Exercise modifies glutamate and other metabolic biomarkers in cerebrospinal fluid from Gulf War Illness and Myalgic encephalomyelitis / Chronic Fatigue Syndrome

Myalgic encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS) and Gulf War Illness (GWI) share many symptoms of fatigue, pain, and cognitive dysfunction that are not relieved by rest. Patterns of serum metabolites in ME/CFS and GWI are different from control groups and suggest potential dysfunction of energy and lipid metabolism. The metabolomics of cerebrospinal fluid was contrasted between ME/CFS, GWI and sedentary controls in 2 sets of subjects who had lumbar punctures after either (a) rest or (b) submaximal exercise stress tests. Postexercise GWI and control subjects were subdivided according to acquired transient postexertional postural tachycardia. Banked cerebrospinal fluid specimens were assayed using Biocrates AbsoluteIDQ® p180 kits for quantitative targeted metabolomics studies of amino acids, amines, acylcarnitines, sphingolipids, lysophospholipids, alkyl and ether phosphocholines. Glutamate was significantly higher in the subgroup of postexercise GWI subjects who did not develop postural tachycardia after exercise compared to nonexercise and other postexercise groups. The only difference between nonexercise groups was higher lysoPC a C28:0 in GWI than ME/CFS suggesting this biochemical or phospholipase activities may have potential as a biomarker to distinguish between the 2 diseases. Exercise effects were suggested by elevation of short chain acylcarnitine C5-OH (C3-DC-M) in postexercise controls compared to nonexercise ME/CFS. Limitations include small subgroup sample sizes and absence of postexercise ME/CFS specimens. Mechanisms of glutamate neuroexcitotoxicity may contribute to neuropathology and “neuroinflammation” in the GWI subset who did not develop postural tachycardia after exercise. Dysfunctional lipid metabolism may distinguish the predominantly female ME/CFS group from predominantly male GWI subjects.

Bioanalytical methodology for determination of glutamate and aspartate for use in pharmacological sciences with application of Integrated Calibration Method

A new calibration approach based on the adaptation of Integrated Calibration Method (ICM) to consecutive two components analysis in separation science is presented. Consecutive ICM method (C-ICM) was conceptually developed and applied to determination of two excitatory amino acids - glutamate and aspartate in cerebrospinal fluids collected by the use of brain microdialysis from freely-moving animals. Both analytes as a neurotransmitters play an important role in formation of the memory trace, and thus the processes of learning and memory. Due to their low concentration and presence of interferences, considered analytical system - animal brain - was a big challenge. High-performance liquid chromatography (HPLC) with electrochemical detection (ECD) was used in all experimental work. The most important feature of proposed method is integration of interpolative and extrapolative ways to calculate analyte concentration in single calibration procedure, which consequently leads to obtain series of six estimations of analytical result. Comparison of individual estimations with each other allows for a more in-depth analysis of systematic errors. It was proved that C-ICM approach enables diagnosis and compensation of systematic errors induced by occurrence of interference effects and improvement of accuracy of analytical results. Most of all, it was demonstrated that application of this method is efficient and useful analytical tool in analysis of complicated biological samples in pharmacology and neuroscience.

Striatal neurometabolite levels in patients with schizophrenia undergoing long-term antipsychotic treatment: A proton magnetic resonance spectroscopy and reliability study

Previous proton magnetic resonance spectroscopy (¹H-MRS) studies have reported disrupted levels of various neurometabolites in patients with schizophrenia. An area of particular interest within this patient population is the striatum, which is highly implicated in the pathophysiology of schizophrenia. The present study examined neurometabolite levels in the striatum of 12 patients with schizophrenia receiving antipsychotic treatment for at least 1 year and 11 healthy controls using 3-Tesla ¹H-MRS (PRESS, TE = 35 ms). Glutamate, glutamate+glutamine (Glx), myo-inositol, choline, N-acetylaspartate, and creatine levels were estimated using LCModel, and corrected for fraction of cerebrospinal fluid in the ¹H-MRS voxel. Striatal neurometabolite levels were compared between groups. Multiple study visits permitted a reliability assessment for neurometabolite levels (days between paired ¹H-MRS acquisitions: average = 90.33; range = 7-306). Striatal neurometabolite levels did not differ between groups. Within the whole sample, intraclass correlation coefficients for glutamate, Glx, myo-inositol, choline, and N-acetylaspartate were fair to excellent (0.576-0.847). The similarity in striatal neurometabolite levels between groups implies a marked difference from the antipsychotic-naïve first-episode state, especially in terms of glutamatergic neurometabolites, and might provide insight regarding illness progression and the influence of antipsychotic medication.

Increased cerebrospinal fluid levels of GABA, testosterone and estradiol in women with polycystic ovary syndrome

STUDY QUESTION

Do cerebrospinal fluid (CSF) concentrations of gamma-aminobutyric acid (GABA), testosterone (T) and estradiol (E2) differ in women with polycystic ovary syndrome (PCOS) as compared to eumenorrheic, ovulatory women (EW)?

SUMMARY ANSWER

Women with PCOS displayed higher CSF levels of GABA and E2, and possibly T, than EW.

WHAT IS KNOWN ALREADY

The chronic anovulation characteristic of PCOS has been attributed to increased central GnRH drive and resulting gonadotropin aberrations. Androgens are thought to regulate GABA, which in turn regulates the neural cascade that modulates GnRH drive.

STUDY DESIGN, SIZE, DURATION

This cross-sectional observational study included 15 EW and 12 non-obese women with PCOS who consented to a lumbar puncture in addition to 24 h of serum blood collection at 15-min intervals.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In total, 27 women were studied at a the General Clinical Research Center (GCRC) at the University of Pittsburgh. Serum analytes included T, E2 and androstenedione. CSF analytes included GABA, glutamate, glucose, T and E2.

MAIN RESULTS AND THE ROLE OF CHANCE

Women with PCOS had higher CSF GABA as compared to EW (9.04 versus 7.04 μmol/L, P < 0.05). CSF glucose and glutamate concentrations were similar between the two groups. CSF T was 52% higher (P = 0.1) and CSF E2 was 30% higher (P < 0.01) in women with PCOS compared to EW. Circulating T was 122% higher (P < 0.01) and circulating E2 was 75% higher (P < 0.01) in women with PCOS than in EW.

LIMITATIONS REASONS FOR CAUTION

The study is limited by its small sample size and the technical limitations of measuring CSF analytes that are pulsatile and have short half-lives.

WIDER IMPLICATIONS OF THE FINDINGS

Women with PCOS displayed significantly higher circulating levels of T and E2, significantly higher CSF levels of E2, and higher levels of CSF testosterone, although the latter was not statistically significant. A better understanding of the central milieu informs our understanding of the mechanisms mediating increased the GnRH drive in PCOS and lends a new perspective for understanding the presentation, pathogenesis and potential health consequences of PCOS, including gender identity issues.

STUDY FUNDING/COMPETING INTEREST(S)

No conflicts of interest. The study was funded by NIH grants to SLB (RO1-MH50748, U54-HD08610) and NIH RR-00056 to the General Clinical Research Center of the University of Pittsburgh.

TRIAL REGISTRATION NUMBER

NCT01674426.

Chronic Treatment with a Clinically Relevant Dose of Methylphenidate Increases Glutamate Levels in Cerebrospinal Fluid and Impairs Glutamatergic Homeostasis in Prefrontal Cortex of Juvenile Rats

The understanding of the consequences of chronic treatment with methylphenidate is very important since this psychostimulant is extensively prescribed to preschool age children, and little is known about the mechanisms underlying the persistent changes in behavior and neuronal function related with the use of methylphenidate. In this study, we initially investigate the effect of early chronic treatment with methylphenidate on amino acids profile in cerebrospinal fluid and prefrontal cortex of juvenile rats, as well as on glutamatergic homeostasis, Na(+),K(+)-ATPase function, and balance redox in prefrontal cortex of rats. Wistar rats at early age received intraperitoneal injections of methylphenidate (2.0 mg/kg) or an equivalent volume of 0.9% saline solution (controls), once a day, from the 15th to the 45th day of age. Twenty-four hours after the last injection, the animals were decapitated and the cerebrospinal fluid and prefrontal cortex were obtained. Results showed that methylphenidate altered amino acid profile in cerebrospinal fluid, increasing the levels of glutamate. Glutamate uptake was decreased by methylphenidate administration, but GLAST and GLT-1 were not altered by this treatment. In addition, the astrocyte marker GFAP was not altered by MPH. The activity and immunocontent of catalytic subunits (α1, α2, and α3) of Na(+),K(+)-ATPase were decreased in prefrontal cortex of rats subjected to methylphenidate treatment, as well as changes in α1 and α2 gene expression of catalytic α subunits of Na(+),K(+)-ATPase were also observed. CAT activity was increased and SOD/CAT ratio and sulfhydryl content were decreased in rat prefrontal cortex. Taken together, our results suggest that chronic treatment with methylphenidate at early age induces excitotoxicity, at least in part, due to inhibition of glutamate uptake probably caused by disturbances in the Na(+),K(+)-ATPase function and/or in protein damage observed in the prefrontal cortex.

