Inhibition Of NMDA Receptors Research Articles

Ketamine inhibits LPS-mediated BV2 microglial inflammation via NMDA receptor blockage.

Microglial inflammation leads to the upregulation of proinflammatory cytokine and proinflammatory enzyme expression, resulting in inflammation-induced neuronal cell apoptosis. Ketamine, an anesthetic mostly used in critical patients, has been reported to possess neuroprotective effects. However, the potential mechanism is still not well understood. In the present study, we investigated how ketamine attenuates lipopolysaccharide (LPS)-mediated BV2 cell inflammation. LPS upregulated proinflammatory cytokine and proinflammatory enzyme expression, increased NF-κB phosphorylation and nuclear translocation, and augmented calcium (Ca2+ )/calmodulin-dependent protein kinase II (CaMK II) phosphorylation and Ca2+ levels in BV2 cells. Ketamine could reverse these LPS-induced effects. Furthermore, AP5, an inhibitor of NMDA receptors, inhibited LPS-induced inflammatory effects in BV2 cells, which was similar to the effects of ketamine. Moreover, these effects of ketamine against LPS-mediated inflammation in BV2 cells could be reversed by D-serine, an activator of NMDA receptors. The present study suggests that ketamine, by inhibiting NMDA receptors, attenuating Ca2+ levels, and inhibiting CaMK II phosphorylation, NF-κB phosphorylation and nuclear translocation, may ameliorate LPS-mediated inflammation in BV2 cells.

Propofol attenuates the adhesion of tumor and endothelial cells through inhibiting glycolysis in human umbilical vein endothelial cells.

Propofol is one of the most commonly used intravenous anesthetics and plays an important role in tumor suppression. In the present study, we aimed to investigate the mechanism by which propofol attenuates tumor endothelial cells (TECs) and tumor cell adhesion to inhibit tumor metastasis in vitro. Human umbilical vein endothelial cells (HUVECs) cultured in Dulbecco's modified Eagle's medium were treated with tumor conditioned medium for 24 h, followed by 4 h of treatment with or without 25 μM of propofol, 10 μM of KN93, 500 μM of MK801, or 20 μM of rapastinel. It was found that propofol inhibited TEC adhesion and the glycolysis level of TECs. Consistently, propofol inhibited the expressions of adhesion molecules (E-selectin, ICAM-1, and VCAM-1) and glycolysis proteins (GLUT1, HK2, and LDHA) in TECs. Moreover, propofol attenuated the expression of HIF-1α, the phosphorylation of AKT and Ca2+/calmodulin-dependent protein kinase II (CaMKII), and the Ca2+ concentration in TECs. MK801, an inhibitor of NMDA receptor, and KN93, an inhibitor of CaMKII, both inhibited the expressions of adhesion molecules and glycolysis proteins, in a manner similar to propofol. Additionally, rapastine, an activator of NMDA receptor, could counteract the effects of propofol. Our results indicated that propofol attenuates intracellular Ca2+ concentration, CaMKII and AKT phosphorylation, and HIF-1α expression, probably via inhibiting the NMDA receptor, thus inhibiting glycolysis and adhesion of tumor and endothelial cells.

S92EXOME VARIATION IN ETHANOL METABOLIZING ENZYME GENES IN IRISH SEVERE ALCOHOL DEPENDENCE (AD) CASES

Lamotrigine is an anticonvulsant agent that shows clinical antidepressant properties. The aim of the present study was to investigate the involvement of N-methyl-d-aspartate (NMDA) receptors and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) synthesis in possible antidepressant-like effect of lamotrigine in forced swimming test (FST) in mice. Intraperitoneal administration of lamotrigine (10 mg/kg) decreased the immobility time in the FST (P < 0.01) without any effect on locomotor activity in the open-field test (OFT), while higher dose of lamotrigine (30 mg/kg) reduced the immobility time in the FST (P < 0.001) as well as the number of crossings in the OFT. Pretreatment of animals with NMDA (75 mg/kg), l-arginine (750 mg/kg, a substrate for nitric oxide synthase [NOS]) or sildenafil (5 mg/kg, a phosphodiesterase [PDE] 5 inhibitor) reversed the antidepressant-like effect of lamotrigine (10 mg/kg) in the FST. Injection of l-nitroarginine methyl ester (l-NAME, 10 mg/kg, a non-specific NOS inhibitor), 7-nitroindazole (30 mg/kg, a neuronal NOS inhibitor), methylene blue (20 mg/kg, an inhibitor of both NOS and soluble guanylate cyclase [sGC]), or MK-801 (0.05 mg/kg), ketamine (1 mg/kg), and magnesium sulfate (10 mg/kg) as NMDA receptor antagonists in combination with a sub-effective dose of lamotrigine (5 mg/kg) diminished the immobility time of animals in the FST compared with either drug alone. None of the drugs produced significant effects on the locomotor activity in the OFT. Based on our findings, it is suggested that the antidepressant-like effect of lamotrigine might mediated through inhibition of either NMDA receptors or NO-cGMP synthesis.

