Glu Release Research Articles

Riluzole attenuates acute neural injury and reactive gliosis, hippocampal-dependent cognitive impairments and spontaneous recurrent generalized seizures in a rat model of temporal lobe epilepsy.

Riluzole exhibits neuroprotective and therapeutic effects in several neurological disease models associated with excessive synaptic glutamate (Glu) release. We recently showed riluzole prevents acute excitotoxic hippocampal neural injury at 3days in the kainic acid (KA) model of temporal lobe epilepsy (TLE). Currently, it is unknown if preventing acute neural injury and the neuroinflammatory response is sufficient to suppress epileptogenesis. The KA rat model of TLE was used to determine if riluzole attenuates acute hippocampal neural injury and reactive gliosis. KA was administered to adult male Sprague-Dawley (250g) rats at 5mg/kg/hr until status epilepticus (SE) was observed, and riluzole was administered at 10mg/kg 1h and 4h after SE and once per day for the next 2days. Immunostaining was used to assess neural injury (FJC and NeuN), microglial activation (Iba1 and ED-1/CD68) and astrogliosis (GFAP and vimentin) at day 7 and day 14 after KA-induced SE. Learning and memory tests (Y-maze, Novel object recognition test, Barnes maze), behavioral hyperexcitability tests, and spontaneous generalized recurrent seizure (SRS) activity (24-hour video monitoring) were assessed at 11-15weeks. Here we show that KA-induced hippocampal neural injury precedes the neuroimmune response and that riluzole attenuates acute neural injury, microglial activation, and astrogliosis at 7 and 14days. We find that reducing acute hippocampal injury and the associated neuroimmune response following KA-induced SE by riluzole attenuates hippocampal-dependent cognitive impairment, behavioral hyperexcitability, and tonic/clonic generalized SRS activity after 3months. We also show that riluzole attenuates SE-associated body weight loss during the first week after KA-induced SE. Riluzole acts on multiple targets that are involved to prevent excessive synaptic Glu transmission and excitotoxic neuronal injury. Attenuating KA-induced neural injury and subsequent microglia/astrocyte activation in the hippocampus and extralimbic regions with riluzole reduces TLE-associated cognitive deficits and generalized SRS and suggests that riluzole could be a potential antiepileptogenic drug.

Melatonin Regulates Neuronal Synaptic Plasticity in the Supramammillary Nucleus and Attenuates Methamphetamine-Induced Conditioned Place Preference and Sensitization in Mice.

Methamphetamine (METH) is an addictive drug that threatens human health. The supramammillary nucleus (SuM) and its neural circuits play key roles in the regulation of spatial memory retrieval, and hippocampal contextual or social memory. Melatonin (MLT), a pineal hormone, can regulate hypothalamic-neurohypophysial activity. Our previous study showed that MLT attenuates METH-induced locomotor sensitization. However, whether MLT regulates SuM function and participates in METH-induced contextual memory retrieval remains unclear. Using a mouse model of METH-conditioned place preference (CPP) and sensitization, we found that METH activated c-Fos expression and elevated calcium (Ca²⁺) levels in SuM neurons. Chemogenetic inhibition of SuM attenuates CPP and sensitization. Pretreatment with MLT decreased c-Fos expression and Ca2+ levels in the SuM and reversed METH-induced addictive behavior, effects that were blocked with the selective MT2 receptors antagonist 4P-PDOT and the MT1 receptors antagonist S26131. Furthermore, MLT reduced SuM synaptic plasticity, glutamate (Glu) release, and neuronal oscillations caused by METH, which were blocked by 4P-PDOT. In conclusion, our data revealed that MLT regulates neuronal synaptic plasticity in the SuM, likely through the MLT receptors (MTs), and plays a role in modulating METH-addictive behavior.

Fully flexible implantable neural probes for electrophysiology recording and controlled neurochemical modulation

