D-aspartate Receptor Research Articles

Review on anti-alzheimer drug development: approaches, challenges and perspectives.

Alzheimer is an irreversible progressive neurodegenerative disease that causes failure of cerebral neurons and disability of the affected person to practice normal daily life activities. There is no concrete evidence to identify the exact reason behind the disease, so several relevant hypotheses emerged, highlighting many possible therapeutic targets, such as acetylcholinesterase, cholinergic receptors, N-methyl d-aspartate receptors, phosphodiesterase, amyloid β protein, protein phosphatase 2A, glycogen synthase kinase-3 beta, β-secretase, γ-secretase, α-secretase, serotonergic receptors, glutaminyl cyclase, tumor necrosis factor-α, γ-aminobutyric acid receptors, and mitochondria. All of these targets have been involved in the design of new potential drugs. An extensive number of these drugs have been studied in clinical trials. However, only galantamine, donepezil, and rivastigmine (ChEIs), memantine (NMDA antagonist), and aducanumab and lecanemab (selective anti-Aβ monoclonal antibodies) have been approved for AD treatment. Many drugs failed in the clinical trials to such an extent that questions have been posed about the significance of some of the aforementioned targets. On the contrary, the data of other drugs were promising and shed light on the significance of their targets for the development of new potent anti-alzheimer drugs.

NMDA Receptor Modulation in COVID-19-Associated Acute Respiratory Syndrome in both In Silico and In Vitro Approach.

The normal function of the N-methyl D-aspartate receptors (NMDAR) in human lungs depends on precisely regulated synaptic glutamate levels. Pathophysiology of the lungs is brought on by the changes in homeostasis of glutamate in the synapsis that leads to abnormal NMDAR activity. Severe acute respiratory syndrome (SARS) primarily results in lung infections, particularly lung muscle stiffening, and NMDA receptor potentiation may increase calcium ion influx and support downstream signaling mechanisms. Hence, NMDAR modulators that depend on glutamate levels could be therapeutically useful medications with fewer unintended side effects. A compound called THP (tetrahydropalmatine) that amplifies Ca2+ influx and potentiates NMDA receptors has been identified in the current study. In asthmatic human airway smooth muscle (HASM) cells, THP regulates the NMDA receptor and helps in asthmatic ASM contraction, and the pharmacological stimulation of ASM depends on both brain and respiratory NMDA receptors. Glutamate potency is altered by this substance without any voltage-dependent side effects. Additionally, a GGPP (geranylgeranyl pyrophosphate)-dependent mechanism of THP reduced the production of pro-inflammatory cytokines in ASM. THP is distinctive in terms of its chemical makeup, functioning, and agonist concentration-dependent and allosteric modulatory activity. To treat COVID-19-related SARS, THP, or any future-related compounds will make good drug-like molecule candidates.

DNA methylation and the opposing NMDAR dysfunction in schizophrenia and major depression disorders: a converging model for the therapeutic effects of psychedelic compounds in the treatment of psychiatric illness.

Psychedelic compounds are being increasingly explored as a potential therapeutic option for treating several psychiatric conditions, despite relatively little being known about their mechanism of action. One such possible mechanism, DNA methylation, is a process of epigenetic regulation that changes gene expression via chemical modification of nitrogenous bases. DNA methylation has been implicated in the pathophysiology of several psychiatric conditions, including schizophrenia (SZ) and major depressive disorder (MDD). In this review, we propose alterations to DNA methylation as a converging model for the therapeutic effects of psychedelic compounds, highlighting the N-methyl D-aspartate receptor (NMDAR), a crucial mediator of synaptic plasticity with known dysfunction in both diseases, as an example and anchoring point. We review the established evidence relating aberrant DNA methylation to NMDAR dysfunction in SZ and MDD and provide a model asserting that psychedelic substances may act through an epigenetic mechanism to provide therapeutic effects in the context of these disorders.

