats, 30 days old, were used in the study. The animals were divided into four groups of 7 rats per group. Group I received NaCl and the groups II; III and IV intraperitoneally received 3, 6 and 12 mg/kg of morphine sulphate, respectively, in a single dose. Animals were sacrificed and the levels of glutathione (GSH), dopamine, tryptophan and 5-hydroxyindole-3-acetic acid (5-HIAA) as well as, Na(+)/K(+) ATPase and total ATPase activity in the brain were measured. Tryptophan levels and Na(+)/K( +) ATPase activity showed non-significant changes in the experimental group. Levels of 5-HIAA decreased significantly (p = .03) in animals that received 12 mg/kg of morphine and in animals that received 3 mg/kg, levels of GSH and dopamine were found to have a significant decrease (p < .05), but a significant increase in the group that received 12 mg/kg of morphine (p < .05). Total ATPase activity increased significantly in the groups that received 3 mg/kg (p = .015) and 6 mg/kg (p = .0001) of morphine. The results show that malnutrition induces changes in cellular regulation and biochemical responses to oxidative stress caused by morphine sulphate.

Multi-criteria decision making approach and experimental design as chemometric tools to optimize HPLC separation of domperidone and pantoprazole

This paper deals with multiple response simultaneous optimization using the Derringer's desirability function for the development of a reversed-phase HPLC method for the simultaneous determination of domperidone and pantoprazole in commercial pharmaceutical preparations. Twenty experiments, taking the retention factor of the first peak, the two resolutions, and three retention times as the responses with three important factors, mobile phase composition, buffer molarity and flow rate, were used to design mathematical models. The experimental responses were fitted into a second order polynomial and the six responses simultaneously optimized to predict the optimum conditions for the effective separation of the studied compounds. The optimum assay conditions were: methanol-acetonitrile-dipotassium hydrogen phosphate (pH 7.0; 15.3 mM) (20:33:47, v/v/v) as the mobile phase and at a flow rate of 1.19 ml/min. While using this optimum condition, baseline separation with a minimum resolution of 2.0 and a run time of less than 6 min were achieved. The method showed good agreement between the experimental data and predictive value throughout the studied parameter space. The optimized assay condition was validated according to ICH guidelines to confirm specificity, linearity, accuracy and precision.

Semi-micro liquid chromatography of aromatic amino acid metabolites using isocratic elution and column switching

The concentrations of catecholamine-related compounds in body fluids reflect sympathetic nerve functions. Measuring the enzyme activity of these metabolic pathways will improve diagnosis since a variety of symptoms are reported. An isocratic elution system with two column switching valves was developed using three types of semi-micro columns for fast chromatographic analysis of catecholamine related compounds. Columns are a pentyl-bonded phase, 50 x 2.1 mm i.d., a phenylhexyl-bonded phase, 100 x 2.1 mm i.d. and an octadecyl-bonded phase, 100 x 2.1 mm i.d. The separation of 20 standard compounds was achieved within 25 min using reversed-phase ion-pair liquid chromatography with an electrochemical detector. This new system was applied for analysis of catecholamine-related compounds in pig brain, since pigs are a widely used animal model for transgenic manipulation of neural genes, and MHPG (or VMA), DOPAC, DOPA, NE, EP, DA, 5HTP and 5HIAA were quantified.

Reversed-phase high-performance liquid chromatography of catecholamines and indoleamines using a simple gradient solvent system and native fluorescence detection

A reversed-phase HPLC method using a C18 column and a two-mobile-phase gradient elution system containing only volatile components has been developed for separation of norepinephrine, octopamine, epinephrine, dopamine, dihydroxyphenylalanine, tyramine, tyrosine, serotonin, 5-hydroxytryptophan, N-acetyl-serotonin and tryptophan. Mobile phase A contains 0.05% aqueous trifluoroacetic acid and methanol (97.5:2.5, v/v) and mobile phase B contains 0.05% aqueous trifluoracetic acid and methanol (40:60, v/v). This method has the advantage that the mobile phase can be removed completely, without salt residues, from the eluted fractions thus simplifying further analytical procedures on isolated fractions. The elution profile of standards is related to structural characteristics allowing prediction of retention times of known compounds and insight into possible structural characteristics of unknown components in a mixture. Detection is via native fluorescence using excitation at 220 nm and emission at 320 nm and under the conditions described has a sensitivity range from 2.5 to 25 pmol, although the sensitivity range can be extended depending on the emission wavelength used.

