Memantine Improves Memory and Neurochemical Damage in a Model of Maple Syrup Urine Disease.

Maple Syrup Urine Disease (MSUD) is a metabolic disease characterized by the accumulation of branched-chain amino acids (BCAA) in different tissues due to a deficit in the branched-chain alpha-ketoacid dehydrogenase complex. The most common symptoms are poor feeding, psychomotor delay, and neurological damage. However, dietary therapy is not effective. Studies have demonstrated that memantine improves neurological damage in neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Therefore, we hypothesize that memantine, an NMDA receptor antagonist can ameliorate the effects elicited by BCAA in an MSUD animal model. For this, we organized the rats into four groups: control group (1), MSUD group (2), memantine group (3), and MSUD + memantine group (4). Animals were exposed to the MSUD model by the administration of BCAA (15.8 µL/g) (groups 2 and 4) or saline solution (0.9%) (groups 1 and 3) and treated with water or memantine (5 mg/kg) (groups 3 and 4). Our results showed that BCAA administration induced memory alterations, and changes in the levels of acetylcholine in the cerebral cortex. Furthermore, induction of oxidative damage and alterations in antioxidant enzyme activities along with an increase in pro-inflammatory cytokines were verified in the cerebral cortex. Thus, memantine treatment prevented the alterations in memory, acetylcholinesterase activity, 2',7'-Dichlorofluorescein oxidation, thiobarbituric acid reactive substances levels, sulfhydryl content, and inflammation. These findings suggest that memantine can improve the pathomechanisms observed in the MSUD model, and may improve oxidative stress, inflammation, and behavior alterations.

Memantine versus Ginkgo biloba Extract: A Comparative Study on Cognitive Dysfunction Treatment in a Novel Rat Model.

Extracellular senile plaques and intraneuronal neurofibrillary tangles are two devastating brain proteinopathies that are indicative of Alzheimer's disease, the most prevalent type of dementia. Currently, no effective medications are available to stop or reverse Alzheimer's disease. Ginkgo biloba extract, commonly referred to as EGb 761, is a natural product made from the leaves of the G. biloba tree. It has long been demonstrated to have therapeutic benefits in Alzheimer's disease. The current study assessed the beneficial effects of EGb 761 against Alzheimer's disease in comparison with memantine, a standard treatment for Alzheimer's disease. The scopolamine-heavy metals mixture rat Alzheimer's disease model is a newly created model to study the effects of EGb 761 oral therapy on cognitive performance and other Alzheimer's disease-like changes over a 28-day experimental period. This new Alzheimer's disease model provides better criteria for Alzheimer's disease hallmarks than the conventional scopolamine model. The EGb 761 reversed memory and learning deficits induced by the scopolamine-heavy metals mixture. These outcomes were linked to a more pronounced inhibitory effect on acetylcholinesterase, caspase-3, hippocampal amyloid-beta protein (Aß1 - 42), phosphorylated tau protein counts, and proinflammatory cytokines (tumor necrosis factor-α and interleukin-1ß) compared to the memantine-treated group. Furthermore, EGb 761 treatment considerably reduced lipid peroxidation (malondialdehyde) and improved reduced glutathione levels compared to memantine. Our results suggest EGb 761's potential in treating central nervous system disorders. It's a promising candidate for future Alzheimer's disease therapeutic exploration. This study also highlights the need for future research to focus on the positive benefits of herbal medicines.

Locally Synthetized 17-ß-Estradiol Reverses Amyloid-ß-42-Induced Hippocampal Long-Term Potentiation Deficits.

Amyloid beta 1-42 (Aß42) aggregates acutely impair hippocampal long-term potentiation (LTP) of synaptic transmission, and 17ß-estradiol is crucial for hippocampal LTP. We tested whether boosting the synthesis of neural-derived 17ß-estradiol (nE2) saves hippocampal LTP by the neurotoxic action of Aß42. Electrophysiological recordings were performed to measure dentate gyrus (DG) LTP in rat hippocampal slices. Using a pharmacological approach, we tested the ability of nE2 to counteract the LTP impairment caused by acute exposure to soluble Aß42 aggregates. nE2 was found to be required for LTP in DG under physiological conditions. Blockade of steroid 5α-reductase with finasteride, by increasing nE2 synthesis from testosterone (T), completely recovered LTP in slices treated with soluble Aß42 aggregates. Modulation of the glutamate N-methyl-D aspartate receptor (NMDAR) by memantine effectively rescued the LTP deficit observed in slices exposed to Aß42, and memantine prevented LTP reduction observed under the blocking of nE2 synthesis. nE2 is able to counteract Aß42-induced synaptic dysfunction. This effect depends on a rapid, non-genomic mechanism of action of nE2, which may share a common pathway with glutamate NMDAR signaling.

