Nootropic Drugs Positively Modulate ?-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid-Sensitive Glutamate Receptors in Neuronal Cultures

Aniracetam: An Evidence-Based Model for Preventing the Accumulation of Amyloid-β Plaques in Alzheimer's Disease

 Alzheimer's disease is the leading cause of dementia in the world. It affects 6 million people in the United States and 50 million people worldwide. Alzheimer's disease is characterized by the accumulation of amyloid-β plaques (Aβ), an increase in tau protein neurofibrillary tangles, and a loss of synapses. Since the 1990s, removing and reducing Aβ has been the focus of Alzheimer's treatment and prevention research. The accumulation of Aβ can lead to oxidative stress, inflammation, neurotoxicity, and eventually apoptosis. These insults impair signaling systems in the brain, potentially leading to memory loss and cognitive decline. Aniracetam is a safe, effective, cognitive-enhancing drug that improves memory in both human and animal studies. Aniracetam may prevent the production and accumulation of Aβ by increasing α-secretase activity through two distinct pathways: 1) increasing brain derived neurotrophic factor expression and 2) positively modulating metabotropic glutamate receptors. This is the first paper to propose an evidence-based model for aniracetam reducing the accumulation and production of Aβ.

Oxiracetam alleviates anti-inflammatory activity and ameliorates cognitive impairment in the early phase of traumatic brain injury

BACKGROUND

We aimed to investigate the effects of oxiracetam on cognitive impairment in the early phase of traumatic brain injury (TBI), for which no specific treatment is currently available.

METHODS

The in vitro study used a cell injury controller to damage SH-SY5Y cells and evaluate the effect of oxiracetam at a dosage of 100 nM. The in vivo study used a stereotaxic impactor to induce a TBI model in C57BL/6 J mice and analyzed immunohistochemical changes and cognitive function after an intraperitoneal injection of oxiracetam (30 mg/kg/day) for 5 days. The number of mice used in this study was 60. They were divided into three groups (sham, TBI, and TBI with oxiracetam treatment) (20 mice in each group).

RESULTS

The in vitro study showed that oxiracetam treatment resulted in increased superoxide dismutase (SOD)1 and SOD2 mRNA expression. The mRNA and protein expression of COX-2, NLRP3, caspase-1, and interleukin (IL)-1 β were decreased after oxiracetam treatment, along with decreases in intracellular reactive oxygen species production and apoptotic effects. TBI mice treated with oxiracetam exhibited the loss of fewer cortical damaged lesions, less brain edema, and fewer Fluoro-Jade B (FJB)-positive and terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL)-positive cells compared to those without oxiracetam treatment. The mRNA and protein expression of COX-2, NLRP3, caspase-1, and IL-1β were decreased significantly after oxiracetam treatment. These inflammation-related markers, which colocalized with Iba-1-positive or GFAP-positive cells after TBI, were also decreased after oxiracetam treatment. TBI mice treated with oxiracetam had a smaller decrease in preference and more latency time than those not treated with oxiracetam, suggesting the amelioration of impaired cognitive impairment.

CONCLUSIONS

Oxiracetam may be helpful in restoring cognitive impairment by ameliorating neuroinflammation in the early phase of TBI.

Pharmacological Profile of MP-101, a Novel Non-racemic Mixture of R- and S-dimiracetam with Increased Potency in Rat Models of Cognition, Depression and Neuropathic Pain

The racemic mixture dimiracetam negatively modulates NMDA-induced glutamate release in rat spinal cord synaptosomal preparations and is orally effective in models of neuropathic pain. In this study, we compared the effects of dimiracetam, its R- or S-enantiomers, and the R:S 3:1 non-racemic mixture (MP-101). In vitro, dimiracetam was more potent than its R- or S-enantiomers in reducing the NMDA-induced [³H]D-aspartate release in rat spinal cord synaptosomes. Similarly, acute oral administration of dimiracetam was more effective than a single enantiomer in the sodium monoiodoacetate (MIA) paradigm of painful osteoarthritis. Then, we compared the in vitro effects of a broad range of non-racemic enantiomeric mixtures on the NMDA-induced [³H]D-aspartate release. Dimiracetam was a more potent blocker than each isolated enantiomer but the R:S 3:1 non-racemic mixture (MP-101) was even more potent than dimiracetam, with an IC₅₀ in the picomolar range. In the chronic oxaliplatin-induced neuropathic pain model, MP-101 showed a significantly improved anti-neuropathic profile, and its effect continued one week after treatment suspension. MP-101 also performed better than dimiracetam in animal models of cognition and depression. Based on the benign safety and tolerability profile previously observed with racemic dimiracetam, MP-101 appears to be a novel, promising clinical candidate for the prevention and treatment of several neuropathic and neurological disorders.

Effects of genetic polymorphism of drug-metabolizing enzymes on the plasma concentrations of antiepileptic drugs in Chinese population

As a chronic brain disease, epilepsy affects ~50 million people worldwide. The traditional antiepileptic drugs (AEDs) are widely applied but showing various problems. Although the new AEDs have partially solved the problems of traditional AEDs, the current clinical application of traditional AEDs are not completely replaced by new drugs, particularly due to the large individual differences in drug plasma concentrations and narrow therapeutic windows among patients. Therefore, it is still clinically important to continue to treat patients using traditional AEDs with individualized therapeutic plans. To date, our understanding of the molecular and genetic mechanisms regulating plasma concentrations of AEDs has advanced rapidly, expanding the knowledge on the effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of AEDs. It is increasingly imperative to summarize and conceptualize the clinical significance of recent studies on individualized therapeutic regimens. In this review, we extensively summarize the critical effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of several commonly used AEDs as well as the clinical significance of testing genotypes related to drug metabolism on individualized drug dosage. Our review provides solid experimental evidence and clinical guidance for the therapeutic applications of these AEDs.