Simultaneous Determination of Dopamine, Serotonin and Their Metabolites in the Rat Brain by HPLC Method with Coulometric Detection

A rapid and sensitive method for simultaneous determination of 3-hydroxytyramine (dopamine), 5-hydroxytryptamine (serotonin) and their metabolites - 3,4-dihydroxyphenylacetic acid, 3-methoxytyramine, 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid) and 5-hydroxyindole-3-acetic acid in the rat brain was developed. Brain samples with the internal standard and heparin were deproteinized by perchloric acid with ethylenediaminetetraacetic acid disodium salt and sodium sulfite. Following homogenization, centrifugation and filtration, the supernatant was directly injected into a reversed-phase HPLC system with coulometric detector. The response of the detected substances was linear in the range 12-700 ng/g of cerebellum homogenate (24-1 400 pg on column). Total recovery of the method was higher than 95%. The method was used for the determination of catecholamines and their metabolites in the chosen part of rat brain following the inhalation exposure to sarin (organophosphate).

A simple high-performance liquid chromatography assay for simultaneous determination of plasma norepinephrine, epinephrine, dopamine and 3,4-dihydroxyphenyl acetic acid

A reversed-phase HPLC assay coupled with electrochemical detection for simultaneously measuring plasma levels of norepinephrine, epinephrine, dopamine, and 3,4-dihydroxyphenylacetic acid (DOPAC) was developed. Separation of the catecholamines and the internal standard isoproterenol was obtained by a mobile phase consisting of 7% methanol in 0.1 M citrate buffer containing 0.3 mM sodium ethylenediaminetetraacetic acid (EDTA), and 0.5 mM 1-octanesulfonic acid, operated under isocratic condition at a flow rate of 1.2 ml/min. The potential of the guard cell was set at +650 mV, the first electrode of the analytical cell at +100 mV and the second at + 350 mV. Using a signal-to-noise ratio of > 3, the minimum detection limit assessed by direct on column injection was < 10 pg for analyte. The assays were linear from basal concentrations to 400 ng/ml. The intra- and inter-assay variations were < 10 and 15%, respectively. The assay has been applied successfully to measure plasma concentrations of these catecholamines in humans, rabbits and rats.

Endogenous catecholamine synthesis, metabolism, storage and uptake in human neutrophils

Evidence is presented that human neutrophils contain catecholamines and several of their metabolites. In vitro, incubation with alpha-methyl-p-tyrosine or pargyline affects intracellular dopamine, norepinephrine and their metabolites, suggesting catecholamine synthesis and degradation by these cells. Reserpine reduces intracellular dopamine and norepinephrine and desipramine reduces intracellular norepinephrine, suggesting the presence of storage and uptake mechanism. In view of the ability of catecholamines to affect neutrophil function, the present results support the hypothesis that autoregulatory adrenergic mechanisms may exist in these cells.

Endogenous catecholamine synthesis, metabolism storage, and uptake in human peripheral blood mononuclear cells

Evidence has been obtained that peripheral blood mononuclear cells contain dopamine, norepinephrine, epinephrine, and their metabolites. Pharmacologic inhibition of tyrosine hydroxylase or monoamine oxidase profoundly affected intracellular catecholamines (CTs) and their metabolites, indicating that these cells are able to synthesize and breakdown CTs. The sensitivity of intracellular CTs to reserpine and the presence of CTs in the extracellular medium suggest that CTs are stored and released. Moreover, the increase of extracellular CTs in the presence of monoamine uptake blockers point to the presence of functional uptake mechanisms. Altogether, these results indicate the existence of a CT lifecycle in human mononuclear cells and warrant further studies to investigate the role of adrenergic autoregulatory mechanisms in modulation of the immune response and in the pathogenesis of diseases involving the immune system.

Half-fraction and full factorial designs versus central composite design for retention modelling in reversed-phase ion-pair liquid chromatography

In a previous paper (J. O. De Beer, C. V. Vandenbroucke and D. L. Massart, J. Pharm. Biomed. Anal., 12, (1994) 1379-1396) liquid chromatographic (LC) retention modelling of the cough-syrup compounds methyl para-hydroxybenzoate (MPHB) and propyl para-hydroxybenzoate (PPHB), phenylephrine hydrochloride (PE) and chlorphenamine maleate (CPM) was studied using a face-centred central composite design. It is examined whether smaller half-fractional and full factorial designs with fewer experiments tend to reliably predict retention times of the latter compounds as well. Simplified regression modelling, however, neglecting more first-order and interactive effects and disregarding pure second-order effects, has to be set up. These smaller designs finally satisfy the prediction of the retention of MPHB, PPHB and PE also. Retention prediction of CPM is much less accurate. CPM has a pKa value of 4.0, which is encompassed by the examined mobile phase pH limits 3.0 and 5.0. Since the largest retention shifts occur near the pKa value, retention prediction in this area becomes more complex. CPM retention modelling from a full factorial design is useful if the mobile phase pH is fixed at 5.0 for methanol as well as for acetonitrile as organic modifers. The full factorial design, applied with acetonitrile as organic modifer, enables the selection of suitable LC parameter combinations for fast and complete separation of the four compounds in cough-syrup analysis.