1H-NMR-based metabolomic analysis of cerebrospinal fluid from adult bilateral moyamoya disease: comparison with unilateral moyamoya disease and atherosclerotic stenosis

Although metabolomics has been increasingly used to observe metabolic pattern and disease-specific metabolic markers, metabolite profiling for moyamoya disease (MMD) has not yet been done in adults. This study investigated cerebrospinal fluid (CSF) metabolites specific to bilateral MMD (B-MMD) and compared them to those of unilateral MMD (U-MMD) or atherosclerotic stenosis with hydrogen-1 nuclear magnetic resonance spectroscopy to identify metabolic biomarkers associated with MMD in adults.CSF samples of B-MMD (n = 29), U-MMD (n = 11), and atherosclerotic cerebrovascular disease (ACVD) (n = 8) were recruited. Principal component analysis, partial least square discriminant analysis, and orthogonal projections to latent structure discriminant analysis (OPLS-DA) were done for the comparisons. Diagnostic performance was acquired by prediction of 1 left-out sample from the distinction model constructed with the rest of the samples.B-MMD showed an increase in glutamine (P < 0.001) and taurine (P = 0.004), and a decrease in glucose (P < 0.001), citrate (P = 0.002), and myo-inositol (P = 0.006) than those in ACVD. U-MMD showed a higher level of glutamine (P = 0.005) and taurine (P = 0.034), and a lower level of glutamate (P < 0.004) than those in ACVD. No difference at the metabolite level was observed between B-MMD and U-MMD. Cross-validation with the OPLS-DA model showed a high accuracy for the prediction of MMD.The results of the study suggest that a metabolomics approach may be helpful in confirming MMD and providing a better understanding of MMD pathogenesis. Elevated glutamine in the CSF may be associated with MMD pathogenesis, which was different from ACVD.

Marked Elevation of Excitatory Amino Acids in Cerebrospinal Fluid Obtained From Patients With Rotavirus-Associated Encephalopathy

Rotavirus is the most common cause of severe gastroenteritis in young children; however, its pathogenesis and immunity are not completely understood. Even less well recognized is rotavirus-induced central nervous system (CNS) involvement, which has been associated with seizure, encephalopathy and death, among others. To elucidate the host response to rotavirus infection, we retrospectively examined neurotransmitter amino acids in the cerebrospinal fluid (CSF) of 19 children with CNS involvement associated with rotavirus infection. Subjects were classified into two groups: those with encephalopathy followed by prolonged seizure (encephalopathy group) and those who had experienced afebrile, brief cluster of seizures without encephalopathy (cluster group). The levels of glutamate, glycine, and taurine in the encephalopathy group were significantly higher than those in the cluster group. Increased levels of excitatory amino acids in the CSF may induce neurological disorders and be related to disorder severity. To the best of our knowledge, this is the first report regarding amino acids in the CSF obtained from patients with rotavirus-induced CNS involvement. Further study is necessary to elucidate the role of CSF amino acid levels in rotavirus-induced CNS involvement.

HPA axis activity in multiple sclerosis correlates with disease severity, lesion type and gene expression in normal-appearing white matter

The hypothalamus-pituitary-adrenal (HPA) axis is activated in most, but not all multiple sclerosis (MS) patients and is implicated in disease progression and comorbid mood disorders. In this post-mortem study, we investigated how HPA axis activity in MS is related to disease severity, neurodegeneration, depression, lesion pathology and gene expression in normal-appearing white matter (NAWM). In 42 MS patients, HPA axis activity was determined by measuring cortisol in cerebrospinal fluid (CSF) and counting hypothalamic corticotropin-releasing hormone (CRH)-expressing neurons. Degree of neurodegeneration was based on levels of glutamate, tau and neurofilament in CSF. Duration of MS and time to EDSS 6 served as indicators of disease severity. Glutamate levels correlated with numbers of CRH-expressing neurons, most prominently in primary progressive MS patients, suggesting that neurodegeneration is a strong determinant of HPA axis activity. High cortisol levels were associated with slower disease progression, especially in females with secondary progressive MS. Patients with low cortisol levels had greater numbers of active lesions and tended towards having less remyelinated plaques than patients with high cortisol levels. Interestingly, NAWM of patients with high cortisol levels displayed elevated expression of glucocorticoid-responsive genes, such as CD163, and decreased expression of pro-inflammatory genes, such as tumor necrosis factor-α. Thus, HPA axis hyperactivity in MS coincides with low inflammation and/or high neurodegeneration, and may impact on lesion pathology and molecular mechanisms in NAWM and thereby be of great importance for suppression of disease activity.

Cerebrospinal fluid levels of glutamate and corticotropin releasing hormone in major depression before and after treatment

BACKGROUND

Glutamate and corticotropin releasing hormone (CRH) are pro-stress neurotransmitters and may be altered in the plasma and cerebrospinal fluid (CSF) of persons with major depressive disorder (MDD). The goal of this study was to compare the CSF levels of glutamate, glutamine and CRH between patients with depression and healthy controls.

METHODS

Eighteen patients with MDD and 25 healthy controls underwent a lumbar puncture (LP); CSF samples were withdrawn and assays were done for glutamine, glutamate, and CRH. Patients with MDD underwent 8 weeks of treatment with the antidepressant venlafaxine and then had a repeat LP post treatment.

RESULTS

Patients had higher baseline scores on depression and suicide rating scales and those scales improved significantly post-treatment. Higher suicidal ratings at baseline were correlated with higher glutamate levels (p=0.016). There were no significant differences between the control and patient group in any baseline CSF measures of glutamate (p=0.761), glutamine (p=0.226) or CRH (p=0.675). Despite no significant change in glutamate (p=0.358) and CRH (p=0.331) in the treatment group, there was a post-treatment decrease in glutamine (p=0.045) in patients.

LIMITATIONS

There was a small sample size, age discordance between patients and controls, lack of a follow-up LP in controls, absence of dexamethasone suppression testing, and fluctuating sample sizes among various measures.

CONCLUSION

Although no significant differences were noted between patients and controls at baseline there was an association of high CSF glutamate and suicidal ideation and lower glutamine post-treatment which may be correlated with attenuation of dysfunction in the glutamatergic system after antidepressant treatment.

The effect of blood glutamate scavengers oxaloacetate and pyruvate on neurological outcome in a rat model of subarachnoid hemorrhage

Blood glutamate scavengers have been shown to effectively reduce blood glutamate concentrations and improve neurological outcome after traumatic brain injury and stroke in rats. This study investigates the efficacy of blood glutamate scavengers oxaloacetate and pyruvate in the treatment of subarachnoid hemorrhage (SAH) in rats. Isotonic saline, 250 mg/kg oxaloacetate, or 125 mg/kg pyruvate was injected intravenously in 60 rats, 60 minutes after induction of SAH at a rate of 0.1 ml/100 g/min for 30 minutes. There were 20 additional rats that were used as a sham-operated group. Blood samples were collected at baseline and 90 minutes after SAH. Neurological performance was assessed at 24 h after SAH. In half of the rats, glutamate concentrations in the cerebrospinal fluid were measured 24 h after SAH. For the remaining half, the blood brain barrier permeability in the frontal and parieto-occipital lobes was measured 48 h after SAH. Blood glutamate levels were reduced in rats treated with oxaloacetate or pyruvate at 90 minutes after SAH (p < 0.001). Cerebrospinal fluid glutamate was reduced in rats treated with pyruvate (p < 0.05). Neurological performance was significantly improved in rats treated with oxaloacetate (p < 0.05) or pyruvate (p < 0.01). The breakdown of the blood brain barrier was reduced in the frontal lobe in rats treated with pyruvate (p < 0.05) and in the parieto-occipital lobes in rats treated with either pyruvate (p < 0.01) or oxaloacetate (p < 0.01). This study demonstrates the effectiveness of blood glutamate scavengers oxaloacetate and pyruvate as a therapeutic neuroprotective strategy in a rat model of SAH.

Neuroprotective effect of Buyang Huanwu decoction against focal cerebral ischemia/reperfusion injury in rats--time window and mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Buyang Huanwu Decoction, a traditional Chinese medicine, consists of different herbal medicines, and has been traditionally used for centuries to treat paralysis and stroke. However, its optimal therapeutic time window and the mechanism are still unclear.

AIM OF THE STUDY

This study was designed to explore the therapeutic time window and mechanism of Buyang Huanwu Decoction on transient focal cerebral ischemia/reperfusion injury.

MATERIALS AND METHODS

Middle cerebral artery occlusion was conducted in male Sprague-Dawley rats, and 40g/kg of Buyang Huanwu Decoction was intragastrically infused at different time points, and the same dose was infused every 24h for 3 days. The level of glutamate in cerebrospinal fluid and the expression of metabotropic glutamate receptor-1 RNA in striatum were detected before, during, and after ischemia/reperfusion. Neurological deficit scores and brain infarction volumes were measured at 72h after reperfusion.