Targeted delivery of neurochemicals and biomolecules for neuromodulation of brain activity is a powerful technique that, in addition to electrical recording and stimulation, enables a more thorough investigation of neural circuit dynamics. We have designed a novel, flexible, implantable neural probe capable of controlled, localized chemical stimulation and electrophysiology recording. The neural probe was implemented using planar micromachining processes on Parylene C, a mechanically flexible, biocompatible substrate. The probe shank features two large microelectrodes (chemical sites) for drug loading and sixteen small microelectrodes for electrophysiology recording to monitor neuronal response to drug release. To reduce the impedance while keeping the size of the microelectrodes small, poly(3,4-ethylenedioxythiophene) (PEDOT) was electrochemically coated on recording microelectrodes. In addition, PEDOT doped with mesoporous sulfonated silica nanoparticles (SNPs) was used on chemical sites to achieve controlled, electrically-actuated drug loading and releasing. Different neurotransmitters, including glutamate (Glu) and gamma-aminobutyric acid (GABA), were incorporated into the SNPs and electrically triggered to release repeatedly. An in vitro experiment was conducted to quantify the stimulated release profile by applying a sinusoidal voltage (0.5 V, 2 Hz). The flexible neural probe was implanted in the barrel cortex of the wild-type Sprague Dawley rats. As expected, due to their excitatory and inhibitory effects, Glu and GABA release caused a significant increase and decrease in neural activity, respectively, which was recorded by the recording microelectrodes. This novel flexible neural probe technology, combining on-demand chemical release and high-resolution electrophysiology recording, is an important addition to the neuroscience toolset used to dissect neural circuitry and investigate neural network connectivity.

Cerebellar Purkinje cell firing promotes conscious recovery from anesthesia state through coordinating neuronal communications with motor cortex.

Background: The neurobiological basis of gaining consciousness from unconscious state induced by anesthetics remains unknown. This study was designed to investigate the involvement of the cerebello-thalamus-motor cortical loop mediating consciousness transitions from the loss of consciousness (LOC) induced by an inhalational anesthetic sevoflurane in mice. Methods: The neural tracing and fMRI together with opto-chemogenetic manipulation were used to investigate the potential link among cerebello-thalamus-motor cortical brain regions. The fiber photometry of calcium and neurotransmitters, including glutamate (Glu), γ-aminobutyric acid (GABA) and norepinephrine (NE), were monitored from the motor cortex (M1) and the 5th lobule of the cerebellar vermis (5Cb) during unconsciousness induced by sevoflurane and gaining consciousness after sevoflurane exposure. Cerebellar Purkinje cells were optogenetically manipulated to investigate their influence on consciousness transitions during and after sevoflurane exposure. Results: Activation of 5Cb Purkinje cells increased the Ca2+ flux in the M1 CaMKIIα+ neurons, but this increment was significantly reduced by inactivation of posterior and parafascicular thalamic nucleus. The 5Cb and M1 exhibited concerted calcium flux, and glutamate and GABA release during transitions from wakefulness, loss of consciousness, burst suppression to conscious recovery. Ca2+ flux and Glu release in the M1, but not in the 5Cb, showed a strong synchronization with the EEG burst suppression, particularly, in the gamma-band range. In contrast, the Glu, GABA and NE release and Ca2+ oscillations were coherent with the EEG gamma band activity only in the 5Cb during the pre-recovery of consciousness period. The optogenetic activation of Purkinje cells during burst suppression significantly facilitated emergence from anesthesia while the optogenetic inhibition prolonged the time to gaining consciousness. Conclusions: Our data indicate that cerebellar neuronal communication integrated with motor cortex through thalamus promotes consciousness recovery from anesthesia which may likely serve as arousal regulation.

Ligustrazine alleviates spinal cord injury-induced neuropathic pain by inhibiting the TLR4/NF-κB signaling pathway.

To investigate the effects of ligustrazine on neuropathic pain (NPP) in rats with sciatic nerve injury and to provide new scientific insight for broadening the clinical application of ligustrazine. Human spinal cord cell line STR cells were transfected with TLR4-mimic or mimic negative control (mimic-NC). After transfection, the STR cells were treated with different concentrations of ligustrazine (0, 0.25, 0.5, 1, 2 μm) for 24 h or 48 h. Cell proliferation was detected by MTT assay and colony formation assay. A rat model was further constructed to evaluate mechanical and cold pain sensitivity behaviors by fiber mechanical stimulation and freezing spray. The extracellular fluids of medial prefrontal cortex (mPFC) and central amygdala (CeA) were collected by intracranial dual-site simultaneous microdialysis. The contents of glutamic acid (Glu), aspartate (Asp), glycine (Gly), and γ-aminobutyric acid (GABA) in extracellular fluids were detected by HPLC. Compared to the 0 μm group, ligustrazine concentration at 0.5 μm significantly decreased the relative cell viability of STR cells and promoted the cell apoptosis rate. Ligustrazine at 0.25 μm significantly reduced the colony number of STR cells (all P<0.05). Compared to the control group, 1 μM ligustrazine significantly increased the protein expression of Bax and cleaved caspase 3 in STR cells but decreased the protein expression of Bcl-2 (all P<0.001). Compared to the control group, 2 μM ligustrazine treatments significantly reduced the protein levels of TLR4 and p-Akt in STR cells (all P<0.001). However, 2 μM ligustrazine treatments did not change the protein expression of Akt (P>0.05). Compared to the control group, the level of TLR4 in STR cells transfected with TLR4-mimic was significantly increased (P<0.001). Compared to the control group, transfection of TLR4-mimic reversed the anti-proliferative and pro-apoptotic effects of ligustrazine on STR cells (all P<0.001). The analgesic effect of Ligustrazine on neuropathic pain caused by spinal cord injury may be related to its inhibition of the release of excitatory amino acid transmitters Glu and Gly through the TLR4/NF-κB pathway, regulation of the dynamic balance of excitatory and inhibitory amino acid neurotransmitters, and alleviation of the central sensitization effect caused by the excitotoxicity of Glu.