Positive AMPA receptor modulation in the treatment of neuropsychiatric disorders: A long and winding road

Glutamatergic transmission is widely implicated in neuropsychiatric disorders, and the discovery that ketamine elicits rapid-acting antidepressant effects by modulating α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) signaling has spurred a resurgence of interest in the field. This review explores agents in various stages of development for neuropsychiatric disorders that positively modulate AMPARs, both directly and indirectly. Despite promising preclinical research, few direct and indirect AMPAR positive modulators have progressed past early clinical development. Challenges such as low potency have created barriers to effective implementation. Nevertheless, the functional complexity of AMPARs sets them apart from other drug targets and allows for specificity in drug discovery. Additional effective treatments for neuropsychiatric disorders that work through positive AMPAR modulation may eventually be developed.

Neuroenhancement: State of the Art and Future Perspectives

Pharmacological neuroenhancement refers to the non-medical use of prescription drugs, alcohol, illegal drugs, or the so-called soft enhancers for the purpose of improving cognition, mood, pro-social behavior, or work and academic performance. This phenomenon is undoubtedly more frequent than previously supposed especially amongst university students. The aim of the present paper was to carefully review and comment on the available literature on neuroenhancement, according to Prisma guidelines. The results showed a great use of all prescribed drugs (benzodiazepines, antidepressants, antipsychotics, nootropic compounds, and especially stimulants) as neuroenhancers amongst healthy subjects, although probably the real prevalence is underestimated. The use of illicit drugs and soft enhancers is similarly quite common. Data on the improvement of cognition by other compounds, such as oxytocin and pheromones, or non-pharmacological techniques, specifically deep brain stimulation and transcranial magnetic stimulation, are still limited. In any case, if it is true that human beings are embedded by the desire to overcome the limits of their intrinsic nature, neuroenhancement practices put into question the concept of authenticity. Therefore, the problem appears quite complex and requires to be deepened and analyzed with no prejudice, although within an ethical conceptual frame.

Cognitive Enhancing Drugs in Sport: Current and Future Concerns

Sporting authorities and policy makers have warned of a radical increase in the availability and use of so-called 'smart' drugs, which putatively deliver cognitive enhancements in the form of improved focus, concentration, alertness, and rapid decision-making. Although the potential for health risks is well documented when it comes to performance enhancing drugs in sport, the health implications of cognitive enhancing drugs (CEDs) remain unclear. Objectives: This article aims to provide a foundational understanding about CEDs and their application in sport. It considers what little is known about the types, nature, impact, and implications of their use for athletes and sport policy. Method: A narrative literature review was undertaken to ascertain the emerging role of CEDs beyond their clinical use to treat prescribed disorders, including the limited studies in the sporting domain. This review also considered literature pertinent to the impact of CEDs in sport and the challenges for sport policy. Results: Given the prospects of negative health impacts, policy-makers interested in preventing and controlling the use of CEDs, as well as reducing harm to athletes at all levels of performance, need guidance. This article highlights multi-faceted concerns and shines a spotlight on key issues for sporting bodies to consider regarding the critical impact that widespread use and adoption of these substances might entail. Conclusion: While the World Anti-Doping Agency (WADA) is seemingly awake to the threat posed, actions to circumvent the spread of CEDs throughout sport are nascent and require greater understanding and attention.

In silico and in vitro evaluation of brain penetration properties of selected nootropic agents

Aim: Predictive ( in silico) data suggested that nootropic supplements may penetrate the blood–brain barrier (BBB). We evaluated, in vitro, the ability of nootropics to enter the brain based on the high throughput screening (HTS) measurement of interactions with the P-gp efflux transporter and physicochemical properties and correlated these data with the in silico predictions. Methods & results: The software predicted that piracetam, docosahexaenoic acid (DHA), amantadine and thioflavin-T can best penetrate the BBB. The lipophilicity of these compounds may be predicted by measuring the critical micelle concentration (CMC). DHA and verapamil demonstrated high lipophilicity. DHA, verapamil and phosphatidylserine (PS) may be good substrates of the P-gp transporter. Conclusion: Permeability of nootropics may be successfully predicted by high throughput screening-lead optimization assay technologies.

Blood mononuclear cells as speculum of emotional stress analyzed by synchrotron infrared spectroscopy and a nootropic drug

Chronic psychological stress is an important public health issue which generates behavioral changes, anxiety, immunosuppression and oxidative damage. Piracetam is a cognitive enhancer, at cellular level it protects from oxidative stress. The aim of this study was to evaluate the effect of psychological stress and of piracetam on circulating mononuclear cells by analyzing the biochemical spectrome using Synchrotron Radiation Fourier Transform Infrared Microspectroscopy (SR-μFTIR). Rats were exposed for five days to a stressor (cat odor) under oral administration of piracetam (600 mg/kg). SR-μFTIR analysis showed a decrease in bands associated to the lipids region (2852 cm^-1, 2923 cm^-1 and 2962 cm^-1) and an increase absorption of the amide I band (1654 cm^-1) under stress conditions. The principal component analysis showed increase oxidation of lipids (decrease of 3010 cm^-1, 2923 cm^-1 and 2852 cm^-1 bands) as well as proteins denaturation (increase of 1610 cm^-1 and 1690 cm^-1 bands) under stress. Piracetam provided protection to polyunsaturated lipids (p ≤ 0.001) and lipids/proteins ratio (p ≤ 0.001). Behaviorally, this drug diminished fear and anxiety in stressed animals by the plus maze test (p ≤ 0.002). However, this drug induced oxidative stress in mononuclear cells from unstressed animals and altered their behavior.