RESULT

Cerebral ischemia/reperfusion resulted in significant neurological deficit and extensive cerebral infarct volume, associated with a large amount of glutamate in cerebrospinal fluid and elevation of metabotropic glutamate receptor-1 RNA expression. Buyang Huanwu Decoction significantly suppressed the release of glutamate, and reduced the expression of metabotropic glutamate receptor-1 RNA. The neurological defect score and infarction volume were significantly improved by administration of Buyang Huanwu Decoction, when compared with the Ischemia group.

CONCLUSIONS

Administration of Buyang Huanwu Decoction, within 4h of post-transient focal stroke, reduced significant cerebral ischemia/reperfusion damage. The neuroprotective mechanism of Buyang Huanwu Decoction is, in part, associated with the down-regulation of metabotropic glutamate receptor-1 RNA and inhibition of glutamate release resulting from cerebral ischemia.

[Effect of (S)-4C3HPG on brain damage in the acute stage of moderate traumatic brain injury model of mice and underlying mechanism]

The aim of this study is to investigate the effect of (S)-4-carboxy-3-hydroxy-phenylglycine [(S)-4C3HPG], a mixed group I glutamate metabotropic receptor antagonist and a group II agonist, on impairment in a cortical impact model of traumatic brain injury (TBI) in mice and to elucidate the possible mechanisms. Mice were injected (i.p.) with saline, 1 mg/kg (S)-4C3HPG, 5 mg/kg (S)-4C3HPG and 10 mg/kg (S)-4C3HPG (n=10 per group), respectively, at 30 min before moderate TBI. Neurological deficit scores, water content in injured brain and glutamate concentration in cerebral spinal fluid (CSF) were detected at 24 h after TBI. The expressions of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) mRNA in injured cortex were also detected by real-time RT-PCR. The results showed that the neurological deficits and cerebral edema were significantly attenuated in mice pretreated with (S)-4C3HPG (5 and 10 mg/kg respectively) compared with those in mice pretreated with saline. Furthermore, (S)-4C3HPG treatment also decreased the glutamate concentration in CSF and the expressions of TNF-α and IL-1β mRNA remarkably in a dose-dependent manner. These results suggest that (S)-4C3HPG treatment attenuates cortical impact-induced brain injury possibly via suppression of glutamate release and inhibition of excessive inflammatory cytokine production. These findings highlight the potential benefit of glutamate metabotropic receptor ligand for preventing TBI.

[Effect of polydatin on dynamic changes of excitatory amino acids in cerebrospinal fluid of cerebral hemorrhage rats]

OBJECTIVE

To observe the effects of polydatin on dynamic changes of excitatory amino acids in cerebrospinal fluid and water content of brain tissue of cerebral hemorrhage rats. And to discuss the therapeutic action and mechanisms of polydatin on brain hemorrhagic injured rats.

METHOD

A quantitative determination method of Asp and Glu was established by microdialysis-HPLC. The cerebral hemorrhage model in rats was induced by local injection of type VII collagenase. The dynamic changes of Asp and Glu in cerebrospinal fluid were observed on 0, 6, 12, 24, 36, 48, 60, 72, 84, 96, 108 h of cerebral hemorrhage rats, and then the water content of brain tissue was detected.

RESULT

The content of Asp and Glu increased rapidly within 24 h after cerebral hemorrhage, and to the highest in 24 h, then decreased gradually. Compared with the cerebral hemorrhage model group, the content of Asp and Glu increased slowly in polydatin group, and there were significant differences in 12-72 h and 6-84 h (P < 0.01, P < 0.05), but there was no significant difference after 84 h and 96 h. Compared with sham group, water content of brain tissue significantly higher in model group, while significantly lower (P < 0.01) in polydatin group.

CONCLUSION

Polydatin can inhibit increasing content of Asp and Glu in cerebrospinal fluid dynamics, and significantly inhibit cerebral edema of cerebral hemorrhage rats. It shows that the mechanisms of anti-cerebral hemorrhage injury of polydatin may be related to increasing of excitatory amino acids after cerebral hemorrhage.

In vitro neurotoxic properties and excitatory aminoacids concentration in the cerebrospinal fluid of amyotrophic lateral sclerosis patients. Relationship with the degree of certainty of disease diagnoses

OBJECTIVE

To determine glutamate and aspartate levels in the cerebrospinal fluid (CSF) in patients with sporadic amyotrophic lateral sclerosis (SALS) grouped according to El Escorial diagnostic criteria, and to perform an in vitro assessment of the neurotoxicity of the CSF in murine cortical neurons.

METHODS

SALS patients were sorted according to El Escorial diagnostic criteria. Glutamate and aspartate were measured in the CSF using high performance liquid chromatography. Cultured cortical neuron viability was determined after exposure to CSF for 24 h.

RESULTS

Glutamate levels were elevated in 28 out of the 29 patients with definite, probable or possible SALS. There were no differences in glutamate concentrations when the three clinical forms of the disease were compared; neither there were significant variation across disease duration and clinical presentation. In agreement with previous reports, we concluded that CSF-SALS-induced in vitro neurotoxicity is mediated by ionotropic glutamate receptors. We found no relationship between the degree of in vitro neurotoxicity and glutamate concentration in the CSF.

CONCLUSIONS

Glutamate but not aspartate CSF levels may contribute to ALS pathogenesis. However, glutamate levels may not influence the degree of diagnosis certainty or lesion extension.

Suppressive effects of intrathecal granulocyte colony-stimulating factor on excessive release of excitatory amino acids in the spinal cerebrospinal fluid of rats with cord ischemia: role of glutamate transporters

Recently, the hematopoietic factor, granulocyte colony-stimulating factor (G-CSF), has been shown to exhibit neuroprotective effects in CNS injuries. Our previous study demonstrated that intrathecal (i.t.) G-CSF significantly improved neurological defects in spinal cord ischemic rats. Considerable evidence indicates that the release of excessive amounts of excitatory amino acids (EAAs) plays a critical role in neuron injury induced by ischemic insult. In the present study, we used a spinal cord ischemia-microdialysis model to examine whether i.t. G-CSF exerted antiexcitotoxicity effects in a rat model of spinal cord ischemia. I.t. catheters and a microdialysis probe were implanted in male Wistar rats. The results revealed that spinal cord ischemia-induced neurological defects were accompanied by a significant increase in the concentration of EAAs (aspartate and glutamate) in the spinal dialysates from 30 min to 2 days after reperfusion. I.t administration of G-CSF immediately after the performance of surgery designed to induce ischemia led to a significant reduction in ischemia-induced increases in the levels of spinal EAAs. Moreover, i.t. G-CSF also brought about a significant reduction in the elevation of spinal EAA concentrations induced by exogenous i.t. administration of glutamate (10 microl of 500 mM). I.t. G-CSF attenuated spinal cord ischemia-induced downregulation of expression of three glutamate transporters (GTs), glial transporter Glu-Asp transporter (GLAST), Glu transporter-1 (GLT-1), and excitatory amino acid carrier 1 (EAAC1) protein 48 h after spinal cord ischemic surgery. Immunohistofluorescent staining showed that i.t. G-CSF significantly upregulated expression of the three GTs in the gray matter of the lumbar spinal cord from 3 to 24 h after injection. We propose that i.t. G-CSF possesses an ability to reduce the extent of spinal cord ischemia-induced excitotoxicity by inducing the expression of glutamate transporters.

[Significance of the glutaminergic system for obsessive-compulsive disorder]

Obsessive-compulsive disorder (OCD) is a frequent disorder and glutamate seems to be an important transmitter. The effect of glutamate depends on the level as well as the effect mediated through glutamate receptors. The level is altered in brain areas that are involved in OCD. Genes encoding receptors, enzymes involved in the metabolism and transport proteins are located in regions that are related to OCD. Pharmacogenetic studies examining the genetic variations in the glutaminate system are lacking. The aim was to examine the current knowledge on the glutaminate system in the development and maintenance of OCD.

[Different effects of adenosine A2A receptors in the models of traumatic brain injury and peripheral tissue injury]

Recently, activation of the adenosine A2A receptors has been shown to exert protection against peripheral tissue injuries but aggravation in the central nervous system (CNS) injuries. To explore the different effects of adenosine A2A receptors and try to perform some new treatment strategies for peripheral tissue and CNS traumas, we constructed the mouse models of skin trauma, skin combined radiation-impaired wound and traumatic brain injury (TBI), respectively. Wild type mice and A2A receptor gene knockout mice were both used in the experiments. In skin trauma and combined radiation-impaired wound models, the time of wound healing was observed, while in TBI model, neurological deficit scores, water content in injured brain and glutamate concentration in cerebral spinal fluid (CSF) were detected at 24 h after TBI. The results showed that in skin trauma and combined radiation-impaired wound models, CGS21680 (an agonist of the A2A receptors) promoted while A2A receptor gene knockout delayed the course of skin wound healing. On the contrary, in TBI model, A2A receptor gene knockout, not CGS21680, showed a protective role by inhibition of glutamate release. These data further indicate that promoting glutamate release may account for the different effects of A2A receptor activation in CNS injury and peripheral tissue injury models. These findings may provide some experimental evidence and a new strategy for clinical treatment of peripheral tissue damages by agonists of A2A receptors, while treatment of CNS injuries by antagonists of A2A receptors.