Simultaneous determination of serotonin, N-acetylserotonin and melatonin in the pineal gland of the juvenile golden hamster by high-performance liquid chromatography with electrochemical detection

A simple and simultaneous determination of melatonin and its precursors, serotonin (5-HT) and N-acetylserotonin, was achieved by reversed-phase high-performance liquid chromatography with electrochemical detection. The addition of an ion-pairing agent, sodium 1-octanesulfonate, to the chromatographic mobile phase caused an increase of the retention time of 5-HT, and resulted in the successful simultaneous resolution of these three indoleamines. This method was used to quantitate these indoleamines in the pineal gland of juvenile golden hamsters.

High-performance liquid chromatographic analysis of corticosteroids

This review presents recent developments in high-performance liquid chromatographic (HPLC) analysis of corticosteroids for the determination of clinically important steroids in biological specimens. Various sample preparation techniques are described.

High-performance liquid chromatographic analysis with electrochemical detection of biogenic amines using microbore columns

High-performance liquid chromatography with electrochemical detection (HPLC-ED) is a popular method for measuring biogenic amines, owing to its simplicity, versatility, sensitivity, and specificity. Recent developments in microbore column HPLC-ED have been facilitated by miniaturization of solvent delivery, column packing, sample injection and micro-flow cell construction. The aim of this paper is to present an overview of recent developments in microbore column HPLC-ED, in terms of advantages and limitations. This paper covers the recent advancements and important factors of HPLC-ED analysis of biogenic amines using microbore columns. Particular emphasis is placed on applying this technique to microdialysis, for which great sensitivity is required. Its potential in future biomedical applications is also discussed.

Methylenedioxyamphetamine: a selective effect on cortical content and turnover of 5-HT

This study examined the effects of the hallucinogen, MDA, on brain content of monoamines and their metabolites in the rabbit. A single 1.8 mg/kg dose of MDA produced 30 to 64% increases in the 5-HT content of frontal cortex from 30 to 120 min after injection and a decrease in 5-HT turnover from 30 min to 8 h, but had no effect in hippocampus, caudate nucleus, or hypothalamus. A single 3.6 mg/kg dose of MDA also reduced the turnover of 5-HT in frontal cortex, but this was accompanied by a decrease in 5-HIAA with no increase in 5-HT. The 1.8 and 3.6 mg/kg doses of MDA had no significant or consistent effects on the contents of DA, DOPAC, HVA, and NE in any brain area examined. Chronic administration of MDA (3.6 mg/kg/day for 4 days) failed to produce any evidence of a neurotoxic action on 5-HT neurons. Higher doses could not be employed because the LD50 of MDA was approximately 5 mg/kg. This study has demonstrated that behaviorally effective and nonneurotoxic doses of MDA produce increases in the content and decreases in turnover of 5-HT in frontal cortex that resemble those of other hallucinogens such as LSD and DOM.

Experimental design for the rapid selection of separation conditions for methyl and propyl parahydroxybenzoate, phenylephrine hydrochloride and chlorphenamine maleate by ion-pair liquid chromatography

Methyl and propyl parahydroxybenzoate (MPHB, PPHB), phenylephrine hydrochloride (PE) and chlorphenamine maleate (CPM) are often combined as ingredients in cough-syrups. Due to distinct chemical structures, pKa values among other chemical properties are different. This may result in a particular chromatographic behaviour on ion-pair reversed-phase liquid chromatographic (LC) systems. A face-centred central composite design was applied to study the impact of four LC mobile phase parameters and parameter interactions on the retention of these four compounds. The mobile phase parameters studied were the concentration of methanol as organic modifier, the concentration of sodium dioctylsulphosuccinate (SDSS) as counter-ion, the concentration of dimethyloctylamine (DMOA) as competitive base and the pH. By means of the proposed design, mathematical regression models and response surface plots were calculated, which could predict the compounds' retention times with good statistical reliability. Adequate combination of the most relevant of these mobile phase parameters enabled complete chromatographic separations within short times of analysis.

