Oral administration of D-alanine in monkeys robustly increases plasma and cerebrospinal fluid levels but experimental D-amino acid oxidase inhibitors had minimal effect.

Hypofunction of the N-methyl-d-aspartate (NMDA) receptor is thought to exacerbate psychosis in patients diagnosed with schizophrenia. Consistent with this hypothesis, D-alanine, a co-agonist at the glycine site of the NMDA receptor, was shown to improve positive and cognitive symptoms when used as add-on therapy for schizophrenia treatment. However, D-alanine had to be administered at high doses (~7 g) to observe clinical effects. One possible reason for the high dose is that D-alanine could be undergoing oxidation by D-amino acid oxidase (DAAO) before it reaches the brain. If this is the case, the dose could be reduced by co-administration of D-alanine with a DAAO inhibitor (DAAOi). Early studies with rodents showed that co-administration of D-alanine with 5-chloro-benzo[d]isoxazol-3-ol (CBIO), a prototype DAAOi, significantly enhanced the levels of extracellular D-alanine in the frontal cortex compared with D-alanine alone. Further, the use of CBIO reduced the dose of D-alanine needed to attenuate prepulse inhibition deficits induced by dizocilpine. The objective of the work reported herein was to confirm the hypothesis that DAAO inhibition can enhance D-alanine exposure in a species closer to humans: non-human primates. We report that while oral D-alanine administration to baboons (10 mg/kg) enhanced D-alanine plasma and CSF levels over 20-fold versus endogenous levels, addition of experimental DAAOi to the regimen exhibited a 2.2-fold enhancement in plasma and no measurable effect on CSF levels. The results provide caution regarding the utility of DAAO inhibition to increase D-amino acid levels as treatment for patients with schizophrenia.

Genome-wide association study of NMDA receptor coagonists in human cerebrospinal fluid and plasma.

The N-methyl-D-aspartate receptor (NMDAR) coagonists glycine, D-serine and L-proline play crucial roles in NMDAR-dependent neurotransmission and are associated with a range of neuropsychiatric disorders. We conducted the first genome-wide association study of concentrations of these coagonists and their enantiomers in plasma and cerebrospinal fluid (CSF) of human subjects from the general population (N=414). Genetic variants at chromosome 22q11.2, located in and near PRODH (proline dehydrogenase), were associated with L-proline in plasma (ß=0.29; P=6.38 × 10(-10)). The missense variant rs17279437 in the proline transporter SLC6A20 was associated with L-proline in CSF (ß=0.28; P=9.68 × 10(-9)). Suggestive evidence of association was found for the D-serine plasma-CSF ratio at the D-amino-acid oxidase (DAO) gene (ß=-0.28; P=9.08 × 10(-8)), whereas a variant in SRR (that encodes serine racemase and is associated with schizophrenia) constituted the most strongly associated locus for the L-serine to D-serine ratio in CSF. All these genes are highly expressed in rodent meninges and choroid plexus, anatomical regions relevant to CSF physiology. The enzymes and transporters they encode may be targeted to further construe the nature of NMDAR coagonist involvement in NMDAR gating. Furthermore, the highlighted genetic variants may be followed up in clinical populations, for example, schizophrenia and 22q11 deletion syndrome. Overall, this targeted metabolomics approach furthers the understanding of NMDAR coagonist concentration variability and sets the stage for non-targeted CSF metabolomics projects.

An NMR metabolomics approach for the diagnosis of leptomeningeal carcinomatosis in lung adenocarcinoma cancer patients.

Leptomeningeal carcinomatosis (LC) is a metastatic cancer invading the central nervous system (CNS). We previously reported a metabolomic diagnostic approach as tested on an animal model and compared with current modalities. Here, we provide a proof of concept by applying it to human LC originating from lung cancer, the most common cause of CNS metastasis. Cerebrospinal fluid from LC (n = 26) and normal groups (n = 41) were obtained, and the diagnosis was established with clinical signs, cytology, MRI and biochemical tests. The cytology on the CSF, the current gold standard, exhibited 69% sensitivity (~100% specificity) from the first round of CSF tapping. In comparison, the nuclear magnetic resonance spectra on the CSF showed a clear difference in the metabolic profile between the LC and normal groups. Multivariate analysis and cross-validation yielded the diagnostic sensitivity of 92%, the specificity of 96% and the area under the curve (AUC) of 0.991. Further spectral and statistical analysis identified myo-inositol (p < 5 × 10(-14)), creatine (p < 7 × 10(-8)), lactate (p < 9 × 10(-4)), alanine (p < 7.9 × 10(-3)) and citrate (p < 3 × 10(-4)) as the most contributory metabolites, whose combination exhibited an receiver-operating characteristic diagnostic AUC of 0.996. In addition, the metabolic profile could be correlated with the grading of radiological leptomeningeal enhancement (R(2) = 0.3881 and p = 6.66 × 10(-4)), suggesting its potential utility in grading LC. Overall, we propose that the metabolomic approach might augment current diagnostic modalities for LC, the accurate diagnosis of which remains a challenge.