(S)-Oxiracetam is the Active Ingredient in Oxiracetam that Alleviates the Cognitive Impairment Induced by Chronic Cerebral Hypoperfusion in Rats

Chronic cerebral hypoperfusion is a pathological state that is associated with the cognitive impairments in vascular dementia. Oxiracetam is a nootropic drug that is commonly used to treat cognitive deficits of cerebrovascular origins. However, oxiracetam is currently used as a racemic mixture whose effective ingredient has not been identified to date. In this study, we first identified that (S)-oxiracetam, but not (R)-oxiracetam, was the effective ingredient that alleviated the impairments of spatial learning and memory by ameliorating neuron damage and white matter lesions, increasing the cerebral blood flow, and inhibiting astrocyte activation in chronic cerebral hypoperfused rats. Furthermore, using MALDI-MSI and LC-MS/MS, we demonstrated that (S)-oxiracetam regulated ATP metabolism, glutamine-glutamate and anti-oxidants in the cortex region of hypoperfused rats. Altogether, our results strongly suggest that (S)-oxiracetam alone could be a nootropic drug for the treatment of cognitive impairments caused by cerebral hypoperfusion.

Non-Pharmacological Treatments for ADHD in Youth

BACKGROUND

Complementary and alternative medicine (CAM) in psychiatry or integrative psychiatry covers a wide range of biological, psychological and mind-body treatments that enhance standard medical practices and patient outcomes. While CAM approaches are popular amongst patients in their practice as well as in self-report because of their ease of use, health professionals have received limited education in these interventions and often are unaware of their patients' use of CAM treatments.

METHOD

This overview highlights evidence-based CAM treatments for attention deficit hyperactivity disorder (ADHD) including dietary interventions, phytomedicines, mind-body practices and neurofeedback.

RESULTS

While conventional treatments are the mainstays for ADHD, there are a large number of available treatments that can be used to enhance treatment response.

CONCLUSION

With improved education and further scientific and clinical research, validated integrative treatments will provide more effective, lower risk and lower cost care for patients with ADHD.

"Messing with the mind": evolutionary challenges to human brain augmentation

The issue of brain augmentation has received considerable scientific attention over the last two decades. A key factor to brain augmentation that has been widely overlooked are the complex evolutionary processes which have taken place in evolving the human brain to its current state of functioning. Like other bodily organs, the human brain has been subject to the forces of biological adaptation. The structure and function of the brain, is very complex and only now we are beginning to understand some of the basic concepts of cognition. Therefore, this article proposes that brain-machine interfacing and nootropics are not going to produce “augmented” brains because we do not understand enough about how evolutionary pressures have informed the neural networks which support human cognitive faculties.

Multiple-Dose Plasma Pharmacokinetic and Safety Study of LY450108 and LY451395 (AMPA Receptor Potentiators) and Their Concentration in Cerebrospinal Fluid in Healthy Human Subjects

The objective of this study was to measure the steady-state cerebrospinal fluid (CSF) concentration of LY450108 and LY451395 (positive modulators of AMPA receptors) in healthy subjects after the administration of 1 mg and 5 mg. Secondary objectives included the evaluation of safety, pharmacokinetics, and steady-state ratio of plasma:CSF concentrations of LY450108 and LY451395 after multiple dosing. This study was an open-label, multiple oral dose study evaluating 1 mg and 5 mg LY450108 and 1 mg and 5 mg LY451395 in 12 (3 subjects per dosing group) healthy subjects, aged 18 to 49 years. Twelve healthy male subjects completed the study. LY450108 and LY451395 were quantifiable in CSF after 1-mg and 5-mg multiple-dose administrations with plasma:CSF ratio of 82:1 and 44:1, respectively. LY450108 and LY451395 1 mg and 5 mg were measured in the CSF. Single and multiple oral doses of LY450108 and LY451395 were determined to be safe and well tolerated in healthy subjects.

Glutamatergic Approaches for the Treatment of Schizophrenia

Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system and plays a key role in most aspects of normal brain function including cognition, learning and memory. Dysfunction of glutamatergic neurotransmission has been implicated in a number of neurological and psychiatric disorders with a growing body of evidence suggesting that hypofunction of glutamatergic neurotransmission via the N-methyl-d-aspartate (NMDA) receptor plays an important role in the pathophysiology of schizophrenia. It thus follows that potentiation of NMDA receptor function via pharmacological manipulation may provide therapeutic utility for the treatment of schizophrenia and a number of different approaches are currently being pursued by the pharmaceutical industry with this aim in mind. These include strategies that target the glycine/d-serine site of the NMDA receptor (glycine transporter GlyT1, d-serine transporter ASC-1 and d-amino acid oxidase (DAAO) inhibitors) together with those aimed at enhancing glutamatergic neurotransmission via modulation of AMPA receptor and metabotropic glutamate receptor function. Such efforts are now beginning to bear fruit with compounds such as the GlyT1 inhibitor RG1678 and mGlu2 agonist LY2140023 proving to have clinical meaningful effects in phase II clinical trials. While more studies are required to confirm long-term efficacy, functional outcome and safety in schizophrenic agents, these agents hold real promise for addressing unmet medical needs, in particular refractory negative and cognitive symptoms, not currently addressed by existing antipsychotic agents.