Lurasidone inhibits NMDA receptor antagonist-induced functional abnormality of thalamocortical glutamatergic transmission via 5-HT7 receptor blockade.

Lurasidone is an atypical mood-stabilizing antipsychotic with a unique receptor-binding profile, including 5-HT7 receptor antagonism; however, the detailed effects of 5-HT7 receptor antagonism on various transmitter systems relevant to schizophrenia, particularly the thalamo-insular glutamatergic system and the underlying mechanisms, are yet to be clarified. We examined the mechanisms underlying the clinical effects of lurasidone by measuring the release of l-glutamate, GABA, dopamine, and noradrenaline in the reticular thalamic nucleus (RTN), mediodorsal thalamic nucleus (MDTN) and insula of freely moving rats in response to systemic injection or local infusion of lurasidone or MK-801 using multiprobe microdialysis with ultra-HPLC. Systemic MK-801 (0.5mg·kg-1 ) administration increased insular release of l-glutamate, dopamine, and noradrenaline but decreased GABA release. Systemic lurasidone (1mg·kg-1 ) administration also increased insular release of l-glutamate, dopamine, and noradrenaline but without affecting GABA. Local lurasidone administration into the insula (3μM) did not affect MK-801-induced insular release of l-glutamate or catecholamine, whereas local lurasidone administration into the MDTN (1μM) inhibited MK-801-induced insular release of l-glutamate and catecholamine, similar to the 5-HT7 receptor antagonist SB269970. The present results indicate that MK-801-induced insular l-glutamate release is generated by activation of thalamo-insular glutamatergic transmission via MDTN GABAergic disinhibition resulting from NMDA receptor inhibition in the MDTN and RTN. Lurasidone inhibited this MK-801-evoked insular l-glutamate release through inhibition of excitatory 5-HT7 receptor in the MDTN. These effects on thalamo-insular glutamatergic transmission may contribute to the antipsychotic and mood-stabilizing actions of lurasidone.

Temporal Sequences of Synapse Disintegration Triggered by Afferent Axon Transection, Time-Lapse Imaging Study of Presynaptic and Postsynaptic Molecules

Traumatic brain injury (TBI) is one of the major causes of death and disability. Multiple animal models have been developed to explore therapeutic targets for TBI. However, heterogeneity of pathophysiology obstructs discovery of therapeutic targets. To facilitate understanding of TBI pathophysiology, each element of neuronal and glial responses should be studied separately. We focused on synapse remodeling which plays an important role in recovery from TBI and developed a new method, afferent elimination, for analyzing synapse remodeling after selective damage to presynaptic axons by mechanical transection in culture of mouse hippocampal neurons. Afferent elimination can induce various events related to synapse remodeling and we could determine their temporal orders and find relationships between them. Specifically, loss of presynaptic sites preceded loss of postsynaptic sites and spines. Some of the postsynaptic sites initially located inside spines showed translocation toward dendritic shafts. These translocation events started after the loss of contacting presynaptic sites. Also, these events could be blocked or delayed by NMDA receptor inhibition. Taken together, these findings suggest that postsynaptic changes occur in afferent elimination are NMDA dependent and imply that these NMDA-dependent events underlie synaptic remodeling of TBI.