Harnessing memantine in Alzheimer's disease therapy through inhibition of microtubule affinity-regulating kinase: Mechanistic insights.

Alzheimer's disease (AD) is one of the neurodegenerative disorder that primarily affects memory, thinking, and behavior, eventually leading to severe cognitive impairment. Therapeutic management of AD is urgently needed to improve the quality and lifestyle of patients. Tau phosphorylating kinases are considered attractive therapeutic targets. Microtubule affinity-regulating kinase 4 (MARK4) is directly linked with pathological phosphorylations of tau, highlighting its role in the therapeutic targeting of AD. The current manuscript shows the MARK4 inhibitory effect of Memantine (MEM), a drug used in treating AD. We have performed fluorescence based binding measurements, enzyme inhibition assay, docking and molecular dynamics (MD) simulations to understand the binding of of MARK4 and MEM and subsequent inhibition in the kinase activity. A 100 ns MD simulations provided a detailed analysis of MARK4-MEM complex and the role of potential critical residues in the binding. Finally, this study provides molecular insights into the therapeutic implication of MEM in AD therapeutics. We propose MEM effectively inhibits MARK4, it may be implicated in the development of targeted and efficient treatments for AD.

Sex differences in the anticompulsive-like effect of memantine: Involvement of nitric oxide pathway but not AMPA receptors.

Memantine, an N-Methyl-D-Aspartate (NMDA) antagonist, has been examined as a potential treatment for Obsessive-Compulsive Disorder (OCD). Yet, there is limited knowledge regarding how it works to reduce compulsive behaviour and whether it has different effects on individuals based on their sex. Herein, we investigated if there are sex differences in the anticompulsive-like effect of memantine in adult Swiss mice. Additionally, we explored whether the nitric oxide (NO) pathway and α-amino-3-hydroxy-5-methyl-4-isoazolepropionic acid (AMPA) receptors play a role in memantine's effects. To start, we assessed the impact of a single intraperitoneal dose of memantine (at 3, 5, and 10 mg/kg) on behaviours exhibited in the open field test (OFT) and the marble-burying test (MBT), the latter being a predictive test for anticompulsive effects. All doses of memantine reduced marble-burying behaviour in both male and female mice without affecting their locomotor activity in the OFT. This anticompulsive-like effect was also confirmed in another predictive test, the nest-building test, with the highest memantine dose (10 mg/kg) reducing nest-building behaviour without significant differences between male and female mice. We observed that pre-treatment with L-arginine, a NO precursor, mitigated the anticompulsive-like effect of memantine in male mice but had no effect in female mice in the MBT. Finally, NBQX, an AMPA receptor antagonist, did not block the anticompulsive-like effect of memantine. In summary, our study suggests that the anticompulsive-like effect of memantine does not appear to be sex-specific, does not depend on AMPA receptors, and involves the NO pathway primarily in male mice.

Time-Dependent Long-Term Effect of Memantine following Repetitive Mild Traumatic Brain Injury.