A novel CaV2.2 channel inhibition by piracetam in peripheral and central neurons

No mechanistic actions for piracetam have been documented to support its nootropic effects. Voltage-gated calcium channels have been proposed as a promising pharmacological target of nootropic drugs. In this study, we investigated the effect of piracetam on Ca(V)2.2 channels in peripheral neurons, using patch-clamp recordings from cultured superior cervical ganglion neurons. In addition, we tested if Ca(V)2.2 channel inhibition could be related with the effects of piracetam on central neurons. We found that piracetam inhibited native Ca(V)2.2 channels in superior cervical ganglion neurons in a dose-dependent manner, with an IC(50) of 3.4 μmol/L and a Hill coefficient of 1.1. GDPβS dialysis did not prevent piracetam-induced inhibition of Ca(V)2.2 channels and G-protein-coupled receptor activation by noradrenaline did not occlude the piracetam effect. Piracetam altered the biophysical characteristics of Ca(V)2.2 channel such as facilitation ratio. In hippocampal slices, piracetam and ω-conotoxin GVIA diminished the frequency of excitatory postsynaptic potentials and action potentials. Our results provide evidence of piracetam's actions on Ca(V)2.2 channels in peripheral neurons, which might explain some of its nootropic effects in central neurons.

Piracetam, an AMPAkine drug, facilitates memory consolidation in the day-old chick

Piracetam is an AMPAkine drug that may have a range of different mechanisms at the cellular level, and which has been shown to facilitate memory, amongst its other effects. This series of experiments demonstrated that a 10mg/kg dose of piracetam facilitated memory consolidation in the day-old chick when injected from immediately until 120min after weak training (i.e. using a 20% v/v concentration of methyl anthranilate) with the passive avoidance learning task. Administration of piracetam immediately after training led to memory facilitation which lasted for up to 24h following training. This dose of the AMPAkine was not shown to facilitate memory reconsolidation. These findings support the contention that application of the AMPAkine piracetam facilitates memory using a weak training task, and extend the range of actions previously noted with NMDA-related agents to those which also facilitate the AMPA receptor.

Glutamate receptor ion channels: structure, regulation, and function

The mammalian ionotropic glutamate receptor family encodes 18 gene products that coassemble to form ligand-gated ion channels containing an agonist recognition site, a transmembrane ion permeation pathway, and gating elements that couple agonist-induced conformational changes to the opening or closing of the permeation pore. Glutamate receptors mediate fast excitatory synaptic transmission in the central nervous system and are localized on neuronal and non-neuronal cells. These receptors regulate a broad spectrum of processes in the brain, spinal cord, retina, and peripheral nervous system. Glutamate receptors are postulated to play important roles in numerous neurological diseases and have attracted intense scrutiny. The description of glutamate receptor structure, including its transmembrane elements, reveals a complex assembly of multiple semiautonomous extracellular domains linked to a pore-forming element with striking resemblance to an inverted potassium channel. In this review we discuss International Union of Basic and Clinical Pharmacology glutamate receptor nomenclature, structure, assembly, accessory subunits, interacting proteins, gene expression and translation, post-translational modifications, agonist and antagonist pharmacology, allosteric modulation, mechanisms of gating and permeation, roles in normal physiological function, as well as the potential therapeutic use of pharmacological agents acting at glutamate receptors.

Piracetam defines a new binding site for allosteric modulators of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors

Glutamate receptors are the most prevalent excitatory neurotransmitter receptors in the vertebrate central nervous system and are important potential drug targets for cognitive enhancement and the treatment of schizophrenia. Allosteric modulators of AMPA receptors promote dimerization by binding to a dimer interface and reducing desensitization and deactivation. The pyrrolidine allosteric modulators, piracetam and aniracetam, were among the first of this class of drugs to be discovered. We have determined the structure of the ligand binding domain of the AMPA receptor subtypes GluA2 and GluA3 with piracetam and a corresponding structure of GluA3 with aniracetam. Both drugs bind to GluA2 and GluA3 in a very similar manner, suggesting little subunit specificity. However, the binding sites for piracetam and aniracetam differ considerably. Aniracetam binds to a symmetrical site at the center of the dimer interface. Piracetam binds to multiple sites along the dimer interface with low occupation, one of which is a unique binding site for potential allosteric modulators. This new site may be of importance in the design of new allosteric regulators.

Evaluation of the pro-cognitive effects of the AMPA receptor positive modulator, 5-(1-piperidinylcarbonyl)-2,1,3-benzoxadiazole (CX691), in the rat

RATIONALE

Positive allosteric modulators of the glutamatergic alpha-amino-3-hydroxy-5-methyl-4-isoazolepropionic acid (AMPA) receptor do not stimulate AMPA receptors directly but delay deactivation of the receptor and/or slow its desensitisation. This results in increased synaptic responses and enhanced long-term potentiation. Thus, it has been suggested that such compounds may have utility for the treatment of cognitive impairment.