D-amino acid aberrations in cerebrospinal fluid and plasma of smokers.

The glutamatergic neurotransmission system and the N-methyl-D-aspartate receptor (NMDAR) have been implicated in smoking and alcohol consumption behavior. Preclinical studies have demonstrated that nicotine and ethanol influence NMDAR functionality, which may have a role in tendencies to consume these substances. Nonetheless, little is known about concentrations of NMDAR coagonists in the cerebrospinal fluid (CSF) and plasma of individuals who smoke or consume alcohol. Glycine and L- and D-stereoisomers of alanine, serine, and proline were therefore measured using ultra-high-performance liquid chromatography-tandem mass spectrometry in 403 healthy subjects. Nicotine and alcohol consumption were quantified using questionnaires. Possible differences in NMDAR coagonist concentrations in plasma and CSF were investigated using ANCOVA with age, body mass index, and storage duration as covariates. The significance threshold was Bonferroni corrected (α=0.00625). Compared with non-smokers, smokers displayed lower levels of D-proline in plasma (p=0.0027, Cohen's d=-0.41) and D-proline in CSF (p=0.0026, Cohen's d=-0.43). D-Serine in CSF was higher in smokers than in non-smokers (p=0.0052, Cohen's d=0.41). After subdividing participants based on smoking quantity, dose-dependent decreases were demonstrated in smokers for D-proline in plasma (F=5.65, p=0.0039) and D-proline in CSF (F=5.20, p=0.0060). No differences in NMDAR coagonist levels between alcohol consumption groups were detected. To our knowledge, this is the first report to implicate D-amino acids in smoking behavior of humans. Whether such concentration differences lie at the root of or result from smoking habits may be addressed in prospective studies.

High-resolution nuclear magnetic resonance spectroscopic study of metabolites in the cerebrospinal fluid of patients with cervical myelopathy and lumbar radiculopathy.

There have been few reports describing substances related to oxidative and intermediary metabolism in the cerebrospinal fluid (CSF) in patients with spinal degenerative disorders. This study investigated whether the concentrations of metabolites in the CSF differed between patients with spinal degenerative disorders and controls, and whether the concentrations of these metabolites correlated with the severity of symptoms. CSF samples were obtained from 30 patients with cervical myelopathy (Group M), 30 patients with lumbar radiculopathy (Group R), and 10 volunteers (control). Metabolites in these CSF samples were measured by nuclear magnetic resonance spectroscopy. There were no differences in the concentrations of lactate, alanine, acetate, glutamate, pyruvate, or citrate between Groups M and R, between Group M and the control, or between Group R and the control. In Group M, neither symptom duration nor the Japanese Orthopaedic Association score correlated with the concentration of any metabolite. In Group R, the symptom duration positively correlated with the concentration of lactate, glutamate, and citrate in CSF. The duration of nerve root block showed a negative correlation with the concentrations of acetate in CSF of the patients in Group R. In patients with lumbar radiculopathy, there is a possibility of increased aerobic metabolic activity or decreased gluconeogenic activity in patients with shorter symptom duration, and increased aerobic metabolic activity in patients with severe inflammation around a nerve root.

A gamma-secretase inhibitor decreases amyloid-beta production in the central nervous system.

