Excitatory Amino Acid Neurotransmitters Research Articles

Esketamine Augmentation in Treatment-Resistant Obsessive-Compulsive Disorder: A Retrospective Chart Review.

Converging evidence supports the role of the glutamate, an excitatory amino acid neurotransmitter, in the pathophysiology of obsessive-compulsive disorder (OCD). Ketamine and esketamine, both noncompetitive N -methyl- d -aspartate antagonists, have emerged as a promising medication for this psychiatric disorder, given its possible efficacy with faster onset and good tolerability. The purpose of this retrospective chart review is to evaluate whether unbiased clinical documentation supports formal clinical trials of esketamine for an OCD indication. A retrospective chart review of patients with treatment-resistant OCD receiving a single dose of esketamine (0.5mg/kg) added to standard therapy was conducted. The Yale-Brown Obsessive-Compulsive Scale and the Montgomery-Åsberg Depression Rating Scale were used to evaluate OCD and depressive symptoms respectively at baseline, 24 hours, and 7 days after esketamine administration. Descriptive statistics were used to analyze the data. Eight subjects were identified in this retrospective chart review: esketamine was administered subcutaneously in 7 and intravenously in 1. One week after infusion, 25% of the sample met criteria for treatment response and 50% for partial response. Major depressive disorder was a comorbid diagnosis in 75% of the sample and 2 of these subjects showed a positive antidepressant response. Our findings provide preliminary evidence that esketamine may reduce obsessive-compulsive symptoms in a subset of treatment-resistant OCD patients.

The effects of hypothermia on glutamate and γ-aminobutyric acid metabolism during ischemia in monkeys: a repeated-measures ANOVA study

During an ischemic stroke, the brain releases various factors, including glutamate and γ-aminobutyric acid. Glutamate can cause neurotoxic effects through certain receptors and exacerbate neurological damage, while γ-aminobutyric acid as an inhibitory neurotransmitter can antagonize the excitotoxic effects of glutamate and enhance the tolerance of neurons to ischemia. Therefore, in this study, the content of amino acid neurotransmitters in brain tissue before ischemia, after 10 min of ischemia, hypothermic perfusion, and rewarming were analyzed by high-performance liquid chromatography-UV in an animal model of ischemic stroke generated by blocking the bilateral common carotid arteries of rhesus monkeys. The changes in amino acid neurotransmitters in the rhesus monkey brain during post-ischemia hypothermic perfusion and rewarming were investigated by statistical methods of repeated measures ANOVA, showing that the concentration change of glutamate had not only a temporal factor but also was influenced by temperature, and there was an interaction effect between the two. Time but not temperature affected the change in γ-aminobutyric acid concentration, and there was an interaction effect between the two. Accordingly, hypoperfusion exerts a protective effect during ischemia by inhibiting the release of excitatory amino acid neurotransmitters, while the antagonistic effect of GABA on Glu is not significant.

Ketamine as an adjunctive therapy for major depression - a randomised controlled pragmatic pilot trial (Karma-Dep Trial).

Background: Depression is a common psychiatric disorder that has become the leading cause of disability worldwide. The standard medical care for depression over the past 50 years has focused on monoamine neurotransmitters. These treatments can take weeks to take effect, highlighting the need for novel treatment strategies. One such approach may be ketamine. Ketamine acts as an antagonist of the N-methyl-D-asparate receptor and thus targets the excitatory amino acid neurotransmitter glutamate. Interestingly, at sub-anaesthetic doses, a single infusion of ketamine can elicit a rapid, though transient, antidepressant response. Methods: The aim of this study was to conduct a pragmatic randomised controlled pilot trial of four once-weekly ketamine infusions as an adjunctive therapy for depression. The main objective was to assess trial procedures to inform a future definitive trial. The primary clinical outcome was the 24-item Hamilton Rating Scale for Depression (HRSD-24). Trial participants were patients admitted to St Patrick's Mental Health Services for treatment of a depressive episode. They underwent usual inpatient care as prescribed by their treating team. Consented participants were randomly allocated to a four-week course of either once-weekly ketamine (0.5mg/kg) or midazolam (0.045mg/kg) infusions given over 40 minutes and with 12 weeks follow-up. Results: In total, 1581 admissions to St Patrick's Hospital were assessed for eligibility over nine months, with 125 (8%) meeting criteria, with 25 (20%) providing consent. In total, 13 were randomly assigned to the ketamine arm and 12 to the midazolam arm. There were no major differences in HRSD-24 scores between the two groups. The infusions were generally safe and well tolerated. Conclusions: This is the first pragmatic pilot trial of adjunctive serial ketamine infusions for hospitalised depression, an important possible use of ketamine. This study suggests that a definitive trial of adjunctive ketamine is feasible. Trial registration: ClinicalTrials.gov NCT03256162 21/08/2017; EudraCT 2016-004764-18 30/11/2016.