Increased Levels of Neurotrophins Are Not Specific for Chronic Migraine: Evidence From Primary Fibromyalgia Syndrome

All data obtained in experimental animal pain models support the role of nerve growth factor (NGF) as a putative candidate intervening in the pathogenesis of chronic pain, including chronic daily headache (CDH). Few studies have been carried out to establish its role in maintaining pain states in humans. The present study was aimed at investigating cerebrospinal fluid (CSF) levels of NGF and brain-derived neurotrophic factor (BDNF), both measured by sensitive immunoassay, in 20 chronic migraine (CM) patients and 20 patients affected by primary fibromyalgia syndrome (PFMS), compared with those of 20 age-matched control subjects. Significantly higher levels of both neurotrophins and glutamate were found. A significantly positive correlation emerged between CSF values of BDNF and those of NGF (r = .61, P < .001; r = .53, P < .01) and glutamate (r = .44, P < .02; r = .51, P < .01) in CM and PFMS patients, respectively. These findings suggest the possibility of a NGF-mediated up-regulation of BDNF involved in the pathophysiological events underlying long-term neuroplastic changes in persistent chronic painful conditions, such as CM and fibromyalgia. NGF might indirectly exert its effect through enhancing glutamatergic transmission via BDNF. The above mechanisms could account for sustained central sensitization in both chronic pain states.

PERSPECTIVE

This article presents findings of higher NGF and BDNF levels correlated to increased glutamate levels in the CSF of both chronic migraine and fibromyalgia patients. This opens new insights into the pathogenic mechanisms of chronic pain and offers clinicians new therapeutic perspectives targeting the above mechanisms in both painful disorders.

Intrathecal substance P (1–7) prevents morphine-evoked spontaneous pain behavior via spinal NMDA-NO cascade

Previous research has shown that injection of high-dose of morphine into the spinal lumbar intrathecal (i.t.) space of rats elicits an excitatory behavioral syndrome indicative of severe vocalization and agitation. Substance P N-terminal fragments are known to inhibit nociceptive responses when injected i.t. into animals. In this study, we investigated the effect of i.t. substance P (1-7) on both the nociceptive response and the extracellular concentrations of glutamate and nitric oxide (NO) metabolites (nitrite/nitrate) evoked by high-dose i.t. morphine (500 nmol). The induced behavioral responses were attenuated dose-dependently by i.t. pretreatment with the substance P N-terminal fragment substance P (1-7) (100-400 pmol). The inhibitory effect of substance P (1-7) was reversed significantly by pretreatment with [d-Pro2, d-Phe7]substance P (1-7) (20 and 40 nmol), a d-isomer and antagonist of substance P (1-7). In vivo microdialysis analysis showed a significant elevation of extracellular glutamate and NO metabolites in the spinal cord after i.t. injection of high-dose morphine (500 nmol). Pretreatment with substance P (1-7) (400 pmol) produced a significant reduction on the elevated concentrations of glutamate and NO metabolites evoked by i.t. morphine. The reduced levels of glutamate and NO metabolites were significantly reversed by the substance P (1-7) antagonist (40 nmol). The present results suggest that i.t. substance P (1-7) may attenuate the excitatory behavior (vocalization and agitation) of high-dose i.t. morphine by inhibiting the presynaptic release of glutamate, and reducing NO production in the dorsal spinal cord.

Allelic and non-allelic heterogeneities in pyridoxine dependent seizures revealed by ALDH7A1 mutational analysis

Pyridoxine dependent seizure (PDS) is a disorder of neonates or infants with autosomal recessive inheritance characterized by seizures, which responds to pharmacological dose of pyridoxine. Recently, mutations have been identified in the ALDH7A1 gene in Caucasian families with PDS. To elucidate further the genetic background of PDS, we screened for ALDH7A1 mutations in five PDS families (patients 1-5) that included four Orientals. Diagnosis as having PDS was confirmed by pyridoxine-withdrawal test. Exon sequencing analysis of patients 1-4 revealed eight ALDH7A1 mutations in compound heterozygous forms: five missense mutations, one nonsense mutation, one point mutation at the splicing donor site in intron 1, and a 1937-bp genomic deletion. The deletion included the entire exon 17, which was flanked by two Alu elements in introns 16 and 17. None of the mutations was found in 100 control chromosomes. In patient 5, no mutation was found by the exon sequencing analysis. Furthermore, expression level or nucleotide sequences of ALDH7A1 mRNA in lymphoblasts were normal. Plasma pipecolic acid concentration was not elevated in patient 5. These observations suggest that ALDH7A1 mutation is unlikely to be responsible for patient 5. Abnormal metabolism of GABA/glutamate in brain has long been suggested as the underlying pathophysiology of PDS. CSF glutamate concentration was elevated during the off-pyridoxine period in patient 3, but not in patient 2 or 5. These results suggest allelic and non-allelic heterogeneities of PDS, and that the CSF glutamate elevation does not directly correlate with the presence of ALDH7A1 mutations.

Changes in immune and glial markers in the CSF of patients with Complex Regional Pain Syndrome

Complex Regional Pain Syndrome is a severe chronic pain condition characterized by sensory, autonomic, motor and dystrophic signs and symptoms. The pain in CRPS is continuous, it worsens over time, and it is usually disproportionate to the severity and duration of the inciting event. This study compares cerebrospinal fluid (CSF) levels of pro- and anti-inflammatory cytokines, chemokines and several biochemical factors (glial fibrillary acidic protein (GFAP), the nitric oxide metabolites (nitrate plus nitrite), the excitatory amino acid neurotransmitter glutamate, calcium, total protein and glucose) in patients afflicted with CRPS to levels found in patients suffering with other non-painful or painful conditions. The aim of the study is to determine the degree of involvement of glial cells and immune system mediators in the pathophysiology of CRPS. There was no elevation or reduction of a CSF marker that was specific for CRPS patients. However, there were several patterns of markers that could be helpful in both elucidating the mechanisms involved in the disease process and supporting the diagnosis of CRPS. The most common pattern was found in 50% (11 out of 22) of the CRPS patients and consisted of; elevated IL-6, low levels of IL-4 or IL-10, increased GFAP or MCP1 and increases in at least two of the following markers NO metabolites, calcium or glutamate. The results from this and other similar studies may aid in elucidating the mechanisms involved in the pathophysiology of CRPS. A better understanding of these mechanisms may lead to novel treatments for this very severe, life-altering illness.

Variations in the response of interleukins in neurosurgical intensive care patients monitored using intracerebral microdialysis

OBJECT

The aim of this study was to make a preliminary evaluation of whether microdialysis monitoring of cytokines and other proteins in severely diseased neurosurgical patients has the potential of adding significant information to optimize care, thus broadening the understanding of the function of these molecules in brain injury.

METHODS

Paired intracerebral microdialysis catheters with high-cutoff membranes were inserted in 14 comatose patients who had been treated in a neurosurgical intensive care unit following subarachnoidal hemorrhage or traumatic brain injury. Samples were collected every 6 hours (for up to 7 days) and were analyzed at bedside for routine metabolites and later in the laboratory for interleukin (IL)-l and IL-6; in two patients, vascular endothelial growth factor and cathepsin-D were also checked. Aggregated microprobe data gave rough estimations of profound focal cytokine responses related to morphological tissue injury and to anaerobic metabolism that were not evident from the concomitantly collected cerebrospinal fluid data. Data regarding tissue with no macroscopic evidence of injury demonstrated that IL release not only is elicited in severely compromised tissue but also may be a general phenomenon in brains subjected to stress. Macroscopic tissue injury was strongly linked to IL-6 but not IL- lb activation. Furthermore, IL release seems to be stimulated by local ischemia. The basal tissue concentration level of IL-lb was estimated in the range of 10 to 150 pg/ml; for IL-6, the corresponding figure was 1000 to 20,000 pg/ml.

CONCLUSIONS

Data in the present study indicate that catheters with high-cutoff membranes have the potential of expanding microdialysis to the study of protein chemistry as a routine bedside method in neurointensive care.