OBJECTIVE: Accumulation of amyloid-beta (Abeta) by overproduction or underclearance in the central nervous system (CNS) is hypothesized to be a necessary event in the pathogenesis of Alzheimer's disease. However, previously, there has not been a method to determine drug effects on Abeta production or clearance in the human CNS. The objective of this study was to determine the effects of a gamma-secretase inhibitor on the production of Abeta in the human CNS. METHODS: We utilized a recently developed method of stable-isotope labeling combined with cerebrospinal fluid sampling to directly measure Abeta production during treatment of a gamma-secretase inhibitor, LY450139. We assessed whether this drug could decrease CNS Abeta production in healthy men (age range, 21-50 years) at single oral doses of 100, 140, or 280mg (n = 5 per group). RESULTS: LY450139 significantly decreased the production of CNS Abeta in a dose-dependent fashion, with inhibition of Abeta generation of 47, 52, and 84% over a 12-hour period with doses of 100, 140, and 280mg, respectively. There was no difference in Abeta clearance. INTERPRETATION: Stable isotope labeling of CNS proteins can be utilized to assess the effects of drugs on the production and clearance rates of proteins targeted as potential disease-modifying treatments for Alzheimer's disease and other CNS disorders. Results from this approach can assist in making decisions about drug dosing and frequency in the design of larger and longer clinical trials for diseases such as Alzheimer's disease, and may accelerate effective drug validation. Ann Neurol 2009.

Neurometabolic effects of ACTH on free amino compounds in opsoclonus-myoclonus syndrome.

To evaluate the possible role of central free amino compounds in pediatric opsoclonus-myoclonus syndrome (OMS), 21 cerebrospinal fluid (CSF) amino compounds were measured by an amino acid analyzer or mass spectroscopy in 74 anesthetized children, 54 with OMS and 20 age-matched neurological controls. In OMS, only phosphoethanolamine was increased compared to controls; OMS severity and duration had significant converse effects on alanine and phosphoethanolamine. In contrast, corticotropin (ACTH) treatment was associated with increased alanine and phenylalanine, and decreased taurine compared to controls and untreated OMS, and increased glutamine, lysine, ornithine, and tyrosine compared to untreated OMS. Other than low taurine, these effects were not found with corticosteroid treatment, and non-steroidogenic immunotherapy had no effect. The ACTH dose-association was most apparent for alanine and phosphoethanolamine, but lysine and ornithine were also higher in the high-dose ACTH group. There were no significant disease- or treatment-associated perturbations in GABA, glycine, or other amino acids. These data suggest a unique pattern of ACTH effects on non-neurotransmitter CSF amino compounds, for the most part not shared by steroids.

Direct correlation between ischemic injury and extracellular glycine concentration in mice with genetically altered activities of the glycine cleavage multienzyme system.

BACKGROUND AND PURPOSE: Ischemia elicits the rapid release of various amino acid neurotransmitters. A glutamate surge activates N-methyl-d-aspartate (NMDA) glutamate receptors, triggering deleterious processes in neurons. Although glycine is a coagonist of the NMDA receptor, the effect of extracellular glycine concentration on ischemic injury remains controversial. To approach this issue, we examined ischemic injury in mice with genetically altered activities of the glycine cleavage multienzyme system (GCS), which plays a fundamental role in maintaining extracellular glycine concentration. METHODS: A mouse line with increased GCS activity (340% of C57BL/6 control mice) was generated by transgenic expression of glycine decarboxylase, a key GCS component (high-GCS mice). Another mouse line with reduced GCS activity (29% of controls) was established by transgenic expression of a dominant-negative mutant of glycine decarboxylase (low-GCS mice). We examined neuronal injury after transient occlusion of the middle cerebral artery in these mice by measuring extracellular amino acid concentrations in microdialysates. RESULTS: High-GCS and low-GCS mice had significantly lower and higher basal concentrations of extracellular glycine than did controls, respectively. In low-GCS mice, the extracellular glycine concentration reached 2-fold of control levels during ischemia, and infarct volume was significantly increased by 69% with respect to controls. In contrast, high-GCS mice had a significantly smaller infarct volume (by 21%). No significant difference was observed in extracellular glutamate concentrations throughout the experiments. An antagonist for the NMDA glycine site, SM-31900, attenuated infarct size, suggesting that glycine operated via the NMDA receptor. CONCLUSIONS: There is a direct correlation between ischemic injury and extracellular glycine concentration maintained by the GCS.

[Detection of amino acid neurotransmitters in cerebrospinal fluid of patients in persistent vegetative state].

OBJECTIVE: To detect the amino acid neurotransmitters in cerebrospinal fluid of patients in persistent vegetative state (PVS) to define their relation to the clinical manifestations of the patients. METHODS: The cerebrospinal fluid from 46 patients in PVS and 20 control patients were collected for detection of glutamic acid, aspartic acid, alanine and glycine by high-performance liquid chromatography. RESULTS: All the four amino acids were separated by chromatography within 25 min. The contents of all the 4 neurotransmitters in PVS group were higher than those in the control group, and their contents were inversely correlated to PVS score of the patients. The differences in the concentration of glycine and alanine were significant between PVS patients and the control patients (P<0.05). CONCLUSION: The patient's clinical manifestations are related to the contents of amino acid neurotransmitters in the cerebrospinal fluid of PVS patients.

