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PubMed2002

[Comparison of the anticonvulsant activity of organic mono- and di-cations and their potential to inhibit NMDA and AMPA glutamate receptors].

Effects of mono- and dicationic derivatives of adamantine and phenylcyclohexyl were studied on: (i) open channels of NMDA and AMPA glutamate receptors in the experiments on the isolated rat brain neurones, and (ii) convulsions induced by intraventricular injections of NMDA or kainate in mice. Monocations inhibited the NMDA receptors in vitro and prevented convulsions induced by NMDA in vivo, but failed to affect both the AMPA receptors and kainite-induced convulsions. Dications (IEM-1754 and IEM-1925) revealed both anti-NMDA and anti-AMPA potency in vitro, were highly effective against kainite-induced convulsions and excelled monocations in preventing the NMDA-induced ones. Evidently some steps connected with the AMPA receptor activity are involved in the genesis of the NMDA-induced convulsions. Anticonvulsant potency of IEM-1754 and IEM-1925 is comparable with those of known NMDA receptor inhibitors: memantine and MK-801. The IEM-1754 and IEM-1925 show no side effects. An incomplete correspondence between the activity in vitro and in vivo found studying some derivatives, may be due to peculiarities of their pharmacokinetics.

Adamantane↗
PubMed2002

Gateways to clinical trials.

Gateways to Clinical Trials is a guide to the most recent clinical trials in current literature and congresses. The data in the following tables has been retrieved from the Clinical Studies knowledge area of Prous Science Integrity, the drug discovery and development portal, http://integrity.prous.com. This issue focuses on the following selection of drugs: Abacavir sulfate, abarelix, adalimumab, adefovir dipivoxil, AdGVVEGF121.10, anastrozole, anecortave acetate, aripiprazole, asulacrine isethionate, atazanavir, ATL-962, 16-Aza-epothilone B; Bevacizumab, bicalutamide, blonanserin, BMS-188667, bosentan; Celecoxib, celmoleukin, cetuximab, cilomilast, cinacalcet hydrochloride, CNTF(Ax15), colesevelam hydrochloride; Daclizumab, delavirdine mesilate, desogestrel, desoxyepothilone B, dexmethylphenidate hydrochloride, duloxetine hydrochloride; Ecogramostim, emtricitabine, epalrestat, escitalopram oxalate, examorelin, exendin-4, ezetimibe; Fidarestat, frovatriptan; HIV-1 Immunogen; Iloperidone, insulin detemir, insulin lispro, irinotecan hydrochloride; Keratinocyte growth factor; Lasofoxifene tartrate, levetiracetam, levormeloxifene, levosimendan, lumiracoxib, LY-307161 SR; Memantine hydrochloride, MEN-10755, metformin hydrochloride, metreleptin, motexafin gadolinium; Naratriptan hydrochloride, natalizumab, nesiritide, nicotine, NN-2211, NN-414; Olanzapine, omalizumab; Pegaptanib sodium, peginterferon alfa-2a, peginterferon alfa-2b, pegvisomant, pimecrolimus, pirfenidone, pramlintide acetate prasterone, pregabalin; Quetiapine fumarate; Rabeprazole sodium, raloxifene hydrochloride, raltitrexed, rDNA insulin, rFGF-2, risedronate sodium, rofecoxib, roflumilast, rosiglitazone maleate; SN-22995; Tacrolimus, tadalafil, tegaserod maleate, tiotropium bromide, tomoxetine hydrochloride, trastuzumab, trimegestone; Voglibose, Voriconazole; Ziprasidone hydrochloride.

Clinical Trials as Topic↗
PubMed2003

[Role of NMDA and AMPA glutamate receptors in the mechanism of korazol-induced convulsions in mice].

The potency of mono- and dikationic derivatives of adamantane and phenylcyclohexyl to prevent seizures induced in mice by intraperitoneal administration of 80 mg/kg pentylenetetrazol (corazol), was studied. Monocationic derivatives of phenylcyclohexyl, being the selective channel blockers of NMDA glutamate receptors, as well memantine and MK-801 in micromolar concentrations, prevented both clonic and tonic components of corazol-induced convulsions. Their dicatonic derivatives which are channel blockers of NMDA and AMPA types of glutamate receptors, failed to prevent clonic seizures but at submicromolar concentrations prevented the tonic extensions provoked by corazol. Evidently, convulsive action of corazol originating from suppression of GABA-ergic inhibition is realized through activation of glutamergic synaptic transmission, and NMDA receptors are mainly involved in genesis of clonic seizures whereas activation of AMPA receptors is important for the tonic component of the corazol-induced syndrome.