Endoplasmic reticulum stress contributes to NMDA-induced pancreatic β-cell dysfunction in a CHOP-dependent manner

AimsAccumulating evidence suggest that endoplasmic reticulum (ER) stress is an important mechanism underlying the development of diabetes. We have reported that sustained treatment with N-methyl-d-aspartate (NMDA) results in apoptotic β-cell death and impairs insulin secretion. However, the molecular mechanism responsible for NMDA-induced β-cell dysfunction remains largely obscure. Thus, this study aimed to determine whether sustained activation of NMDA receptors (NMDARs) causes β-cell dysfunction through ER stress. Main methodsPrimary mouse islets and MIN6 mouse pancreatic β-cells were treated with NMDA for 24 h or high-glucose for 72 h. After the treatment, glucose-stimulated insulin secretion (GSIS) and the expression of ER stress markers were measured, respectively. In vivo, the expression of ER stress markers was measured in the pancreas of diabetic mice treated with or without NMDARs inhibitor Memantine. Key findingsNMDA treatment caused an increase in the expression of ER stress markers (ATF4, CHOP, GRP78, and Xbp1s) in primary islets. While, tauroursodeoxycholic acid (TUDCA), an inhibitor of ER stress, significantly attenuated NMDA-induced β-cell dysfunction, including the loss of glucose-stimulated insulin secretion and reduction of pancreas duodenum homeobox factor-1 (Pdx-1) mRNA expression, a transcription factor regulating insulin synthesis. Besides, NMDA-induced ER stress strongly promoted pro-inflammatory cytokines synthesis (IL-1β and TNF-α) in β cells. Interestingly, knockdown of CHOP attenuated β-cell dysfunction evoked by NMDA. Furthermore, we demonstrated that blockade of NMDARs ameliorated high-glucose-induced ER stress in vitro and in vivo. SignificanceThis study confirms that ER stress is actively involved in the activation of NMDARs-related β-cell dysfunction.

NMDA receptor and nitric oxide synthase activity in the central amygdala is involved in the acquisition and consolidation of conditioned odor aversion

Rats readily learn to avoid a tasteless odorized solution if they experience visceral malaise after consuming it. This phenomenon is referred to as conditioned odor aversion (COA). Several studies have shown that COA depends on the functional integrity of the amygdala, with most studies focusing on the basolateral nucleus. On the other hand, the role of the central amygdala (CeA) which is known to be involved in the consolidation of conditioned taste aversion (CTA) remains to be established. To address this issue, we evaluated the effect of inhibiting NMDA receptor activity in this structure on COA memory formation. Intra-CeA infusions of non-competitive NMDA receptor inhibitor MK-801 prevented memory formation both when administered before and up to 15 min after COA conditioning, while no effect of this drug was observed when given before long-term memory test. We next evaluated the role of one of the main downstream effectors of brain NMDA receptor signaling, nitric oxide synthase (NOS), known to play a key role in a wide variety learning tasks including some types of olfactory conditioning. Similar results were obtained with inhibition of either NOS or neuron-specific NOS; which proved to be required both during and after COA training, though for a shorter time span than NMDA receptors. Also, neither isoform showed to be required to memory retrieval. These results suggest that the US signaling during acquisition and the initial consolidation step of COA depends on glutamate-NO system activation in the CeA.

Modulation of Burst Firing of Neurons in Nucleus Reticularis of the Thalamus by GluN2C-Containing NMDA Receptors

The GluN2C subunit of the NMDA receptor is enriched in the neurons in nucleus reticularis of the thalamus (nRT), but its role in regulating their function is not well understood. We found that deletion of GluN2C subunit did not affect spike frequency in response to depolarizing current injection or hyperpolarization-induced rebound burst firing of nRT neurons. D-cycloserine or CIQ (GluN2C/GluN2D positive allosteric modulator) did not affect the depolarization-induced spike frequency in nRT neurons. A newly identified highly potent and efficacious co-agonist of GluN1/GluN2C NMDA receptors, AICP, was found to reduce the spike frequency and burst firing of nRT neurons in wildtype but not GluN2C knockout. This effect was potentially due to facilitation of GluN2C-containing receptors because inhibition of NMDA receptors by AP5 did not affect spike frequency in nRT neurons. We evaluated the effect of intracerebroventricular injection of AICP. AICP did not affect basal locomotion or prepulse inhibition but facilitated MK-801-induced hyperlocomotion. This effect was observed in wildtype but not in GluN2C knockout mice demonstrating that AICP produces GluN2C-selective effects in vivo Using a chemogenetic approach we examined the role of nRT in this behavioral effect. Gq or Gi coupled DREADDs were selectively expressed in nRT neurons using cre-dependent viral vectors and PV-Cre mouse line. We found that similar to AICP effect, activation of Gq but not Gi coupled DREADD facilitated MK-801-induced hyperlocomotion. Together, these results identify a unique role of GluN2C-containing receptors in the regulation of nRT neurons and suggest GluN2C-selective in vivo targeting of NMDA receptors by AICP. SIGNIFICANCE STATEMENT: The nucleus reticularis of the thalamus composed of GABAergic neurons is termed as guardian of the gateway and is an important regulator of corticothalamic communication which may be impaired in autism, non-convulsive seizures and other conditions. We found that strong facilitation of tonic activity of GluN2C subtype of NMDA receptors using AICP, a newly identified glycine-site agonist of NMDA receptors, modulates the function of reticular thalamus neurons. AICP was also able to produce GluN2C-dependent behavioral effects <I>in vivo</I>. Together, these finding identify a novel mechanism and a pharmacological tool to modulate activity of reticular thalamic neurons in disease states.