NMDAR activation attenuates the protective effect of BM-MSCs on bleomycin-induced ALI via the COX-2/PGE2 pathway

N-methyl-d-aspartate (NMDA) receptor (NMDAR) activation mediates glutamate (Glu) toxicity and involves bleomycin (BLM)-induced acute lung injury (ALI). We have reported that bone marrow-derived mesenchymal stem cells (BM-MSCs) are NMDAR-regulated target cells, and NMDAR activation inhibits the protective effect of BM-MSCs on BLM-induced pulmonary fibrosis, but its effect on ALI remains unknown. Here, we found that Glu release was significantly elevated in plasma of mice at d 7 after intratracheally injected with BLM. BM-MSCs were pretreated with NMDA (the selective agonist of NMDAR) and transplanted into the recipient mice after the BLM challenge. BM-MSCs administration significantly alleviated the pathological changes, inflammatory response, myeloperoxidase activity, and malondialdehyde content in the damaged lungs, but NMDA-pretreated BM-MSCs did not ameliorate BLM-induced lung injury in vivo. Moreover, NMDA down-regulated prostaglandin E2 (PGE2) secretion and cyclooxygenase (COX)-2 expression instead of COX-1 expression in BM-MSCs in vitro. We also found that NMDAR1 expression was increased and COX-2 expression was decreased, but COX-1 expression was not changed in primary BM-MSCs of BLM-induced ALI mice. Further, the cultured supernatants of lipopolysaccharide (LPS)-pretreated RAW264.7 macrophages were collected to detect inflammatory factors after co-culture with NMDA-pretreated BM-MSCs. The co-culture experiments showed that NMDA precondition inhibited the anti-inflammatory effect of BM-MSCs on LPS-induced macrophage inflammation, and PGE2 could partially alleviate this inhibition. Our findings suggest that NMDAR activation attenuated the protective effect of BM-MSCs on BLM-induced ALI in vivo. NMDAR activation inhibited COX-2 expression and PGE2 secretion in BM-MSCs and weakened the anti-inflammatory effect of BM-MSCs on LPS-induced macrophage inflammation in vitro. In conclusion, NMDAR activation attenuates the protective effect of BM-MSCs on BLM-induced ALI via the COX-2/PGE2 pathway. Keywords: Acute Lung Injury, BM-MSCs, NMDA receptor, COX-1/2, PGE2.

Effects of Cyfluthrin Exposure on Neurobehaviour, Hippocampal Tissue and Synaptic Plasticity in Wistar Rats.

This experiment was conducted to study the effects of Cyfluthrin (Cy) exposure on neurobehaviour, hippocampal tissue and synaptic plasticity in Wistar rats. First, it was found that high-dose Cy exposure could cause nerve injury, resulting in symptoms such as deficits in learning and memory ability, spatial exploration and autonomic motor function. Moreover, it was found that medium- and high-dose Cy exposure could cause an abnormal release of the neurotransmitter Glu. Second, brain tissue pathology showed that the middle and high doses of Cy caused tissue deformation, reduced the number of hippocampal puramidal cells, caused a disorder of these cells, decreased the number of Nissl bodies, and caused pyknosis of the hippocampal cell nuclear membrane and serious damage to organelles, indicating that exposure to these doses of Cy may cause hippocampal tissue damage in rats. Third, as the exposure dose increased, morphological changes in hippocampal synapses, including blurred synaptic spaces, a decreased number of synaptic vesicles and a decreased number of synapses, became more obvious. Moreover, the expression levels of the key synaptic proteins PSD-95 and SYP also decreased in a dose-dependent manner, indicating obvious synaptic damage. Finally, the study found that medium and high doses of Cy could upregulate the expression of A2AR in the hippocampus and that the expression levels of inflammatory factors and apoptosis-related proteins increased in a dose-dependent manner. Moreover, the expression of A2AR mRNA was correlated with neurobehavioural indicators and the levels of inflammatory factors, synaptic plasticity-related factors and apoptosis-related factors, suggesting that Cy may cause nerve damage in rats and that this effect is closely related to A2AR.