Cerebrospinal fluid glutamine, tryptophan, and tryptophan metabolite concentrations in dogs with portosystemic shunts.

OBJECTIVE: To determine whether glutamine (GLN), tryptophan (TRP), and tryptophan metabolite concentrations are higher in cerebralspinal fluid (CSF) dogs with naturally occurring portosystemic shunts (PSS), compared with control dogs. ANIMALS: 11 dogs with confirmed PSS and 12 control dogs fed low- and high-protein diets. PROCEDURE: Cerebrospinal fluid and blood samples were collected from all dogs. Serum and CSF concentrations of GLN, alanine, serine, TRP, 5-hydroxyindoleacetic acid (5-HIAA), and quinolinic acid (QUIN) were measured. RESULTS: Cerebrospinal fluid concentrations of GLN, TRP, and 5-HIAA were significantly higher in PSS dogs, compared with control dogs fed high- or low-protein diets. Cerebrospinal fluid QUIN concentration was significantly higher in PSS dogs, compared with control dogs fed the low-protein diet. Serum QUIN concentration was significantly lower in PSS dogs, compared with control dogs fed either high- or low-protein diets. CONCLUSIONS AND CLINICAL RELEVANCE: An increase in CNS GLN concentration is associated with high CSF concentrations of TRP and TRP metabolites in dogs with PSS. High CSF 5-HIAA concentrations indicate an increased flux of TRP through the CNS serotonin metabolic pathway, whereas high CSF QUIN concentrations indicate an increased metabolism of TRP through the indolamine-2,3-dioxygenase pathway. The high CSF QUIN concentrations in the face of low serum QUIN concentrations in dogs with PSS indicates that QUIN production from TRP is occurring in the CNS. High concentrations of QUIN and other TRP metabolites in the CNS may contribute to neurologic abnormalities found in dogs with PSS and hepatic encephalopathy.

Thiopental and midazolam do not seem to impede metabolism of glutamate in brain-injured patients.

Increased extracellular glutamate levels are related to glial and neuronal damage. Glutamate-mediated toxicity is limited by glial uptake and metabolic transformation of glutamate to glutamine and the energetic compounds alanine and lactate which are utilized by surrounding neurons. Under in vitro conditions, barbiturates have been shown to reduce glutamate uptake and its further metabolism, possibly impeding metabolic coupling between astrocytes and neurons. The aims were to investigate if under clinical conditions, the barbiturate thiopental reduces important detoxification of glutamate, resulting in lower CSF glutamine, alanine and lactate levels as opposed to patients receiving midazolam. During long-term administration of thiopental and midazolam, pathologically elevated ventricular CSF glutamate levels were associated with significantly increased glutamine and alanine levels up to 14 days after trauma. CSF lactate, however, remained normal. These data suggest that long-term administration of thiopental and midazolam under clinical conditions does not impede enzymatic activities responsible for detoxification and metabolism of glutamate.

Tardive dyskinesia and substrates of energy metabolism in CSF.

OBJECTIVE: This study was undertaken to assess the relationships among CSF concentrations of substrates of mitochondrial energy metabolism, neuroleptic medication, and neurological side effects. METHOD: CSF was obtained from 25 patients with schizophrenia; seven were unmedicated and 11 had tardive dyskinesia. CSF concentrations of four substrates of mitochondrial energy metabolism (Krebs cycle)--alanine, aspartate, lactate, and pyruvate--were determined. Tardive dyskinesia was measured with the Abnormal Involuntary Movement Scale (AIMS), and parkinsonism was measured with the Simpson-Angus Rating Scale. RESULTS: CSF concentrations of alanine were significantly elevated in the medicated patients when tardive dyskinesia status was controlled for. CSF aspartate concentrations were significantly elevated in patients with tardive dyskinesia when medication status was controlled for and were significantly correlated with total scores on the AIMS. CONCLUSIONS: These results are consistent with a model linking neuroleptic-induced neurological side effects with impairment of mitochondrial energy metabolism, possibly mediated by inhibition of complex 1 of the electron transport chain.

Inhibitory and excitatory amino acids in cerebrospinal fluid of neurolathyrism patients, a highly prevalent motorneurone disease.