OBJECTIVES

The objective of the study was to investigate the effect of an AMPA positive modulator, CX691, (1) in three rodent models of learning and memory, (2) on neurochemistry in the dorsal hippocampus and medial prefrontal cortex following acute administration, and (3) on brain-derived neurotrophic factor (BDNF) messenger RNA (mRNA) expression in the rat hippocampus following acute and sub-chronic administration.

RESULTS

CX691 attenuated a scopolamine-induced impairment of cued fear conditioning following acute administration (0.1 mg/kg p.o.) and a temporally induced deficit in novel object recognition following both acute (0.1 and 1.0 mg/kg p.o.) and sub-chronic (bi-daily for 7 days) administration (0.01, 0.03, 0.1 mg/kg p.o.). It also improved attentional set-shifting following sub-chronic administration (0.3 mg/kg p.o.). Acute CX691 (0.1, 0.3 and 1.0 mg/kg, p.o.) increased extracellular levels of acetylcholine in the dorsal hippocampus and medial prefrontal cortex and dopamine in the medial prefrontal cortex. Sub-chronic administration of CX691 (0.1 mg/kg, p.o.) elevated BDNF mRNA expression in both the whole and CA(1) sub-region of the hippocampus (P < 0.05).

CONCLUSIONS

Collectively, these data support the pro-cognitive activity reported for AMPA receptor positive modulators and suggest that these compounds may be of benefit in treating disorders characterised by cognitive deficits such as Alzheimer's disease and schizophrenia.

Ampakine CX516 ameliorates functional deficits in AMPA receptors in a hippocampal slice model of protein accumulation

AMPAkines are positive modulators of AMPA receptors, and previous work has shown that these compounds can facilitate synaptic plasticity and improve learning and memory in both animals and humans; thus, their role in the treatment of cognitive impairment is worthy of investigation. In this study, we have utilized an organotypic slice model in which chloroquine-induced lysosomal dysfunction produces many of the pathogenic attributes of Alzheimer's disease. Our previous work demonstrated that synaptic AMPA receptor function is impaired in hippocampal slice cultures exhibiting lysosomal dysfunction leading to protein accumulation. The present study investigated the effect of the AMPAkine CX516 on AMPAR-mediated synaptic transmission as well as the CX516 induced modification of single channel AMPA receptor properties in this organotypic slice-culture model. In whole cell recordings from CA1 pyramidal neurons in chloroquine-treated slices we observed a significant decrease in AMPAR-mediated mEPSC frequency and amplitude indicating synaptic dysfunction. Following application of CX516, these parameters returned to nearly normal levels. Similarly, we report chloroquine-induced impairment of AMPAR single channel properties (decreased probability of opening and mean open time), and significant recovery of these properties following CX516 administration. These results suggest that AMPA receptors may be potential pharmaceutical targets for the treatment of neurodegenerative diseases, and highlights AMPAkines, in particular, as possible therapeutic agents.

Cerebroprotective effect of a new taurine derivative during cerebral ischemia

A new taurine derivative chlorohydrate-N-isopropylamide-2-(1-phenylethyl)aminoethanesulfonic acid normalized energy metabolism, inhibited lipid peroxidation, and reactivated antioxidant enzymes in the brain of rats exposed to ischemia. This taurine derivative decreased the mortality rate of animals with ischemic changes in cerebral circulation. The test compound was more potent than piracetam in producing the cerebroprotective effect.

The AMPA receptor potentiator LY404187 increases cerebral glucose utilization and c-fos expression in the rat

AMPA receptor potentiators enhance AMPA receptor-mediated glutamatergic neurotransmission and may have therapeutic potential as cognitive enhancers or antidepressants. The anatomical basis for the action of AMPA receptor potentiators is unknown. The aim of this study was to determine the effects of the biarylpropylsulfonamide AMPA receptor potentiator, LY404187 (0.05 to 5 mg/kg subcutaneously), upon cerebral glucose utilization and c-fos expression using 14C-2-deoxglucose autoradiography and c-fos immunocytochemistry. LY404187 (0.5 mg/kg) produced significant elevations in glucose utilization in 28 of the 52 anatomical regions analyzed, which included rostral neocortical areas and the hippocampus, as well the dorsal raphe nucleus, lateral habenula, and locus coeruleus. No significant decreases in glucose utilization were observed in any region after LY404187 administration. The increases in glucose utilization with LY404187 (0.5 mg/kg) were blocked by pretreatment with the AMPA receptor antagonist LY293558 (25 mg/kg), indicating that LY404187 acts through AMPA receptor-mediated mechanisms. LY404187 (0.5 mg/kg) also produced increases in c-fos immunoreactivity in the cortex, locus coeruleus, and the dorsal raphe nucleus. These studies demonstrate neuronal activation in key brain areas that are associated with memory processes and thus provide an anatomical basis for the cognitive enhancing effects of AMPA receptor potentiators.

The expression of the PDZ protein MALS-1/velis is regulated by calcium and calcineurin in cerebellar granule cells

Activity-dependent gene expression is thought to be important in shaping neuronal development and in modifying the protein content of neurons. Ca(2+) entry into neurons appears to be one of the key effectors of activity-dependent gene expression. Among the possible downstream targets of calcium, the protein phosphatase calcineurin represents a prime candidate. We hereby report that in cultured cerebellar granule cells the activation of the Ca(2+)/calcineurin pathway via either voltage- or ligand- operated Ca(2+) channels regulates MALS-1 and MALS-2 expression at the transcriptional level. These proteins are integral parts of the post-synaptic density and are also involved in receptor trafficking. MALS regulation is not at the level of mRNA stability and does not require de novo protein synthesis, thereby suggesting a direct pathway. These data suggest that Ca(2+) entry by means of calcineurin is capable of controlling the structure of the post-synaptic density by controlling the expression of key components at the transcriptional level.