Efficient preparation of oyster hydrolysate with aroma and umami coexistence derived from ultrasonic pretreatment assisted enzymatic hydrolysis

In the study, an efficient protease Neutrase®-Flavourzyme® (NF) was screened to prepare the umami-aroma flavor oyster hydrolysate. The effect of protease and ultrasonic pretreatment (UP) assisted by the optimal protease on the flavor substances was investigated. The results demonstrated that the optimal UP-NF (450 W) showed a higher amino acid nitrogen content of 0.34 g/100 mL compared to the NF, and 19 major aroma compounds including octanal, decanal, nonanal, benzaldehyde, 2-undecanone, and 1-octen-3-ol were obtained. Additionally, the free amino acid and fatty acid spectrum indicated that the formation of flavor compounds was primarily due to the oxidation of linoleic and linolenic acids and the degradation of amino acids. Furthermore, taste analysis proved that increased umami and saltiness resulted from the accelerated release of Glu, Asp and 5′-IMP. Overall, UP-NF proved to be an effective method for producing umami-aroma flavor, facilitating further processing of oyster products for the application.

Blue and green light responsive caged glutamate

Glutamate (Glu) is an excitatory neurotransmitter that plays a critical role in memory. Brain mapping activities of such pathways relied heavily on the ability to release Glu with spatiotemporal precision. Several photo-protecting groups (PPGs), referred to as photocages or cages, were designed to accomplish the release of Glu upon irradiation. Previously reported Glu cages responded to UV upon irradiation with single photons, which limited their use in vivo experiments due to cytotoxicity. Other caged designs suffered from lower quantum efficiency (QE) of release necessitating higher concentrations and/or longer photoirradiation times. There have been limited examples of cages that respond to visible light with single photon irradiation. Herein, we report the efficient preparation of 11 caged Glu examples that respond to two visible wavelengths, 467 nm (thiocoumarin based) and 515–540 nm (BODIPY based). The kinetics of photo-uncaging were studied for all caged designs, and we report all quantum efficiencies, i.e., quantum yields (Φ), that ranged from 0.0001 to 0.65. Two of the BODIPY cages are reported here for the first time, and one, Me-BODIPY-Br-Glu, shows the most efficient Glu release with a QE of 0.65. Similar caged designs can be extended to the inhibitory neurotransmitter, GABA. This would enable the use of two visible wavelengths to modulate the release of excitatory and inhibitory neurotransmitters upon demand via optical control.

Perinatal blockade of neuronal glutamine transport sex-differentially alters glutamatergic synaptic transmission and organization of neurons in the ventrolateral ventral media hypothalamus of adult rats.

Compared to male pups, perinatal female rats rely heavily on neuronal glutamine (Gln) transport for sustaining glutamatergic synaptic release in neurons of the ventrolateral ventral media nucleus of the hypothalamus (vlVMH). VMH mainly regulates female sexual behavior and increases glutamate release of perinatal hypothalamic neurons, permanently enhances dendrite spine numbers and is associated with brain and behavioral defeminization. We hypothesized that perinatal interruption of neuronal Gln transport may alter the glutamatergic synaptic transmission during adulthood. Perinatal rats of both sexes received an intracerebroventricular injection of a neuronal Gln uptake blocker, alpha-(methylamino) isobutyric acid (MeAIB, 5 mM), and were raised until adulthood. Whole-cell voltage-clamp recordings of miniature excitatory postsynaptic currents (mEPSCs) and evoked EPSCs (eEPSCs) of vlVMH neurons in adult rats with the perinatal pretreatment were conducted and neuron morphology was subjected to post hoc examination. Perinatal MeAIB treatment sex-differentially increased mEPSC frequency in males, but decreased mEPSC amplitude and synaptic Glu release in females. The pretreatment sex-differentially decreased eEPSC amplitude in males but increased AMPA/NMDA current ratio in females, and changed the morphology of vlVMH neurons of adult rats to that of the opposite sex. Most alterations in the glutamatergic synaptic transmission resembled the changes occurring during MeAIB acute exposure in perinatal rats of both sexes. We conclude that perinatal blockade of neuronal Gln transport mediates changes via different presynaptic and postsynaptic mechanisms to induce sex-differential alterations of the glutamatergic synaptic transmission and organization of vlVMH neurons in adult rats. These changes may be permanent and associated with brain and behavior feminization and/or defeminization in rats.