High-performance liquid chromatographic determination of catecholamine metabolites and 5-hydroxyindoleacetic acid in human urine using a mixed-mode column and an eight-channel electrode electrochemical detector

An HPLC system for the simultaneous determination of acidic catecholamine metabolites, related compounds and 5-hydroxyindoleacetic acid (5-HIAA) in human urine was developed. A mixed-mode (C18/anion-exchange) column with isocratic elution using citrate buffer and an eight-channel electrochemical detector were used. Vanilmandelic acid (VMA), 3,4-dihydroxyphenylacetic acid (DOPAC), 4-hydroxy-3-methoxyphenyllactic acid (vanillactic acid, VLA), homovanillic acid (HVA), vanillic acid (VA) and 5-HIAA in urine were determined simultaneously. Detection limits and inter (n = 5) and intra-assay (n = 5) coefficients of variation were satisfactory. The mean of analytical recoveries (n = 3, +/- C.V. (%)) were between 97 +/- 3.2 (VMA) and 105 +/- 4.8 (VA). Correlations between the analytical results for VMA, HVA and 5-HIAA obtained by an established method and the present method were satisfactory. The mean +/- 2 S.D. of the excretion rates of VMA, DOPAC, VLA, HVA, 5-HIAA and VA in urine from healthy adult volunteers were 0.61-4.36, 0.13-1.02, 0-0.35, 0.67-6.55, 0.50-5.14 and 0-0.55 mg/g creatinine, respectively.

Experimental design on liquid chromatographic parameters in the analysis of tetracycline on poly(styrene-divinylbenzene)

A previously described isocratic liquid chromatographic (LC) method for the analysis of tetracycline on poly(styrene-divinylbenzene) allows the complete separation and resolution of tetracycline (TC), 4-epitetracycline (ETC), anhydrotetracycline (ATC) and 4-epianhydrotetracycline (EATC). By means of a half-fraction factorial design, the importance of the individual chromatographic parameters and parameter interactions of this LC method was examined. The influence on the retention of ETC, TC and EATC is measured. A mathematical regression model was derived which predicts retention times with good reliability. Both the retentions of ETC and EATC are strongly affected by chromatographic parameters and parameter interactions, which only slightly affect the retention of TC. Adequate combination of the most relevant of these parameters enables optimization of the chromatographic separation if necessary.

Repeated reserpine increases striatal dopamine receptor and guanine nucleotide binding protein RNA

In the present study the effects of repeated administration of reserpine on striatal dopamine receptor and guanine nucleotide binding protein mRNAs were determined. Twenty-four hours after seven consecutive daily injections of reserpine--a treatment that is known to produce functional sensitization of D1 and D2 dopamine receptors--the level of striatal D1 dopamine receptor mRNA was unchanged. However, the level of mRNA for the G protein Gs alpha was increased by 127%. After extended reserpine treatment for 14 days, levels of both striatal D1 DA receptor and Gs alpha mRNAs were elevated by 99 and 78%, respectively. Seven days of reserpine treatment also increased levels of mRNA of the striatal D2 dopamine receptor and of G proteins Gi2 alpha and Go alpha by 200, 79, and 32%, respectively. After 14 days of reserpine treatment the level of striatal D2 dopamine receptor mRNA was increased by twofold. In contrast, levels of the mRNAs coding for the G proteins Gi2 alpha and Go alpha were unchanged. These data suggest that dopamine receptors and their respective G proteins play important roles in the development of sensitization of striatal dopamine receptors during repeated reserpine treatment. Furthermore, the persistent increase in level of striatal Gs alpha mRNA suggests that this G protein is necessary to maintain supersensitivity of the striatal D1 dopamine receptor system following long-term dopamine depletion.

Ischemia-induced extracellular release of serotonin plays a role in CA1 neuronal cell death in rats

BACKGROUND AND PURPOSE

Serotonin, via 5-HT2 receptors, exerts an excitatory effect on CA1 neurons and may play a role in ischemia-induced excitotoxic damage. To evaluate the role of serotonin in ischemia, both neurochemical and histopathological studies were performed.

METHODS

Neurochemical studies included rats that were subjected to 12.5 or 20 minutes of normothermic ischemia by two-vessel occlusion plus hypotension, and extracellular serotonin levels were measured in the hippocampus (12.5 minutes' ischemia, n = 5) or striatum (20 minutes' ischemia, n = 13) by microdialysis. In the histopathological study the effect of 8 mg/kg ritanserin, a 5-HT2 antagonist, administered continuously from 30 minutes prior to ischemia until 1 hour of recirculation was evaluated in five rats subjected to 10 minutes of ischemia. After 3 days, the numbers of normal-appearing neurons in the CA1 subregions were counted.