Measurement of brain metabolites in patients with type 2 diabetes and major depression using proton magnetic resonance spectroscopy

Type 2 diabetes and major depression are disorders that are mutual risk factors and may share similar pathophysiological mechanisms. To further understand these shared mechanisms, the purpose of our study was to examine the biochemical basis of depression in patients with type 2 diabetes using proton MRS. Patients with type 2 diabetes and major depression (n=20) were scanned along with patients with diabetes alone (n=24) and healthy controls (n=21) on a 1.5 T MRI/MRS scanner. Voxels were placed bilaterally in dorsolateral white matter and the subcortical nuclei region, both areas important in the circuitry of late-life depression. Absolute values of myo-inositol, creatine, N-acetyl aspartate, glutamate, glutamine, and choline corrected for CSF were measured using the LC-Model algorithm. Glutamine and glutamate concentrations in depressed diabetic patients were significantly lower (p<0.001) in the subcortical regions as compared to healthy and diabetic control subjects. Myo-inositol concentrations were significantly increased (p<0.05) in diabetic control subjects and depressed diabetic patients in frontal white matter as compared to healthy controls. These findings have broad implications and suggest that alterations in glutamate and glutamine levels in subcortical regions along with white matter changes in myo-inositol provide important neurobiological substrates of mood disorders.

Glutamate Levels in Cerebrospinal Fluid and Triptans Overuse in Chronic Migraine

OBJECTIVE

Chronic migraine (CM) is a common disorder, affecting 2% to 3% of the general population. Glutamate is implicated in cortical spreading depression, trigeminovascular activation, central sensitization, and may be linked to migraine chronification. Triptans brought a novel option for the acute migraine treatment. As the development of central sensitization impacts upon the effectiveness of triptan therapy, we hypothesized that glutamate might be related to triptan response mechanisms.

METHODS

We studied 19 patients diagnosed with CM according to the International Headache Society (2004) criteria. Patients were divided in those overusing analgesics (NSAIDs); those without overuse, and those overusing triptans.

RESULTS

Cerebrospinal fluid (CSF) glutamate levels were similar in patients overusing acute medications (0.335 +/- 0.225 micromol) compared to those without overuse (0.354 +/- 0.141 micromol), P= NS). In contrast, patients overusing triptans had CSF glutamate levels significantly lower than that observed in nonoverusers (0.175 +/- 0.057 vs 0.354 +/- 0.141 micromol, P= 0.015), and significantly higher than controls (0.175 +/- 0.057 vs 0.109 +/- 0.066 micromol, P= 0.039). In triptan overusers, CSF glutamate levels, although lower, were not significantly different from patients overusing other types of analgesics.

CONCLUSIONS

Our study showed lower glutamate levels in CSF of CM patients overusing triptans. Glutamate may be implicated in triptan response mechanisms, triptans may work in part by reducing extracellular glutamate levels in the brain.

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.

Fluoxetine partly exerts its actions through GABA: a neurochemical evidence

Fluoxetine, as a serotonin re-uptake inhibitor augments serotonin concentration within the synapse by inhibiting the serotonin transporter. The contribution of amino acids has also been shown in depression. We hypothesized that fluoxetine exerts its actions at least in part by intervening brain signaling operated by amino acid transmitters. Therefore the aim of this study is to supply neurochemical evidence that fluoxetine produces changes in amino acids in cerebrospinal fluid of rats. Sprague-Dawley rats were anesthetized and concentric microdialysis probes were implanted stereotaxically into the right lateral ventricle. Intraperitoneal fluoxetine (2.5 or 5 mg/kg) or physiological saline was administered and the probes were perfused with artificial cerebrospinal fluid at a rate of 1 mul/min. In the chronic fluoxetine group, the rats were treated daily with oral fluoxetine solution or inert syrup for 3 weeks. The microdialysis probes were placed on the 21st day and perfused the next day. Fluoxetine was ineffective in changing the cerebrospinal fluid GABA levels at the dose of 2.5 mg/kg but produced a significant increase in the perfusates following injection of 5 mg/kg of fluoxetine (P < 0.05). Oral fluoxetine administration (5 mg/kg) for 21 days also elevated the CSF GABA levels by approximately 2-fold (P < 0.05). L: -glutamic acid levels were not affected in all groups. These neurochemical findings show that fluoxetine, a selective serotonin re-uptake inhibitor affects brain GABA levels indirectly, and our results suggest that acute or chronic effects may be involved in beneficial and/or adverse effects of the drug.

[Spinal cord protection and opioids]

Opioids, when administered in large doses, were reported to produce brain damage primarily in limbic system and association areas in animals. We recently found the result that intrathecal (IT) morphine after a short interval of aortic occlusion in the rodent model induced transient spastic paraparesis via opioid receptor-coupled effects in the spinal cord. Histopathological analysis revealed the possibility that IT morphine could induce degeneration of spinal ventral neurons even after a short lasting of spinal cord ischaemia in rats, and this degeneration was associated with the activation of spinal N-methyl-D-aspartate receptors by elevation of glutamate release in cerebrospinal fluid after IT morphine. Therefore, we would like to emphasize that all anesthesiologists should be aware of the possibility of morphine-induced paraplegia after thoracic aortic surgery and that we should carefully select appropriate analgesic agents from the several available opioids for these patients.

A CSF and postmortem brain study of D-serine metabolic parameters in schizophrenia

Clinical trials demonstrated that D-serine administration improves schizophrenia symptoms, raising the possibility that altered levels of endogenous D-serine may contribute to the N-methyl D-aspartate receptor hypofunction thought to play a role in the disease. We hypothesized that cerebro-spinal fluid (CSF) D-serine levels are decreased in the patients due to reduced synthesis and/or increased degradation in brain. We now monitored amino acid levels in CSF from 12 schizophrenia patients vs. 12 controls and in postmortem parietal-cortex from 15 control subjects and 15 each of schizophrenia, major-depression and bipolar patients. In addition, we monitored postmortem brain serine racemase and D-amino acid oxidase protein levels by Western-blot analysis. We found a 25% decrease in D-serine levels and D/L-serine ratio in CSF of schizophrenia patients, while parietal-cortex D-serine was unaltered. Levels of L-serine, L-glutamine and L-glutamate were unaffected. Frontal-cortex (39%) and hippocampal (21%) serine racemase protein levels and hippocampal serine racemase/D-amino acid oxidase ratio (34%) were reduced. Hippocampal D-amino-acid-oxidase protein levels significantly correlated with duration of illness (r=0.6, p=0.019) but not age. D-amino acid oxidase levels in patients with DOI>20 years were 77% significantly higher than in the other patients and controls. Our results suggest that reduced brain serine racemase and elevated D-amino acid oxidase protein levels may contribute to the lower CSF D-serine levels in schizophrenia.

Low cerebrospinal fluid glutamate and glycine in refractory affective disorder

BACKGROUND

Glutamatergic dysregulation has been documented in schizophrenia but has received less systematic study in affective illness.

METHODS

Cerebrospinal fluid (CSF) levels of the excitatory amino acids glutamate (Glu) and aspartate (Asp) and the N-methyl-D-aspartate (NMDA) receptor modulator, glycine (GLY) were measured by high performance liquid chromatography in 32 patients with refractory affective disorder (16 female/16 male, 12 bipolar I, 12 bipolar II, and 8 unipolar) and in 14 age-matched controls.

RESULTS

There was a significant reduction in CSF glutamate and glycine in patients versus controls. A diagnosis by sex interaction was present for CSF glycine with lower levels in female patients compared to female controls. Levels of the excitatory amino acids were highly inter-correlated in patients, but not in controls. In patients studied after 6 weeks of lamotrigine, there was a trend for CSF glutamate levels to increase.

CONCLUSIONS

These data suggest that in patients with refractory affective disorder, excitatory amino acids are dysregulated, as exemplified both by the decreased CSF glutamate and glycine and their high intercorrelation compared to controls. Further controlled study of glutamatergic dysregulation and its relationship to the pathophysiology of affective disorders and potential mechanism of action of mood stabilizers appears indicated.

Hypolocomotion in rats with chronic liver failure is due to increased glutamate and activation of metabotropic glutamate receptors in substantia nigra

BACKGROUND/AIMS

Patients with hepatic encephalopathy show altered motor function, psychomotor slowing and hypokinesia. The underlying mechanisms remain unclear. This work's aims were: (1) to analyse in rats with chronic liver failure due to portacaval shunt (PCS) the neurochemical alterations in the basal ganglia-thalamus-cortex circuits; (2) to correlate these alterations with those in motor function and (3) to normalize motor activity of PCS rats by pharmacological means.

METHODS

Extracellular neurotransmitters levels were analysed by in vivo brain microdialysis. Motor activity was determined by counting crossings in open field.

RESULTS

Extracellular glutamate is increased in substantia nigra pars reticulata (SNr) of PCS rats. Blocking metabotropic receptor 1 (mGluR1) in SNr normalizes motor activity in PCS rats. In ventro-medial thalamus of PCS rats GABA is increased and it is normalized by blocking mGluR1 in SNr. Blocking mGluR1 in SNr increases and mGluR1 activation reduces glutamate in motor cortex and motor activity.