Effects of Zinc, Mercury, or Lead on [3H]MK-801 and [3H]Fluorowillardiine Binding to Rat Synaptic Membranes.

Glutamate (Glu) is considered the most important excitatory amino acid neurotransmitter in the mammalian Central Nervous System. Zinc (Zn) is co-released with Glu during synaptic transmission and interacts with Glutamate receptors and transporters. We performed binding experiments using [3H]MK-801 (NMDA), and [3H]Fluorowillardine (AMPA) as ligands to study Zn-Glutamate interactions in rat cortical synaptic membranes. We also examined the effects of mercury and lead on NMDA or AMPA receptors. Zinc at 1nM, significantly potentiates [3H]MK-801 binding. Lead inhibits [3H]MK-801 binding at micromolar concentrations. At millimolar concentrations, Hg also has a significant inhibitory effect. These effects are not reversed by Zn (1nM). Zinc displaces the [3H]FW binding curve to the right. Lead (nM) and Hg (μM) inhibit [3H]FW binding. At certain concentrations, Zn reverses the effects of these metals on [3H]FW binding. These specific interactions serve to clarify the role of Zn, Hg, and Pb in physiological and pathological conditions.

Cerebrolysin restores balance between excitatory and inhibitory amino acids in brain following concussive head injury. Superior neuroprotective effects of TiO2 nanowired drug delivery.

Concussive head injury (CHI) often associated with military personnel, soccer players and related sports personnel leads to serious clinical situation causing lifetime disabilities. About 3-4k head injury per 100k populations are recorded in the United States since 2000-2014. The annual incidence of concussion has now reached to 1.2% of population in recent years. Thus, CHI inflicts a huge financial burden on the society for rehabilitation. Thus, new efforts are needed to explore novel therapeutic strategies to treat CHI cases to enhance quality of life of the victims. CHI is well known to alter endogenous balance of excitatory and inhibitory amino acid neurotransmitters in the central nervous system (CNS) leading to brain pathology. Thus, a possibility exists that restoring the balance of amino acids in the CNS following CHI using therapeutic measures may benefit the victims in improving their quality of life. In this investigation, we used a multimodal drug Cerebrolysin (Ever NeuroPharma, Austria) that is a well-balanced composition of several neurotrophic factors and active peptide fragments in exploring its effects on CHI induced alterations in key excitatory (Glutamate, Aspartate) and inhibitory (GABA, Glycine) amino acids in the CNS in relation brain pathology in dose and time-dependent manner. CHI was produced in anesthetized rats by dropping a weight of 114.6g over the right exposed parietal skull from a distance of 20cm height (0.224N impact) and blood-brain barrier (BBB), brain edema, neuronal injuries and behavioral dysfunctions were measured 8, 24, 48 and 72h after injury. Cerebrolysin (CBL) was administered (2.5, 5 or 10mL/kg, i.v.) after 4-72h following injury. Our observations show that repeated CBL induced a dose-dependent neuroprotection in CHI (5-10mL/kg) and also improved behavioral functions. Interestingly when CBL is delivered through TiO2 nanowires superior neuroprotective effects were observed in CHI even at a lower doses (2.5-5mL/kg). These observations are the first to demonstrate that CBL is effectively capable to attenuate CHI induced brain pathology and behavioral disturbances in a dose dependent manner, not reported earlier.