Aniracetam improves contextual fear conditioning and increases hippocampal gamma-PKC activation in DBA/2J mice

DBA/2J (D2) mice display poor contextual learning and have less membrane-bound hippocampal protein kinase C (PKC) compared with C57BL/6 (B6) mice. Aniracetam and oxiracetam were previously shown to improve contextual learning in D2 mice and increase PKC activity. This study investigated a possible mechanism for learning enhancement by examining the effects of aniracetam on contextual fear conditioning and activation of the y isoform of PKC (gamma-PKC) in male D2 mice. In comparison to animals treated with vehicle only (10% 2-hydroxypropyl-beta-cyclodextrin), mice treated with aniracetam (100 mg/kg) 30 min prior to fear conditioning training demonstrated significantly improved contextual learning when tested 30 min and 24 h after training. This corresponded with a significant increase in activated, membrane-bound hippocampal gamma-PKC 30 min after training. No increase in learning or gamma-PKC was found 5 min after training. These results suggest an altered time course of activation of gamma-PKC in response to treatment with aniracetam, which improves learning in D2 mice.

Aniracetam attenuates apoptosis of astrocytes subjected to simulated ischemia in vitro

The aim of the present study was to establish whether aniracetam is capable of protecting cultured rat astrocytes against ischemic injury. Treatment of the cultures with aniracetam (1, 10 and 100 mM) during 24 h ischemia simulated in vitro significantly decreased the number of apoptotic cells. The antiapoptotic effects of the drug were confirmed by the increase of intracellular ATP and phosphocreatine (PCr) levels and the inhibition of the caspase-3 activity. Aniracetam also attenuated cellular oxidative stress by decreased production of reactive oxygen species (ROS). These effects were associated with the decrease in levels of c-fos and c-jun mRNA in primary astrocyte cultures exposed to 24 h ischemia. When cultured astrocytes were incubated during 24 h simulated ischemia with wortmannin, a phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor or PD98059, a mitogen-activated protein (MAP)/extracellular signal regulated kinase (ERK) (MEK) inhibitor the cell apoptosis was accelerated. This effect was antagonized by adding 100 mM aniracetam to the culture medium. These findings suggest that the protective effect of aniracetam is mediated by PI 3-kinase and MEK pathways in the downstream mechanisms.

Novel AMPA receptor potentiators LY392098 and LY404187: effects on recombinant human AMPA receptors in vitro

The present study describes the activity of two novel potent and selective AMPA receptor potentiator molecules LY392098 and LY404187. LY392098 and LY404187 enhance glutamate (100 microM) stimulated ion influx through recombinant homomeric human AMPA receptor ion channels, GluR1-4, with estimated EC(50) values of 1.77 microM (GluR1(i)), 0.22 microM (GluR2(i)), 0.56 microM (GluR2(o)), 1.89 microM (GluR3(i)) and 0.20 microM (GluR4(i)) for LY392098 and EC(50) values of 5.65 microM (GluR1(i)), 0.15 microM (GluR2(i)), 1.44 microM (GluR2(o)), 1.66 microM (GluR3(i)) and 0.21 microM (GluR4(i)) for LY404187. Neither compound affected ion influx in untransfected HEK293 cells or GluR transfected cells in the absence of glutamate. Both compounds were selective for activity at AMPA receptors, with no activity at human recombinant kainate receptors. Electrophysiological recordings demonstrated that glutamate (1 mM)-evoked inward currents in human GluR4 transfected HEK293 cells were potentiated by LY392098 and LY404187 at low concentrations (3-10 nM). In addition, both compounds removed glutamate-dependent desensitization of recombinant GluR4 AMPA receptors. These studies demonstrate that LY392098 and LY404187 allosterically potentiate responses mediated by human AMPA receptor ion channels expressed in HEK 293 cells in vitro.

LY392098, a novel AMPA receptor potentiator: electrophysiological studies in prefrontal cortical neurons

The present experiments investigated the ability of LY392098, a novel positive allosteric modulator of AMPA receptors, to potentiate AMPA receptor-mediated currents of neurons in the prefrontal cortex (PFC). Co-application of LY392098 (0.03-10 microM) with AMPA (5 microM) enhanced current through AMPA receptor/channels in acutely isolated PFC neurons in a concentration-dependent manner. Estimates of the potency (EC(50)) and efficacy for LY392098 yielded an EC(50) value of 1.7+/-0.5 microM and a maximal potentiation of a 31.0+/-4.1-fold increase relative to current evoked by AMPA alone. The potentiation was activity-dependent, becoming evident only in the presence of agonist, and time-dependent, continuously developing over prolonged application times. An extracellular site of action was inferred by the absence of potentiation when the compound was applied intracellularly. LY392098 also increased the potency of agonist for the receptor by approximately sevenfold. Selectivity assays showed that the effects of LY392098 were exclusive for AMPA receptors, having no activity at N-methyl-D-aspartate (NMDA) receptors in PFC neurons. Extracellular recordings from single PFC neurons in vivo showed that administration of LY392098 (0.001-10 microg/kg, i.v.) enhanced the probability of evoked action potential discharge in response to stimulation of glutamatergic afferents from the ventral subiculum of the hippocampal formation. Spontaneous activity of PFC neurons was also increased. Collectively, these results demonstrate that LY392098 is a highly potent, selective and centrally active positive modulator of native AMPA receptors.