(R)-Ketamine exerts antidepressant actions partly via conversion to (2R,6R)-hydroxynorketamine, while causing adverse effects at sub-anaesthetic doses.

(R)-Ketamine (arketamine) may have utility as a rapidly acting antidepressant. While (R)-ketamine has lower potency than (R,S)-ketamine to inhibit NMDA receptors in vitro, the extent to which (R)-ketamine shares the NMDA receptor-mediated adverse effects of (R,S)-ketamine in vivo has not been fully characterised. Furthermore, (R)-ketamine is metabolised to (2R,6R)-hydroxynorketamine (HNK), which may contribute to its antidepressant-relevant actions. Using mice, we compared (R)-ketamine with a deuterated form of the drug (6,6-dideutero-(R)-ketamine, (R)-d2 -ketamine), which hinders its metabolism to (2R,6R)-HNK, in behavioural tests predicting antidepressant responses. We also examined the actions of intracerebroventricularly infused (2R,6R)-HNK. Further, we quantified putative NMDA receptor inhibition-mediated adverse effects of (R)-ketamine. (R)-d2 -Ketamine was identical to (R)-ketamine in binding to and functionally inhibiting NMDA receptors but hindered (R)-ketamine's metabolism to (2R,6R)-HNK. (R)-Ketamine exerted greater potency than (R)-d2 -ketamine in several antidepressant-sensitive behavioural measures, consistent with a role of (2R,6R)-HNK in the actions of (R)-ketamine. There were dose-dependent sustained antidepressant-relevant actions of (2R,6R)-HNK following intracerebroventricular administration. (R)-Ketamine exerted NMDA receptor inhibition-mediated behaviours similar to (R,S)-ketamine, including locomotor stimulation, conditioned-place preference, prepulse inhibition deficits, and motor incoordination, with approximately half the potency of the racemic drug. Metabolism of (R)-ketamine to (2R,6R)-HNK increases the potency of (R)-ketamine to exert antidepressant-relevant actions in mice. Adverse effects of (R)-ketamine require higher doses than those necessary for antidepressant-sensitive behavioural changes in mice. However, our data revealing that (R)-ketamine's adverse effects are elicited at sub-anaesthetic doses indicate a potential risk for sensory dissociation and abuse liability.

Assessment of NMDA receptor inhibition of phencyclidine analogues using a high-throughput drebrin immunocytochemical assay

IntroductionIn recent years, new psychoactive substances (NPS) have been widely distributed for abuse purposes. Effective measures to counter the spread of NPS are to promptly legislate them through the risk assessment. Phencyclidine analogues having inhibitory effects toward NMDA receptor (NMDAR) have recently emerged in Japan. Therefore, it is important to establish a high-throughput system for efficiently detecting NPS that can inhibit NMDAR activity. MethodsHippocampal neurons prepared from embryonic rats were incubated in 96-well microplates. After 3 weeks in vitro, cultured neurons were preincubated with phencyclidine (PCP) or PCP-analogues, including 3-methoxyphencyclidine (3-MeO-PCP) and 4-[1-(3-methoxyphenyl)cyclohexyl]morpholine (3-MeO-PCMo), and then treated with 100 μM glutamate for 10 min. After fixation, cultured neurons were immunostained with anti-drebrin and anti-MAP2 antibodies. The linear cluster density of drebrin along the dendrites was automatically quantified using a protocol that was originally developed by us. ResultsThe high-throughput immunocytochemical assay, measuring drebrin cluster density of cultured neurons, demonstrated that glutamate-induced reduction of drebrin cluster density in 96-well plates is competitively inhibited by NMDAR antagonist, APV. The reduction was also antagonized by PCP, 3-MeO-PCP and 3-MeO-PCMo. The inhibitory activity of 3-MeO-PCMo was lower than that of PCP or 3-MeO-PCP, with IC50 values of 26.67 μM (3-MeO-PCMo), 2.02 μM (PCP) and 1.51 μM (3-MeO-PCP). DiscussionThe relative efficacy among PCP, 3-MeO-PCP and 3-MeO-PCMo calculated from IC50 are similar to those from Ki values. This suggests that the high-throughput imaging analysis is useful to speculate the Ki values of new PCP analogues without performing the kinetic studies.