Neurolathyrism is caused by overconsumption of seeds containing 3-N-oxalyl-L-2,3-diaminopropanoic acid (beta-ODAP). Amino acids levels of cerebrospinal fluid (CSF) were studied in 50 patients with neurolathyrism and 12 healthy volunteers. The levels of excitatory amino acids glutamate and aspartate were 281% and 71% respectively of control values. The concentration of inhibitory amino acids glycine and taurine were 277% and 198% respectively of the levels in CSF from control individuals. There was a significant correlation between the level of glycine and the duration of the disease. We also found increased levels of threonine, serine and alanine. In contrast to reports on other motor neurone diseases where an increase of isoleucine was observed we found a significant decrease of isoleucine. The results suggest a disturbance of amino acid metabolism due to excitotoxic damages caused by beta-ODAP, a dietary excitatory amino acid.

Decreased plasma alanine and isoleucine in Huntington's disease.

Amino acid concentrations in plasma of patients with Huntington's disease (HD) were determined in 16 patients and 21 age- and sex-matched healthy controls. Alanine and isoleucine were significantly decreased in HD plasma whereas arginine, histidine, leucine, lysine, ornithine, proline, serine, threonine, tyrosine, and valine showed no significant changes. Our findings confirm the decreases of alanine and isoleucine that were described in plasma and cerebrospinal fluid by other investigators. A possible defect in cellular uptake or metabolism of neutral amino acids seems to be a consistent feature of HD.

An assessment of progression of brain edema with amino acid levels in cerebrospinal fluid and changes in electroencephalogram in an adult cat model of cold brain injury.

We investigated the relationship between the changes of the electroencephalogram (EEG) and concentration of amino acids (AAs) in cerebrospinal fluid (CSF) using a model of cold brain injury. A cold injury was made over the motor area of anesthetized adult cats (n = 45). The AAs in CSF from cisterna magna and in the blood were assayed by liquid chromatography. Frequency components and spike discharges/100 s in EEG were evaluated. Data were obtained before production of the lesion and every hour for 8 hours after the lesion was made. The AA-levels and EEG after the lesion was made were compared with those obtained in the controls and the sham operation group: S-group (n = 10) which were not significantly different. Glutamate and aspartate were not detected but methionine and serine were detected in the control CSF and S-group. These AAs increased during the first 4 hours (p < 0.05) and decreased thereafter. Significant increases in spike discharge and disappearance of fast wave (p < 0.02), and increase in AAs were concurrently detected. The AAs originated from necrosis in the lesion. During the next 4 hours, increase of phenylalanine, tyrosine, and valine continued (p < 0.05). Slow wave components (p < 0.02) and precursor AAs of neurotransmitters in CSF increased in association with expansion of edema fluid. In conclusion, our findings showed that changes in the concentration of AAs in CSF are useful indices of progression of edema associated with brain contusion.

Neurotoxicity of panipenem/betamipron, a new carbapenem, in rabbits: correlation to concentration in central nervous system.

The neurotoxic potential of panipenem/betamipron (PAPM/BP), a new carbapenem antibiotic, was compared with that of imipenem/cilastatin (IPM/CS). The drug concentration in cerebrospinal fluid (CSF) at the onset of epileptogenic electroencephalographic (EEG)-activity and the drug distribution into the central nervous system (CNS) were evaluated. Epileptogenic reactions correlated well with drug levels in CSF, but not with drug levels in circulating plasma. The concentration of PAPM in CSF at the onset of epileptogenic EEG-activity was almost twice that of IPM, suggesting that neurotoxic activity of PAPM is about half that of IPM. In addition, in terms of incidence percent for the epileptogenic EEG-activity, PAPM/BP was found to be less toxic than IPM/CS within the dose of 1.0-1.2 g/kg. Concentrations of PAPM in CSF and brain extracellular fluid after PAPM/BP i.v. infusion were comparable with those of IPM after IPM/CS infusion, indicating the similar characteristics of distribution into the CNS for the two antibiotics. From these results of pharmacologic effects and drug distributions, it is suggested that the neurotoxicity of PAPM/BP is less than half that of IPM/CS.

Perilymphatic fistula: analysis of free amino acids in middle ear microaspirates.

