Glutamate and GABA concentration changes in the globus pallidus internus of Parkinson’s patients during performance of implicit and declarative memory tasks: A report of two subjects

Sleep disorders cause Parkinson's disease or the reverse is true: Good GABA good night

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative brain disease due to degeneration of dopaminergic neurons (DNs) presented with motor and non-motor symptoms. PD symptoms are developed in response to the disturbance of diverse neurotransmitters including γ-aminobutyric acid (GABA). GABA has a neuroprotective effect against PD neuropathology by protecting DNs in the substantia nigra pars compacta (SNpc). It has been shown that the degeneration of GABAergic neurons is linked with the degeneration of DNs and the progression of motor and non-motor PD symptoms. GABA neurotransmission is a necessary pathway for normal sleep patterns, thus deregulation of GABAergic neurotransmission in PD could be the potential cause of sleep disorders in PD.

AIM

Sleep disorders affect GABA neurotransmission leading to memory and cognitive dysfunction in PD. For example, insomnia and short sleep duration are associated with a reduction of brain GABA levels. Moreover, PD-related disorders including rigidity and nocturia influence sleep patterns leading to fragmented sleep which may also affect PD neuropathology. However, the mechanistic role of GABA in PD neuropathology regarding motor and non-motor symptoms is not fully elucidated. Therefore, this narrative review aims to clarify the mechanistic role of GABA in PD neuropathology mainly in sleep disorders, and how good GABA improves PD. In addition, this review of published articles tries to elucidate how sleep disorders such as insomnia and REM sleep behavior disorder (RBD) affect PD neuropathology and severity. The present review has many limitations including the paucity of prospective studies and most findings are taken from observational and preclinical studies. GABA involvement in the pathogenesis of PD has been recently discussed by recent studies. Therefore, future prospective studies regarding the use of GABA agonists in the management of PD are suggested to observe their distinct effects on motor and non-motor symptoms.

CONCLUSION

There is a bidirectional relationship between the pathogenesis of PD and sleep disorders which might be due to GABA deregulation.

A review of the neurotransmitter system associated with cognitive function of the cerebellum in Parkinson's disease

The dichotomized brain system is a concept that was generalized from the 'dual syndrome hypothesis' to explain the heterogeneity of cognitive impairment, in which anterior and posterior brain systems are independent but partially overlap. The dopaminergic system acts on the anterior brain and is responsible for executive function, working memory, and planning. In contrast, the cholinergic system acts on the posterior brain and is responsible for semantic fluency and visuospatial function. Evidence from dopaminergic/cholinergic imaging or functional neuroimaging has shed significant insight relating to the involvement of the cerebellum in the cognitive process of patients with Parkinson's disease. Previous research has reported evidence that the cerebellum receives both dopaminergic and cholinergic projections. However, whether these two neurotransmitter systems are associated with cognitive function has yet to be fully elucidated. Furthermore, the precise role of the cerebellum in patients with Parkinson's disease and cognitive impairment remains unclear. Therefore, in this review, we summarize the cerebellar dopaminergic and cholinergic projections and their relationships with cognition, as reported by previous studies, and investigated the role of the cerebellum in patients with Parkinson's disease and cognitive impairment, as determined by functional neuroimaging. Our findings will help us to understand the role of the cerebellum in the mechanisms underlying cognitive impairment in Parkinson's disease.

Blood neuroexosomal excitatory amino acid transporter-2 is associated with cognitive decline in Parkinson’s disease with RBD

Background

Rapid eye movement (REM) sleep behavior disorder (RBD) predicts cognitive decline in Parkinson’s disease (PD) patients without dementia. However, underlying mechanisms remain unknown. Accumulating studies suggest glutamatergic system dysregulation is associated.

Objective

To examine the effect of RBD on the rate of cognitive decline in PD patients and investigate whether plasma levels of the neuroexosomal vesicular glutamate transporter-1 (VGLUT-1) and excitatory amino acid transporter-2 (EAAT-2) are altered in PD patients with RBD.