Insight into Pain Modulation: Nociceptors Sensitization and Therapeutic Targets.

Pain is a complex multidimensional concept that facilitates the initiation of the signaling cascade in response to any noxious stimuli. Action potential generation in the peripheral nociceptor terminal and its transmission through various types of nociceptors corresponding to mechanical, chemical or thermal stimuli lead to the activation of receptors and further neuronal processing produces the sensation of pain. Numerous types of receptors are activated in pain sensation which vary in their signaling pathway. These signaling pathways can be regarded as a site for modulation of pain by targeting the pain transduction molecules to produce analgesia. On the basis of their anatomic location, transient receptor potential ion channels (TRPV1, TRPV2 and TRPM8), Piezo 2, acid-sensing ion channels (ASICs), purinergic (P2X and P2Y), bradykinin (B1 and B2), α-amino-3-hydroxy-5- methylisoxazole-4-propionate (AMPA), N-methyl-D-aspartate (NMDA), metabotropic glutamate (mGlu), neurokinin 1 (NK1) and calcitonin gene-related peptide (CGRP) receptors are activated during pain sensitization. Various inhibitors of TRPV1, TRPV2, TRPM8, Piezo 2, ASICs, P2X, P2Y, B1, B2, AMPA, NMDA, mGlu, NK1 and CGRP receptors have shown high therapeutic value in experimental models of pain. Similarly, local inhibitory regulation by the activation of opioid, adrenergic, serotonergic and cannabinoid receptors has shown analgesic properties by modulating the central and peripheral perception of painful stimuli. This review mainly focused on various classes of nociceptors involved in pain transduction, transmission and modulation, site of action of the nociceptors in modulating pain transmission pathways and the drugs (both clinical and preclinical data, relevant to targets) alleviating the painful stimuli by exploiting nociceptor-specific channels and receptors.

Bis(propyl)-cognitin potentiates rehabilitation of treadmill exercise after a transient focal cerebral ischemia, possibly via inhibiting NMDA receptor and regulating VEGF expression

Combination therapies may have greater efficacy compared with monotherapy in treating stroke. We investigated the molecular mechanisms by which the combination of bis(propyl)-cognitin, an uncompetitive antagonist of NMDA receptor, and treadmill exercise promote rehabilitation after ischemic stroke. Rats were distributed into 3 treatment groups: infarct/bis(propyl)-cognitin(drug only group, DO); infarct/treadmill exercise(exercise only group, EO); infarct/bis(propyl)-cognitin + treadmill exercise (drug + exercise group, DE). The DE group had further separated to 3 sub-groups to investigate the effects achieved by different time for drug administration (60 min before stroke (DE-60 m), 15 min (DE+15 m) and 60 min (DE+60 m) after stroke). Although all infarct groups improved over time, the combination of bis(propyl)-cognitin and treadmill exercise effectively enhanced motor recovery during 14-day intervention. Early drug intervention has a best recovery result, the DE+15 m group with drug intervention at 15-min after stroke had better motor recovery than DE+60 m, DO, EO and control groups. Both bis(propyl)-cognitin and treadmill exercise significantly elevated brain VEGF expression and decreased brain infarct volume at 14 day post-ischemia. Our study reveals that bis(propyl)-cognitin potentiated rehabilitation of treadmill exercise after ischemic stroke, possibly via regulating brain VEGF expression, indicating that the combination of NMDA receptor antagonists and exercise might be useful for stroke rehabilitation.