Ketamine as an adjunctive therapy for major depression - a randomised controlled pragmatic pilot trial (Karma-Dep Trial)

Background: Depression is a common psychiatric disorder that has become the leading cause of disability worldwide. The standard medical care for depression over the past 50 years has focused on monoamine neurotransmitters. These treatments can take weeks to take effect, highlighting the need for novel treatment strategies. One such approach may be ketamine. Ketamine acts as an antagonist of the N-methyl-D-asparate receptor and thus targets the excitatory amino acid neurotransmitter glutamate. Interestingly, at sub-anaesthetic doses, a single infusion of ketamine can elicit a rapid, though transient, antidepressant response. Methods: The aim of this study was to conduct a pragmatic randomised controlled pilot trial of four once-weekly ketamine infusions as an adjunctive therapy for depression. The main objective was to assess trial procedures to inform a future definitive trial. The primary clinical outcome was the 24-item Hamilton Rating Scale for Depression (HRSD-24). Trial participants were patients admitted to St Patrick’s Mental Health Services for treatment of a depressive episode. They underwent usual inpatient care as prescribed by their treating team. Consented participants were randomly allocated to a four-week course of either once-weekly ketamine (0.5mg/kg) or midazolam (0.045mg/kg) infusions given over 40 minutes and with 12 weeks follow-up. Results: In total, 1581 admissions to St Patrick’s Hospital were assessed for eligibility over nine months, with 125 (8%) meeting criteria, with 25 (20%) providing consent. In total, 13 were randomly assigned to the ketamine arm and 12 to the midazolam arm. There were no major differences in HRSD-24 scores between the two groups. The infusions were generally safe and well tolerated. Conclusions: This is the first pragmatic pilot trial of adjunctive serial ketamine infusions for hospitalised depression, an important possible use of ketamine. This study suggests that a definitive trial of adjunctive ketamine is feasible. Trial registration: ClinicalTrials.gov NCT03256162 21/08/2017; EudraCT 2016-004764-18 30/11/2016.

Ketamine as an adjunctive therapy for major depression - a randomised controlled pragmatic pilot trial (Karma-Dep Trial).

Background: Depression is a common psychiatric disorder that has become the leading cause of disability worldwide. The standard medical care for depression over the past 50 years has focused on monoamine neurotransmitters. These treatments can take weeks to take effect, highlighting the need for novel treatment strategies. One such approach may be ketamine. Ketamine acts as an antagonist of the N-methyl-D-asparate receptor and thus targets the excitatory amino acid neurotransmitter glutamate. Interestingly, at sub-anaesthetic doses, a single infusion of ketamine can elicit a rapid, though transient, antidepressant response. Methods: The aim of this study was to conduct a pragmatic randomised controlled pilot trial of four once-weekly ketamine infusions as an adjunctive therapy for depression. The main objective was to assess trial procedures to inform a future definitive trial. The primary clinical outcome was the 24-item Hamilton Rating Scale for Depression (HRSD-24). Trial participants were patients admitted to St Patrick's Mental Health Services for treatment of a depressive episode. They underwent usual inpatient care as prescribed by their treating team. Consented participants were randomly allocated to a four-week course of either once-weekly ketamine (0.5mg/kg) or midazolam (0.045mg/kg) infusions given over 40 minutes and with 12 weeks follow-up. Results: In total, 1581 admissions to St Patrick's Hospital were assessed for eligibility over nine months, with 125 (8%) meeting criteria, with 25 (20%) providing consent. In total, 13 were randomly assigned to the ketamine arm and 12 to the midazolam arm. There were no major differences in HRSD-24 scores between the two groups. The infusions were generally safe and well tolerated. Conclusions: This is the first pragmatic pilot trial of adjunctive serial ketamine infusions for hospitalised depression, an important possible use of ketamine. This study suggests that a definitive trial of adjunctive ketamine is feasible. Trial registration: ClinicalTrials.gov NCT03256162 21/08/2017; EudraCT 2016-004764-18 30/11/2016.