Methods

This study included 157 newly diagnosed cognitive normal PD patients and 70 healthy controls (HCs). Based on one-night polysomnography recordings, the PD subjects were divided into PD with and without RBD (PD-RBD and PD-nRBD) groups. All participants received a complete clinical and neuropsychological evaluation at baseline. Plasma levels of neuroexosomal VGLUT-1 and EAAT-2 were measured by ELISA kits. After a 3-year follow-up, we evaluated baseline plasma levels of neuroexosomal glutamate transporters in each group as a predictor of cognitive decline using MoCA score changes over 3 years in regression models.

Results

Plasma levels of neuron-derived exosomal EAAT-2 and VGLUT-1 were significantly lower in PD patients than in HCs. Plasma levels of neuroexosomal EAAT-2 were significantly lower in PD-RBD than PD-nRBD group at baseline. At the 3-year follow-up, PD-RBD patients presented greater cognitive decline. Lower baseline blood neuroexosomal EAAT-2 predicted cognitive decline over 3 years in PD-RBD patients (β = 0.064, P = 0.003).

Conclusion

These findings indicate that blood neuroexosomal EAAT-2 is associated with cognitive decline in PD with RBD.

Xylazole inhibits NO-cGMP pathway in fetal rat nerve cells

Background

Xylazole (Xyl) is a veterinary anesthetic that is structurally and functionally similar to xylazine. However, the effects of Xyl in vitro remain unknown.

Objectives

This study aimed to investigate the anesthetic mechanism of Xyl using fetal rat nerve cells treated with Xyl.

Methods

Fetal rat nerve cells cultured for seven days were treated with 10, 20, 30, and 40 μg/ mL Xyl for 0, 5, 10, 15, 20, 25, 30, 45, 60, 90, and 120 min. Variations of amino acid neurotransmitters (AANTs), Nitric oxide-Cyclic GMP (NO-cGMP) signaling pathway, and ATPase were evaluated.

Results

Xyl decreased the levels of cGMP and NO in nerve cells. Furthermore, Xyl affected the AANT content and Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase activity in nerve cells. These findings suggested that Xyl inhibited the NO-cGMP signaling pathway in nerve cells in vitro.

Conclusions

This study provided new evidence that the anesthetic and analgesic effects of Xyl are related to the inhibition of the NO-cGMP signaling pathway.

Manganese-induced reactive oxygen species activate IκB kinase to upregulate YY1 and impair glutamate transporter EAAT2 function in human astrocytes in vitro

Dysregulation of the astrocytic glutamate transporter excitatory amino acid transporter 2 (EAAT2) is associated with several neurological disorders, including Parkinson's disease, Alzheimer's disease, and manganism, the latter induced by chronic exposure to high levels of manganese (Mn). Mechanisms of Mn-induced neurotoxicity include impairment of EAAT2 function secondary to the activation of the transcription factor Yin Yang 1 (YY1) by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). However, the upstream mechanisms by which Mn-induced NF-κB activates YY1 remain to be elucidated. In the present study, we used the H4 human astrocyte cell line to test if Mn activates YY1 through the canonical NF-κB signaling pathway, leading to EAAT2 repression. The results demonstrate that Mn exposure induced phosphorylation of the upstream kinase IκB kinase (IKK-β), leading to NF-κB p65 translocation, increased YY1 promoter activity, mRNA/protein levels, and consequently repressed EAAT2. Results also demonstrated that Mn-induced oxidative stress and subsequent TNF-α production were upstream of IKK-β activation, as antioxidants attenuated Mn-induced TNF-α production and IKK-β activation. Moreover, TNF-α inhibition attenuated the Mn-induced activation of IKK-β and YY1. Taken together, Mn-induced oxidative stress and TNF-α mediates activation of NF-κB signaling and YY1 upregulation, leading to repression of EAAT2. Thus, targeting reactive oxygen species (ROS), TNF-α and IKK-β may attenuate Mn-induced YY1 activation and consequent EAAT2 repression.