Pharmacological effects of AMPA receptor potentiators LY392098 and LY404187 on rat neuronal AMPA receptors in vitro

The present study describes the pharmacological activity of two novel positive allosteric modulators at AMPA receptors in acutely isolated rat cerebellar Purkinje neurons and cultured rat hippocampal neurons. Currents elicited by application of glutamate (100 microM) to isolated cerebellar Purkinje neurons were potentiated by LY392098, LY404187, cyclothiazide, CX516 and aniracetam. The rank order of potency was LY404187> LY392098> cyclothiazide > CX516> aniracetam. LY392098 displayed a higher maximal efficacy than the other compounds examined. AMPA-activated inward currents in cultured rat hippocampal neurons were potentiated by LY392098, LY404187 and cyclothiazide in a reversible and concentration-dependent manner although considerable heterogeneity in the magnitude of response from cell to cell was observed. LY392098 was ineffective in potentiating AMPA receptor responses when dialyzed via the intracellular solution. The selectivity profiles of the two novel AMPA receptor potentiators were examined. LY392098 or LY404187 had minimal activity on NMDA receptor responses, on voltage-gated calcium channel currents in cultured hippocampal neurons and on GluR5 kainate receptor currents in acutely isolated rat dorsal root ganglion neurons.

Potentiation of responses to AMPA on central neurones by LY392098 and LY404187 in vivo

Enhancement of AMPA receptor mediated synaptic excitation has the potential to aid in the treatment of several psychiatric conditions. To test such claims there is a need to develop more potent compounds than those presently available and to demonstrate that they cross the blood-brain barrier to affect responses at central AMPA receptors. We have now completed in vivo tests with two such compounds, the newly discovered biarylpropylsulfonamides, LY392098 and LY404187, on spinal and hippocampal neurones in anaesthetised rats. In the initial study on spinal neurones, LY392098 (30-1000 microg/kg i.v.) dose-dependently increased responses to iontophoretically administered AMPA but not those to NMDA. Subsequently in a more detailed follow-up study on hippocampal neurones, LY392098 (1-100 microg/kg i.v.) and LY404187 (1-100 microg/kg i.v.) enhanced in a dose-dependent manner responses to AMPA. Responses to NMDA were also enhanced but to a less extent. Such enhanced responses to NMDA, but not those to AMPA, were reduced by the NMDA antagonist, ketamine (0.5-1 mg/kg i.v.) whereas the selective AMPA antagonist, LY300168 (GYKI53655; 1 mg/kg i.v.), reduced responses to both NMDA and AMPA. LY392098 also potentiated the synaptic excitation of dentate granule cells following perforant path stimulation. These combined data show that, at doses not dissimilar to those affecting behavioural responses (1-1000 microg/kg; see accompanying papers), the two new drugs cross the blood-brain barrier to affect directly the sensitivity of central AMPA receptors and enhance synaptic excitation in vivo.

Synaptic and non-synaptic AMPA receptors permeable to calcium

For a long time, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors permeable to calcium have been considered to be either non-existent or as "atypical". There is now ample evidence that these receptors exist in numerous regions of the nervous system and in many neuronal as well as non-neuronal cell populations. This evidence has been accumulated by several methods, including electrophysiological recording, calcium imaging and cobalt-loading. Functional AMPA receptors permeable to calcium are already expressed at very early stages of embryonic development, well before the onset of synaptogenesis. They are probably involved in the paracrine signaling necessary for construction of the nervous system before becoming involved in synaptic transmission. In immature cells, cyclothiazide strongly increases the steady-state level of responses not only to AMPA, but also to kainate. Ingestion, during pregnancy, of food or drug substances that can cross the placental barrier and act upon the embryonic receptors may constitute a risk for normal development. In the adult nervous system, synaptic as well as non-synaptic (paracrine) AMPA receptors permeable to calcium are probably widely expressed in both glial and neuronal cells. They may also participate in controlling some aspects related to adult neurogenesis, in particular the migration of newly formed neurons.

Piracetam and levetiracetam, two pyrrolidone derivatives, exert antidystonic activity in a hamster model of paroxysmal dystonia

The effects of the nootropic drug piracetam and its analogue, the antiepileptic drug levetiracetam (ucb L059) on severity of dystonic attacks were studied in a mutant hamster model of idiopathic generalized dystonia. Both drugs significantly decreased the severity of dystonia. In contrast to seizure models, in which levetiracetam is much more potent as an anticonvulsant than piracetam, the antidystonic potency of levetiracetam was only moderately higher than that of piracetam. The antidystonic activity of piracetam and levetiracetam was not associated with any behavioral side effects. The data indicate that piracetam and levetiracetam are interesting novel treatments for idiopathic dystonia.

AMPA prevents glutamate-induced neurotoxicity and apoptosis in cultured cerebellar granule cell neurons

Exposure of cultured cerebellar neurons to alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) in the presence of aniracetam protects all of the vulnerable neurons against the excitotoxic actions of glutamate acting on N-methyl-D-aspartate receptors. The protective effect of AMPA was both time- and concentration-dependent. Aniracetam alone did not protect the neurons against the excitotoxic effects of glutamate. Pretreatment of cerebellar neurons with the AMPA antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione blocked the neuroprotective effect mediated by AMPA indicating that the neuroprotective effect is mediated specifically by AMPA receptors. An excitotoxic concentration of glutamate, which killed between 60-80% of granule cell neurons on day 8 in vitro, mediated its toxic effect via a time-dependent apoptotic pathway. Pretreatment of cerebellar granule cell neurons with AMPA (500 microM) completely blocked glutamate-mediated apoptosis. Our results suggest that AMPA receptors may play an important role in neuronal survival.