Simulation of nanocarrier-based targeted delivery of an antidepressant for major depressive disorder

ABSTRACT Although Depression or Major Depressive Disorder (MDD) affects nearly 15% of the adult population, yet, common antidepressants that work through the monoamine hypothesis of depression are not effective against all types of MDD. The other hypothesis, blocking N-methyl D-aspartate (NMDA) receptors (NMDAR) with antagonists to promote antidepressant effects, is not very useful because of the adverse side effects of the NMDA antagonists. In this study, we have proposed a method involving the specific drug delivery of an antidepressant, using nanocarriers. The introduction of nanocarrier encapsulated potent NMDAR antagonist, R-ketamine, in the target neuronal environments of varying membrane potentials of the central nervous system was studied using in-silico coarse grain simulation of hollow spherical polypyrrole nanocarriers or increasing size. The membrane potential ruptures the nanocarrier and releases the drug R-ketamine, which has a high-binding affinity for NMDAR. Such coarse grain simulations are an interesting and emerging field of study and shed preliminary light on the theoretical behaviour of nanopharmaceuticals in vivo. The results of these in silico findings need to be validated with in vivo experimentation to develop an improved antidepressant delivery nanoformulation.

Chinese Tuina remodels the synaptic structure in neuropathic pain rats by downregulating the expression of N-methyl D-aspartate receptor subtype 2B and postsynaptic density protein-95 in the spinal cord dorsal horn.

To investigate whether the Chinese massage system, Tuina, exerts analgesic effects in a rat model of chronic constriction injury (CCI) by remodeling the synaptic structure in the spinal cord dorsal horn (SCDH). Sixty-nine male Sprague-Dawley rats were randomly and evenly divided into the normal group, sham group, CCI group, CCI + Tuina group, CCI + MK-801 [an -methyl D-aspartate receptor subtype 2B (NR2B) antagonist] group, and CCI + MK-801 + Tuina group. The neuropathic pain model was established using CCI with right sciatic nerve ligation. Tuina was administered 4 d after CCI surgery, using pressing manipulation for 10 min, once daily. Motor function was observed with the inclined plate test, and pain behaviors were observed by the Von Frey test and acetone spray test. At 19 d after surgery, the L3-L5 spinal cord segments were removed. Glutamate, interleukin 1β (IL-1β), and tumor necrosis factor-α (TNF-α) levels were detected by enzyme-linked immunosorbent assay. The protein expression levels of NR2B and postsynaptic density protein-95 (PSD-95) were detected by Western blot, and the synaptic structure was observed by transmission electron microscopy (TEM). CCI reduced motor function and caused mechanical and cold allodynia in rats, increased glutamate concentration and TNF-α and IL-1β levels, and increased expression of synapse-related proteins NR2B and PSD-95 in the SCDH. TEM revealed that the synaptic structure of SCDH neurons was altered. Most of these disease-induced changes were reversed by Tuina and intrathecal injection of MK-801 ( < 0.05 or < 0.01). For the majority of experiments, no significant differences were found between the CCI + MK-801 and CCI + MK-801 + Tuina groups. Chinese Tuina can alleviate pain by remodeling the synaptic structure, and NR2B and PSD-95 receptors in the SCDH may be among its targets.

Altered Synaptic Plasticity: Plausible Mechanisms Associated With Viral Infections

Neurotropic viruses target the central nervous system through various mechanisms: they have the potential to modulate synaptic plasticity, causing cognitive impairments by blocking N-methyl d-aspartate receptors; they alter the Ca2+ ion-signaling pathways modulating long-term potentiation, leading to a severe inflammatory response in brain cells, increased reactive oxygen species and lipid peroxidation through mitochondria and peroxisomes. Inflammatory pathways have a key role in modulating the plasticity of neurons, linked to numerous neurological disorders. Advanced neuroimaging techniques facilitate the early diagnosis of impaired synaptic function in viral infections and neurodegenerative disorders. Here we discuss the understanding of the interplay between neurotropic viral infections and their effects on synaptic plasticity and diagnosis through neuroimaging techniques.

Low-dose ketamine improves animals' locomotor activity and decreases brain oxidative stress and inflammation in ammonia-induced neurotoxicity.