Inhibition of Vesicular Glutamate Transporters (VGLUTs) with Chicago Sky Blue 6B Before Focal Cerebral Ischemia Offers Neuroprotection

Brain ischemia is one of the leading causes of death and long-term disability in the world. Interruption of the blood supply to the brain is a direct stimulus for many pathological events. The massive vesicular release of glutamate (Glu) after ischemia onset induces excitotoxicity, which is a potent stress on neurons. Loading of presynaptic vesicles with Glu is the first step of glutamatergic neurotransmission. Vesicular glutamate transporters 1, 2, and 3 (VGLUT1, 2, and 3) are the main players involved in filling presynaptic vesicles with Glu. VGLUT1 and VGLUT2 are expressed mainly in glutamatergic neurons. Therefore, the possibility of pharmacological modulation to prevent ischemia-related brain damage is attractive. In this study, we aimed to determine the effect of focal cerebral ischemia on the spatiotemporal expression of VGLUT1 and VGLUT2 in rats. Next, we investigated the influence of VGLUT inhibition with Chicago Sky Blue 6B (CSB6B) on Glu release and stroke outcome. The effect of CSB6B pretreatment on infarct volume and neurological deficit was compared with a reference model of ischemic preconditioning. The results of this study indicate that ischemia upregulated the expression of VGLUT1 in the cerebral cortex and in the dorsal striatum 3 days after ischemia onset. The expression of VGLUT2 was elevated in the dorsal striatum and in the cerebral cortex 24 h and 3 days after ischemia, respectively. Microdialysis revealed that pretreatment with CSB6B significantly reduced the extracellular Glu concentration. Altogether, this study shows that inhibition of VGLUTs might be a promising therapeutic strategy for the future.

Ca2+-regulated expression of high affinity methylaminoisobutryic acid transport in hippocampal neurons inhibited by riluzole and novel neuroprotective aminothiazoles

High affinity methylaminoisobutyric acid(MeAIB)/glutamine(Gln) transport activity regulated by neuronal firing occurs at the plasma membrane in mature rat hippocampal neuron-enriched cultures. Spontaneous Ca2+-regulated transport activity was similarly inhibited by riluzole, a benzothiazole anticonvulsant agent, and by novel naphthalenyl substituted aminothiazole derivatives such as SKA-378. Here, we report that spontaneous transport activity is stimulated by 4-aminopyridine (4-AP) and that phorbol-myristate acetate (PMA) increases high K+ stimulated transport activity that is inhibited by staurosporine. 4-AP-stimulated spontaneous and PMA-stimulated high K+-induced transport is not present at 7 days in vitro (DIV) and is maximal by DIV∼21. The relative affinity for MeAIB is similar for spontaneous and high K+-stimulated transport (Km ∼ 50 μM) suggesting that a single transporter is involved. While riluzole and SKA-378 inhibit spontaneous transport with equal potency (IC50 ∼ 1 μM), they exhibit decreased (∼3-5 X) potency for 4-AP-stimulated spontaneous transport. Interestingly, high K+-stimulated MeAIB transport displays lower and differential sensitivity to the two compounds. SKA-378-related halogenated derivatives of SKA-75 (SKA-219, SKA-377 and SKA-375) preferentially inhibit high K+-induced expression of MeAIB transport activity at the plasma membrane (IC50 < 25 μM), compared to SKA-75 and riluzole (IC50 > 100 μM). Ca2+-dependent spontaneous and high K+-stimulated MeAIB transport activity is blocked by ω-conotoxin MVIIC, ω-agatoxin IVA, ω-agatoxin TK (IC50 ∼ 500 nM) or cadmium ion (IC50 ∼ 20 μM) demonstrating that P/Q-type CaV channels that are required for activity-regulated presynaptic vesicular glutamate (Glu) release are also required for high-affinity MeAIB transport expression at the plasma membrane. We suggest that neural activity driven and Ca2+ dependent trafficking of the high affinity MeAIB transporter to the plasma membrane is a unique target to understand mechanisms of Glu/Gln recycling in synapses and acute neuroprotection against excitotoxic presynaptic Glu induced neural injury.

Depression of synaptic NMDA responses by xenon and nitrous oxide.