CONCLUSIONS

Increased extracellular glutamate and activation of mGluR1 in SNr are responsible for reduced motor activity in rats with chronic liver failure. Blocking mGluR1 in SNr normalizes motor activity in PCS rats, suggesting that, under appropriate conditions, similar treatments could be useful to treat the psychomotor slowing and hypokinesia in patients with hepatic encephalopathy.

Activin A Release into Cerebrospinal Fluid in a Subset of Patients with Severe Traumatic Brain Injury

Activin A is a member of the transforming growth factor-beta superfamily and has been demonstrated to be elevated during inflammation and to have neuroprotective properties following neural insults. In this study, we examined whether traumatic brain injury (TBI) induced a response in activin A or in the concentrations of its binding protein, follistatin. Thirty-nine patients with severe TBI had daily, matched cerebrospinal fluid (CSF) and serum samples collected post-TBI and these were assayed for activin A and follistatin using specific immunoassays. Concentrations of both molecules were assessed relative to a variety of clinical parameters, such as the Glasgow Coma Score, computer tomography classification of TBI, measurement of injury markers, cell metabolism and membrane breakdown products. In about half of the patients, there was a notable increase in CSF activin A concentrations in the first few days post-TBI. There were only minor perturbations in either serum activin or in either CSF or serum follistatin concentrations. The CSF activin A response was not related to any of the common TBI indices, but was strongly correlated with two common markers of brain damage, neuronal specific enolase and S100-beta. Further, activin A levels were also associated with indices of metabolism, such as lactate and pyruvate, excitotoxicity (glutamate) and membrane lipid breakdown products such as glycerol. In one of the two patients who developed a CSF infection, activin A concentrations in CSF became markedly elevated. Thus, some TBI patients have an early release of activin A into the CSF that may result from activation of inflammatory and/or neuroprotective pathways.

Alterations of plasma and cerebrospinal fluid glutamate levels in rats treated with the N-methyl-D-aspartate receptor antagonist, ketamine

It has been reported that the repeated administration of a sub-anesthetic dose of an N-methyl-D-aspartate receptor antagonist, ketamine, can produce an animal model of schizophrenia. Since no information is available on the alterations of the amino acid levels in ketamine-treated rats, we investigated the amino acid composition in the plasma and cerebrospinal fluid of rats that were repeatedly administered with ketamine for 5 consecutive days (30 mg/kg/day). The plasma and cerebrospinal fluid amino acid compositions in the fifth week after cessation of repeated ketamine administration were determined by highperformance liquid chromatography with fluorescence detection using a pre-column fluorescence reagent, i.e. 4-fluoro-7nitro-2,1,3-benzoxadiazole. Among the amino acids investigated in the present study, the level of plasma glutamic acid increased significantly (p < 0.05), while that of the cerebrospinal fluid glutamic acid decreased significantly in the ketamine-treated rats as compared with these levels in control rats injected with saline (p < 0.05, n = 7). These alterations in the glutamic acid level in the plasma and cerebrospinal fluid resemble those in schizophrenic patients, suggesting that ketamine-treated rats may be a useful model for performing research on the pathophysiology of schizophrenia.

Excitatory amino acid release and electrocortical brain activity after hypoxemia in near-term lambs

BACKGROUND

Energy failure due to insufficient cerebral O(2)-supply leads to excess accumulation of calcium ions in presynaptic neurons, followed by excess release of excitatory amino acids (EAAs), which are potent neurotoxins, into the synaptic cleft.

AIM

The aim of the present study was to determine whether extracellular EAAs release after prolonged hypoxemia affects electrocortical brain activity (ECBA), as a measure of brain cell function, in near-term born lambs.

METHODS

Ten near-term lambs (term: 147 days) were delivered at 131 days of gestation. After a stabilization period, prolonged hypoxemia (FiO(2): 0.10; duration 2.5h) was induced. Mean values of physiologic variables, including ECBA, were calculated over the last 3 min of normoxemia as well as of hypoxemia. Cerebral arterial and venous blood gases were determined at the end of the normoxemic and hypoxemic periods. Cerebrospinal fluid (CSF) was obtained at the end of the hypoxemic period. CSF from six normoxemic sibs was used for comparison. HPLC was used to measure EAAs in the CSF.

RESULTS

During hypoxemia, aspartate and glutamate concentration increased significantly (4.8 and 6.0 times, respectively), while asparagine and glutamine did not. ECBA decreased to 30% of the normoxemic value. Glutamate was significantly higher in lambs with a flat cerebral function monitor (CFM) tracing than in lambs with a burst-suppression pattern.

CONCLUSIONS

After prolonged hypoxemia aspartate and glutamate accumulated excessively in the CSF of near-term born lambs. Especially glutamate concentrations in CSF were related to the decline in brain cell function.

Excitatory amino acids and magnesium sulfate in neonatal asphyxia

The excitatory amino acids (EAA); glutamate and aspartate are released into the cerebrospinal fluids (CSF) of asphyxiated newborns. The objectives of this study were: (a) to examine the relation of the concentration of EAA in the CSF with the degree of brain injury, (b) To determine the time of the release of these EAA into the CSF, and (c) to detect the effect of magnesium sulfate (MgSO(4)) on their levels. DESIGNS AND METHODS. A randomized controlled trial was conducted on 47 full term asphyxiated newborns. Twenty three infants received an intravenous 10% solution of MgSO(4) at a dose of 250 mg/kg within the first 24h of life while the other 24 newborns received isotonic saline (0.9%) of an equal volume. Levels of glutamate and aspartate were measured before and 72 h after giving the trial solution. Results. In the study population (n=47) both glutamate and aspartate were significantly elevated in infants with higher grades of HIE compared to those with lower grades (P=0.013 and 0.031, respectively). Compared to baseline level, glutamate decreased significantly over time in placebo group (-8.28+/-14.26, P=0.025) and in MgSO(4) group (-14.39+/-18.72, P=0.005). Glutamate concentration did not differ between groups when measured at baseline (29.26+/-16.31 vs. 31.27+/-22.62, P=0.82) and at 72 h (19.28+/-15.63 vs. 19.6+/-16.54, P=0.87). The change in aspartate concentration over time was not significant in placebo group (-0.45+/-1.96, P=0.34) or in MgSO(4) group (-0.7+/-3.19, P=0.37). Aspartate did not differ between groups when measured at baseline (3.52+/-2.4 vs. 3.92+/-2.59, P=0.49) or at 72 h (2.79+/-1.24 vs. 3.05+/-2.48, P=0.92). Conclusions. The EAA; glutamate and aspartate are released in the CSF of asphyxiated newborns immediately after birth and declined by 72 h. Their initial concentrations correlated with the severity of HIE. Postnatal administration of MgSO(4) did not alter the levels of these 2 EAA.

Granulocyte colony-stimulating factor does not affect contusion size, brain edema or cerebrospinal fluid glutamate concentrations in rats following controlled cortical impact

INTRODUCTION

Granulocyte colony-stimulating factor (G-CSF) is an established treatment in the neutropenic host. Usage in head-injured patients at risk for infection may aggravate brain damage. In contrast, evidence of G-CSF neuroprotective effects has been reported in rodent models of focal cerebral ischemia. We investigated effects of G-CSF in acute focal traumatic brain injury (TBI) in rats.

METHODS

Thirty-six male Sprague-Dawley rats were anesthetized with 1.2%) to 2.0% isoflurane and subjected to controlled cortical impact injury (CCII). Thirty minutes following CCII, either vehicle or G-CSF was administered intravenously. Animals were sacrificed 24 hours following CCII. Glutamate concentrations were determined in cisternal cerebrospinal fluid (CSF). Brain edema was assessed gravimetrically. Contusion size was estimated by 2,3,5-triphenyltetrazolium chloride staining and volumetric analysis.

RESULTS

Dose-dependent leukocytosis was induced by infusion of G-CSF. Physiological variables were unaffected. Water content of the traumatized hemisphere and CSF glutamate concentrations were unchanged by treatment. Contusion volume was similar in all groups.

CONCLUSIONS

A single injection of G-CSF did not influence cortical contusion volume, brain edema, or glutamate concentrations in CSF determined 24 hours following CCII in rats. G-CSF, administered 30 minutes following experimental TBI, failed to exert neuroprotective effects.

Multiparametric analysis of cerebral substrates and nitric oxide delivery in cerebrospinal fluid in patients with intracerebral haemorrhage: correlation with hemodynamics and outcome

BACKGROUND

There is no information regarding the possible role of cerebral substrates in the pathogenesis of neuronal injury in intracerebral haemorrhages (ICHs). Purposes of this prospective study were to clarify whether changes in substrates are the consequence of the initial brain damage in ICH and to elucidate the relationship among the biochemical mechanisms and clinical course of patients with ICH.