Ammonium ion (NH4 + ) is the major suspected molecule responsible for neurological complications of hepatic encephalopathy (HE). No specific pharmacological action for NH4 + -induced brain injury exists so far. Excitotoxicity is a well-known phenomenon in the brain of hyperammonemic cases. The hyperactivation of the N-Methyl- d-aspartate (NMDA) receptors by agents such as glutamate, an NH4 + metabolite, could cause excitotoxicity. Excitotoxicity is connected with events such as oxidative stress and neuroinflammation. Hence, utilizing NMDA receptor antagonists could prevent neurological complications of NH4 + neurotoxicity. In the current study, C57BL6/J mice received acetaminophen (APAP; 800 mg/kg, i.p) to induce HE. Hyperammonemic animals were treated with ketamine (0.25, 0.5, and 1 mg/kg, s.c) as an NMDA receptor antagonist. Animals' brain and plasma levels of NH4 + were dramatically high, and animals' locomotor activities were disturbed. Moreover, several markers of oxidative stress were significantly increased in the brain. A significant increase in brain tissue levels of TNF-α, IL-6, and IL-1β was also detected in hyperammonemic animals. It was found that ketamine significantly normalized animals' locomotor activity, improved biomarkers of oxidative stress, and decreased proinflammatory cytokines. The effects of ketamine on oxidative stress biomarkers and inflammation seem to play a key role in its neuroprotective mechanisms in the current study.

Intensive exercise ameliorates motor and cognitive symptoms in experimental Parkinson's disease restoring striatal synaptic plasticity.

Intensive physical activity improves motor functions in patients with Parkinson's disease (PD) at early stages. However, the mechanisms underlying the beneficial effects of exercise on PD-associated neuronal alterations have not been fully clarified yet. Here, we tested the hypothesis that an intensive treadmill training program rescues alterations in striatal plasticity and early motor and cognitive deficits in rats receiving an intrastriatal injection of alpha-synuclein (α-syn) preformed fibrils. Improved motor control and visuospatial learning in active animals were associated with a recovery of dendritic spine density alterations and a lasting rescue of a physiological corticostriatal long-term potentiation (LTP). Pharmacological analyses of LTP show that modulations of N-methyl-d-aspartate receptors bearing GluN2B subunits and tropomyosin receptor kinase B, the main brain-derived neurotrophic factor receptor, are involved in these beneficial effects. We demonstrate that intensive exercise training has effects on the early plastic alterations induced by α-syn aggregates and reduces the spread of toxic α-syn species to other vulnerable brain areas.

NMDA receptor activation induces damage of alveolar type II cells and lung fibrogenesis through ferroptosis

Ferroptosis, a newly discovered type of regulated cell death, has been implicated in numerous human diseases. Idiopathic pulmonary fibrosis (IPF) is a progressive and ultimately fatal interstitial lung disease with poor prognosis and limited treatment options. Emerging evidence has linked ferroptosis and glutamate-determined cell fate which is considered a new light on the etiology of pulmonary fibrosis. Here, we observed that N-methyl d-aspartate receptor (NMDAR) activation promoted cell damage and iron deposition in MLE-12 cells in a dose-, time-, and receptor-dependent manner. This mediated substantial Ca2+ influx, upregulated the expression levels of nNOS and IRP1, and affected intracellular iron homeostasis by regulating the expression of iron transport-related proteins (i.e., TFR1, DMT1, and FPN). Excessive iron load promoted the continuous accumulation of total intracellular and mitochondrial reactive oxygen species, which ultimately led to ferroptosis. NMDAR inhibition reduced lung injury and pulmonary fibrosis in bleomycin-induced mice. Bleomycin stimulation upregulated the expression of NMDAR1, nNOS, and IRP1 in mouse lung tissues, which ultimately led to iron deposition via regulation of the expression of various iron metabolism-related genes. NMDAR activation initiated the pulmonary fibrosis process by inducing iron deposition in lung tissues and ferroptosis of alveolar type II cells. Our data suggest that NMDAR activation regulates the expression of iron metabolism-related genes by promoting calcium influx, increasing nNOS and IRP1 expression, and increasing iron deposition by affecting cellular iron homeostasis, ultimately leading to mitochondrial damage, mitochondrial dysfunction, and ferroptosis. NMDAR activation-induced ferroptosis of alveolar type II cells might be a key event to the initiation of pulmonary fibrosis.

Algorithm for multimodal medication therapy in patients with complex regional pain syndrome.