Optimization of Ultra-High-Performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry Detection of Glutamine-FMOC Ad-Hoc Derivative by Central Composite Design

Glutamine (Gln) is converted to excitatory (glutamate, aspartate) and inhibitory (γ-amino butyric acid) amino acid neurotransmitters in brain, and is a source of energy during glucose deprivation. Current research utilized an Analytical Quality by Design approach to optimize levels and combinations of critical gas pressure (sheath, auxiliary, sweep) and temperature (ion transfer tube, vaporizer) parameters for high-sensitivity mass spectrometric quantification of brain tissue glutamine. A Design of Experiments (DOE) matrix for evaluation of relationships between these multiple independent variables and a singular response variable, e.g. glutamine chromatogram area, was developed by statistical response surface methodology using central composite design. A second-order polynomial equation was generated to identify and predict singular versus combinatory effects of synergistic and antagonistic factors on chromatograph area. Predicted versus found outcomes overlapped, with enhanced area associated with the latter. DOE methodology was subsequently used to evaluate liquid chromatographic variable effects, e.g. flow rate, column temperature, and mobile phase composition on the response variable. Results demonstrate that combinatory AQbD-guided mass spectrometric/liquid chromatographic optimization significantly enhanced analytical sensitivity for Gln, thus enabling down-sized brain tissue sample volume procurement for quantification of this critical amino acid.

A contemporary review of obstructive sleep apnea.

This review provides a contemporary review of sleep apnea with emphasis on definitions, epidemiology, and consequences. Amyloid β-42 is one of the main peptides forming amyloid plaques in the brains of Alzheimer patients. Poorer sleep quality and shorter sleep duration have been associated with a higher amyloid burden. Decreased sleep time in the elderly is a precipitating factor in amyloid retention. Studies have shown that the dysregulation of the homeostatic balance of the major inhibitory and excitatory amino acid neurotransmitter systems of gamma-aminobutyric acid (GABA) and glutamate play a role in sleep disordered breathing (SDB). Untreated sleep disordered breathing (obstructive sleep apnea and/or central sleep apnea) are an important cause of medical mortality and morbidity. OSA is characterized by recurrent episodes of partial or complete collapse of the upper airway during sleep followed by hypoxia and sympathetic activation. Apneic events are terminated by arousal, followed by increases in pulse and blood pressure, and re-oxygenation and the release of inflammatory factors. Individuals with OSA have an increased risk of developing atrial fibrillation. Hypoxemia and poor sleep quality because of OSA increase the risk of cognitive decline in the elderly.

Targeted lipidomics and metabolomics evaluations of cortical neuronal stress in schizophrenia

BackgroundCortical neuronal dysfunction has been proposed to underlie the psychopathology and cognitive dysfunction of schizophrenia. Previously we have reported altered sphingolipid and N-acylphosphatidylserine (NAPS) metabolism in the frontal cortex in schizophrenia. We continue to expand these investigations to define the biochemical basis for these critical neuropathologies. MethodsWe undertook a targeted high resolution mass spectrometric analysis to validate our previous reports of elevated sphingolipids and NAPS in the frontal cortex of a new cohort of schizophrenia subjects. Furthermore we expanded these analyses to include ceramides, N-acylphosphatidylethanolamines (NAPE), and N-acylethanolamines (NAE). In the same tissue samples we examined N-acetylaspartylglutamate (NAAG), a modulator of excitatory amino acid transmission, hypothesized to be involved in the pathology of schizophrenia. ResultsWe repeated our observations of elevated sulfatides in the frontal cortex in schizophrenia. An in-depth analysis of other sphingolipids revealed decrements in ceramide levels and increased levels of lactosylceramides. NAPS also were found to be augmented in schizophrenia as we previously reported. In addition, levels of NAPES, established biomarkers of neuronal stress, were elevated while their metabolites, NAEs were decreased. With regard to excitatory amino acid neurotransmission, NAAG levels were decreased by 50% while the metabolic precursor, N-acetylaspartate was unaltered. ConclusionsOur data support the concept of cortical neuronal dysfunction in schizophrenia as indicated by altered metabolism of structural sphingolipids and NAAG, a modulator of excitatory amino acid neurotransmission.