RESULTS

Ischemia of 12.5 minutes' duration induced a fourfold increase in serotonin in the hippocampus (mean +/- SEM baseline, 1.86 +/- 0.25 pmol/ml perfusate; during ischemia, 8.14 +/- 0.89 pmol/ml; p < 0.05 by analysis of variance). Twenty minutes of ischemia induced a 25-fold increase in serotonin in the dorsolateral striatum (baseline, 0.98 +/- 0.15 pmol/ml; ischemia, 24.4 +/- 5.93 pmol/ml; p < 0.001). The histopathological study demonstrated severe ischemic damage in all CA1 subregions of nontreated animals (medial, 34 +/- 16 normal-appearing neurons, middle, 52.2 +/- 22.9 neurons; lateral, 56.6 +/- 21.8 neurons). Treatment with ritanserin significantly attenuated ischemic damage (medial, 117.6 +/- 6.5 neurons; middle, 131.4 +/- 4.9 neurons; lateral, 130 +/- 7.5 neurons; p < 0.01 different from nontreated).

CONCLUSIONS

Taken together, these results suggest that serotonin plays a detrimental role, mediated by 5-HT2 receptors, in the development of ischemic damage.

Rapid and simultaneous assay of monoamine neurotransmitters and their metabolites in discrete brain areas of mice by HPLC with Coulometric detection

For simultaneous assay of the three monoamine neurotransmitters, norepinephrine, dopamine, and serotonin, and four respective metabolites in brain tissue, a rapid and simple method using high-performance liquid chromatography with coulometric detection is described. Because the present method permits the determination of these target substrates within 10 min or less in one chromatographic run, 150 samples can be analyzed using an autosampler and an integrator in a 24-h period. Within-run coefficients of variation for the target substrates in the standard solution and the whole brain sample were less than 3% and 2% (n = 40), respectively. The quantitative detection limits were 0.01-0.1 pmol. The present procedure was applied to measure the target substrates in several discrete brain areas in mice.

Serotonin release into plasma during common carotid artery thrombosis in rats

BACKGROUND AND PURPOSE

We have tested the hypothesis that platelet-derived serotonin is released into the bloodstream during cerebrovascular thrombosis.

METHODS

Nonocclusive common carotid artery thrombosis was produced photochemically in 22 anesthetized adult male Wistar rats using the photosensitizing dye rose bengal and irradiation with an argon-pumped dye laser. Plasma serotonin levels were recorded before, during, and after photothrombosis by intra-arterial in vivo microdialysis with the probe placed distal to the site of thrombosis.

RESULTS

During and immediately after the common carotid artery thrombosis, serotonin levels increased significantly to a peak value of 781 nmol/l (p less than 0.001 by analysis of variance), representing a 15-fold increase compared with baseline levels. The increased serotonin levels gradually decreased but remained significantly elevated for 90 minutes. Ultrastructural analysis of the carotid thrombi identified a dense mass of aggregated platelets at various stages of degranulation.

CONCLUSIONS

These results are the first to demonstrate directly that serotonin accumulation occurs in plasma during and after the acute phase of common carotid artery thrombosis. Increased plasma serotonin levels may play a major role in the cerebral blood flow and blood-brain barrier abnormalities previously documented in this model of large-vessel thrombotic stroke.

Preparation of an optimum mobile phase for the simultaneous determination of neurochemicals in mouse brain tissues by high-performance liquid chromatography with electrochemical detection

A systematic method is described for the optimization of a mobile phase for the simultaneous determination of 24 neurochemicals consisting of catecholamine, serotonin, their precursors and metabolites and related materials. This mobile phase contained sodium acetate (0.04 M), citric acid (0.01 M), sodium chloride (0.0126 M), sodium octyl sulfate (91 mg/l), tetrasodium EDTA (50 mg/l) and 10% (v/v) methanol. When this optimum mobile phase was applied to the analysis of brain tissues of the Swiss male mouse, twelve neurochemicals were quantified in the free state: tyrosine, L-beta-3,4-dihydroxyphenylanine, dopamine, 3,4-dihydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenylacetic acid, norepinephrine, 3-methoxy-4-hydroxyphenylglycol, DL-3,4-dihydroxymandelic acid, DL-4-hydroxy-3-methoxymandelic acid, serotonin, L-tryptophan, 5-hydroxyindole-3-acetic acid and DL-synephrine and normetanephrine, appearing as a fused peak. This fused peak was present on the chromatogram tracings of all the mouse brain tissues. The separable neurochemicals not found by this procedure in the Swiss male mouse tissues were DL-3,4-dihydroxyphenylglycol,5-hydroxytryptophan, epinephrine, DL-octopamine, metanephrine, deoxyepinephrine, homovanillyl alcohol, N-acetylserotonin, tyramine and 3-methyltyramine.