Complex regional pain syndrome (CRPS), previously known as reflex sympathetic dystrophy and causalgia, is a clinical entity characterized by classic neuropathic pain, autonomic involvement, motor symptoms, and trophic changes in the skin, nails, and hair. Although various therapeutic modalities are used to control CRPS-related pain, severe pain due to CRPS often persists and progresses to the chronic phase. In this study, we constructed an algorithm for multimodal medication therapy for CRPS based on the established pathology of CRPS. Oral steroid pulse therapy is recommended for initial pain management in patients with CRPS. Oral steroid therapy can reduce peripheral and central neuroinflammation, contributing to the development of neuropathic pain during the acute and chronic phases. If steroid pulse therapy offers poor relief or is ineffective, treatment to control central sensitization in the chronic phase should be initiated. If pain persists despite all drug adjustments, ketamine with midazolam 2 mg before and after ketamine injection can be administered intravenously to inhibit the N-methyl D-aspartate receptor. If this treatment fails to achieve sufficient efficacy, intravenous lidocaine can be administered for 2 weeks. We hope that our proposed drug treatment algorithm to control CRPS pain will help clinicians appropriately treat patients with CRPS. Further clinical studies assessing patients with CRPS are warranted to establish this treatment algorithm in clinical practice.

The role of lateral habenula NMDA receptors in tramadol-induced conditioning.

The role of the lateral habenula (LHb) as a hub for receiving and relaying signals from the limbic system to serotonergic, dopaminergic, and norepinephrinergic regions in the brainstem makes this area a critical region in the control of reward and addiction. Behavioral evidence reveals the vital role of the LHb in negative symptoms during withdrawal. In this investigation, we study the role of the LHb N-Methyl D-Aspartate receptor (NMDAR) in the modulation of tramadol reward. Male adult Wistar rats were used in this study. The effect of intra-LHb micro-injection of NMDAR agonist (NMDA, 0.1, 0.5, 2 µg/rat) and antagonist (D-AP5, 0.1, 0.5, 1 µg/rat) was evaluated in conditioned place preference (CPP) paradigm. The obtained results showed that intra-LHb administration of NMDA induced place aversion dose-dependently, while blockade of NMDAR in the LHb using D-AP5 micro-injection led to an increased preference score in the CPP task. Co-administration of NMDA (0.5 µg/rat) with tramadol (4 mg/kg) reduced preference score, while co-administration of D-AP5 (0.5 µg/rat) with a non-effective dose of tramadol (1 mg/kg) potentiate the rewarding effect of tramadol. LHb receives inputs from the limbic system and projects to the monoaminergic nuclei in the brainstem. It has been declared that NMDAR is expressed in LHb, and as obtained data revealed, these receptors could modulate the rewarding effect of tramadol. Therefore, NMDA receptors in the LHb might be a new target for modulating tramadol abuse.

Structure-Based Virtual Screening and Discovery of New Bi-functional DAPK1 Inhibitors.

Recently, a new signaling complex Death-Associated Protein Kinase 1 (DAPK1)-N-methyl D-aspartate receptor subtype 2B (NR2B) engaged in the neuronal death cascade was identified where it was found that after stroke injury, N-methyl-D-aspartate glutamate (NMDA) receptors interact with DAPK1 through NR2B subunit and lead to excitotoxicity via overactivation of NMDA receptors. In this study, we used ZINC-12 database to find out potential inhibitor of DAPK1 and found some natural compounds showing good binding affinity towards DAPK1. These natural compounds showed interactions with ATP-binding site residues as well as substrate-recognition motifs. Thus, it has been concluded that the ligands those are showing interactions with both the sites could be considered as potential inhibitors for DAPK1.

Ketamine exerts dual effects on the apoptosis of primary cultured hippocampal neurons from fetal rats in vitro.

