Further characterization of in vitro conditions appropriate for GABA determination in human CSF: impact of acid deproteinization and freeze/thaw

Analysis of cerebrospinal fluid γ-aminobutyric acid by capillary electrophoresis with laser-induced fluorescence detection

The measurement of γ-aminobutyric acid (GABA) is suitable for investigating various neurological disorders. In this study, a sensitive and selective method for free GABA quantification in cerebrospinal fluid (CSF) has been standardised. This method is based on CE with LIF detection using 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-F) as a derivatisating agent. The reaction conditions (NBD-F concentration, pH, temperature and reaction time) and the electrophoretic parameters (run buffer composition and pH and separation voltage) were optimised to obtain the maximum derivatisation efficiency and electrophoretic resolution. The best resolution was obtained using 200 mM sodium borate, 10 mM SDS, 8.5 mM β-CD, pH 10 and 20 kV voltage. The method was linear in the concentration range of 2.5-1000 nM with good inter- and intra-assay precision values. The effects of CSF handling on free GABA concentrations were also evaluated. Our results show that the time delay between CSF collection and freezing strongly increases the CSF GABA values. Age-related reference values were established in 55 paediatric controls. The influence of antiepileptic therapy on free CSF GABA was studied in 38 neuropaediatric patients. Significantly, higher GABA values were obtained in patients taking valproic acid or vigabatrin therapy, which are antiepileptic drugs that modulate GABA metabolism.

Free-GABA levels in the cerebrospinal fluid of patients suffering from several neurological diseases Its potential use for the diagnosis of diseases which course with inflammation and tissular necrosis

Free GABA levels were measured in the cerebrospinal fluid (CSF) of 74 neurological patients suffering from cerebral cysticercosis (n = 9), Parkinson's disease (n = 5), multiple sclerosis (n = 6), epilepsy (n = 24), meningeal tuberculosis (n = 6), viral encephalitis (n = 3), cerebrovascular disease (n = 8) and several kinds of dystonia (n = 5). A statistical significant four-fold elevation in free GABA levels was found in patients with cerebral cysticercosis. A non statistical significant two-fold increase in free GABA levels was also encountered in the CSF of patients affected by cerebrovascular disease and viral encephalitis. No changes in CSF free GABA levels were found in patients suffering from any of the other disorders. It is suggested that free GABA levels may be elevated in the CSF of patients suffering from neurological diseases which course with inflammation and tissular necrosis such as cerebral cysticercosis. Much work is needed however to establishd whether CSF free GABA levels can be used as a diagnostic tool in at least some type of these patients.

Neurochemical biomarkers in the differential diagnosis of movement disorders

In recent years, the neurochemical analysis of neuronal proteins in cerebrospinal fluid (CSF) has become increasingly accepted for the diagnosis of neurodegenerative dementia diseases such as Alzheimer's disease and Creutzfeldt-Jakob disease. CSF surrounds the central nervous system, and in the composition of CSF proteins one finds brain-specific proteins that are prioritized from blood-derived proteins. Levels of specific CSF proteins could be very promising biomarkers for central nervous system diseases. We need the development of more easily accessible biomarkers, in the blood. In neurodegenerative diseases with and without dementia, studies on CSF and blood proteins have investigated the usefulness of biomarkers in differential diagnosis. The clinical diagnoses of Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration still rely mainly on clinical symptoms as defined by international classification criteria. In this article, we review CSF biomarkers in these movement disorders and discuss recent published reports on the neurochemical intra vitam diagnosis of neurodegenerative disorders (including recent CSF alpha-synuclein findings).

Interictal behavioral alterations and cerebrospinal fluid amino acid changes in a chronic seizure model of temporal lobe epilepsy

This study extends our previous work in which we described the presence of an interictal behavioral disturbance in a chronic animal model of temporal lobe epilepsy (TLE). In this study, we investigated the cerebrospinal fluid (CSF) neurotransmitter changes underlying the development of chronic recurrent seizures of temporal lobe origin and interictal behavioral disturbance in cats made epileptic after intrahippocampal injection of kainic acid (KA). Using high-performance liquid chromatography, we measured 22 putative neurotransmitter amino acids. After intrahippocampal KA injection, cats developed an initial acute period of intense seizure activity. Cisternal CSF amino acids, which were repeatedly sampled during the acute period through a permanent indwelling cannula, were unchanged apart from a mild elevation in CSF alanine. The high-level seizure activity gradually decreased, and cats entered a chronic epileptic period characterized by recurrent yet intermittent temporal lobe seizures. CSF GABA levels during the chronic epileptic period were significantly decreased. In contrast, CSF levels of other amino acids--alanine, tyrosine, taurine, aspartic acid, and glutamic acid--did not change significantly. Behavioral testing also showed a heightened interictal defensive reactivity during the chronic epileptic period. To the extent that CSF GABA concentration reflects brain GABA concentration, this study suggests that a decrease in brain GABA may contribute both to the epilepsy and interictal emotional lability of animals with a chronic seizure disorder of temporal lobe origin.