Simple and fast chromatographic method for the simultaneous determination of vanillylmandelic acid and homovanillic acid in human urine

A high-performance liquid chromatographic method for the determination of vanillylmandelic acid and homovanillic acid is described. The method is fast despite the great polarity differences between the two acids. Moreover the sample pretreatment is quick and it does not need complex or expensive equipment. The only requirement is the disposition of two pumps (or at least two eluent reservoirs) operated alternatively by means of a switching valve placed before the injection device. This makes the method available for most routine laboratories.

Monoaminergic dysfunction in Sjögren-Larsson syndrome

The anteroposterior distribution of monoamine and monoamine metabolite concentrations was determined in subcortical brain nuclei of two cases of Sjögren-Larsson syndrome (SLS) and was compared to two control cases. The brains were divided into halves and sectioned coronally. For biochemical analyses, caudate nucleus, putamen, globus pallidus, substantia nigra, nucleus accumbens, amygdala, and hippocampus were dissected macroscopically. Monoamine and its metabolites were determined by reverse-phase liquid chromatography with electrochemical detection. The other hemisphere was studied neuropathologically. The SLS cases revealed cell loss in substantia nigra and putamen and a widespread white-matter destruction. Biochemically, most pronounced alterations were seen in the dopamine system in putamen with severely reduced concentrations of dopamine (DA; 14% of control values) and the catabolic metabolites 3-methoxytyramine (3-MT; 9% of control values) and homovanillic acid (HVA; 20% of control values). In substantia nigra and the other striatal regions studied, a general decrease of 3-MT and HVA concentrations was observed in the SLS subjects compared to the controls, although the decrease was less pronounced than in putamen. Generally, somewhat reduced noradrenaline and 3-methoxy-4-hydroxyphenylglycol (MHPG) concentrations were seen in the SLS cases, whereas serotonin and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were increased compared to the controls in most regions studied. These data suggest a specific monoaminergic dysfunction in patients with SLS. The severe decline in the dopaminergic system in putamen suggests that supplementation of dopamine agonists may ameliorate the symptoms of SLS patients.

Two-parameter mobile phase optimization for the simultaneous high-performance liquid chromatographic determination of dopamine, serotonin and related compounds in microdissected rat brain nuclei

A new high-pressure liquid chromatography method with electrochemical detection is described that allows the simultaneous determination of dopamine, serotonin, 3,4-dihydroxyphenylacetic acid, 3-methoxy-4-hydroxyphenylacetic acid, 5-hydroxytryptophan and 5-hydroxyindoleacetic acid in microdissected nuclei from individual rat brains. No sample pre-treatment steps are required. Resolution and analysis time were optimized by a simple limited optimization procedure, involving two-parameter factorial design.

Determination of 5-methoxyindoles in pineal gland and plasma samples by high-performance liquid chromatography with electrochemical detection

A liquid chromatographic analysis with electrochemical detection of 5-methoxytryptamine, 5-methoxytryptophol, 5-methoxyindoleacetic acid and melatonin is described. Optimal elution conditions were determined by studying several variables: pH, buffer salt, counter ion and organic modifier. Measurement of 5-methoxyindoles in the pineal gland and plasma of hamsters has been performed after extraction. This method is specific and sensitive, and enables detection of 5-methoxyindoles in a pool of two hamster pineal glands. This is also the first time that these three 5-methoxyindoles have been measured simultaneously in plasma.

CSF monoamine metabolites, cholinesterases and lactate in the adult hydrocephalus syndrome (normal pressure hydrocephalus) related to CSF hydrodynamic parameters

Monoamine metabolites, cholinesterases and lactic acid in lumbar cerebrospinal fluid (CSF) were investigated on patients with the adult hydrocephalus syndrome (idiopathic normal pressure syndrome; AHS, n = 15), Alzheimer's disease (AD, n = 14), multi-infarct dementia (MID, n = 13) and controls (n = 21). Patients had clinical and CSF hydrodynamic investigations. Monoamine concentrations were determined by reversed-phase liquid chromatography, cholinesterases and lactate were determined photometrically. In the AHS patients, CSF monoamine concentrations were not significantly different compared with controls, AD or MID patients. AHS and AD patients showed a similar reduction of CSF acetylcholinesterase activity compared with controls. Positive correlations were found in concentrations of CSF homovanillic acid, CSF 5-hydroxyindoleacetic acid and CSF lactic acid versus CSF outflow conductance (that is, resistance against CSF outflow) in the AHS patients. A similar pattern was observed in a subgroup of MID patients characterised by dilated ventricles and disturbed CSF hydrodynamics. These data suggest that a low CSF outflow conductance may facilitate the clearance of acidic substances from the arachnoid space at the probenecid sensitive active transport site. Alternative explanations would be that a pathologically low CSF outflow conductance is accompanied by an inverse caudorostral flow of CSF or a compromised trans-ependymal diffusion.