GLAST Activity is Modified by Acute Manganese Exposure in Bergmann Glial Cells.

Glutamate is the major excitatory amino acid neurotransmitter in the vertebrate brain. It exerts its actions through the activation of specific plasma membrane receptors expressed in neurons and glial cells. Overactivation of glutamate receptors results in neuronal death, known as excitotoxicity. A family of sodium-dependent glutamate transporters enriched in glial cells are responsible of the vast majority of the removal of this amino acid form the synaptic cleft. Therefore, a precise and exquisite regulation of these proteins is required not only for a proper glutamatergic transmission but also for the prevention of an excitotoxic insult. Manganese is a trace element essential as a cofactor for several enzymatic systems, although in high concentrations is involved in the disruption of brain glutamate homeostasis. The molecular mechanisms associated to manganese neurotoxicity have been focused on mitochondrial function, although energy depletion severely compromises the glutamate uptake process. In this context, in this contribution we analyze the effect of manganese exposure in glial glutamate transporters function. To this end, we used the well-established model of chick cerebellar Bergmann glia cultures. A time and dose dependent modulation of [3H]-D-aspartate uptake was found. An increase in the transporter catalytic efficiency, most probably linked to a discrete increase in the affinity of the transporter was detected upon manganese exposure. Interestingly, glucose uptake was reduced by this metal. These results favor the notion of a direct effect of manganese on glial cells, this in turn alters their coupling with neurons and might lead to changes in glutamatergic transmission.

Ethanol-induced changes in synaptic amino acid neurotransmitter levels in the nucleus accumbens of differentially sensitized mice.

Ethanol-induced behavioural sensitization (EBS) does not occur uniformly in mice exposed to the sensitization paradigm. This suggests innate differential responses to ethanol (EtOH) in the reward circuitry of individual animals. To better characterize the adaptive differences between low-sensitized (LS) and high-sensitized (HS) mice, we examined excitatory amino acid (EAA) and inhibitory amino acid (IAA) neurotransmitter levels in the nucleus accumbens (NAc) during EBS expression. Male DBA/2J mice received five ethanol (EtOH) (2.2g/kg) or saline injections, and locomotor activity (LMA) was assessed during EBS induction. EtOH mice were classified as LS or HS on the basis of final LMA scores. Following an EtOH challenge (1.8g/kg) 2weeks later, LMA was re-evaluated and in vivo microdialysis samples were collected from the NAc. Most differences in amino acid levels were observed within the first 20min after EtOH challenge. LS mice exhibited similar glutamate levels compared with acutely treated (previously EtOH naïve) mice, and generally increased levels of the IAAs GABA, glycine, and taurine. By contrast, HS mice exhibited increased glutamate and attenuated levels of GABA, glycine, and taurine. These data suggest that the profile of amino acid neurotransmitters in the NAc of LS and HS mice significantly differs. Elucidating these adaptive differences contributes to our understanding of factors that confer susceptibility/resilience to alcohol use disorder.

EFFECTS OF DRINKING WATER CONTAINING ALUMINUM AND FLUORIDE SALTS ON THE LEARNING BEHAVIOR AND BRAIN NEUROTRANSMITTERS OF MALE RAT OFFSPRING

The widely existence of aluminum and fluoride in the environment makes the exposure to these pollutants unavoidable. Few studies reported the toxic impact of these pollutants separately on the neurotransmitters involved in the cognitive behavior of rodent offspring. The present study aimed to evaluate the potential impact of these pollutants together on the amino acid neurotransmitters of different brain regions (cerebral cortex, hypothalamus and hippocampus) and the learning ability of male rat offspring. The rat offspring were exposed to deionized water containing 0.5 g AlCl3/L, 0.15 g NaF/L, or their combination throughout the prenatal period of brain growth in the uterus (via the placenta) and the postnatal period until 70 days old (via lactation and drinking water). The results indicated that the levels of most excitatory and inhibitory amino acid neurotransmitters were significantly affected in the three brain regions of exposed male offspring to AlCl3 and/or NaF, as compared with the control male offspring. In addition, the learning ability was more affected in the male offspring exposed to AlCl3 plus NaF, a finding that indicates a synergistic effect. The alteration in the learning ability of rat offspring exposed to AlCl3 plus NaF was concomitant with the increase in the cerebral cortical glycine, hypothalamic and hippocampal γ-aminobutyric acid, and hippocampal glutamate. In conclusion, administration of the AlCl3 plus NaF was more neurotoxic than each salt alone.