In "synapse bouton preparation" of rat hippocampal CA3 neurons, we examined how Xe and N2O modulate N-methyl-D-aspartate (NMDA) receptor-mediated spontaneous and evoked excitatory post-synaptic currents (sEPSCNMDA and eEPSCNMDA) excluded extrasynaptic, glial and other neuronal tonic currents. This preparation is a mechanically isolated single neuron attached with nerve endings (boutons) preserving normal physiological function and promotes the exact evaluation of sEPSCNMDA and eEPSCNMDA These sEPSC and eEPSC are elicited by spontaneous glutamate (Glu) release from many homologous glutamatergic boutons and by focal paired-pulse electric stimulation of a single bouton, respectively. The s/eEPSCAMPA/KA and s/eEPSCNMDA were isolated pharmacologically by their specific antagonists. Thus, independent contributions of pre- and postsynaptic responses be could also quantified. All kinetic properties of s/eEPSCAMPA/KA and s/eEPSCNMDA were detected clearly. The s/eEPSCNMDA showed smaller amplitude, slower rise and 1/e decay time constant (τDecay) than s/eEPSCAMPA/KA Xe (70%) and N2O (70%) significantly decreased the frequency and amplitude without altering the τDecay of sEPSCNMDA They also decreased the amplitude but increased the Rf and PPR without altering the τDecay of the eEPSCNMDA These data show clearly that "synapse bouton preparation" can be an accurate model for evaluating s/eEPSCNMDA Such inhibitory effects of gas anesthetics are primarily due to presynaptic mechanisms. Present results may explain partially the powerful analgesic effects of Xe and N2O. Significance Statement We could record pharmacologically isolated sEPSCNMDA and eEPSCNMDA and clearly detect all kinetic parameters of sEPSCNMDA and eEPSCNMDA at synaptic levels by using "synapse bouton preparation" of rat hippocampal CA3 neurons. We found that Xe and N2O clearly suppressed both sEPSCNMDA and eEPSCNMDA Different from previous studies, present results suggest that Xe and N2O predominantly inhibit the NMDA responses by presynaptic mechanisms.

Evaluation of Prefrontal γ-Aminobutyric Acid and Glutamate Levels in Individuals With Major Depressive Disorder Using Proton Magnetic Resonance Spectroscopy

Major depressive disorder (MDD) is one of the most prevalent illnesses worldwide. Perturbations of the major inhibitory and excitatory neurotransmitters, γ-aminobutyric acid (GABA) and glutamate (Glu), respectively, as well as Glx (Glu or glutamine [Gln]) have been extensively reported in a multitude of brain areas of individuals with depression, but few studies have examined changes in Gln, the metabolic counterpart of synaptic Glu. To investigate changes in GABA, Glx, Glu, and Gln levels in a voxel in the left dorsolateral prefrontal cortex of participants with no, past, and current MDD using proton magnetic resonance spectroscopy (1H-MRS). This community-based study used a cross-sectional design using 3-T 1H-MRS in participants not taking MDD medication recruited from the community. The sample consisted of 251 healthy controls, 98 participants with a history of past MDD, and 47 participants who met the diagnostic criteria for current MDD. Diagnostic groups were comparable regarding age, education, income, and diet. Data were collected from March 2014 to October 2021, and data were analyzed from October 2021 to June 2022. GABA, Glx, Glu, and Gln concentrations in the left dorsolateral prefrontal cortex. Of 396 included participants, 258 (65.2%) were female, and the mean (SD) age was 25.0 (4.7) years. Compared with healthy controls, those with past MDD and current MDD had lower GABA concentrations (mean [SEM] concentration: healthy controls, 2.70 [0.03] mmol/L; past MDD, 2.49 [0.05] mmol/L; current MDD, 2.54 [0.07] mmol/L; 92 with past MDD vs 236 healthy controls: r = 0.18; P = .002; 44 with current MDD vs 236 healthy controls: r = 0.13; P = .04). Compared with healthy controls, those with past MDD also had lower Glu concentrations (mean [SEM] concentration: healthy controls, 7.52 [0.06] mmol/L; past MDD, 7.23 [0.11] mmol/L; 93 with past MDD vs 234 healthy controls: r = 0.16; P = .01) and higher Gln concentrations (mean [SEM] concentration: healthy controls, 1.63 [0.04] mmol/L; past MDD, 1.84 [0.07] mmol/L; 66 with past MDD 153 healthy controls: r = 0.17; P = .04). In a large, mostly medication-free community sample, reduced prefrontal GABA concentrations were associated with past MDD, consistent with histopathologic studies reporting reduced glial cell and GABA cell density in the prefrontal cortex in individuals with depression. Patients with MDD also demonstrated increased Gln levels, indicative of increased synaptic Glu release, adding to previous evidence for the Glu hypothesis of MDD.