Ginsenoside Rk1 is a novel inhibitor of NMDA receptors in cultured rat hippocampal neurons

BackgroundGinsenoside Rk1, a saponin component isolated from heat-processed Panax ginseng Meyer, has been implicated in the regulation of antitumor and anti-inflammatory activities. Although our previous studies have demonstrated that ginsenoside Rg3 significantly attenuated the activation of NMDA receptors (NMDARs) in hippocampal neurons, the effects of ginsenosides Rg5 and Rk1, which are derived from heat-mediated dehydration of ginsenoside Rg3, on neuronal NMDARs have not yet been elucidated. MethodsWe examined the regulation of NMDARs by ginsenosides Rg5 and Rk1 in cultured rat hippocampal neurons using fura-2–based calcium imaging and whole-cell patch-clamp recordings. ResultsThe results from our investigation showed that ginsenosides Rg3 and Rg5 inhibited NMDARs with similar potencies. However, ginsenoside Rk1 inhibited NMDARs most effectively among the five compounds (Rg3, Rg5, Rk1, Rg5/Rk1 mixture, and protopanaxadiol) tested in cultured hippocampal neurons. Its inhibition is independent of the NMDA- and glycine-binding sites, and its action seems to involve in an interaction with the polyamine-binding site of the NMDAR channel complex. ConclusionTaken together, our results suggest that ginsenoside Rk1 might be a novel component contributable to the development of ginseng-based therapeutic treatments for neurodegenerative diseases.

Anxiolytic effects of Formononetin in an inflammatory pain mouse model

Chronic pain is commonly accompanied with anxiety disorder, which complicates treatment. In this study, we investigated the analgesic and anxiolytic effects of Formononetin (FMNT), an active component of traditional Chinese medicine red clover (Trifolium pratense L.) that is capable of protecting neurons from N-methyl-D-aspartate (NMDA)-evoked excitotoxic injury, on mice suffering from complete Freund’s adjuvant (CFA)-induced chronic inflammatory pain. The results show that FMNT administration significantly reduces anxiety-like behavior but does not affect the nociceptive threshold in CFA-injected mice. The treatment reverses the upregulation of NMDA, GluA1, and GABAA receptors, as well as PSD95 and CREB in the basolateral amygdala (BLA). The effects of FMNT on NMDA receptors and CREB binding protein (CBP) were further confirmed by the potential structure combination between these compounds, which was analyzed by in silico docking technology. FMNT also inhibits the activation of the NF-κB signaling pathway and microglia in the BLA of mice suffering from chronic inflammatory pain. Therefore, the anxiolytic effects of FMNT are partially due to the attenuation of inflammation and neuronal hyperexcitability through the inhibition of NMDA receptor and CBP in the BLA.

Acid-Sensing Ion Channel 1a Modulates NMDA Receptor Function Through Targeting NR1/NR2A/NR2B Triheteromeric Receptors

The over-activation of N-methyl-D-aspartate receptors (NMDARs) is the main cause of neuronal death in brain ischemia. Both the NMDAR and the Acid-sensing ion channel 1a (ASIC1a) are present in the postsynaptic membrane of the central nervous system (CNS) and participate in physiological and pathological processes. However, the specific role played by ASIC1a in these processes remains elusive. We hypothesize that NMDARs are the primary mediators of normal synaptic transmission and excitatory neuronal death, while ASIC1a plays a modulatory role in facilitating NMDAR function. Using various experimental approaches including patch-clamp recordings on hippocampal slices and CHO cells, primary cultures of hippocampal neurons, calcium imaging, Western blot, cDNA transfection studies, and transient middle cerebral artery occlusion (tMCAO) mouse models, we demonstrate that stimulation of ASIC1a facilitates NMDAR function and inhibition of ASIC1a suppresses NMDAR over-activation. One of our key findings is that activation of ASIC1a selectively facilitates the NR1/NR2A/NR2B triheteromeric subtype of NMDAR currents. In accordance, inhibition of ASIC1a profoundly reduced the NMDAR-mediated EPSCs in older mouse brains, which are known to express much higher levels of triheteromeric NMDARs than younger brains. Furthermore, brain infarct sizes were reduced by a greater degree in older mice compared to younger ones when ASIC1a activity was suppressed. These data suggest that ASIC1a activity selectively enhances the function of triheteromeric NMDARs and exacerbates ischemic neuronal death especially in older animal brains. We propose ASIC1a as a novel therapeutic target for preventing and reducing the detrimental effect of brain ischemia in humans.