Simultaneous determination of levodopa, its main metabolites and carbidopa in plasma by liquid chromatography

An ion-pair reversed-phase liquid chromatographic method for the simultaneous determination of levodopa, 3-O-methyldopa, 3,4-dihydroxyphenylacetic acid, homovanillic acid and carbidopa in plasma designed for clinical trials performed to study the effect of peripheral catechol-O-methyltransferase inhibitors on the metabolism of levodopa is described. The high sample throughput of over 50 samples per day of the method makes it ideal for the assay of the large number of samples encountered in clinical trials. After protein precipitation with perchloric acid the analytes are completely separated within 15 min and determined down to a plasma concentration of 20 ng ml-1 using amperometric detection at 800 mV relative to an Ag/AgCl reference electrode. For all analytes the within-day precision defined as a relative standard deviation (n = 8) is lower than 7 and 3% at plasma concentrations of 20 and 40 ng ml-1, respectively. As the method is specific and highly reproducible, the most important factor affecting accuracy is the stability of the analytes during storage and analysis.

Ventricular cerebrospinal fluid monoamine transmitter and metabolite concentrations reflect human brain neurochemistry in autopsy cases

Concentrations of dopamine (DA), its metabolites 3-methoxytyramine and homovanillic acid (HVA), noradrenaline (NA), its metabolites normetanephrine (NM) and 3-methoxy-4-hydroxyphenylglycol (MHPG), 5-hydroxytryptamine (5-HT, serotonin), and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) were measured in 14 brain regions and in CSF from the third ventricle of 27 human autopsy cases. In addition, in six cases, lumbar CSF was obtained. Monoamine concentrations were determined by reversed-phase liquid chromatography with electrochemical detection. Ventricular/lumbar CSF ratios indicated persistence of rostrocaudal gradients for HVA and 5-HIAA post mortem. Ventricular CSF concentrations of DA and HVA correlated positively with striatal DA and HVA. CSF NA correlated positively with NA in hypothalamus, and CSF MHPG with levels of MHPG in hypothalamus, temporal cortex, and pons, whereas CSF NM concentration showed positive correlations with NM in striatum, pons, cingulate cortex, and olfactory tubercle. CSF 5-HT concentrations correlated positively with 5-HT in caudate nucleus, whereas the concentration of CSF 5-HIAA correlated to 5-HIAA levels in thalamus, hypothalamus, and the cortical areas. These data suggest a specific topographic origin for monoamine neurotransmitters and their metabolites in human ventricular CSF and support the contention that CSF measurements are useful indices of central monoaminergic activity in man.

Optimization of an isocratic reversed phase liquid chromatographic system for the separation of fourteen steroids using factorial design and computer simulation

An optimization strategy for an isocratic reversed phase high performance liquid chromatographic system (RP-HPLC) is described. Factorial design and a computer program are used to predict the retention time and resolution of fourteen steroids. An optimized rapid (less than 25 min) isocratic RP-HPLC system for the satisfactory separation of cortisone, cortisol, corticosterone, 11-deoxycortisol, 11-deoxycorticosterone, 17 alpha-hydroxyprogesterone, progesterone, androstenedione, testosterone, estrone, estradiol, estriol, prednisone acetate and dexamethasone acetate has been developed using this strategy through eight experiments.

Effects of mobile phase composition on the chromatographic and electrochemical behaviour of catecholamines and selected metabolites. Reversed-phase ion-paired high-performance liquid chromatography using multiple-electrode detection

The effects of pH, ionic strength, organic modifier, heptanesulphonic acid and citric acid content of a high-performance liquid chromatography mobile phase on the chromatographic and electrochemical behaviour of norepinephrine, epinephrine, dopamine, 3,4-dihydroxybenzylamine, 3,4-dihydroxyphenylethylene glycol, 3,4-dihydroxyphenylalanine and 3,4-dihydroxyphenylacetic acid in a reversed-phase system have been systematically studied. Optimal mobile phase conditions have been derived allowing the separation and reductive-mode detection of these compounds, applicable to both alumina and ion-paired solvent extracts of plasma. It is demonstrated that mobile phase composition significantly affects the sensitivity of a triple-electrode electrochemical detection system, in reductive and oxidative modes, and that electrochemical pre-treatment of mobile phase is required to attain maximum detector sensitivity in the reductive mode.