Repetitive mild traumatic brain injury (rmTBI, e.g., sports concussions) may be associated with both acute and chronic symptoms and neurological changes. Despite the common occurrence of these injuries, therapeutic strategies are limited. One potentially promising approach is N-methyl-D-aspartate receptor (NMDAR) blockade to alleviate the effects of post-injury glutamatergic excitotoxicity. Initial pre-clinical work using the NMDAR antagonist, memantine, suggests that immediate treatment following rmTBI improves a variety of acute outcomes. It remains unclear (1) whether acute memantine treatment has long-term benefits and (2) whether delayed treatment following rmTBI is beneficial, which are both clinically relevant concerns. To test this, animals were subjected to rmTBI via a weight drop model with rotational acceleration (five hits in 5 days) and randomized to memantine treatment immediately, 3 months, or 6 months post-injury, with a treatment duration of one month. Behavioral outcomes were assessed at 1, 4, and 7 months post-injury. Neuropathological outcomes were characterized at 7 months post-injury. We observed chronic changes in behavior (anxiety-like behavior, motor coordination, spatial learning, and memory), as well as neuroinflammation (microglia, astrocytes) and tau phosphorylation (T231). Memantine treatment, either immediately or 6 months post-injury, appears to confer greater rescue of neuroinflammatory changes (microglia) than vehicle or treatment at the 3-month time point. Although memantine is already being prescribed chronically to address persistent symptoms associated with rmTBI, this study represents the first evidence of which we are aware to suggest a small but durable effect of memantine treatment in mild, concussive injuries. This effect suggests that memantine, although potentially beneficial, is insufficient to treat all aspects of rmTBI alone and should be combined with other therapeutic agents in a multi-therapy approach, with attention given to the timing of treatment.

Spectrum of NMDA Receptor Variants in Neurodevelopmental Disorders and Epilepsy.

N-methyl-D-aspartate receptors (NMDAR) are ligand-gated ion channels mediating excitatory neurotransmission and are important for normal brain development, cognitive abilities, and motor functions. Pathogenic variants in the Glutamate receptor Ionotropic N-methyl-D-aspartate (GRIN) genes (GRIN1, GRIN2A-D) encoding NMDAR subunits have been associated with a wide spectrum of neurodevelopmental disorders and epilepsies ranging from treatable focal epilepsies to devastating early-onset developmental and epileptic encephalopathies. Genetic variants in NMDA receptor genes can cause a range of complex alterations to receptor properties resulting in various degrees of loss-of-function, gain-of-function, or mixtures thereof. Understanding how genetic variants affect the function of the receptors, therefore, represents an important first step in the ongoing development towards targeted therapies. Currently, targeted treatment options for GRIN-related diseases are limited. However, treatment with memantine has been reported to significantly reduce seizure frequency in a few individuals with developmental and epileptic encephalopathies harboring de novo gain-of-function GRIN2A missense variants, and supplementary treatment with L-serine has been associated with improved motor and cognitive performance as well as reduced seizure frequency in patients with GRIN2B loss-of-function missense variants as well as GRIN2A and GRIN2B null variants.

Fluoroethylnormemantine (FENM) shows synergistic protection in combination with a sigma-1 receptor agonist in a mouse model of Alzheimer's disease.

Fluoroethylnormemantine (FENM) is a Memantine derivative with anti-amnesic and neuroprotective activities showed in the Aß25-35 pharmacological mouse model of Alzheimer's disease (AD). As AD is a complex multi-factorial neurodegenerative pathology, combination therapies relying on drugs acting through different pathways, have been suggested to more adequately address neuroprotection. As several agonists of the sigma-1 receptor (S1R), an intracellular chaperone, are presently in phase 2 or 3 clinical trials in neurodegenetrative diseases including AD, we examined the potentialities of S1R drug-based combinations with FENM, or Memantine. Aß25-35-treated mice were treated with S1R agonists (PRE-084, Igmesine, Cutamesine) and/or FENM, or Memantine, during 7 days after intracerebroventricular administration of oligomerized Aß25-35. Mice were then tested for spatial short-term memory on day 8 and non-spatial long-term memory on days 9-10, using the spontaneous alternation or passive avoidance tests, respectively. The FENM or Memantine combination with Donepezil, that non-selectively inhibits acetylcholinesterase and activates S1R, was also tested. The efficacy of combinations using maximal non-active or minimal active doses of S1R agonist or FENM was analyzed using calculations of the combination index, based on simple isobologram representation. Data showed that most of the FENM-based combinations led to synergistic protection against Aß25-35-induced learning deficits, for both long- and short-term memory responses, with a higher efficiency on the latter. Memantine led to synergistic combination in short-term memory but poorly in long-term memory responses, with either PRE-084 or Donepezil. These study showed that drug combinations based on FENM and S1R agonists may lead to highly effective and synergistic protection in AD, particularly on short-term memory.

Combination strategy employing BACE1 inhibitor and memantine to boost cognitive benefits in Alzheimer's disease therapy.