Microinjection of Gabazine and Kynurenic Acid into the PreBotzinger Complex Alter Cough Phase Durations in the Cat

The preBotzinger complex (preBotC) is important in breathing rhythmogenesis, but its role in cough patterning is unknown. We previously microinjected an excitatory neurotransmitter, 5 mM DL‐Homocysteic acid (DLH), into the preBotC, which altered breathing phase timing, but not cough phase timing. To further understand the role of the preBotC in cough rhythmogenesis, we hypothesized that inhibiting the preBotC would also have no effect on cough phase timing but would inhibit coughing. To test this hypothesis, we bilaterally microinjected 50 mM kynurenic acid (KYN, n=6), a broad spectrum excitatory amino acid blocker, and separately 0.1 mM gabazine (GBZ, n=5), a GABA‐A receptor antagonist, into the preBotC in anesthetized, spontaneously breathing adult cats. We recorded electromyograms (EMG) from parasternal (PS), diaphragm (DIA) and internal oblique (ABD) muscles. Cough was elicited by mechanical stimulation of the tracheobronchial tree. KYN microinjection significantly increased breathing frequency (21±2 to 43±10 breaths/min, p<0.05) by changing both inspiratory (TI) and expiratory (TE) durations (TI 1.0±0.1 to 0.6±0.1, p<0.05; TE 1.8±0.3 to 0.9±0.2 s, p<0.05). DIA EMG magnitude and cough number did not change (4.5±0.6 to 3.9±1.4). However, inspiratory duration decreased (TI 1.1±0.1 to 0.7±0.06 s, p<0.05), and while active expiratory duration (TE1) did not change significantly (TE1 1.0±0.11 to 0.8±0.04 s, n.s.), passive expiratory duration (TE2) was altered but not until 2 hours after injection (TE2 baseline: 0.9±0.2; 20 min after injection: 0.6±0.3 s; 2 hrs after injection: 0.50±0.2 s, p<0.05). Both DIA (55±5 % of baseline) and ABD EMG (56±11 % of baseline) amplitudes decreased during cough. GBZ microinjection had the opposite effect on breathing compared to KYN, where breathing frequency decreased (21.0±4.0 to 12.0±1.0 breaths/minute, p<0.05) by altering both TI and TE (TI 1.1±0.1 to 2.1 ±0.3 s, p<0.05; TE 1.9±0.4 to 2.7±0.4 s, p<0.05). With respect to cough, GBZ decreased cough number (5.1±0.6 to 1.5±0.4, p<0.05) and ABD EMG magnitude (38±4 % of baseline, p<0.05), although PS EMG magnitude did not change significantly (147±34 % of baseline). Microinjection of GBZ increased the duration of all phases of cough (TI 1.1±0.1 to 2.1±0.4 s, p<0.05, TE1 0.9±0.05 to 1.8±0.2 s, p<0.05, TE2 1.1±0.70 to 2.4±0.9 s, p=0.06). These data indicate that the preBotC participates in the regulation of cough phase timing and magnitudes in the anesthetized cat. Disruption of excitatory amino acid neurotransmission with KYN primarily affected inspiratory duration whereas GBZ‐induced blockade of GABA‐A receptor transmission had a generalized effect on cough. These data support an important but more complex role for the preBotC in the regulation of the cough motor pattern than that for breathing.Support or Funding InformationSupported by OT2OD023854‐01, HL131716.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Modeling of excitatory amino acid transporters and clearance of synaptic cleft on millisecond time scale