New insight into the effect of riluzole on cadmium tolerance and accumulation in duckweed (Lemna turionifera)

Cadmium (Cd) damages plant photosynthesis, affects roots and leaves growth, and triggers molecular responses. Riluzole (RIL), which protected neuronal damage via inhibiting excess Glu release in animals, has been found to improve Cd tolerance in duckweed in this study. Firstly, RIL treatment alleviated leaf chlorosis by protecting chlorophyll and decreased root abscission under Cd stress. Secondly, RIL declines Cd accumulation by alleviating excess Glu release during Cd shock. RIL mitigate Glu outburst in duckweed during Cd stress by a decline in Glu in roots. The Cd2+ influx was repressed by RIL addition with Cd shock. Finally, differentially expressed genes (DEGs) of duckweed under Cd stress with RIL have been investigated. 2141 genes were substantially up-regulated and 3282 genes were substantially down-regulated with RIL addition. RIL down-regulates the genes related to the Glu synthesis, and genes related to DNA repair have been up-regulated with RIL treatment under Cd stress. These results provide new insights into the possibility of RIL to reduce Cd accumulation and increase Cd tolerance in duckweed, and lay the foundation for decreasing Cd accumulation in crops.

Surface Treatment With Hydrophobic Coating Reagents (Organosilanes) Strongly Reduces the Bioactivity of Synthetic Amorphous Silica in vitro.

Synthetic amorphous silica (SAS) is industrially relevant material whose bioactivity in vitro is strongly diminished, for example, by protein binding to the particle surface. Here, we investigated the in vitro bioactivity of fourteen SAS (pyrogenic, precipitated, or colloidal), nine of which were surface-treated with organosilanes, using alveolar macrophages as a highly sensitive test system. Dispersion of the hydrophobic SAS required pre-wetting with ethanol and extensive ultrasonic treatment in the presence of 0.05% BSA (Protocol 1). Hydrophilic SAS was suspended by moderate ultrasonic treatment (Protocol 2) and also by Protocol 1. The suspensions were administered to NR8383 alveolar macrophages under serum-free conditions for 16 h, and the release of LDH, GLU, H2O2, and TNFα was measured in cell culture supernatants. While seven surface-treated hydrophobic SAS exhibited virtually no bioactivity, two materials (AEROSIL® R 504 and AEROSIL® R 816) had minimal effects on NR8383 cells. In contrast, non-treated SAS elicited considerable increases in LDH, GLU, and TNFα, while the release of H2O2 was low except for CAB-O-SIL® S17D Fumed Silica. Dispersing hydrophilic SAS with Protocol 1 gradually reduced the bioactivity but did not abolish it. The results show that hydrophobic coating reagents, which bind covalently to the SAS surface, abrogate the bioactivity of SAS even under serum-free in vitro conditions. The results may have implications for the hazard assessment of hydrophobic surface-treated SAS in the lung.

Pharmacodynamics assessment of β-carboline from the roots of Psammosilene tunicoides as analgesic compound

Ethnopharmacological relevanceThe root of Psammosilene tunicoides (W. C. Wu et C. Y. Wu) is a well-known medicinal herb for the treatment of pain, hemostasia and rheumatoid arthritis among Chinese people. Aim of the studyThe present study aimed to investigate the antinociceptive activity and mechanism of β-carboline alkaloids 1–4 which were extracted from the roots of P. tunicoides. Materials and methodsThe analgesic effects were evaluated using peripheral and central pain mouse models of nociception, including the formalin test and the tail flick test. The levels of glutamic acid (Glu) and nitric oxide (NO) in cerebellar cortexes and spinal cords (L4-6) were determined. The anti-inflammatory of all compounds were then assessed on RAW264.7 cells. ResultsOur results showed that compounds 1–4 had significant analgesic effects on both phases of formalin test of mice. Furthermore, all compounds showed suppressive effects on Glu in the brain and NO levels in the brain cortex and the spinal cord. Except for compound 1, the others could extend the pain threshold of hot water tail-flick in mice. In addition, compounds 2 and 3 (60 μmol/kg) could decrease GABAAα1 protein levels in spinal cord. All compounds exhibited anti-inflammatory effects by inhibiting lipopolysaccharide (LPS)-induced NO production in RAW264.7 cells with half-maximal inhibitory concentration (IC50) 1.1–34.9 μM. Conclusionβ-carboline alkaloids from the roots of P. tunicoides had significant analgesic activity by both central and peripheral mechanisms. Our findings suggested that regulating the release of NO or Glu or GABAα1 are some of the mechanisms of analgesic activity of β-carboline alkaloids.

Upregulation of Striatal Metabotropic Glutamate Receptor Subtype 1 (mGluR1) in Rats with Excessive Glutamate Release Induced by N-Acetylcysteine.