RATIONALE: The ß-secretase BACE1 initiates amyloid-ß (Aß) generation and represents a long-standing prime therapeutic target for the treatment of Alzheimer's disease (AD). However, BACE1 inhibitors tested to date in clinical trials have yielded no beneficial outcomes. In fact, prior BACE1 inhibitor trials targeted at ~ 50-90% Aß reductions in symptomatic or prodromal AD stages have ended in the discontinuation due to futility and/or side effects, including cognitive worsening rather than expected improvement at the highest dose. OBJECTIVES: We tested whether a combination strategy with the selective BACE1 inhibitor GRL-8234 and the FDA-approved symptomatic drug memantine may provide synergistic cognitive benefits within their safe dose range. METHODS: The drug effects were evaluated in the advanced symptomatic stage of 5XFAD mice that developed extensive cerebral Aß deposition. RESULTS: Chronic combination treatment with 33.4-mg/kg GRL-8234 and 10-mg/kg memantine, but not either drug alone, rescued cognitive deficits in 5XFAD mice at 12 months of age (the endpoint after 60-day drug treatment), as assessed by the contextual fear conditioning, spontaneous alternation Y-maze and nest building tasks. Intact baseline performances of wild-type control mice on three cognitive paradigms demonstrated that combination treatment did not augment potential cognitive side effects of individual drugs. Biochemical and immunohistochemical examination showed that combination treatment did not synergistically reduce the ß-amyloidogenic processing of amyloid precursor protein or Aß levels in 5XFAD mouse brains. CONCLUSIONS: A combination strategy with BACE1 inhibitors and memantine may be able to increase the effectiveness of individual drugs within their safe dose range in AD therapy.

Minocycline mitigates tau pathology via modulating the TLR-4/NF-Ðºß signalling pathway in the hippocampus of neuroinflammation rat model.

INTRODUCTION: The neuroinflammatory response was seen to impact the formation of phosphorylated tau protein in Alzheimer's disease (AD). This study aims to investigate the molecular mechanism of minocycline in reducing phosphorylated tau protein formation in the hippocampus of lipopolysaccharide (LPS)-induced rats. METHODS: Fifty adult male Sprague Dawley (SD) rats were randomly allocated to 1 of 5 groups: control, LPS (5 mg/kg), LPS + minocycline (25 mg/kg), LPS + minocycline (50 mg/kg) and LPS + memantine (10 mg/kg). Minocycline and memantine were administered intraperitoneally (i.p) for two weeks, and LPS was injected i.p. once on day 5. ELISA was used to determine the level of phosphorylated tau protein in SD rats' hippocampal tissue. The density and expression of Toll-like receptor-4 (TLR-4), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-кß), tumour necrosis factor-alpha (TNF-α), and cyclooxygenase (COX)-2 were determined using Western blot and immunohistochemistry. RESULTS: Minocycline, like memantine, prevented LPS-induced increasein phosphorylated tau protein level suggested via reduced density and expression of TLR-4, NF-кß, TNF-αand COX-2 proteins in rat hippocampal tissue. Interestingly, higher doses were shown to be more neuroprotective than lower doses. CONCLUSION: This study suggests that minocycline suppresses the neuroinflammation signalling pathway and decreased phosphorylated tau protein formation induced by LPS in a dose-dependent manner. Minocycline can be used as a preventative and therapeutic drug for neuroinflammatory diseases such as AD.

Impact of NMDA receptors block versus GABA-A receptors modulation on synaptic plasticity and brain electrical activity in metabolic syndrome.

PURPOSE: Metabolic syndrome (MetS) is a common disorder associated with disturbed neurotransmitter homeostasis. Memantine, an N-methyl-d-aspartate receptor (NMDAR) antagonist, was first used in Alzheimer's disease. Allopregnanolone (Allo), a potent positive allosteric modulator of the Gamma-Amino-Butyric Acid (GABA)-A receptors, decreases in neurodegenerative diseases. The study investigated the impact of Memantine versus Allo administration on the animal model of MetS to clarify whether the mechanism of abnormalities is related more to excitatory or inhibitory neurotransmitter dysfunction. MATERIALS AND METHODS: Fifty-six male rats were allocated into 7 groups: 4 control groups, 1 MetS group, and 2 treated MetS groups. They underwent assessment of cognition-related behavior by open field and forced swimming tests, electroencephalogram (EEG) recording, serum markers confirming the establishment of MetS model and hippocampal Glial Fibrillary Acidic Protein (GFAP) and Brain-Derived Neurotrophic Factor (BDNF). RESULTS: Allo improved anxiety-like behavior and decreased grooming frequency compared to Memantine. Both drugs increased GFAP and BDNF expression, improving synaptic plasticity and cognition-related behaviors. The therapeutic effect of Allo was more beneficial regarding lipid profile and anxiety. We reported progressive slowing of EEG waves in the MetS group with Memantine and Allo treatment with increased relative theta and decreased relative delta rhythms. CONCLUSIONS: Both Allo and Memantine boosted the outcome parameters in the animal model of MetS. Allo markedly improved the anxiety-like behavior in the form of significantly decreased grooming frequency compared to the Memantine-treated groups. Both drugs were associated with increased hippocampal GFAP and BDNF expression, indicating an improvement in synaptic plasticity and so, cognition-related behaviors.