Animals↗
PubMed2003

Dexanabinol: a novel cannabinoid with neuroprotective properties.

Dexanabinol was developed as a synthetic analog of the cannabinoid tetrahydrocannabinol, however, the action of the drug is as a weak, uncompetitive antagonist at the N-methyl-D-aspartate (NMDA) receptor. Dexanabinol is an effective neuroprotectant in animal models of hypoxemia/ischemia, neurotoxin exposure and nerve crush. Unlike some other uncompetitive NMDA receptor antagonists, dexanabinol does not produce psychotrophic effects and is generally well tolerated in humans. In this respect it is similar to the uncompetitive NMDA receptor antagonist memantine. Dexanabinol is currently in phase III clinical trials for severe head injury. It is a promising drug that appears to be able to provide the therapeutic benefits of uncompetitive NMDA-receptor antagonists without the adverse side effects associated with some of the earlier drugs of this type.

Animals↗
PubMed2003

[Pharmacotherapy in heroin addiction: pharmacological approaches to remission stabilization and recurrence prevention].

After withdrawal arrest in many heroin addicts, they displayed the syndrome of anhedonia including affective disorders (depression, dysphoria, anxiety), dyssomnia and a pathologic craving for opiates. Anhedonia is often the cause for recurrence in heroine addiction, therefore, an appropriate treatment is an important aspect in recurrence prevention and remission stabilization. Since depression and drive for heroin are the key symptoms in anhedonia, we undertook the efficiency study of therapy (in anhedonia) by antidepressants belonging to the selective serotonin reuptake inhibitors (SSRI) and NMDA receptor antagonists, citalopram and memantine, respectively, which have a clinical antidepressant action and an experimental anti-addictive action. Both drugs were found to arrest effectively virtually all signs of anhedonia, however, their action on remission stabilization was rather moderate. It looked to be more promising to use, in remission stabilization, the uttermost antagonist of opiate receptors (naltrexone) blocking reliably all heroine effects. A double blind placebo-controlled study, undertaken by us, convincingly showed a significantly smaller number of relapses with naltrexone in heroin addicts. At the same time, the drug had no valuable effect on the anhedonia symptoms, which worsened the compliance entailing a poorer therapy efficiency. Finally, a combination of naltrexone (blocking the heroin action and reducing the recurrence rate) with SSRI antidepressants (effectively arresting the anhedonia symptoms and improving the compliance with naltrexone medication and remission quality) is a most promising approach to remission stabilization and recurrence prevention.

Adult↗
PubMed2003

Therapeutic N-methyl-D-aspartate receptor antagonists: will reality meet expectation?

The initial promise of the N-methyl-D-aspartate (NMDA) receptor antagonists gave hope for the therapeutic treatment of neurological disorders, which ultimately was unfulfilled. In many cases, their adverse psychotomimetic effects were too severe for them to be used therapeutically in the way that most had envisaged. The last decade has seen significant progress in our understanding of the NMDA receptor complex and the site(s) of action of various uncompetitive antagonists. In particular, this has led to the development of a family of low-affinity, uncompetitive, cation channel antagonists that seem to offer many of the benefits of the older channel blockers but with a more acceptable side effect profile. Drugs such as memantine have demonstrated beneficial effects in clinical trials for Alzheimer's disease and ischemia, with few adverse side effects. Likewise, the NMDA receptor NR2B subunit antagonists derived from drugs such as ifenprodil, have proven beneficial in the treatment of neuropathic pain, and are also associated with few adverse side effects. These, and other new experimental agents, are demonstrating that it may yet be possible to tap the enormous potential of NMDA receptor antagonists as therapeutic drugs, without necessarily incurring the adverse side effects associated with the first generation compounds.

Animals↗
PubMed2004

Renaissance of NMDA receptor antagonists: do they have a role in the pharmacotherapy for alcoholism?