Glutamic Acid Transporters: Targets for Neuroprotective Therapies in Parkinson's Disease

Parkinson's disease (PD) is a common neurodegenerative disease in middle-aged and elderly individuals. At present, no effective drug has been developed to treat PD. Although a variety of drugs exist for the symptomatic treatment of PD, they all have strong side effects. Most studies on PD mainly focus on dopaminergic neurons. This review highlights the function of glutamic acid transporters (GLTs), including excitatory amino acid transporters (EAATs) and vesicular glutamate transporters (VGLUTs), during the development of PD. In addition, using bioinformatics, we compared the expression of different types of glutamate transporter genes in the cingulate gyrus of PD patients and healthy controls. More importantly, we suggest that the functional roles of glutamate transporters may prove beneficial in the treatment of PD. In summary, VGLUTs and EAATs may be potential targets in the treatment of PD. VGLUTs and EAATs can be used as clinical drug targets to achieve better efficacy. Through this review article, we hope to enable future researchers to improve the condition of PD patients.

Fidelity of the PINK1 knockout rat to oxidative stress and other characteristics of Parkinson disease

Parkinson disease (PD) is the second most common age-related neurodegenerative disease in the world, and PD significantly impacts the quality of life, especially as in general people are living longer. Because of the numerous and complex features of sporadic PD that progressively develops, it is difficult to build an ideal animal model for PD research. Genetically modified PD rodent animal models are considered as a major tool with which to study the mechanisms and potential therapeutic targets for PD. Up to now, none of the rodent animal models displays all PD characteristics. The Michael J. Fox Foundation for Parkinson's Research (MJFF) funded SAGE Laboratories to generate a PTEN-induced putative kinase-1 (PINK1) knockout (KO) rat model for familial PD using zinc finger nuclease (ZFN) technology. In the current paper, we review all papers from PubMed that report studies with PINK1 KO rats, presenting the research results, and discussing the fidelity of this rat model to PD according to its phenotypes studied by several laboratories. This review will serve as a critical reference for future studies with this rodent model, providing a better understanding of PD etiology, pathology, and potential treatment strategies.

Chronic aerobic exercise: Autoradiographic assessment of GABA(a) and mu-opioid receptor binding in adult rats

Exercise programs have shown great potential for both the prevention and treatment of substance use disorder (SUD). As exercise has been shown to have potent effects on physical and psychological health, it is reasonable to examine the mechanism of how exercise can be used as an adjunct treatment for addiction. The present study examined the effects of chronic aerobic (treadmill) exercise on both GABA(a) and mu-opioid receptor levels in the brains of male and female rats. GABA(a) receptor binding, measured by [³H] Flunitrazepam, was increased in the cingulate cortex following exercise, but only in females. Mu-opioid receptor expression, measured by [³H] ([D-Ala², N-MePhe⁴, Gly-ol]-enkephalin) (DAMGO), showed no effect of exercise while showing an effect of sex, with increased [³H] DAMGO binding in the brains of sedentary males compared to that of sedentary females. Our findings support the potential role for GABA(a) signaling in the cingulate cortex as part of the mechanism of action of aerobic exercise. These data, along with prior reports, aid our understanding of the neurochemical impact and mechanism of chronic aerobic exercise on neuropsychiatric disease, particularly regarding addiction.

The Effect of Different Exercise Modes on Domain-Specific Cognitive Function in Patients Suffering from Parkinson's Disease: A Systematic Review of Randomized Controlled Trials

BACKGROUND

Supervised exercise training alleviates motor symptoms in people with Parkinson's disease (PD). However, the efficacy of exercise to improve nonmotor symptoms such as cognitive function is less well known.

OBJECTIVE

To systematically review evidence on the efficacy of different exercise modes (coordination exercise, resistance exercise, aerobic exercise) on domain-specific cognitive function in patients with PD.