The aim of this study is to investigate the changes in expression of metabotropic glutamate (Glu) receptor subtype 1 (mGluR1), a key molecule involved in neuroexcitetoxicity, during excessive Glu release in the brain by PET imaging. An animal model of excessive Glu release in the brain was produced by intraperitoneally implanting an Alzet osmotic pump containing N-acetylcysteine (NAC), an activator of the cysteine/Glu antiporter, into the abdomen of rats. Basal Glu concentration in the brain was measured by microdialysis, which showed that basal Glu concentration in NAC-treated rats (0.31µM) was higher than that in saline-treated rats (0.17µM) at day 7 after the implantation of the osmotic pump. Similarly, PET studies with [11C]ITDM, a useful radioligand for mGluR1 imaging exhibited that the striatal binding potential (BPND) of [11C]ITDM for mGluR1 in PET assessments was increased in NAC-treated animals at day 7 after implantation (2.30) compared with before implantation (1.92). The dynamic changes in striatal BPND during the experimental period were highly correlated with basal Glu concentration. In conclusion, density of mGluR1 is rapidly upregulated by increases in basal Glu concentration, suggesting that mGluR1 might to be a potential biomarker of abnormal conditions in the brain.

Mechanisms of Electroacupuncture Pretreatment in Alleviating Myocardial Ischemia Reperfusion Injury: Interactions between the Cerebellar Fastigial Nucleus and Lateral Hypothalamic Area.

Myocardial ischemia reperfusion injury (MIRI) is an important mechanism of post-myocardial infarction injury and a main cause of death in patients with ischemic heart disease. Electroacupuncture (EA) pretreatment is effective for the prevention and treatment of MIRI, but mechanisms mediating the effects of cardiovascular disease EA treatments remain unclear. To determine whether the lateral hypothalamus (LHA) and the cerebellar fastigial nucleus (FN) are involved in the protective effects of EA stimulation on MIRI. EA pretreatment was performed for 7 days before the establishment of the MIRI model. ST-segment changes on electrocardiograms were recorded and the Curtis-Walker arrhythmia score was used to evaluate changes in reperfusion injury. Hematoxylin-eosin staining was applied to evaluate the pathological and morphological changes in myocardial tissue. c-fos expression in the LHA and FN was determined by immunofluorescence staining. Glutamic (Glu) and γ-Aminobutyric acid (GABA) levels were measured using a high-performance liquid chromatography-electrochemical method. EA pretreatment reduced ST-segment elevation, arrhythmia scores, and morphological changes in MIRI myocardial cells in rats, and decreased the c-fos protein expression in LHA/FN nuclei. MIRI was associated with an imbalance between GABA and Glu levels, whereas EA pretreatment increased GABA levels and decreased Glu levels in the LHA/FN. FN and LHA are involved in the EA-mediated attenuation of MIRI. Pretreatment with EA plays a protective role in the myocardium by regulating Glu and GABA release in the LHA and FN.

Opioid receptors modulate parallel fiber-Purkinje cell synaptic transmission in mouse cerebellum

Opioid receptors play important roles in, among others, learning and memory, emotional responses, addiction, and pain. In recent years, the cerebellum has received increasing attention for its role in non-motor functions. The Purkinje cell (PC) is the only efferent neuron in the cerebellar cortex, and receives glutamatergic synaptic inputs from the parallel fibers (PF) formed by the axons of granule cells. Studies have shown that opioid receptors are expressed during the development of cerebellar cells. However, the distribution of opioid receptors, their subtypes in cerebellar PF-PC synapses, and their effects on synaptic transmission remain unclear. To examine these questions, we used whole-cell patch clamp recordings and pharmacological methods to determine the effects of activating three different opioid receptor subtypes on synaptic transmission at PF-PC synapses. In the presence of picrotoxin, mouse cerebellar slices were perfused with agonists or blockers of different opioid receptor subtypes, and the changes in excitatory postsynaptic currents (EPSCs) were examined. Both agonists of µ-opioid receptors (MOR) and δ-opioid receptors (DOR) significantly reduced the amplitude and area under the curve of PF-PC EPSCs in a concentration-dependent manner, accompanied by an increase in the paired-pulsed ratio (PPR). These effects could be blocked by respective receptor antagonists. In contrast, no significant changes were found after the application of κ-opioid receptor (KOR) agonists. In conclusion, MOR and DOR are present at the axon terminals of PF in the mouse cerebellar cortex, whereas no or negligible amounts of KOR are found. Activation of MOR and DOR regulates PF-PC synaptic transmission via inhibition of glutamate (Glu) release in cerebellar cortex in mice. We also found that endogenous opioid peptides are present in PF-PC synapses of mouse cerebellum, which also can inhibit the release of Glu.