Cellular Mechanisms of Cognitive Enhancement: The In Vivo Modulation of the Firing Activity and the Responsiveness of Rat Hippocampal Neurons by Memantine and Alpha7 Nicotinic Acetylcholine Receptor Ligands.

Promising new pharmacological strategies for the enhancement of cognition target either nicotinic acetylcholine receptors (nAChR) or N-methyl-D-aspartate receptors (NMDAR). There is also an increasing interest in low-dose combination therapies co-targeting the above neurotransmitter systems to reach greater efficacy over the monotreatments and to reduce possible side effects of high-dose monotreatments. In the present study, we assessed modulatory effects of the α7 nAChR-selective agonist PHA-543613 (PHA), a novel α7 nAChR positive allosteric modulator compound (CompoundX) and the NMDAR antagonist memantine on the in vivo firing activity of CA1 pyramidal neurons in the rat hippocampus. Three different test conditions were applied: spontaneous firing activity, NMDA-evoked firing activity and ACh-evoked firing activity. Results showed that high but not low doses of memantine decreased NMDA-evoked firing activity, and low doses increased the spontaneous and ACh-evoked firing activity. Systemically applied PHA robustly potentiated ACh-evoked firing activity with having no effect on NMDA-evoked activity. In addition, CompoundX increased both NMDA- and ACh-evoked firing activity, having no effects on spontaneous firing of the neurons. A combination of low doses of memantine and PHA increased firing activity in all test conditions and similar effects were observed with memantine and CompoundX but without spontaneous firing activity increasing effects. Our present results demonstrate that α7 nAChR agents beneficially interact with Alzheimer's disease medication memantine. Moreover, positive allosteric modulators potentiate memantine effects on the right time and the right place without affecting spontaneous firing activity. All these data confirm previous behavioral evidence for the viability of combination therapies for cognitive enhancement.

γ-Oryzanol from Rice Bran Antagonizes Glutamate-Induced Excitotoxicity in an In Vitro Model of Differentiated HT-22 Cells.

The excessive activation of glutamate in the brain is a factor in the development of vascular dementia. γ-Oryzanol is a natural compound that has been shown to enhance brain function, but more research is needed to determine its potential as a treatment for vascular dementia. This study investigated if γ-oryzanol can delay or improve glutamate neurotoxicity in an in vitro model of differentiated HT-22 cells and explored its neuroprotective mechanisms. The differentiated HT-22 cells were treated with 0.1 mmol/L glutamate for 24 h then given γ-oryzanol at appropriate concentrations or memantine (10 µmol/L) for another 24 h. Glutamate produced reactive oxygen species and depleted glutathione in the cells, which reduced their viability. Mitochondrial dysfunction was also observed, including the inhibition of mitochondrial respiratory chain complex I activity, the collapse of mitochondrial transmembrane potential, and the reduction of intracellular ATP levels in the HT-22 cells. Calcium influx triggered by glutamate subsequently activated type II calcium/calmodulin-dependent protein kinase (CaMKII) in the HT-22 cells. The activation of CaMKII-ASK1-JNK MAP kinase cascade, decreased Bcl-2/Bax ratio, and increased Apaf-1-dependent caspase-9 activation were also observed due to glutamate induction, which were associated with increased DNA fragmentation. These events were attenuated when the cells were treated with γ-oryzanol (0.4 mmol/L) or the N-methyl-D-aspartate receptor antagonist memantine. The results suggest that γ-oryzanol has potent neuroprotective properties against glutamate excitotoxicity in differentiated HT-22 cells. Therefore, γ-oryzanol could be a promising candidate for the development of therapies for glutamate excitotoxicity-associated neurodegenerative diseases, including vascular dementia.