METHODS

Parallel-group randomized controlled trials published before March 2018 were included. Primary outcome measures included global cognitive function and its subdomains, and the Unified Parkinson's Disease Rating Scale was included as a secondary outcome. Methodological quality was assessed using the Physiotherapy Evidence Database scale.

RESULTS

The literature search yielded 2,000 articles, of which 11 met inclusion criteria. 508 patients (mean age 68±4 years) were included with a disease severity from 1 to 4 on the Hoehn & Yahr stage scale. Overall study quality was modest (mean 6±2, range 3-8/10). In 5 trials a significant between-group effect size (ES) was identified for tests of specific cognitive domains, including a positive effect of aerobic exercise on memory (ES = 2.42) and executive function (ES = 1.54), and of combined resistance and coordination exercise on global cognitive function (ES = 1.54). Two trials found a significant ES for coordination exercise (ES = 0.84-1.88), which led to improved executive function compared with that of non-exercising control subjects.

CONCLUSION

All modes of exercise are associated with improved cognitive function in individuals with PD. Aerobic exercise tended to best improve memory; however, a clear effect of exercise mode was not identified.

Inactivation of endopeduncular nucleus impaired fear conditioning and hippocampal synaptic plasticity in rats

The internal globus pallidus (GPi) is one part of basal ganglion nucleuses which play fundamental role in motor function. Recent studies indicated that GPi could modulate emotional processing and learning, but the possible mechanism remains still unknown. In this study, the effects of endopeduncular nucleus (EP, a rodent homolog of GPi) on fear conditioning were tested in rats. GABA_A receptor agonist muscimol was bilaterally delivered into the EP 15 min before or immediately after fear conditioning in rats. We found that EP inactivation impaired the acquisition but not consolidation of fear memory in rats. Furthermore, the long-term potentiation (LTP) in hippocampal CA1 area was impaired, and the learning related phosphorylation of α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor (AMPAR) subunit 1 (GluA1) at the Ser845 site in hippocampus was decreased in muscimol treated group. These results demonstrated that dysfunction of EP impaired hippocampal dependent learning and memory in rats.

Contribution of the GABAergic System to Non-Motor Manifestations in Premotor and Early Stages of Parkinson's Disease

Non-motor symptoms are common in Parkinson’s disease (PD) and they represent a major source of disease burden. Several non-motor manifestations, such as rapid eye movement sleep behavior disorder, olfactory loss, gastrointestinal abnormalities, visual alterations, cognitive and mood disorders, are known to precede the onset of motor signs. Nonetheless, the mechanisms mediating these alterations are poorly understood and probably involve several neurotransmitter systems. The dysregulation of GABAergic system has received little attention in PD, although the spectrum of non-motor symptoms might be linked to this pathway. This Mini Review aims to provide up-to-date information about the involvement of the GABAergic system for explaining non-motor manifestations in early stages of PD. Therefore, special attention is paid to the clinical data derived from patients with isolated REM sleep behavior disorder or drug-naïve patients with PD, as they represent prodromal and early stages of the disease, respectively. This, in combination with animal studies, might help us to understand how the disturbance of the GABAergic system is related to non-motor manifestations of PD.

Network neurobiology of electroconvulsive therapy in patients with depression

Graph theory, a popular analytic tool for resting state fMRI (rsfMRI) has provided important insights in the neurobiology of depression. We aimed to analyze the changes in the network measures of segregation and integration associated with the administration of ECT in patients with depression and to correlate with both clinical response and cognitive deficits. Changes in normalised clustering coefficient (γ), path length (λ) and small-world (σ) index were explored in 17 patients with depressive episode before 1st and after 6th brief-pulse bifrontal ECT (BFECT) sessions. Significant brain regions were then correlated with differences in clinical and cognitive scales. There was significantly increased γ and σ despite significant increase in λ in several brain regions after ECT in patients with depression. The brain areas revealing significant differences in γ before and after ECT were medial left superior frontal gyrus, left paracentral lobule, right pallidum and left inferior frontal operculum; correlating with changes in verbal fluency, HAM-D scores and delayed verbal memory (last two regions) respectively. BFECT reorganized the brain network topology in patients with depression and made it more segregated and less integrated; these correlated with clinical improvement and associated cognitive deficits.