Long-term alcohol exposure leads to the development of alcohol dependence, which is possibly induced by changes in specific neurotransmitter functions. Accumulating evidence suggests that the N-methyl-D-aspartate (NMDA) type of ionotropic glutamate receptor is a particularly important site of action for ethanol. Ethanol potently and selectively inhibits NMDA receptors (NMDARs) and prolonged ethanol exposure produces a compensatory 'upregulation' of NMDAR functions. These changes are believed to underlie the development of ethanol tolerance and dependence as well as acute and delayed signs of withdrawal. Therefore, negative modulators of NMDARs may be useful agents for the pharmacotherapy of alcoholism. NMDAR antagonists attenuate not only the physical symptoms but also some affective and motivational components of alcohol withdrawal. Encouraging experimental results have been obtained with novel uncompetitive (memantine and neramexane (Merz & Co GmbH/Forest Laboratories Inc)), glycine site and NR2B subunit-selective NMDA antagonists (SSNAs). Recently emerged NR2B SSNAs (CP-101606 (Pfizer Inc), Co-101244 (Pfizer Inc/Purdue Neuroscience Corp/Senju Pharmaceutical Co Ltd), CI-1041 (Purdue Neuroscience Corp/Pfizer Inc) and indole-2-carboxamide derivatives) have demonstrated excellent in vitro potency against withdrawal-induced cytotoxicity. Although in vivo data are few, according to their in vitro efficacy and good tolerability, novel NMDA antagonists, especially the NR2B-selective antagonists, may offer a preferable alternative to the presently available pharmacotherapies for treating alcoholism.

Alcoholism↗
PubMed2004

[Current antidementive therapy].

Current antidementive treatment can delay further progress of the symptoms of dementia and should therefore be initiated as early as possible and be of adequate duration. Wherever possible, maximum permissible doses should be given. The efficacy of current antidementive drugs in Alzheimer's disease has been sufficiently documented by relevant studies. The acetylcholinesterase inhibitors, donepezil, galantamine and rivastigmine have been approved for the treatment of mild-to-moderate Alzheimer's dementia, the NMDA inhibitor memantine is approved for moderate-to-severe Alzheimer's disease. Ginkgo biloba or piracetam are alternatives for patients with mild-to-moderate dementia, in whom acetylcholinesterase inhibitors cannot be used.

Activities of Daily Living↗
PubMed2004

[Neurochemical early and differential diagnostics for Alzheimer's disease].

Current medication procedures for Alzheimer's dementia (AD) such as inhibitors of acetyl cholinesterase or Memantine and future therapeutic approaches demand improved early diagnostics. However, the differentiation between early cognitive impairments due to primary progressive demential conditions and cognitive deficits in geriatric or depressive people is a great clinical challenge. The detection of biochemical markers such as beta-amyloid peptide and tau proteins in the cerebrospinal fluid can lead to improved diagnostics of the early stages and premonitory symptoms of AD. As a result, future preventive drug treatment strategies can be employed early and selectively.

Aged↗
PubMed1998

Alzheimer's disease therapy - an update.

The 5th International Geneva/Springfield Symposium on Advances in Alzheimer Therapy focused on new therapeutic approaches for the treatment of Alzheimer 's disease (AD) based on the latest basic science data. The two major pharmacological principles of cholinergic therapy are 1) reduction of acetylcholine hydrolysis by means of acetylcholinesterase (AChE) inhibitors; and 2) direct stimulation of nicotinic or muscarinic receptors with selective agonists. Currently used AChE inhibitors are tacrine, donepezil hydrochloride, rivastigmine and metrifonate. In the area of muscarinic and nicotinic receptor modulation, studies were presented on AF-102B and AF-150(S), BIBN-99, CI-1017, RJR-2403, ABT-418, ABT-089, GTS-21 and SIB-1553A. Based on evidence of inflammatory mechanisms in the pathogenesis of AD, selective COX-2 inhibitors for the prevention and treatment of AD are a target of several pharmaceutical companies. Concerning known antiinflammatory drugs, results from controlled trials are expected soon. Estrogen replacement has been reported to produce cognitive and affective improvement in women with AD, and results from a number of studies were presented. Age-associated increases in oxidative stress may play a role in AD and thus antioxidants may also have a place in the therapy of this disease. The antioxidants vitamin E and selegiline are being investigated. Other drugs under investigation are propentofylline, Cerebrolysin, citicoline sodium, CDP-choline, memantine, Egb-761, calagualine and AIT-082. Iododoxorubicin may represent a new class of compounds able to interfere with the beta-amyloid cascade in AD and other brain amyloid diseases. Future preventive strategies in AD include genotype analysis and screening, presymptomatic diagnosis and avoidance of environmental risk factors.

Journal Article↗
PubMed2004

New therapeutic approaches in Alzheimer's disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects a large proportion of the elderly population. It causes a progressive decline in memory and other cognitive functions. There is no effective treatment of AD despite the great effort in trying to find one. Herein new therapeutic approaches including those closely targeting the pathogenesis of the disease have been discussed. Potential disease modifying treatments that are being considered as future treatment of AD include avaccination, secretase inhibitors, cholesterol lowering drugs, metal chelators and anti- inflammatory agents. According to Evidence Based Dementia Practice, only inhibitors of acetylcholinesterase (AChE) are approved in mild and moderate stages of AD treatment. From the end of 2003, FDA also approved memantine for much severer phases of AD. When all the presented possibilities are taken into account, the most important target for scientists and physicians is not only to find ways for causative cure of AD, but also to be ready for that moment. There is a great need for finding routine biomarkers and sensitive enough clinical tests for diagnosis of AD in which the lasting pathological process does not destroy too many neurones.