METHOD

During a period of two years, patients (GCS < or =8) who had ICH secondary to an aneurysm (SAH), stroke (sICH), or trauma (tICH) and underwent ventriculostomy with ICP monitoring and/or underwent cranial surgery were randomly enrolled in this study. Extracellular concentrations of glutamate, aspartate, glycine, GABA, lactate, lactate/pyruvate ratio, and glucose in the CSF were measured by use of high-performance liquid chromatography (HPLC). The nitric oxide (NO) concentration in the CSF was analyzed by chemiluminescence.

FINDINGS

There were 75 patients (38 women and 37 men) with ICH included in this study. Twenty-one patients had SAH, 28 sICH, and 26 tICH. In tICH patients, there was a 30-fold increase in glutamate and a 10-fold in aspartate over reference values. The levels of glutamate, aspirate, GABA, lactate, glucose, and NO differed significantly among the three groups (p<0.001). There were no significant differences in glycine and L/P ratio among the groups. The initial GCS, the mean CPP and outcome six months after the insult were all significantly correlated with the concentration of substrates (p<0.01), both within groups and among the total sample. The CSF levels of glutamate lactate, NO and glucose correlated significantly with outcome (p<0.005).

CONCLUSIONS

This study confirms the correlation between the level of EAAs and the outcome of ICHs, suggesting that neurochemical monitoring of these substances may have a role in caring for patients.

Glutamate-modulating drugs as novel pharmacotherapeutic agents in the treatment of obsessive-compulsive disorder

SUMMARY

Obsessive-compulsive disorder (OCD) is a common psychiatric disorder that produces significant morbidity. The introduction of serotonin reuptake inhibitors in the 1980s represented an important advance in the treatment of OCD. However, few patients show complete remission of their symptoms, and some patients show minimal improvement with existing treatments. We review current treatment strategies and initial data supporting the efficacy of glutamate modulating agents as a novel class of pharmaceuticals for the treatment of OCD. Functional neuroimaging studies repeatedly reported metabolic hyperactivity in the cortico-striato-thalamo-cortical circuitry in patients with OCD. Recent magnetic resonance spectroscopy studies provide evidence of elevated glutamate levels in several brain regions in patients suffering from OCD. These findings raised the possibility that agents that reduce glutamate hyperactivity or its consequences in the CNS might be efficacious as novel therapeutic interventions. Indeed, initial evidence from our group suggests that the antiglutamatergic agent riluzole (Rilutek), which was developed for the treatment of amyotrophic lateral sclerosis, is effective in treatment-resistant OCD. Case reports suggest that other agents that modulate glutamatergic activity may likewise be effective. This new application of glutamate modulating agents holds promise for the treatment of this disabling and often inadequately treated disease.

Cerebral cortical tissue damage after hemorrhagic hypotension in near-term born lambs

Hypotension reduces cerebral O(2) supply, which may result in brain cell damage and loss of brain cell function in the near-term neonate. The aim is to elucidate 1) to what extent the functional disturbance of the cerebral cortex, as measured with electrocortical brain activity (ECBA), is related to cerebral cortical tissue damage, as estimated by MAP2; and 2) whether there is a relationship between the glutamate, nitric oxide (NO), cGMP pathway and the development of cerebral cortical tissue damage after hemorrhagic hypotension. Seven lambs were delivered at 131 d of gestation. Hypotension was induced by withdrawal of blood until mean arterial blood pressure was reduced to 30% of normotension. Cerebral O(2) supply, consumption, and ECBA were calculated in normotensive conditions and after 2.5 h of hypotension. Concentrations of glutamate and aspartate in cerebrospinal fluid (CSF), NO(2) and NO(3) (NOx) in plasma, and cGMP in cortical brain tissue were determined in both conditions. CSF and brain tissue from siblings were used to determine normotensive values. Cortical neuronal damage was detected after 2.5 h of hypotension. ECBA was negatively related to the severity of the cortical damage. ECBA was related to respectively glutamate, NOx, and cGMP concentrations. In conclusion, cortical neuronal damage is detected after 2.5 h of hemorrhagic hypotension in the near-term born lamb. The damage is reflected by a reduction of ECBA. The glutamate, NOx, cGMP pathway is likely to be involved in the pathogenesis of cerebral cortical damage.

Glutamatergic dysfunction in OCD

The role of glutamatergic dysfunction in the pathophysiology of OCD has hardly been explored despite recent reports implicating glutamatergic dysfunction in OCD. We decided to investigate CSF glutamate levels in adult OCD probands compared to psychiatrically normal controls. In total, 21 consenting psychotropic drug-naïve adult OCD patients, diagnosed using SCID-IV-CV, and 18 consenting psychiatrically normal controls with age within 10 years of age of the patients, who did not have any history of head injury or neurological illness, were included into the study. Aseptically collected and stored CSF samples obtained from the patients and control subjects were used for glutamate estimation, which was carried out by a modification of the procedure described by Lund (1986). CSF glutamate (micromol/l) level was found to be significantly higher [F(1,31)=6.846, p=0.014] in OCD patients (47.12+/-4.25) compared to control subjects (41.36+/-3.63) on analysis of covariance. There was no effect of gender, age, duration of illness, Y-BOCS score, or CGI-S score on CSF glutamate levels. Our study provides preliminary evidence implicating glutamatergic excess in the pathophysiology of OCD, which needs to be further explored by studies from other centers involving larger sample sets from different age groups.

Anesthesia increases circulating glutamate in neurosurgical patients

BACKGROUND

The excitotoxic amino acid glutamate is known to aggravate pre-existing neuropathology. Since volatile anesthetics increase plasma amino acid levels, we investigated if the anesthetics isoflurane and propofol increase plasma and cerebrospinal fluid (CSF) glutamate in neurosurgical patients.

METHODS

In discectomized patients (n = 15), plasma glutamate was determined at 30 minute intervals before and during isoflurane anesthesia. In craniotomized patients (n = 66), plasma glutamate was assessed during and up to 24 hours after routine isoflurane or propofol anesthesia. CSF samples were withdrawn upon opening of the dura, before surgical manipulations.

FINDINGS

During isoflurane anesthesia, plasma glutamate was significantly and reversibly increased in discectomized and craniotomized patients compared to healthy controls (56+/-6 microM; p<0.05), which was mostly sustained in male patients (males: 126+/-12 vs. females: 96+/-6 microM; p<0.05). With propofol, plasma glutamate was increased equally in men and women but to a lesser extent than with isoflurane (mean: 72+/-7 microM). CSF glutamate was significantly increased during isoflurane and propofol anesthesia compared to control lumbar CSF (1.2+/-0.1 microM; p<0.0001), being more prominent in patients with pre-existing brain edema receiving isoflurane (76+/-8 vs. propofol: 40+/-6 microM; p<0.05).

CONCLUSIONS

The significant increases in plasma and CSF glutamate which were mostly sustained during isoflurane compared to propofol anesthesia should prompt the identification of anesthetic agents which do not impose a possible burden of glutamate-mediated excitotoxicity in patients with underlying compromised cerebral homeostasis. Detailed neuropsychological investigations following different anesthesia regimen are important to determine if transient elevations in CSF and plasma glutamate levels are of clinical relevance.

Kinetics of glutamate and gamma-aminobutyric acid in cerebrospinal fluid in a canine model of complex partial status epilepticus induced by kainic acid

An imbalance of excitatory and inhibitory transmitters in the brain has been suggested to cause epileptic seizures. In this study, we investigated the kinetics of glutamate (GLU) and gamma-aminobutyric acid (GABA) in cerebrospinal fluid (CSF-GLU and CSF-GABA, respectively) using a high performance liquid chromatography (HPLC) in a canine model of complex partial status epilepticus (CPSE) induced by the microinjection of kainic acid (KA) into the unilateral amygdala. During the acute phase (3, 6, 12 and 48 hr after the onset of CPSE), CSF-GLU was significantly increased, while CSF-GABA was decreased, although not significantly. In the chronic phase, both CSF-GLU and CSF-GABA were significantly lower than normal at 72 hr after the onset of CPSE, and their levels returned to normal at 2 months. Results of the present study demonstrate that CSF-GLU is gradually increased in relation with seizure severity, and suggested the possibility that CSF-GABA was consistently decreased during CPSE induced by KA in dogs.

The Activation of Spinal N-Methyl-d-Aspartate Receptors May Contribute to Degeneration of Spinal Motor Neurons Induced by Neuraxial Morphine After a Noninjurious Interval of Spinal Cord Ischemia

We investigated the relationship between the degeneration of spinal motor neurons and activation of N-methyl-d-aspartate (NMDA) receptors after neuraxial morphine following a noninjurious interval of aortic occlusion in rats. Spinal cord ischemia was induced by aortic occlusion for 6 min with a balloon catheter. In a microdialysis study, 10 muL of saline (group C; n = 8) or 30 mug of morphine (group M; n = 8) was injected intrathecally (IT) 0.5 h after reflow, and 30 mug of morphine (group SM; n = 8) or 10 muL of saline (group SC; n = 8) was injected IT 0.5 h after sham operation. Microdialysis samples were collected preischemia, before IT injection, and at 2, 4, 8, 24, and 48 h of reperfusion (after IT injection). Second, we investigated the effect of IT MK-801 (30 mug) on the histopathologic changes in the spinal cord after morphine-induced spastic paraparesis. After IT morphine, the cerebrospinal fluid (CSF) glutamate concentration was increased in group M relative to both baseline and group C (P < 0.05). This increase persisted for 8 hrs. IT MK-801 significantly reduced the number of dark-stained alpha-motoneurons after morphine-induced spastic paraparesis compared with the saline group. These data indicate that IT morphine induces spastic paraparesis with a concomitant increase in CSF glutamate, which is involved in NMDA receptor activation. We suggest that opioids may be neurotoxic in the setting of spinal cord ischemia via NMDA receptor activation.