High-performance liquid chromatography was used to determine 19 free amino acid concentrations in perilymph, serum/plasma, and red blood cell intracellular fluid. Significant differences were found between perilymph and these fluids. Free amino acid analysis was then used to quantitatively analyze middle ear microaspirates in order to test the hypothesis that perilymph is a potential source of clear fluid in perilymphatic fistulas (PLF). Fourteen unknown samples from patients with visually identified PLF, including patients with no identifiable otic capsule defect, were studied. Six samples on amino acid pattern analysis were correlated most similarly with perilymph (rrho greater than 0.95). Four of these six samples were scored on the basis of quantitative amino acid values as similar to perilymph. However, three samples of clear fluid were more similar to serum/plasma than to perilymph on both amino acid pattern and quantitative amino acid score analysis. These results objectively suggest perilymph as a potential source of clear fluid in some patients with a diagnosis of PLF. Not all clear fluid observed in the middle ear, however, is potentially perilymph.

Elevation of taurine in hippocampal extracellular fluid and cerebrospinal fluid of acutely hypoosmotic rats: contribution by influx from blood?

Previous work has demonstrated that there is a selective increase in extracellular taurine in the brain during acute water intoxication. One aim of the present study was to investigate whether plasma taurine contributes to this increase. To this end, the concentrations of taurine, other amino acids, and ethanolamine (EA) were measured in plasma and CSF of urethane-anesthetized rats injected with 150 ml/kg body weight of distilled water. Blood pressure, blood gases, and pH, as well as plasma and CSF osmolality, were also measured. The CSF level of albumin was quantitated to study the function of the blood-CSF barrier. In separate experiments, hippocampal microdialysis was performed to determine the effects of acute plasma hypoosmolality on extracellular amino acids. Finally, the effect of water injection on hippocampal specific gravity and tissue amino acids was assessed. Blood gases and pH were essentially unchanged after water administration. Mean arterial blood pressure increased to peak levels approximately 50 mm Hg above control. Plasma osmolality decreased rapidly, whereas the depression of CSF osmolality was slower and less pronounced. The average volume of the hippocampus increased by 8%. Water injection was accompanied by a 25-fold elevation of taurine in plasma, whereas phosphoethanolamine (PEA) and EA increased moderately. A small fraction of the increase in plasma taurine might derive from blood cells because dilution of blood in vitro led to doubled plasma levels of the amino acid. Taurine, PEA, and EA increased consistently in CSF and hippocampal microdialysates. Plasma hypoosmolality transiently opened the blood-CSF barrier is reflected by augmented CSF concentrations of albumin.(ABSTRACT TRUNCATED AT 250 WORDS)

High resolution proton nuclear magnetic resonance studies of human cerebrospinal fluid.

One- and two-dimensional (correlated shift spectroscopy) high resolution proton n.m.r. spectra of human cerebrospinal fluid (CSF) are reported. The merits of water suppression by freeze drying or irradiation, and spectral simplification by spin-echo methods, are discussed. Well-resolved resonances for a range of low molecular weight metabolites such as lactate, 3-D-hydroxybutyrate, alanine, acetate, citrate, glucose, valine and formate were observed. Resonances for glutamine were observed only from freeze dried samples. Concentrations determined by n.m.r. were in reasonable agreement with those from conventional methods. The n.m.r. spectra of CSF were related to the clinical conditions of the subjects. No resonances for citrate were present in spectra of CSF from subjects (three infants) with bacterial meningitis; high lactate and lowered glucose levels were observed. Strong resonances for glucose and glycine were observed for mildly diabetic subjects. Both the aromatic and the aliphatic regions of the CSF spectra from subjects suffering from liver failure contained distinctive features characteristic for hepatic coma: Intense resonances for lactate, alanine, valine, methionine, tyrosine, phenylalanine and histidine. In some cases guanine was also present, which does not appear to have been reported previously. The two-dimensional spectrum suggested the presence of abnormally high levels of a number of endogenous metabolites. Such assignments were not possible using one-dimensional spectra alone because of signal overlap.

Cerebrospinal fluid amino acid concentrations in chronic schizophrenia.

The concentrations of the excitatory amino acid, glutamate, the inhibitory amino acids, glycine and taurine, and the inactive amino acids, glutamine and alanine, were determined in cerebrospinal fluid samples from 12 neurological control and 17 chronic schizophrenic patients. No significant differences were observed in any amino acid between the study groups. Within the schizophrenic group, no differences were observed between paranoid and undifferentiated patients. The concentrations of these amino acids in samples obtained from six schizophrenic patients during drug-free as compared to haloperidol-treatment periods also did not differ. These results do not support the glutamate hypothesis of schizophrenia.