Alzheimer Disease↗
PubMed2005

The NMDA receptor complex: a long and winding road to therapeutics.

Advances in our basic understanding of inhibitory and excitatory amino acid neurotransmission have provided the foundation for directed drug discovery programs to modulate inhibitory GABAergic and excitatory N-methyl-D-aspartate (NMDA) receptor-mediated synapses. Gamma-Amino butyric acid (GABA(A)) and NMDA receptors are complex ion channels formed by multiple protein subunits that act as binding sites for transmitter amino acids and as allosteric regulatory binding sites to regulate ion channel activity. In the case of the NMDA receptor complex, one such allosteric site binds the obligatory glycine and/or d-serine co-agonist. Historical data from preclinical and clinical studies of GABAergic agents have clearly demonstrated that direct receptor modulators lack sufficient therapeutic indices to warrant clinical utility. However, pharmacological modulation of allosteric sites of the GABA multimeric receptor has resulted in the clinical development of safe and efficacious agents, exemplified by the benzodiazepines. Research has also revealed a similar outcome for the NMDA receptor, with allosteric modulators demonstrating improved safety profiles in the modulation of excitatory amino acid (EAA) transmission compared with direct NMDA receptor antagonists. First-generation EAA drugs were low affinity channel blockers of the NMDA multimeric receptor complex and included the anesthetic agent ketamine and the Alzheimer's drug memantine. As predicted by preclinical studies, direct NMDA receptor antagonists (eg, selfotel (Novartis AG) and high-affinity channel blockers (eg, dizocilpine) failed in the clinic as a result of narrow therapeutic indices. More recent efforts have focused on glycine/d-serine co-agonist function. These approaches include partial glycine agonists, in their agonist dose-range, for cognitive improvement and for treating schizophrenia. Such partial glycine agonists are also being advanced for the treatment of neuropathic pain in the antagonist dose range. An alternate approach to partial glycine agonists is to inhibit the uptake carrier(s) for glycine (ie, GlyT-1 and GlyT-2), thereby potentiating the lifetime of synaptic glycine. A number of glycine uptake inhibitors have been reported and their preclinical profiles support investigation into their utility in treating schizophrenia.

Clinical Trials, Phase III as Topic↗
PubMed2005

[Gerontology].

What are the benefits of proteino-energetic supplementation in malnourished elderly persons? How many days should lower urinary tract infections be treated in elderly women? Is vitamin D supplementation effective in preventing falls? Does treatment with cholinesterase inhibitors and memantine benefit patients with Alzheimer's disease or Mild Cognitive Impairment (MCI)? This overview presents data from recent studies that attempted to answer these questions and contributed to improving the management of these important conditions in elderly persons.

Aged↗
PubMedDate not supplied

Effect of NMDA receptor antagonists on behavioral impairment induced by chronic treatment with dexamethasone.

Severe and prolonged stress but also long-term treatment with glucocorticoids (GCs) have been described to cause brain damage (especially hippocampal and striatal neurons) in humans as well as in animals. GCs potentiate stress or ischemia-induced accumulation of excitatory amino acids (EAA) in the extracellular space of the hippocampus. It was shown that EAA play a major role in various neurologic disorders with cognitive dysfunction. Many authors suggested the neuroprotective effect of N-methyl-D-aspartate (NMDA) glutamate receptor antagonists in some acute or chronic neurodegenerative diseases. On the other hand, many NMDAreceptor antagonists produce highly undesirable side-effects at the doses within their putative therapeutic range. The aim of the present study was to evaluate the behavioral effects (memory performance, motor coordination, lethality and body weight) of MK-801 or memantine (MEMAN, non-competitive NMDAreceptor antagonists) (at the doses of 25 and 50 microg/kg/day or 2.5 and 5.0 mg/kg/day, respectively) on neurotoxicity induced by dexamethasone (DEX) administered chronically at the doses of 40 or 80 mg/kg/day in mice. It was shown that prolonged treatment (for 10 days) with DEX at the dose of 80 mg/kg/day (but not at 40 mg/kg/day) significantly decreased the retention time in the memory task in mice and impaired the motor coordination in "chimney" test. Neither MK-801 nor MEMAN (at the both doses used) were able to counteract the behavioral impairment induced by DEX administration. Moreover, the potentiation of the body weight reduction and lethality induced by DEX were noted in mice co-treated with MK-801 or MEMAN. The above findings suggest that MK-801 or MEMAN at the doses used have no neuroprotective effect. On the contrary, both NMDA receptor antagonists potentiate the toxicity of DEX given chronically.