Ketamine, a noncompetitive N-methyl D-aspartate (NMDA) receptor antagonist, is widely used in pediatric clinical practice. The neuroprotective and neurotoxic effects of ketamine on brain neurons during development remain controversial. The reason may be related to the different concentrations of ketamine used in practice and the small range of concentrations used in previous studies. In this study, cultured hippocampal neurons were treated with ketamine in a wide range of concentrations to comprehensively observe the effects of different concentrations of ketamine on neurons. We demonstrated that low concentrations of ketamine (10 μM, 100 μM and 1000 μM) promoted neuronal survival (p < 0.05) and reduced neuronal apoptosis (p < 0.05) compared with those of the control group. High concentrations of ketamine (2000 μM, 2500 μM and 3000 μM) reduced neuronal survival (p < 0.05) and promoted neuronal apoptosis (p < 0.05). The p38 MAPK inhibitor SB203580 reduced neuronal apoptosis induced by high concentrations of ketamine (2500 μM) (p < 0.05). Our findings indicate that ketamine exerts a dual effect on the apoptosis of primary cultured fetal rat hippocampal neurons in vitro and that the neurotoxic effects of ketamine are related to activation of the p38 MAPK signaling pathway.

ASC Transporters Mediate D-Serine Transport into Astrocytes Adjacent to Synapses in the Mouse Brain.

D-serine is an important signalling molecule, which activates N-methyl D-aspartate receptors (NMDARs) in conjunction with its fellow co-agonist, the neurotransmitter glutamate. Despite its involvement in plasticity and memory related to excitatory synapses, its cellular source and sink remain a question. We hypothesise that astrocytes, a type of glial cell that surrounds synapses, are likely candidates to control the extracellular concentration of D-Serine by removing it from the synaptic space. Using in situ patch clamp recordings and pharmacological manipulation of astrocytes in the CA1 region of the mouse hippocampal brain slices, we investigated the transport of D-serine across the plasma membrane. We observed the D-serine-induced transport-associated currents upon puff-application of 10 mM D-serine on astrocytes. Further, O-benzyl-L-serine and trans-4-hydroxy-proline, known substrate inhibitors of the alanine serine cysteine transporters (ASCT), reduced D-serine uptake. These results indicate that ASCT is a central mediator of astrocytic D-serine transport and plays a role in regulating its synaptic concentration by sequestration into astrocytes. Similar results were observed in astrocytes of the somatosensory cortex and Bergmann glia in the cerebellum, indicative of a general mechanism expressed across a range of brain areas. This removal of synaptic D-serine and its subsequent metabolic degradation are expected to reduce its extracellular availability, influencing NMDAR activation and NMDAR-dependent synaptic plasticity.

Nonparaneoplastic anti-NMDA receptor encephalitis in an adolescent girl: a case report.

A 17-year-old female presented to the hospital with an 11-day history of fever, altered behavior, abnormal body movements, and altered sensorium. Upon examination, she was found to be febrile, tachycardic, and tachypneic, with a Glasgow Coma Scale score of 8. The diagnosis of anti-NMDA receptor encephalitis is usually confirmed by the presence of anti-NMDA receptor antibodies in the cerebrospinal fluid. The first-line treatment options include steroids, intravenous immunoglobulin, and plasmapheresis, while second-line therapies such as rituximab and cyclophosphamide may be necessary for some patients. While most patients respond well to treatment, complications can arise, and as in this case, death can occur. New onset symptoms like alteration in behavior, abnormal body movement, altered sensorium, and psychiatric symptoms in a young female should raise suspicion of this disease. Immunotherapy is promising; however, anticipation and management of complication are essential in reducing mortality.

Pulsed Radiofrequency Decreases pERK and Affects Intracellular Ca2+ Influx, Cytosolic ATP Level, and Mitochondrial Membrane Potential in the Sensitized Dorsal Root Ganglion Neuron Induced by N-Methyl D-Aspartate.