Mitigating radiation-induced brain injury via NLRP3/NLRC4/Caspase-1 pyroptosis pathway: Efficacy of memantine and hydrogen-rich water.

Radiation-induced brain injury (RIBI) is a significant challenge in radiotherapy for head and neck tumors, impacting patients' quality of life. In exploring potential treatments, this study focuses on memantine hydrochloride and hydrogen-rich water, hypothesized to mitigate RIBI through inhibiting the NLRP3/NLRC4/Caspase-1 pathway. In a controlled study involving 40 Sprague-Dawley rats, divided into five groups including a control and various treatment groups, we assessed the effects of these treatments on RIBI. Post-irradiation, all irradiated groups displayed symptoms like weight loss and salivation, with notable variations among different treatment approaches. Particularly, hydrogen-rich water showed a promising reduction in these symptoms. Histopathological analysis indicated substantial hippocampal damage in the radiation-only group, while the groups receiving memantine and/or hydrogen-rich water exhibited significant mitigation of such damage. Molecular studies, revealed a decrease in oxidative stress markers and an attenuated inflammatory response in the treatment groups. Immunohistochemistry further confirmed these molecular changes, suggesting the effectiveness of these agents. Echoing recent scientific inquiries into the protective roles of specific compounds against radiation-induced damages, our study adds to the growing body of evidence on the potential of memantine and hydrogen-rich water as novel therapeutic strategies for RIBI.

Memantine suppresses the excitotoxicity but fails to rescue the ataxic phenotype in SCA1 model mice.

Spinocerebellar ataxia type 1 (SCA1) is a debilitating neurodegenerative disorder of the cerebellum and brainstem. Memantine has been proposed as a potential treatment for SCA1. It blocks N-methyl-D-aspartate (NMDA) receptors on neurons, reduces excitotoxicity and decreases neurodegeneration in Alzheimer models. However, in cerebellar neurodegenerative diseases, the potential value of memantine is still unclear. We investigated the effects of memantine on motor performance and synaptic transmission in the cerebellum in a mouse model where mutant ataxin 1 is specifically targeted to glia. Lentiviral vectors (LVV) were used to express mutant ataxin 1 selectively in Bergmann glia (BG). In mice transduced with the mutant ataxin 1, chronic treatment with memantine improved motor activity during initial tests, presumably due to preserved BG and Purkinje cell (PC) morphology and numbers. However, mice were unable to improve their rota rod scores during next days of training. Memantine also compromised improvement in the rota rod scores in control mice upon repetitive training. These effects may be due to the effects of memantine on plasticity (LTD suppression) and NMDA receptor modulation. Some effects of chronically administered memantine persisted even after its wash-out from brain slices. Chronic memantine reduced morphological signs of neurodegeneration in the cerebellum of SCA1 model mice. This resulted in an apparent initial reduction of ataxic phenotype, but memantine also affected cerebellar plasticity and ultimately compromised motor learning. We speculate that that clinical application of memantine in SCA1 might be hampered by its ability to suppress NMDA-dependent plasticity in cerebellar cortex.

Targeting the autophagy-NAD axis protects against cell death in Niemann-Pick type C1 disease models.

Impairment of autophagy leads to an accumulation of misfolded proteins and damaged organelles and has been implicated in plethora of human diseases. Loss of autophagy in actively respiring cells has also been shown to trigger metabolic collapse mediated by the depletion of nicotinamide adenine dinucleotide (NAD) pools, resulting in cell death. Here we found that the deficit in the autophagy-NAD axis underpins the loss of viability in cell models of a neurodegenerative lysosomal storage disorder, Niemann-Pick type C1 (NPC1) disease. Defective autophagic flux in NPC1 cells resulted in mitochondrial dysfunction due to impairment of mitophagy, leading to the depletion of both the reduced and oxidised forms of NAD as identified via metabolic profiling. Consequently, exhaustion of the NAD pools triggered mitochondrial depolarisation and apoptotic cell death. Our chemical screening identified two FDA-approved drugs, celecoxib and memantine, as autophagy activators which effectively restored autophagic flux, NAD levels, and cell viability of NPC1 cells. Of biomedical relevance, either pharmacological rescue of the autophagy deficiency or NAD precursor supplementation restored NAD levels and improved the viability of NPC1 patient fibroblasts and induced pluripotent stem cell (iPSC)-derived cortical neurons. Together, our findings identify the autophagy-NAD axis as a mechanism of cell death and a target for therapeutic interventions in NPC1 disease, with a potential relevance to other neurodegenerative disorders.