Reference values for amino acids in cerebrospinal fluid of children determined using ion-exchange chromatography with fluorimetric detection

One thousand specimens of CSF were collected from subjects ranging in age from newborn to 18 yr, who were undergoing a diagnostic lumbar puncture. Sixty-two samples were judged retrospectively as being suitable for calculating reference age-related values. The analyses were performed by an amino acid analyser using ion-exchange chromatography with fluorimetric detection giving a tenfold increase in sensitivity, thereby enhancing the diagnostic capabilities. As many as 36 known compounds could be detected, additionally 10 we could not identify. In children older than 3 yr nine of the identified compounds showed age-dependency. We found 22 amino acids to be significantly higher in infants younger than 1 yr, with only gamma-aminobutyric acid being significantly lower in infants. Alpha-aminoadipic acid showed a sex difference, being slightly higher in girls.

Diazepam binding inhibitor-like immunoreactivity (DBI-LI) in human CSF. Correlations with neurological disorders

Cerebrospinal fluid (CSF) levels of the anxiogenic neuropeptide diazepam binding inhibitor (DBI) were determined by radioimmunoassay in 281 patients who underwent evaluation for neurological problems. Serial dilution curves and reverse-phase high pressure liquid chromatography showed that the immunoreactive material in CSF behaved just as authentic DBI extracted from human brain. Furthermore in the assay there was no evidence of interference from CSF samples deprived of DBI by immunoaffinity. In 82 patients with no evidence of major lesions in the central nervous system, who acted as controls, the CSF DBI content was shown to be age- and sex-related. No correlation was observed with the CSF protein concentration. In patients with different types of dementia, the levels of CSF DBI were significantly increased in a group with normal pressure hydrocephalus. No significant differences were found between Alzheimer's disease, multi-infarct dementia, or dementia with Parkinson's disease and controls. In non-demented patients with Parkinson's disease the levels of DBI were increased in a subgroup with depressive disturbances whereas no differences was observed in the non-depressed cases. The content of DBI was markedly reduced in 5 cases with olivopontocerebellar atrophy and in 4 with spinocerebellar ataxia. In all the other disorders studied the levels of DBI were similar to or slightly lower (multiple sclerosis) than those of the controls. The origin of DBI in cerebrospinal fluid is uncertain; a number of various possibilities are discussed concerning the proposed role of DBI as modulator of brain GABAergic transmission.

Histamine metabolites in cerebrospinal fluid of the rhesus monkey (Macaca mulatta): cisternal-lumbar concentration gradients

Similar to metabolites of other aminergic transmitters, histamine metabolites of brain, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), could have a concentration gradient between rostral and caudal sites of CSF. To test this hypothesis, cisternal and lumbar CSF samples were collected in pairs from eight monkeys (Macaca mulatta), and levels of t-MH and t-MIAA were measured by gas chromatography-mass spectrometry. pros-Methylimidazoleacetic acid (p-MIAA), an endogenous isomer of t-MIAA that is not a histamine metabolite, was also measured. Cisternal levels (in picomoles per milliliter, mean +/- SEM) of t-MH (9.9 +/- 1.4) and t-MIAA (40.8 +/- 7.6), but not of p-MIAA (9.7 +/- 1.2), exceeded those in lumbar CSF (t-MH, 1.8 +/- 0.3; t-MIAA, 6.8 +/- 0.9; p-MIAA, 8.6 +/- 0.6) in every monkey. The magnitudes of the mean cisternal-lumbar concentration gradients for t-MH (6.6 +/- 1.1) and t-MIAA (6.5 +/- 1.3) were indistinguishable. These gradients exceed those of metabolites of most other transmitters. There was no gradient for the levels of p-MIAA. The cisternal, but not lumbar, levels of t-MH and t-MIAA were correlated. There was no significant difference between the means of the metabolite concentration ratios (t-MIAA/t-MH) in cisternal (4.0 +/- 0.4) and lumbar (4.4 +/- 0.9) CSF. The steepness of these gradients suggests that levels of t-MH and t-MIAA in lumbar CSF might be useful probes of histaminergic metabolism in brain.

Free and conjugated CSF and plasma GABA in Huntington's chorea

Free and conjugated GABA concentrations were measured in CSF and plasma from 28 patients with manifest Huntington's chorea (HC) and 30 age- and sex-matched controls. GABA was determined by ion-exchange chromatography with fluorimetric detection (IE/F). Free and conjugated CSF GABA was significantly decreased in prolonged HC with advanced disease states and was suggested practicable as an additional diagnostic tool. However, in younger patients (less than 40 yrs) with a short period of HC (less than 2 yrs) an overlap with the age-matched normal range indicated GABA measurement inadequate to early diagnosis nor predictive for offspring at risk. An age-dependent decrease of conjugated CSF GABA was observed in patients and controls. The more pronounced decrease in patients might reflect the neurodegenerative feature of HC.