Animals↗
PubMed2005

[Is there a treatment for Alzheimer's disease?].

Alzheimer's disease is a frequent neurodegenerative disease, which affects more than one third of elderly persons over 80 years. No curative treatment is currently available for this disease, but symptomatic treatments have produced significant improvements in patients' condition. Cholinesterase inhibitors should be prescribed for early and moderate stages and memantine for more severe stages of the disease. These drugs have an impact on cognitive performances, may delay functional decline and improve behaviour disturbances. From a preventive perspective, evidence of benefit from early management of vascular risk factors is accumulating. In the near future, the improved comprehension of the underlying mechanisms of Alzheimer's disease will hopefully bring new treatments, thats will delay or modify its course.

Alzheimer Disease↗
PubMed2005

Physiology and pathology of NMDA receptors.

Ionotropic glutamate receptors of the N-methyl-D-aspartate (NMDA) subtype are highly expressed in the central nervous system and are involved in excitatory synaptic transmission and synaptic plasticity. Prolonged activation of NMDA receptors can lead to excitotoxicity, which is implicated in the pathogenesis of neurodegeneration occurring in various acute and chronic disorders of the central nervous system. Recent advances in understanding the function, pharmacology, genetics and structure of NMDA receptors has promoted a search for new compounds that could be therapeutically used. These compounds act on agonist binding sites, either apart from them or directly within the ion channel pore. Members of the last group are called open channel blockers, and some of them, such as memantine and ketamine, are already clinically used. Kinetic modeling of NMDA receptor activity was employed to define the effects of various groups of modulators. Quantifying the action of these substances by kinetic parameters can help us to reveal the molecular mechanism of action at the receptor and to characterize the dependence of its action on the mode of NMDA receptor activation. Two modes are considered: phasic activation, induced by synaptically released glutamate, and tonic activation, which is expected to occur under pathological conditions when low, but sustained levels of glutamate activate NMDA receptors. The aim of our review is to summarize the recent data about the structural and functional properties of NMDA receptors and their role in long-term potentiation and excitotoxicity.

Animals↗
PubMedDate not supplied

[Neuropsychological assessment in the diagnosis and differential diagnosis of fronto-temporal dementia].

Clinical diagnosis of fronto-temporal dementia (FTD) and its rare variants (semantic dementia and primary progressive aphasia) represents a special challenge bearing in mind its difficulties and is important due to therapeutic differences with the most common Alzheimer's dementia. Of note, cholinesterase inhibitors commonly prescribed in Alzheimer's disease are not effective in FTD and a novel drug, memantine, has not been evaluated as yet. Neuropsychological evaluation is an important add-on to neurological, psychiatric and neuroimaging assessments in the clinical diagnosis of FTD. In this paper, we have described characteristics of neuropsychological deficits observed in FTD (such as attention, language, visuospatial and memory impairments) as well as tools used (tests) in clinical practice. Special attention is paid to the utility of neuropsychological examination in the differential diagnosis of FTD versus Alzheimer's disease, vascular dementia and other, less common forms of dementia.

Alzheimer Disease↗
PubMed2005

[Perspective of dementia therapy].

As growing population of the elderly over 65 years of age, dementia will be one of the most important diseases in Japan. To defeat the dementia, the following strategies would be needed; 1) acceleration of basic research for dementia, 2) acceleration of clinical research for dementia, 3) development of care system for patients with dementia, and 4) provision of social basis for the elderly. On the basis of an understanding of the pathophysiology, treatments of Alzheimer's disease includes the following components: antiamyloid therapies including secretase inhibitors, metal binding agents and Abeta vaccine, neuroprotective strategies, cholinesterase inhibitors, memantine, immunotherapy including Abeta vaccine, anti-inflammatory therapy, hormone-replacement therapy, psychopharmacologic agents, nonpharmacologic interventions and health maintenance activities, and an alliance between clinicians and family members and other caregivers responsible for the patient. The combination therapies with pharmacologic and nonpharmacologic components are probably useful for patients with Alzheimer disease or other dementia. In addition, development of accurate diagnostic methods of dementia and the early detection system of amyloid in the brain are expected. Responsibility of neurologist for dementia is getting important next 10 years in Japan.

Aged↗