The molecular mechanism of pulsed radiofrequency (PRF) in chronic pain management is not fully understood. Chronic pain involves the activation of specific N-Methyl D-Aspartate receptors (NMDAR) to induce central sensitization. This study aims to determine the effect of PRF on central sensitization biomarker phosphorylated extracellular signal-regulated kinase (pERK), Ca2+ influx, cytosolic ATP level, and mitochondrial membrane potential (Δψm) of the sensitized dorsal root ganglion (DRG) neuron following NMDAR activation. This study is a true experimental in-vitro study on a sensitized DRG neuron induced with 80 µM NMDA. There are six treatment groups including control, NMDA 80 µM, Ketamine 100 µM, PRF 2Hz, NMDA 80 µM + PRF 2 Hz, and NMDA 80 µM + PRF 2 Hz + ketamine 100 µM. We use PRF 2 Hz 20 ms for 360 seconds. Statistical analysis was performed using the One-Way ANOVA and the Pearson correlation test with α=5%. In the sensitized DRG neuron, there is a significant elevation of pERK. There is a strong correlation between Ca2+, cytosolic ATP level, and Δψm with pERK intensity (p<0.05). PRF treatment decreases pERK intensity from 108.48 ± 16.95 AU to 38.57 ± 5.20 AU (p<0.05). PRF exposure to sensitized neurons also exhibits a Ca2+ influx, but still lower than in the unexposed neuron. PRF exposure in sensitized neurons has a higher cytosolic ATP level (0.0458 ± 0.0010 mM) than in the unexposed sensitized neuron (0.0198 ± 0.0004 mM) (p<0.05). PRF also decreases Δψm in the sensitized neuron from 109.24 ± 6.43 AU to 33.21 ± 1.769 AU (p<0.05). PRF mechanisms related to DRG neuron sensitization are by decreasing pERK, altering Ca2+ influx, increasing cytosolic ATP level, and decreasing Δψm which is associated with neuron sensitization following NMDAR activation.

COMPARISION OF DEXAMETHASONE AND MAGNESIUM SULPHATE AS ADJUVANTS TO BUPIVACAINE FOR POSTOPERATIVE ANALGESIA IN LOWER ABDOMINAL SURGERIES USING TRANSVERSUS ABDOMINIS PLANE BLOCK

Background:Transversus abdominis plane block is regional anaesthesia technique that provides analgesia to the parietal peritoneum as well as skin and muscles of the anterior abdominal wall.Magnesium is N-methyl D-aspartate receptor and physiological calcium antagonist.Dexamethasone is a potent glucocorticoid,has anti-inflammatory as well as analgesic properties. Objectives: To compare the duration of postoperative analgesia,time of administration of first rescue analgesia,systemic side effects of Bupivacaine with Magnesium sulphate and Dexamethasone using Transversus abdominis plane block. Methods: After approval of ethical committee and informed written consent A total of Sixty ASA grade I and II patients aged between 18-60 years undergoing lower abdominal surgeries were randomnly allocated to receive TAP block and divided into two groups of 30 each . Group BD received 20ml of 0.25% Bupivacaine +2ml(8mg) Dexamethasone , Group BM received 20ml 0f 0.25% Bupivacaine+1ml of 25% Magnesium sulphate(250mg)+1ml of normal saline respectively.Heart rate,mean arterial pressure,VAS score,time for first rescue analgesia and side effects were recorded postoperatively. Analgesia was given when VAS score was more than 4. Results: The postoperative visual analogue scale scores was significantly less in group BM.Time for first rescue analgesia was more in group BM compared to group BD without any systemic side effects . Conclusion:Administration of Magnesium sulphate with Bupivacaine reduces postoperative pain scores, prolongs the postoperative analgesia compared with Dexamethasone without any systemic side effects.

Evidence for Prepulse Inhibition of Visually Evoked Motor Response in Drosophila melanogaster.

Prepulse inhibition (PPI) is a widely investigated behavior to study the mechanisms of disorders such as anxiety, schizophrenia, and bipolar mania. PPI has been observed across various vertebrate and invertebrate species; however, it has not yet been reported in adult Drosophila melanogaster. In this study, we describe the first detection of PPI of visually evoked locomotor arousal in flies. To validate our findings, we demonstrate that PPI in Drosophila can be partially reverted by the N-methyl D-aspartate (NMDA) receptor antagonist MK-801, known for inducing sensorimotor gating deficits in rodent models. Additionally, we show that the visually evoked response can be inhibited by multiple stimuli presentation, which can also be affected by MK-801. Given the versatility of Drosophila as a model organism for genetic screening and analysis, our results suggest that high-throughput behavioral screenings of adult flies can become a valuable tool for investigating the mechanisms behind PPI.