A comparative study on influences of static electric field and power frequency electric field on cognition in mice

Recently, electromagnetic fields around ultra-high voltage transmission lines have received considerable attentions for their potential biological effects. This study aimed to investigate the effects of static electric field (SEF) and power frequency electric field (PFEF) on cognition. Mice were exposed to SEF and PFEF with the same strength (35 kV/m) for 49 days, respectively. Behaviors in Morris water maze test and amino acid neurotransmitter levels in hippocampus were examined during exposure. Results indicated that the exposure of 35 kV/m SEF would not cause significant influences on learning and memory ability in mice, while the exposure of 35 kV/m PFEF would cause significant positive effects on learning and memory ability in mice on day 33. This difference in effects from SEF and PFEF on cognition was possibly induced by the difference in the degree of molecular polarization and ion migration in organisms under exposure of two kinds of electric fields with different frequency.

Sodium p-Aminosalicylic Acid Reverses Sub-Chronic Manganese-Induced Impairments of Spatial Learning and Memory Abilities in Rats, but Fails to Restore γ-Aminobutyric Acid Levels

Excessive manganese (Mn) exposure is not only a health risk for occupational workers, but also for the general population. Sodium para-aminosalicylic acid (PAS-Na) has been successfully used in the treatment of manganism, but the involved molecular mechanisms have yet to be determined. The present study aimed to investigate the effects of PAS-Na on sub-chronic Mn exposure-induced impairments of spatial learning and memory, and determine the possible involvements of γ-aminobutyric acid (GABA) metabolism in vivo. Sprague-Dawley male rats received daily intraperitoneal injections MnCl₂ (as 6.55 mg/kg Mn body weight, five days per week for 12 weeks), followed by daily subcutaneous injections of 100, 200, or 300 mg/kg PAS-Na for an additional six weeks. Mn exposure significantly impaired spatial learning and memory ability, as noted in the Morris water maze test, and the following PAS-Na treatment successfully restored these adverse effects to levels indistinguishable from controls. Unexpectedly, PAS-Na failed to recover the Mn-induced decrease in the overall GABA levels, although PAS-Na treatment reversed Mn-induced alterations in the enzyme activities directly responsible for the synthesis and degradation of GABA (glutamate decarboxylase and GABA-transaminase, respectively). Moreover, Mn exposure caused an increase of GABA transporter 1 (GAT-1) and decrease of GABA A receptor (GABA_A) in transcriptional levels, which could be reverted by the highest dose of 300 mg/kg PAS-Na treatment. In conclusion, the GABA metabolism was interrupted by sub-chronic Mn exposure. However, the PAS-Na treatment mediated protection from sub-chronic Mn exposure-induced neurotoxicity, which may not be dependent on the GABA metabolism.

Metabolic profiling of tyrosine, tryptophan, and glutamate in human urine using gas chromatography-tandem mass spectrometry combined with single SPE cleanup