The effects of memantine on recovery, cognitive functions, and pain after propofol anesthesia / Efeitos da memantina sobre a recuperação, funções cognitivas e dor após a anestesia com propofol

Abstract Objectives: Postoperative cognitive dysfunction refers to the problems associated with thought and memory that are often experienced after major surgery. The aim of this study is to evaluate the effects of intraperitoneally administered memantine on recovery, cognitive functions, and pain after propofol anesthesia. Methods: The study was conducted in Gazi University Animal Research Laboratory, Ankara, Turkey in January 2012. Twenty-four adult female Wistar Albino rats weighing 170-270 g were educated for 300 s in the radial arm maze (RAM) over three days. Group P was administered 150 mg kg−1 of intraperitoneal (IP) propofol; Group M was given 1 mg kg−1 of IP memantine; and Group MP was given 1 mg kg−1 of IP memantine before being administered 150 mg kg−1 of IP propofol. The control group received only IP saline. RAM and hot plate values were obtained after recovery from the groups that received propofol anesthesia and 30 min after the administration of drugs in other two groups. Results: The duration of recovery for Group MP was significantly shorter than Group P (p < 0.001), and the number of entries and exits in the RAM by Group MP was significantly higher during the first hour when compared to Group P (p < 0.0001). Hot plate values, on the other hand, were found to be significantly increased in all groups when compared to the control values, aside from Group C (p < 0.0001). Conclusion: In this study, memantine provided shorter recovery times, better cognitive functions, and reduced postoperative pain. From this study, we find that memantine has beneficial effects on recovery, cognitive functions, and pain after propofol anesthesia.

Resumo Objetivos: A disfunção cognitiva no pós-operatório refere-se a problemas associados ao pensamento e à memória que são frequentemente manifestados após uma cirurgia de grande porte. O objetivo deste estudo foi avaliar os efeitos da memantina administrada por via intraperitoneal sobre a recuperação, as funções cognitivas e a dor após a anestesia com propofol. Métodos: O estudo foi feito no Laboratório de Pesquisa com Animais da Universidade de Gazi, Ankara, Turquia, em janeiro de 2012. Vinte e quatro ratos albinos do sexo feminino, adultos, da linhagem Wistar, com 170-270 g, foram treinados durante 300 segundos no labirinto radial de oito braços (LRB) durante três dias. O Grupo P recebeu 150 mg/kg−1 de propofol por via intraperitoneal (IP), o Grupo H recebeu 1 mg/kg−1 de memantina IP e o Grupo MP recebeu 1 mg/kg−1 de memantina IP antes da administração de 150 mg/kg−1 de propofol (IP). O grupo controle recebeu apenas solução salina IP. Os valores do LRB e da placa quente foram obtidos após a recuperação dos grupos que receberam propofol e 30 minutos após a administração dos fármacos nos outros dois grupos. Resultados: O tempo de recuperação do Grupo MP foi significativamente menor do que o do Grupo P (p < 0,001) e o número de entradas e saídas do LRB do Grupo MP foi significativamente maior durante a primeira hora, em comparação com o Grupo P (p < 0,0001). Os valores da placa quente, por outro lado, foram significativamente maiores em todos os grupos, em comparação com os valores do grupo controle, exceto pelo Grupo C (p < 0,0001). Conclusão: No presente estudo, memantina proporcionou tempos mais curtos de recuperação, funções cognitivas melhores e reduziu a dor no pós-operatório. A partir deste estudo, descobrimos que a memantina tem efeitos benéficos sobre a recuperação, as funções cognitivas e a dor após anestesia com propofol.