5613260 A PHASE -- IIA-IIB, OPEN LABEL, SINGLE CENTER TRIAL TO STUDY SAFETY, TOLERABILITY AND EFFICACY OF MEMANTINE AS SUPPORTIVE LONG-TERM TREATMENT OF SICKLE CELL PATIENTS: TRIAL DESIGN AND ENROLLMENT

Background: Sickle cell disease (SCD) is a life-threatening hematological disorder with a high rate of long-term comorbidities and a significant socioeconomic burden. Anemia, vaso-occlusive and pain crises, infections, and a high rate of long-term comorbidities are hallmarks of SCD. The pathophysiology of SCD is due to a single point mutation (Glu6Val) that causes polymerization of the mutant hemoglobin (HbS), resulting in red blood cells (RBC) sickling. Inflammation, hemolysis, microvascular obstruction, and organ damage characterize the clinical expression of SCD. The standard of care includes Hydroxycarbamide, symptomatic treatment, blood transfusions, new drugs, and bone marrow transplant as curative therapy. Our recent findings showed that N-methyl D-aspartate receptors (NMDARs) are up-regulated SCD-RBCs and Ca2+ uptake via NMDARs affects SCD-RBC hydration, and hypoxia-induced sickling (Hanggi P. et al., 2014). Inhibition of NMDARs with Memantine, a drug used in Alzheimer’s disease, emerges as a novel treatment in SCD. Memantine administration in 6 SCD adults demonstrated safety (Hegemann I. et al., 2020); and suggested a reduction of RBCs irreversible sickling (Makhro A, et al., 2020). Aims: This phase IIa-IIb open-label, single-center trial aims to study the safety, tolerability, and efficacy of Memantine in adults and teenagers with SCD (NCT03247218). Methods: This trial enrolled 23 SCD (SS and Sβ Thalassemia) 17 patients received Memantine for at least one year period, Hydroxycarbamide was continued administered. Starting dose of Memantine was 5 mg/day with escalation every 3 months, up to 15 mg/day in teenagers and up to 20 mg/day for adults. Patients were followed up monthly, a total of 6762 patients/days of follow-up were summarized. Results: The only safety events reported were transient headache and constipation in two patients; no adverse side effects were noticed. Overall, the number of admission days and emergency room visits decreased compared to the pre-screen period. The hemoglobin and fetal hemoglobin levels remain stable despite less use of blood transfusions; based on preliminary laboratory analysis a trend of reduction in hemolytic and inflammatory parameters can be noticed. Conclusions: The results of this phase IIa-IIb trial suggested safety and probable clinical benefit in long-term treatment with Memantine in SCD adolescents and adults. Full results of this trial are anticipated at the end of 2022 and a phase III trial will be required for the final assessment of the clinical benefit of Memantine treatment in SCD.

A COMPARATIVE STUDY OF DEXMEDETOMIDINE AND MAGNESIUM SULPHATE AS AN ADJUVANT TO BUPIVACAINE FOR POSTOPERATIVE EPIDURAL ANALGESIA IN LOWER LIMB SURGERIES

Background:Pain is pathologic entity,noxious stimulus and a most common problems challenging the anaesthetist.Regional anaesthesia is a safe,inexpensive technique that inhibits the nerve transmission to relieve pain and also provide postoperative analgesia.Magnesium is N-methyl D-aspartate receptor and physiological calcium antagonist.Dexmedetomedine is α2 receptor antagonist with analgesic and sedative properties. Objectives: To compare the duration of postoperative analgesia,time of administration of first rescue analgesia,systemic side effects of epidural bupivacaine with Magnesium sulphate and dexmedetomidine. Methods: After approval of ethical committee and informed written consent A prospective randomised study was conducted with Sixty ASA grade I and II patients aged between 18-60 years undergoing lower limb surgeries were divided into two groups of 30 each .Group BM and Group BD received 10ml of 0.125% bupivacaine with 100mg of 20%MgSo4 and 12.5mcg of dexmedetomidine respectively.Heart rate,mean arterial pressure,VAS score,time for first rescue analgesia were recorded postoperatively.Epidural analgesia was given when VAS score was more than 4. Results:VAS was significantly less in group BM,time for first rescue analgesia was more in group BM compared to group BD without any systemic side effects . Conclusion:Administration of Magnesium sulphate with bupivacaine provides prolonged postoperative analgesia compared with Dexmedetomidine without any systemic side effects.