The tyrosine, tryptophan, and glutamate metabolic pathways play key roles on pathological state of neuronal functions and the change of their levels in biological systems reflects the progress degree of neuronal diseases. Comprehensive profiling of these metabolites is important to find new biomarkers for diagnosis or prognosis of various neuronal diseases. However, the overall profiling analysis of various neurochemicals in biological sample is confronted with several limitations due to their low concentration and physicochemical properties and the coexistence of matrices. We developed an efficient and feasible method using gas chromatography-tandem mass spectrometry (GC-MS/MS). Wide-bore mixed cation exchange (MCX) SPE process enables a rapid and effective cleanup of 20 neurochemicals even including acidic and basic neurochemicals in a single SPE cartridge by using different composition of eluents. Selective derivatization of various types of metabolites was applied to achieve highly chromatographic separation and sensitive mass detection. Appropriate selection of precursor and product transition ions used in multiple reaction-monitoring (MRM) mode based on the MS/MS fragmentations of the derivatized neurochemicals could be significantly minimized the matrix effects and enhanced the reliability of quantification results. The developed method was validated in terms of linearity, limits of detection, precision, accuracy, and matrix effects. The intra- and inter-assay analytical variations were less than 10%. The overall linearity for all of the targets was excellent (R²≥0.996). The detection limits ranged between 0.38 and 8.13ng/mL for the acidic neurochemicals and between 0.02 and 11.1ng/mL for the basic neurochemicals. The developed protocol will be expected to be a promising tool for the understanding of the pathological state and diagnosis of various neuronal diseases.

Influence of static electric field on cognition in mice

With the rapid development of high voltage direct current transmission, the possibility of health effects associated with static electric field (SEF) has caused wide public concern. To examine the effects of long-lasting, full-body exposure to SEF on cognition, Institute of Cancer Research mice were exposed to SEF for 35 d. The intensities of SEF in experimental group I (EG-I), experimental group II (EG-II) and control group (CG) were 2.30∼15.40 kV/m, 9.20∼21.85 kV/m and 0 kV/m, respectively. The performance in learning and memory of mice were tested by Morris water maze (MWM) on days 2∼6, 16∼20 and 30∼34 during the exposure period. The concentrations of hippocampal amino acid neurotransmitters were evaluated on days 7, 21 and 35. Results showed that the latency in the MWM test had no significant difference among the EG-I, EG-II and CG (P > 0.05) during the exposure period. The percentage of time spent in the target quadrant was significantly decreased in the EG-II on day 34 during the exposure period (P < 0.05), whereas the percentage of time spent in the opposite quadrant increased markedly (P < 0.01). The glutamate and gamma-aminobutyric acid concentrations showed no significant differences among the EG-I, EG-II and CG (P > 0.05) during the exposure period. These results indicated that long-lasting, full-body exposure to SEF with certain intensity would not cause significant influence on learning ability, but it might associate with memory impairment of receptors. Meanwhile, this effect of memory impairment was dose-dependent and not causally linked to the glutamate and gamma-aminobutyric acid levels in the hippocampus.

Atp13a2 expression in the periaqueductal gray is decreased in the Pink1 -/- rat model of Parkinson disease

Vocal communication deficits are common in Parkinson disease (PD). Widespread alpha-synuclein pathology is a common link between familial and sporadic PD, and recent genetic rat models based on familial genetic links increase the opportunity to explore vocalization deficits and their associated neuropathologies. Specifically, the Pink1 knockout (-/-) rat presents with early, progressive motor deficits, including significant vocal deficits, at 8 months of age. Moreover, this rat model exhibits alpha-synuclein pathology compared to age-matched non-affected wildtype (WT) controls. Aggregations are specifically dense within the periaqueductal gray (PAG), a brainstem region involved in the coordination of emotional and volitional control of vocalizations. Here, we investigated changes in gene expression within the PAG at 8 months of age in Pink1 -/- rats compared to WT. Our data demonstrate that Pink1 -/- rat mRNA expression levels of alpha-synuclein are comparable to WT. However, Pink1 -/- rats show significantly decreased levels of Atp13a2, a transmembrane lysosomal P5-type ATPase suggesting a potential mechanism for the observed abnormal aggregation. We found no difference in the expression of glucocerebrosidase (Gba) or the CASP8 and FADD-like apoptosis regulator (Cflar). Further, we show that mRNA expression levels of dopaminergic markers including Th, D1 and D2 receptor as well as GABA signaling markers including Gaba-A and glutamate decarboxylase 2 (Gad2) do not differ between genotypes. However, we found that glutamate decarboxylase 1 (Gad1) is significantly reduced in this PD model suggesting possible disruption of neurotransmission within the PAG. These results are the first to suggest the hypothesis that alpha-synuclein aggregation in this model is not a result of increased transcription, but rather a deficit in the breakdown and clearance, and that the observed vocal deficits may be related to impaired neural transmission. Altogether, these findings are consistent with the hypothesis that differences in neural substrate sensitivity contribute to the early pathogenesis of vocalizations and motivation to communicate in the Pink1 -/- rat model of PD. Our results suggest novel therapeutic pathways, including the lysosomal degradation pathway, which can be used in to further study the pathogenesis and treatment of vocal dysfunction PD.