Ketamine inhibits colorectal cancer cells malignant potential via blockage of NMDA receptor

Ketamine, a common N-methyl-d-aspartate receptor (NMDAR) antagonist, is an option for cancer pain treatment in clinical practice. Ketamine has been shown to have the capacity to attenuate cancer cells malignancy. However, the underlying mechanism remains elusive. In the present study, we reported that ketamine inhibited the malignant potential of colorectal cancer cells and investigated the possible mechanisms involved. Ketamine suppressed the expression of VEGF, HIF-1α, p-AKT, p-ERK, and p-CaMK II, and reduced intracellular Ca2+ level in a concentration dependent manner (1, 5, 10 μg/ml). Furthermore, AP5 and MK801 (NMDAR inhibitors), and KN93 (CaMK II inhibitor), decreased the expression of VEGF, HIF-1a, p-AKT, p-ERK, and p-CaMK II, which were similar to the effect of ketamine. Further, the anti-tumor effect of ketamine was reversed by d-serine (NMDAR activator). Ketamine did not affect NMDA receptor expression, however knockdown of NMDA receptor using siRNA attenuated the effect of ketamine on cell migration. Collectively, these findings demonstrated that ketamine attenuated the expression of VEGF and cell migration ability in colorectal cancer cells, probably via blockage of NMDA receptor.

Interaction between NMDA Receptor- and Endocannabinoid-Mediated Modulation of Nociceptive Synapses

Nociceptors, sensory neurons that detect damage or potential damage to the body, are the first stage of communicating noxious stimuli from the periphery to central nervous system (CNS). In this study, long-term potentiation (LTP) in the CNS of the medicinal leech, Hirudo verbana, was examined, taking advantage of the ability to selectively record from nociceptive synapses in this model organism. High frequency stimulation (HFS) of nociceptors produced a persistent increase in synaptic transmission and this LTP was both NMDA receptor-mediated and synapse-specific. Surprisingly, inhibition of NMDA receptors during HFS “uncovered” a persistent form of depression. This long-term depression (LTD) was mediated by the endocannabinoid 2-arachidonoyl glycerol (2-AG) acting on a TRPV (transient receptor potential vanilloid) –like channel. These observations suggest that (1) NMDA receptor mediated LTP is observed in nociceptors across both vertebrate and invertebrate phyla and (2) there may be an interaction between NMDA receptor-mediated and endocannabinoid-mediated forms of synaptic plasticity in nociceptors. Specifically, the NMDA receptor mediated processes may suppress endocannabinoid signaling. Such findings could be significant for understanding cellular mechanisms behind nociceptive sensitization and perhaps their contribution to chronic pain.

Carbonic anhydrase enzymes: Likely targets for inhalational anesthetics

Inhalational anesthetics such as isoflurane, desflurane and halothane are the mainstay medications for surgical procedures; upon inhalation, they produce anesthesia described as reversible unconsciousness with the features of amnesia, sleep, immobility and analgesia. To date, how they produce anesthesia is unknown. This study proposes that carbonic anhydrase enzymes are likely targets mediating the actions of inhalational anesthetics. Carbonic anhydrase enzymes, commonly expressed in living organisms, utilize carbon dioxide (CO2) as a substrate and can generate H+ and HCO3− from CO2 with a great efficiency. There are remarkable lines of evidence for their likely roles in mediating anesthetic actions. Firstly, carbonic anhydrase enzymes are extensively expressed in the brain and spinal cord, and their importance in the brain activity, especially for the GABA and NMDA receptor signaling pathways, has been demonstrated in numerous studies. According to these studies, they provide HCO3− for GABA-A receptor activities and also buffer HCO3− excess resulting from NMDA receptor activation. Activation of GABA-A and inhibition of NMDA receptors are associated with the induction of anesthesia by the intravenous general anesthetics propofol and ketamine, respectively. Secondly, the carbonic anhydrase inhibitors topiramate and zonisamide are effectively used in the treatment of epilepsy for decades; their chronic use results in the requirement of increased levels of amobarbital in order to produce anesthesia in the epileptic patients during WADA test. In addition, given that CO2 is a substrate for these enzymes, their tertiary structure is likely has a hydrophobic pocket suitable for the anesthetic molecules to bind. Inhalational anesthetic molecules, which are lipophilic and inert in nature, have an ability to cross the membranes and inhibit carbonic anhydrases, which might not be accessible by topiramate and zonisamide. Unlike carbonic anhydrase inhibitors, they could bind to the hydrophobic pocket for CO2 molecules and produce a profound effect called anesthesia. Finally, there is a great deal of similarities between the physiological actions of inhalational anesthetics and carbonic anhydrase inhibitors; moreover well-known side effects of inhalational anesthetics could be associated with the inhibition of carbonic anhydrases. Therefore, this article presents a hypothesis that the anesthetic actions of inhalational anesthetics could be due to their inhibitory effects on the carbonic anhydrases. Investigating this hypothesis might lead to the development of new safer anesthetics, and more importantly it might reveal an endogenous anesthetic pathway, in which the carbonic anhydrase system is a component along with the GABA-A and NMDA receptor systems.