Gender associations with cerebrospinal fluid glutamate and lactate/pyruvate levels after severe traumatic brain injury

OBJECTIVE

Female sex hormones appear to be neuroprotective after traumatic brain injury by attenuating multiple mechanisms of secondary insult, including excitotoxicity and ischemia. The purpose of this study was to evaluate associations between gender and cerebrospinal fluid glutamate and lactate/pyruvate production and the role of hypothermia with gender in attenuating these markers.

DESIGN

Prospectively collected data were analyzed for adult patients with severe traumatic brain injury. Gender comparisons for cerebrospinal fluid glutamate and lactate/pyruvate production were determined using ventricular samples obtained over the first 48 hrs postinjury.

SETTING

University-based level I trauma center.

PATIENTS

There were 123 patients, male n = 93 and female n = 30 (n = 686 cerebrospinal fluid samples), with severe traumatic brain injury (Glasgow Coma Scale score < or =8).

INTERVENTIONS

A portion of these patients were part of a randomized controlled trial evaluating the effect of (48 hrs) therapeutic hypothermia after severe traumatic brain injury. The remainder received hypothermia (24 hrs) if they met clinical care criteria. Patients were cooled to 32-33 degrees C (within approximately 8 hrs) for either 24 or 48 hrs and then were rewarmed or remained normothermic.

MEASUREMENTS AND MAIN RESULTS

Regression analyses using generalized estimating equations for repeated measures showed significant increases in cerebrospinal fluid glutamate production for males compared with females (p = .0023) and a significant interaction between glutamate concentration, gender, and time (p = .0035) by 24 hrs postinjury. Females had lower lactate/pyruvate ratios than males (p = .0006), and there was a significant interaction between lactate/pyruvate, gender, and time (p = .0045) throughout the first 48 hrs postinjury. Hypothermia attenuated glutamate levels, particularly for males, over the time course studied.

CONCLUSIONS

These data suggest significant gender differences with glutamate and lactate/pyruvate production after severe traumatic brain injury. Gender- and hormone-mediated differences in central nervous system pathophysiology should be considered with clinical trials in traumatic brain injury.

Elevated glutamine/glutamate ratio in cerebrospinal fluid of first episode and drug naive schizophrenic patients

BACKGROUND

Recent magnetic resonance spectroscopy (MRS) studies report that glutamine is altered in the brains of schizophrenic patients. There were also conflicting findings on glutamate in cerebrospinal fluid (CSF) of schizophrenic patients, and absent for glutamine. This study aims to clarify the question of glutamine and glutamate in CSF of first episode and drug naive schizophrenic patients.

METHOD

Levels of glutamine and glutamate in CSF of 25 first episode and drug-naive male schizophrenic patients and 17 age-matched male healthy controls were measured by a high performance liquid chromatography.

RESULTS

The ratio (126.1 (median), 117.7 +/- 27.4 (mean +/- S.D.)) of glutamine to glutamate in the CSF of patients was significantly (z = -3.29, p = 0.001) higher than that (81.01 (median), 89.1 +/- 22.5 (mean +/- S.D.)) of normal controls although each level of glutamine and glutamate in patients was not different from that of normal controls.

CONCLUSION

Our data suggests that a disfunction in glutamate-glutamine cycle in the brain may play a role in the pathophysiology of schizophrenia.

Inhibition of glutamate carboxypeptidase II (NAALADase) protects against dynorphin A-induced ischemic spinal cord injury in rats

Glutamate carboxypeptidase (GCP) II (EC 3.4.17.21), which is also known as N-acetylated-alpha-linked acidic dipeptidase (NAALADase), hydrolyses the endogenous acidic dipeptide N-acetylaspartylglutamate (NAAG), yielding N-acetyl-aspartate and glutamate. Inhibition of this enzyme by 2-(phosphonomethyl) pentanedioic acid (2-PMPA) has been shown to protect against ischemic injury to the brain and hypoxic and metabolic injury to neuronal cells in culture, presumably by increasing and decreasing the extracellular concentrations of NAAG and glutamate, respectively. Since both NAAG and GCP II are found in especially high concentrations in the spinal cord, injuries to the spinal cord involving pathophysiological elevations in extracellular glutamate might be particularly responsive to GCP II inhibition. Lumbar subarachnoid injections of dynorphin A in rats cause ischemic spinal cord injury, elevated extracellular glutamate and a persistent hindlimb paralysis that is mediated through excitatory amino acid receptors. We therefore used this injury model to evaluate the protective effects of 2-PMPA. When coadministered with dynorphin A, 2-PMPA significantly attenuated the dynorphin A-induced elevations in cerebrospinal fluid glutamate levels and by 24 h postinjection caused significant dose-dependent improvements in motor scores that were associated with marked histopathological improvements. These results indicate that 2-PMPA provides effective protection against excitotoxic spinal cord injury.

[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.

Dexamethasone modulates the development of morphine tolerance and expression of glutamate transporters in rats

We recently demonstrated an increase in spinal cerebrospinal fluid (CSF) excitatory amino acids (EAAs) in morphine-tolerant rats after morphine challenge. The present study examined whether co-infusion of the glucocorticoid dexamethasone (DEX) co-infusion inhibited morphine tolerance and the morphine challenge-induced EAAs increase after long-term morphine infusion. Intrathecal (i.t.) catheters and one microdialysis probe were implanted to male Wistar rats. Rats were divided into four groups: i.t. morphine (15 microg/h), saline (1 microl/h), DEX (2 microg/h), or DEX (2 microg/h) plus morphine (15 microg/h) infusion for 5 days. Tail-flick responses were examined before drug infusion and daily after the start of infusion for 5 days. Moreover, on day 5 after morphine challenge (50 microg, i.t.), CSF EAAs was also measured. Rat spinal cords were removed on day 5, and prepared for Western blot analysis of different glutamate transporters (GTs). The AD50 (analgesic dose) on day 5 was 1.33 microg in saline-infused rats, 83.84 microg in morphine-tolerant rats, and 10.15 microg in DEX plus morphine co-infused rats. Single DEX (2 microg, i.t.) injection did not enhance morphine's antinociceptive effect in either naïve or morphine-tolerant rats. No difference in CSF EAA level was observed in all groups between baseline (before drug infusion) and on day 5 after tolerance developed. Surprisingly, on day 5, after morphine challenge, an increase in glutamate and aspartate (284+/-47% and 201+/-18% of basal) concentration was observed, and morphine lost its antinociceptive effect (maximum percent effect, MPE = 41+/-12%), whereas DEX/morphine co-infusion inhibited morphine-evoked EAA increase with a MPE = 97+/-2%. DEX co-infusion prevented the downregulation of glial glutamate transporters (GLAST (Glu-Asp transporter) and GLT-1 (Glu transporter-1)), but not the neuronal GT EAAC1 (excitatory amino acid carrier). Upregulation of GLT-1 was also observed (204+/-20% of basal). DEX co-infusion inhibits the morphine-challenge induced EAA increase and prevents the loss of morphine's antinociceptive effect after long-term morphine infusion.

Cerebrospinal fluid glutamate levels in chronic migraine

Both preclinical and clinical data link glutamate to the migraine pathophisiology. Altered plasma, platelets and cerebrospinal (CSF) glutamate levels have been reported in migraine patients. Chronic migraine is comorbid with several conditions. It has been recently shown chronic migraine comorbidity with fibromyalgia. The objective of this study was to study cerebrospinal fluid glutamate levels in chronic migraine patients with and without fibromyalgia. We studied 20 chronic migraine patients, with and without fibromyalgia, compared to age-sex matched controls. CSF glutamate levels were measured by HPLC. CSF glutamate demonstrated significantly higher levels in patients with fibromyalgia compared to those without fibromyalgia. Patients overall had higher CSF glutamate levels than controls. Mean pain score correlated with glutamate levels in chronic migraine patients. Tender points, the hallmark of fibromyalgia, can be considered as pressure allodynia, and is probably mediated by central sensitization, with increase in CSF glutamate levels. We postulate chronic migraine patients with fibromyalgia, in addition to have more disabling headaches, suffer from a more severe central sensitization process. This subtype of patients may respond to medications modulating glutamate receptors. Headache intensity correlate with glutamate levels in chronic migraine patients.