Measurement of catecholamines, their precursor and metabolites in human urine and plasma by solid-phase extraction followed by high-performance liquid chromatography with fluorescence derivatization

A high-performance liquid chromatographic method is described for the determination in human urine and plasma of catecholamines, their precursor and metabolites [amino compounds (norepinephrine, epinephrine, dopamine, normetanephrine, metanephrine, 3-methoxytyramine and L-DOPA), acidic compounds (3,4-dihydroxymandelic acid, 3,4-dihydroxyphenylacetic acid, vanillylmandelic acid and homovanillic acid) and alcoholic compounds (3,4-dihydroxyphenylethyleneglycol and 4-hydroxy-3-methoxyphenylethyleneglycol)]. Urine (0.5 ml) containing 3,4-dihydroxybenzylamine and 4-hydroxy-3-methoxycinnamic acid (internal standards) is deproteinized with perchloric acid, and the resulting solution is fractionated by solid-phase extraction on a strong cation-exchange resin cartridge (Toyopak IC-SP S) into two fractions (amine fraction and acid-alcohol fraction), which include 3,4-dihydroxybenzylamine and 4-hydroxy-3-methoxycinnamic acid, respectively. Plasma (0.7 ml) is deproteinized in the presence of 3,4-dihydroxybenzylamine (internal standard) in the same manner, and the resulting solution is directly used as an acid-alcohol fraction, while an amine fraction is obtained as for urine. Each fraction is subjected to the previously established ion-pair reversed-phase chromatography with post-column derivatization involving coulometric oxidation followed by fluorescence reaction with 1,2-diphenylethylenediamine. The detection limits, at a signal-to-noise ratio of 5, of the compounds measured in urine are 300 pmol/ml for the two mandelic acids, 2-7 pmol/ml for the other acidic and alcoholic compounds, 12 pmol/ml for L-DOPA and 0.6-2 pmol/ml for the other amino compounds; the corresponding values for plasma samples are 80, 0.5-3, 10 and 0.6-3 pmol/ml, respectively.

Simultaneous high-performance liquid chromatographic determination of catecholamine-related compounds by post-column derivatization involving coulometric oxidation followed by fluorescence reaction

A highly selective and sensitive high-performance liquid chromatographic method for the determination of catecholamines (norepinephrine, epinephrine and dopamine) and related compounds (L-DOPA, normetanephrine, metanephrine, 3-methoxytyramine, 3,4-dihydroxymandelic acid, 3,4-dihydroxyphenylacetic acid, homovanillic acid, vanillylmandelic acid, 3,4-dihydroxyphenylethylene glycol, 4-hydroxy-3-methoxyphenylethylene glycol and 4-hydroxy-3-methoxyphenylethanol) with a post-column technique involving coulometric oxidation followed by fluorescence derivatization is described. These compounds, 3,4-dihydroxybenzylamine and ferulic acid are separated within 35 min by ion-pair reversed-phase chromatography using acidic buffers (pH 3.1) with methanol-acetonitrile (3:2, v/v) gradient elution, and then oxidized by a commercial coulometric detector to the corresponding o-quinones, which are converted into fluorescent derivatives by reaction with 1,2-diphenylethylenediamine. The detection limits (signal-to-noise ratio = 3) on-column are 1.5-4 pmol for the two mandelic acids, 600 fmol for L-DOPA and 20-70 fmol for the others.

Simultaneous quantitation of catecholamines and O-methylated metabolites in urine by isocratic ion-pairing high-performance liquid chromatography with amperometric detection

A simple high-performance liquid chromatographic procedure was developed for the simultaneous determination of catecholamines and metanephrines in urine. One-step sample preparation was achieved with Bio-Rex 70 ion-exchange resin. The extract was assayed on a C18 reversed-phase column. Dihydroxybenzylamine was used as an internal standard. The eluent was monitored by an electrochemical detector with an oxidation potential of +0.85 V. The use of 1-heptanesulphonic acid in the mobile phase permitted the separation of norepinephrine, epinephrine, dopamine, normetanephrine and metanephrine in a single chromatogram. The corresponding detection limits were 5, 9, 14, 10 and 30 nmol/l, respectively. For the between-day precision, the coefficients of variation at physiological and pathological concentrations were less than 11%. Compounds with similar chemical structures and drugs commonly prescribed for the treatment of hypertension were assayed and found not to cause interferences in the chromatogram. The assay is reliable and is suitable for the analysis of clinical specimens. Reference values were established for normotensive Chinese patients with no neurological or endocrine disorders and also for patients suffering from essential hypertension.