Excitatory Amino Acid Transporters (EAATs) operate over wide time scales in the brain. They maintain low ambient concentrations of the primary excitatory amino acid neurotransmitter glutamate, but they also seem to play a significant role in clearing glutamate from the synaptic cleft in the millisecond time-scale process of chemical communication that occurs between neurons. The detailed kinetic mechanisms underlying glutamate uptake and clearance remain incompletely understood. In this work we used a combination of methods to model EAAT kinetics and gain insight into the impact of transport on glutamate dynamics in a general sense. We derive reliable estimates of the turnover rates of the three major EAAT subtypes expressed in the mammalian cerebral cortex. Previous studies have provided transporter kinetic estimates that vary over an order of magnitude. The values obtained in this study are consistent with estimates that suggest the unitary transporter rates are approximately 20-fold slower than the time course of glutamate in the synapse. A combined diffusion/transport model provides a possible mechanism for the apparent discrepancy.

Isoniazid-induced hepatotoxicity and neurotoxicity in rats investigated by 1H NMR based metabolomics approach

Isoniazid (INH) is a well-known therapeutic and preventive agent against tuberculosis. However, high rates of side effects with various symptoms concerning hepatotoxicity and neurotoxicity have been reported, hindering its wide and safe application in clinic. In this investigation, rats were intoxicated with INH by gavage at doses of 200 and 400 mg/kg for 7 consecutive days to develop a rat model of acute INH-induced toxicity, which was investigated by a 1H NMR-based metabolomics complemented with clinical assays, histopathological inspection and western blotting. INH decreased the weights of dosed rats and induced seizure and hepatic steatosis dose-dependently. Orthogonal signal correction partial least-squares discriminant analysis (OSC-PLS-DA) of the NMR profiles of rat livers, brains and serum revealed that INH dose-dependently induced oxidative stress, disorders of excitatory and inhibitory amino acid neurotransmitters, and disturbances of energy metabolism and osmotic balance, which could help clarify the mechanisms of INH-induced hepatotoxicity and neurotoxicity. This integrated metabolomics approach showcased its ability to characterize the global metabolic status of organism, providing a powerful and feasible tool to probe drug induced toxicity or side effects.

85. Brain Resilience for Mood Disorders: Role of Hormones and Neural Factors

The brain is a plastic and vulnerable organ of the body. Experiences cause adaptive changes in dendrite length and branching, turnover of spine synapses and neurogenesis in the dentate gyrus region of the hippocampal formation. This adaptive plasticity is mediated by the excitatory amino acid neurotransmitter, glutamate, acting in concert with endogenous mediators such as neurotrophic factors, endogenous acetyl-L-carnitine (LAC) and other cellular messengers, along with circulating hormones.

Direct and indirect nigrofugal projections to the nucleus reticularis pontis caudalis mediate in the motor execution of the acoustic startle reflex.

The acoustic startle reflex (ASR) is a short and intense defensive reaction in response to a loud and unexpected acoustic stimulus. In the rat, a primary startle pathway encompasses three serially connected central structures: the cochlear root neurons, the giant neurons of the nucleus reticularis pontis caudalis (PnC), and the spinal motoneurons. As a sensorimotor interface, the PnC has a central role in the ASR circuitry, especially the integration of different sensory stimuli and brain states into initiation of motor responses. Since the basal ganglia circuits control movement and action selection, we hypothesize that their output via the substantia nigra (SN) may interplay with the ASR primary circuit by providing inputs to PnC. Moreover, the pedunculopontine tegmental nucleus (PPTg) has been proposed as a functional and neural extension of the SN, so it is another goal of this study to describe possible anatomical connections from the PPTg to PnC. Here, we made 6-OHDA neurotoxic lesions of the SN pars compacta (SNc) and submitted the rats to a custom-built ASR measurement session to assess amplitude and latency of motor responses. We found that following lesion of the SNc, ASR amplitude decreased and latency increased compared to those values from the sham-surgery and control groups. The number of dopamine neurons remaining in the SNc after lesion was also estimated using a stereological approach, and it correlated with our behavioral results. Moreover, we employed neural tract-tracing techniques to highlight direct projections from the SN to PnC, and indirect projections through the PPTg. Finally, we also measured levels of excitatory amino acid neurotransmitters in the PnC following lesion of the SN, and found that they change following an ipsi/contralateral pattern. Taken together, our results identify nigrofugal efferents onto the primary ASR circuit that may modulate motor responses.