Elevated concentrations of glutamate and aspartate in human ventricular cerebrospinal fluid (vCSF) during episodes of increased CSF pressure and clinical signs of impaired brain circulation

In the ventricular cerebrospinal fluid (vCSF) of 10 hydrocephalic patients the mean (+/- S.D.) concentrations of glutamate and asparate were 2.9 +/- 0.2 and 0.2 +/- 0.2 microM, respectively. Significantly higher concentrations of these amino acids were found in two patients (glutamate 37.8 and 22.4 microM, aspartate 2.2 and 0.6 microM) with symptoms of impaired brain tissue perfusion, i.e. relative ischemia due to severely increased intraventricular CSF pressure. Our results are consistent with recent experiments in rats showing increased extracellular concentrations of glutamate and aspartate during transient cerebral ischemia.

Free and conjugated amino acids in human CSF: influence of age and sex

An extended baseline characterization of amino acids (AAs) and related amino compounds in CSF is reported. Thirty-one amino compounds were measured in deproteinized CSF before and after acid hydrolysis using a triple-column HPLC/fluorometric analyzer. CSF specimens were collected under strictly controlled conditions from neurologically normal myelogram patients and carefully pooled with regard to subject age and sex. Consideration was given to factors which may produce artifactual alterations in AA levels during CSF collection, storage and handling. Conjugated AAs were determined as the difference between levels of free AAs (measured in CSF prior to hydrolysis) and total AAs (measured in hydrolyzed CSF) and are taken as an index of total CSF peptide AAs. Results documented conjugated forms of all non-acid-labile CSF AAs except citrulline and ethanolamine. In general, ratios of conjugated to free AAs were relatively low, however for the neurotransmitter AAs aspartate, glutamate, glycine and GABA as well as for beta-alanine hydrolysis produced marked increases indicating that these compounds are present predominantly in bound form in CSF. Results also revealed the significant influence of both age and sex on levels of a number of CSF free and conjugated AAs. Compared to younger individuals (those less than 40 years of age), older individuals exhibited significantly higher levels of free aspartate, glycine, alpha-aminobutyric acid, valine, isoleucine, leucine, phenylalanine and 3-methylhistidine as well as significantly lower levels of free phosphoethanolamine, serine, GABA, homocarnosine, conjugated GABA and conjugated beta-alanine. Additionally, significantly higher levels of free tyrosine, ethanolamine, arginine and conjugated aspartate were documented in males compared to females.(ABSTRACT TRUNCATED AT 250 WORDS)

Triple-column ion-exchange physiological amino acid analysis with fluorescent detection: baseline characterization of human cerebrospinal fluid

A highly resolving triple-column amino acid analyzer with fluorometric detection is described. The reliability of this technique was evaluated and it was used in a baseline investigation of amino acids and related compounds in human cerebrospinal fluid (CSF). The procedure employs three distinct ion-exchange columns to elute the acidic, neutral, and basic amino acids, respectively. Each column is run isocratically with lithium citrate buffers designed to provide overlapping elution profiles. Studies using CSF collected under strictly controlled conditions documented nanomolar concentrations of aspartate, gamma-aminobutyric acid (GABA), beta-alanine, 1-methylhistidine, and 3-methylhistidine, as well as low levels of glutamate, methyllysine, and ammonia. In addition, other common amino acids were also quantified. Chromatograms of CSF from all three systems (acidic, neutral, and basic) exhibited numerous uncharacterized compounds emphasizing the resolution and sensitivity of the analytical procedure. In vitro stability studies revealed that levels of aspartate, glutamate, GABA, homocarnosine, and ammonia are subject to significant change when CSF is maintained at room temperature for various periods of time up to 24 h. It is concluded that the valid and accurate measurement of CSF amino compounds, especially the neurotransmitter amino acids, requires a highly specific and sensitive assay procedure as well as strict control of CSF manipulation in vitro.

Free and conjugated GABA in human cerebrospinal fluid: effect of degenerative neurologic diseases and isoniazid

gamma-Aminobutyric acid (GABA) was measured in CSF as such and following acid hydrolysis by the ion-exchange/fluorometric method. The conjugated GABA level was obtained by subtracting the free GABA level from the total GABA level. Results showed that at room temperature, while the free GABA level increased, the level of conjugated GABA decreased in a linear fashion during the first 24 h (r = -0.974; P less than 0.001). Aging and CSF conjugated GABA levels were inversely correlated (r = -0.613; P less than 0.05). Unlike free GABA levels, the levels of conjugated GABA were not altered in Huntington's disease, Parkinson's disease, cerebellar ataxias, dementias, epilepsy and multiple sclerosis compared to controls. In patients with Huntington's disease, on administration of isoniazid at 900 mg/day, along with pyridoxine at 100 mg/day, a 4-fold increase of both free (P less than 0.005) and conjugated GABA (P less than 0.0025) was seen. The results indicate that while total GABAergic peptides are not altered in several of the neurologic diseases studied, drugs such as isoniazid and/or pyridoxine can significantly elevate both free and conjugated GABA levels in human CSF.