SOD2 Mediates Amifostine-Induced Protection against Glutamate in PC12 Cells

Background. Cytoprotectant amifostine attenuates radiation-induced oxidative injury by increasing intracellular manganese superoxide dismutase (SOD2) in peripheral tissue. However, whether amifostine could protect neuronal cells against oxidative injury has not been reported. The purpose of this study is to explore the protection of amifostine in PC12 cells. Methods. PC12 cells exposed to glutamate were used to mimic neuronal oxidative injury. SOD assay kit was taken to evaluate intracellular Cu/Zn SOD (SOD1) and SOD2 activities; western blot analysis and immunofluorescence staining were performed to investigate SOD2 protein expression; MTT, lactate dehydrogenase (LDH), release and cell morphology were used to evaluate cell injury degree, and apoptotic rate and cleaved caspase-3 expression were taken to assess apoptosis; mitochondrial superoxide production, intracellular reactive oxygen species (ROS), and glutathione (GSH) and catalase (CAT) levels were evaluated by reagent kits. Results. Amifostine increased SOD2 activity and expression, decreased cell injury and apoptosis, reduced mitochondrial superoxide production and intracellular ROS generation, and restored intracellular GSH and CAT levels in PC12 cells exposed to glutamate. SOD2-siRNA, however, significantly reversed the amifostine-induced cytoprotective and antioxidative actions. Conclusion. SOD2 mediates amifostine-induced protection in PC12 cells exposed to glutamate.

In vivo measurements of limbic glutamate and GABA concentrations in epileptic patients during affective and cognitive tasks: A microdialysis study

Limbic system structures such as the amygdala (AMG) and the hippocampus (HIPP) are involved in affective and cognitive processing. However, because of the limitations in noninvasive technology, absolute concentrations of the neurotransmitters underlying limbic system engagement are not known. Here, we report changes in the concentrations of the neurotransmitters glutamate (Glu) and gamma-aminobutyric acid (GABA) in the HIPP and the AMG of patients with nonlesional temporal lobe epilepsy undergoing surgery for intracranial subdural and depth electrode implantation. We utilized an in-vivo microdialysis technique while subjects were engaged in cognitive tasks with or without emotional content. The performance of an emotion learning task (EmoLearn) was associated with a significant increase in the concentration of glutamate in the HIPP when images with high valence content were processed, as compared to its concentration while processing images with low valence. In addition, significantly decreased levels of glutamate were found in the AMG when images with predominantly low valence content were processed, as compared to its concentration at baseline. The processing of face stimuli with anger/fear content (FaceMatch task) was accompanied with significantly decreased concentrations of GABA in the AMG and HIPP compared to its levels at the baseline. The processing of shapes on the other hand was accompanied with a significantly decreased concentration of the glutamate in the AMG as well as in the HIPP compared to the baseline. Finally, the performance of a nondeclarative memory task (weather prediction task-WPT) was associated with relatively large and opposite changes in the GABA levels compared to the baseline in the AMG (decrease) and the HIPP (increase). These data are relevant for showing an involvement of the amygdala and the hippocampus in emotional processing and provide additional neurochemical clues towards a more refined model of the functional circuitry of the human limbic system.