Regulation of Aqueous Humor Dynamics by Hydrogen Sulfide: Potential Role in Glaucoma Pharmacotherapy

Hydrogen sulfide (H2S) is a gaseous transmitter with well-known biological actions in a wide variety of tissues and organs. The potential involvement of this gas in physiological and pathological processes in the eye has led to several in vitro, ex vivo, and in vivo studies to understand its pharmacological role in some mammalian species. Evidence from literature demonstrates that 4 enzymes responsible for the biosynthesis of this gas (cystathionine β-synthase, CBS; cystathionine γ-lyase, CSE; 3-mercaptopyruvate sulfurtransferase, 3MST; and d-amino acid oxidase) are present in the cornea, iris, ciliary body, lens, and retina. Studies of the pharmacological actions of H2S (using several compounds as fast- and slow-releasing gas donors) on anterior uveal tissues reveal an effect on sympathetic neurotransmission and the ability of the gas to relax precontracted iris and ocular vascular smooth muscles, responses that were blocked by inhibitors of CSE, CBS, and KATP channels. In the retina, there is evidence that H2S can inhibit excitatory amino acid neurotransmission and can also protect this tissue from a wide variety of insults. Furthermore, exogenous application of H2S-releasing compounds was reported to increase aqueous humor outflow facility in an ex vivo model of the porcine ocular anterior segment and lowered intraocular pressure (IOP) in both normotensive and glaucomatous rabbits. Taken together, the finding that H2S-releasing compounds can lower IOP and can serve a neuroprotective role in the retina suggests that H2S prodrugs could be used as tools or therapeutic agents in diseases such as glaucoma.

The Modulation of NMDA and AMPA/Kainate Receptors by Tocotrienol-Rich Fraction and Α-Tocopherol in Glutamate-Induced Injury of Primary Astrocytes.

Astrocytes are known as structural and supporting cells in the central nervous system (CNS). Glutamate, as a main excitatory amino acid neurotransmitter in the mammalian central nervous system, can be excitotoxic, playing a key role in many chronic neurodegenerative diseases. The aim of the current study was to elucidate the potential of vitamin E in protecting glutamate-injured primary astrocytes. Hence, primary astrocytes were isolated from mixed glial cells of C57BL/6 mice by applying the EasySep® Mouse CD11b Positive Selection Kit, cultured in Dulbecco’s modified Eagle medium (DMEM) and supplemented with special nutrients. The IC20 and IC50 values of glutamate, as well as the cell viability of primary astrocytes, were assessed with 100 ng/mL, 200 ng/mL, and 300 ng/mL of tocotrienol-rich fraction (TRF) and alpha-tocopherol (α-TCP), as determined by an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The mitochondrial membrane potential (MMP) detected in primary astrocytes was assessed with the same concentrations of TRF and α-TCP. The expression levels of the ionotropic glutamate receptor genes (Gria2, Grin2A, GRIK1) were independently determined using RT-PCR. The purification rate of astrocytes was measured by a flow-cytometer as circa 79.4%. The IC20 and IC50 values of glutamate were determined as 10 mM and 100 mM, respectively. Exposure to 100 mM of glutamate in primary astrocytes caused the inhibition of cell viability of approximately 64.75% and 61.10% in pre- and post-study, respectively (p < 0.05). Both TRF and α-TCP (at the lowest and highest concentrations, respectively) were able to increase the MMP to 88.46% and 93.31% pre-treatment, and 78.43% and 81.22% post-treatment, respectively. Additionally, the findings showed a similar pattern for the expression level of the ionotropic glutamate receptor genes. Increased extracellular calcium concentrations were also observed, indicating that the presence of vitamin E altered the polarization of astrocytes. In conclusion, α-TCP showed better recovery and prophylactic effects as compared to TRF in the pre-treatment of glutamate-injured primary astrocytes.