Graph theoretical analysis, in silico modeling, prediction of toxicity, metabolism and synthesis of novel 2-(methyl/phenyl)-3-(4-(5-substituted-1,3,4-oxadiazol-2-yl) phenyl) quinazolin-4(3H)-ones as NMDA receptor inhibitor.

Hit, Lead & Candidate Discovery A variety of novel 2-(methyl/phenyl)-3-(4-(5-substituted-1,3,4-oxadiazol-2-yl)phenyl) quinazolin-4(3H)-ones have been synthesized by treating 3-(4-(5-mercapto-1,3,4-oxadiazol-2-yl)phenyl)-2-(methyl/phenyl)-quinazolin-4(3H)-one with a variety of secondary amines. Graph theoretical analysis was used in identification of drug target that is, NMDAR (N-methyl-d-aspartate receptors). The observed reports of in silico modeling and ligand based toxicity, metabolism prediction studies were encouraging us to synthesize of title compounds and evaluate their antiepileptic effects. The title compounds were tested for its antiepileptic potency by MES and scPTZ model. Rotorod test is used to assess its neurotoxicity. In the preliminary test it was found that in MES test, analogs 6d, 6e, 6f, and 6l were potent; whereas in scPTZ test analogs 6d, 6e, 6f, and 6k displayed potent antiepileptic activity. Additionally these five derivatives were tested in rats orally at a dose of 30 mg/kg and found that compounds 2-methyl-3-(4-(5-morpholino-1,3,4-oxadiazol-2-yl)phenyl)quinazolin-4(3H)-one 6e and 2-methyl-3-(4-(5-(piperidin-1-yl)-1,3,4-oxadiazol-2-yl)phenyl)quinazolin-4(3H)-one 6f exhibited superior activity than reference Phenytoin. In MES test, these derivatives 6e and 6f showed activity at 30 mg/kg i.p. dose after 0.5 hr and 4.0 hr. In scPTZ test these derivatives 6e and 6f showed activity at 100 and 300 mg/kg i.p. dose after 0.5 hr and 4.0 hr, respectively.

Влияние гомоцистеина и его производных на спонтанную сетевую активность в гиппокампе новорожденных крысят

Homocysteine is a sulfur-containing amino acid, which at high concentrations induces neurotoxic effects and causes impairments in the development of the nervous system. In the blood homocysteine is rapidly oxidized, forming disulfide bonds with proteins and low-molecular thiols, and is also converted into homocysteine-thiolactone. Therefore during chronic exposure, homocysteine neurotoxicity is mediated by its derivatives. Our work aimed to study the effects of homocysteine, homocystine, and homocysteine-thiolactone on the network spontaneous activity of rat hippocampal neurons during the first postnatal week. Giant depolarizing potentials (GDP) and multiple-unit activities (MUA) were recorded using the extracellular electrode in the CA3 zone of the hippocampus. It was shown that all three thiol compounds induced an increase of the frequency of GDP and MUA in concentrations of 100 and 500 μM, while homocystine exerted the most profound effects on the network activity. Inhibition of NMDA and AMPA receptors completely prevented the effects of homocysteine and its derivatives on the spontaneous neuronal activity. Thus, homocysteine and its derivatives lead to the increase of network activity of hippocampal neurons of neonatal rats, which may impair the formation of hippocampal neuronal networks in chronic hyperhomocysteinemia; and may cause hyperexcitability and the risk of epilepsy development in the postnatal period.