Memantine prevents cardiomyocytes nuclear size reduction in the left ventricle of rats exposed to cold stress

OBJECTIVES: Memantine is an N-methyl-d-aspartate (NMDA) glutamate receptor antagonist used to treat Alzheimer's disease. Previous studies have suggested that receptor blockers act as neuroprotective agents; however, no study has specifically investigated the impact that these drugs have on the heart. We sought to evaluate the effects of memantine on nuclear size reduction in cardiac cells exposed to cold stress. METHOD: We used male EPM-Wistar rats (n=40) divided into 4 groups: 1) Matched control (CON); 2) Memantine-treated rats (MEM); 3) Rats undergoing induced hypothermia (IH) and 4) Rats undergoing induced hypothermia that were also treated with memantine (IHM). Animals in the MEM and IHM groups were treated by oral gavage administration of 20 mg/kg/day memantine over an eight-day period. Animals in the IH and IHM groups were submitted to 4 hours of hypothermia in a controlled environment with a temperature of - 8ºC on the last day of the study. RESULTS: The MEM group had the largest cardiomyocyte nuclear size (151 ± 3.5 μm³ vs. CON: 142 ± 2.3 μm³; p<0.05), while the IH group had the smallest mean value of nuclear size. The nuclear size of the IHM group was preserved (125 ± 2.9 μm³) compared to the IH group (108 ± 1.7 μm³; p<0.05). CONCLUSION: Memantine prevented the nuclear size reduction of cardiomyocytes in rats exposed to cold stress.

Efectos diferenciales del bloqueo de los receptores de N-metil-D-aspartato en los reflejos nociceptivos somáticos y viscerales / Differential effects of Nmethyl-D-aspartate receptor blockade on nociceptive somatic and visceral reflexes

Los receptores de N-metil-D-aspartato (NMDA) parecen desempeñar una función poco importante en las respuestas nociceptivas provocadas por la estimulación aguda de tejidos somáticos normales, interviniendo, eso sí, en las respuestas hiperalgésicas que aparecen después de una lesión periférica o inflamación. Estudios anteriores de este laboratorio han demostrado la existencia de diferencias importantes en la organización neural de las rutas nociceptivas somáticas y viscerales. En este caso, hemos explorado la función de los re c e p t o res de NMDA en el procesamiento de los estímulos dolorosos viscerales frente a los estímulos dolorosos somáticos. Canulamos cerca de la vejiga el uréter izquierdo de ratas Wistar hembras adultas anestesiadas con fentobarbitona (50 mg.kg- 1 i.p.) La distensión gradual del uréter (30 s, 25-80 mmHg) provocó un aumento de la presión arterial. Esa respuesta fue inhibida de una form a dependiente de la dosis por quetamina y memantina, dos sustancias que bloquean los canales de iones de los receptores de NMDA (DI5 0 = 2,4 ñ 1,6 y 14,5 ñ 1,3 mg.kg- 1, i.v.), así como por Mrz 2/576, un antagonista del sitio de la glicina de Merz (DI5 0 = 0,2 ñ 0,2 mg.kg- 1). Los estímulos graduales provocados por un pellizco (30s, 2-4 N) en la pata trasera provocaron una respuesta similar de la presión, si bien dicha respuesta no se vio afectada por la quetamina (hasta 10 mg.kg- 1). Tampoco Mrz 2/576 influyó en la re spuesta a los pellizcos dolorosos, mientras que la memantina (DI5 0 = 17 ñ 12 mg.kg- 1) sí inhibió la respuesta a ese tipo de estímulo. Sin embargo, en el rango de dosis utilizado, ni la quetamina ni Mrz 2/576 inhibieron la re spuesta de la presión a un estímulo de origen no nociceptivo (oclusión carótida bilateral), mientras que la memantina sí la inhibió. Por tanto, los efectos de la memantina se deban probablemente a una acción cardiovascular inespecífica. Estos resultados demuestran que los antagonistas de los receptores de NMDA inhiben los reflejos nociceptivos provocados en el uréter normal, y sugieren que los receptore s de NMDA están implicados en el procesamiento de los estímulos nociceptivos agudos en las vísceras. Hemos concluido que la estimulación aguda del tejido visceral normal provoca intensas respuestas por activación de mecanismos neurales mediados por los re c e p t o res de NMDA. No obstante, en las rutas somáticas estos mecanismos se activan sólo ante un estímulo periférico de mayor intensidad, como el producido por una lesión o inflamación. 1999 Asociación Internacional para el Estudio del Dolor (AU)