Piracetam in the treatment of schizophrenia: implications for the glutamate hypothesis of schizophrenia

OBJECTIVE

There is a growing interest in investigating the role of glutamate receptors in the pathophysiology of schizophrenia. Indeed, the hyperdopaminergic theory of schizophrenia can explain only the positive symptoms of schizophrenia, whereas the glutamate hypothesis may provide a more comprehensive view of the illness. We undertook a trial to investigate whether the combination of haloperidol with piracetam, a nootropic agent which modulates the glutamate receptor positively was more effective than haloperidol alone.

METHODS

Thirty patients who met the DSM IV criteria for schizophrenia completed the study. Patients were allocated in a random fashion, 14 to haloperidol 30 mg/day plus piracetam 3200 mg/day and 16 to haloperidol 30 mg/day plus placebo.

RESULTS

Although both protocols significantly decreased the score of the positive symptoms, the negative symptoms, the general psychopathological symptoms and the total score of PANSS scale over the trial period, the combination of haloperidol and piracetam showed a significant superiority over haloperidol alone in the treatment of schizophrenic patients.

CONCLUSION

Piracetam, a member of the nootropic class of drugs and a positive modulator of glutamate receptor, may be of therapeutic benefit in treating schizophrenic patients in combination with typical neuroleptics. However, a larger study to confirm our results is warranted

Modulation of the neuronal nicotinic acetylcholine receptor-channel by the nootropic drug nefiracetam

The effects of nefiracetam (DM-9384) on the neuronal nicotinic acetylcholine (ACh) receptor-channel were studied by the whole-cell patch clamp technique using PC12 cells. Nefiracetam had a dual effect on ACh-induced currents: it augmented the currents induced by low concentrations (10-30 microM) of ACh and suppressed those induced by high concentrations (100-1000 microM) of ACh. These effects were reversible after washing with drug-free solution. The stimulating effect of nefiracetam was clearly observed at a concentration of 10 microM, and slight increases in currents were detected even at 0.1 microM or 1 microM. Nefiracetam at 100 microM suppressed the currents induced by a low concentration (10 microM) of ACh. The rate of desensitization of ACh-induced current was greatly accelerated by nefiracetam, and this effect could not be reversed by washing with drug-free solution. When added to the internal pipette solution, the protein kinase A inhibitor KT 5720 (0. 6 microM), but not the protein kinase C inhibitor calphostin C (0.5 microM), abolished the nefiracetam stimulation of the ACh receptor. Pre-incubation of cells with 200 ng/ml pertussis toxin for 24 h also abolished the nefiracetam action. Thus, the nefiracetam modulation of the neuronal nicotinic ACh receptor-channel is exerted via G proteins and protein kinase A. The stimulation of the ACh receptor may be directly related to the cognitive enhancing action of nefiracetam.

The effect of aniracetam on cerebral glucose metabolism in rats after lesioning of the basal forebrain measured by PET

To evaluate the effect of aniracetam, a potent modulator of the glutamatergic and cholinergic systems, on the altered cerebral glucose metabolism after lesioning of the basal forebrain, we measured the cerebral metabolic rate of glucose (CMRGlc) with positron emission tomography and the choline acetyltransferase (ChAT) activity in the frontal cortex of the lesioned rats after treating them with aniracetam. Continuous administration of aniracetam for 7 days after the surgery prevented CMRGlc reduction in the frontal cortex ipsilateral to the lesion while the lesioned rats without aniracetam showed significant CMRGlc reduction in the frontal cortex. The level of CMRGlc in the lesion-side basal forebrain was lower in all rats regardless of the aniracetam treatment. Biochemical studies showed that aniracetam did not alter the reduction in the frontal ChAT activity. These results showed that aniracetam prevents glucose metabolic reduction in the cholinergically denervated frontal cortex with little effect on the cortical cholinergic system. The present study suggested that a neurotransmitter system other than the cholinergic system, e.g. the glutamatergic system, plays a central role in the cortical metabolic recovery after lesioning of the basal forebrain.

Enhancement of contextual fear-conditioning by putative (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor modulators and N-methyl-D-aspartate (NMDA) receptor antagonists in DBA/2J mice

Previous studies demonstrated that DBA/2J (DBA) mice performed poorly while C57BL/6J (C57) mice performed normally on a number of complex learning and memory tasks. Chronic oxiracetam treatment dramatically improved the performance of DBA mice but not that of C57 mice on the Morris water task and in contextual fear conditioning. The present study demonstrates that acute treatment with nootropics, oxiracetam (10-1000 mg/kg) or aniracetam (10-100 mg/kg), and N-methyl-D-Aspartate (NMDA) antagonists, (+)-MK-801 (0.1-3 microg/kg), CPP (0.01-0.3 mg/kg), and (+)-HA-966 (0.1-3 mg/kg), administered prior to training and testing, reversed the contextual learning impairment in DBA mice in a dose-dependent manner without affecting auditory cue conditioning. These effects appeared to be independent of testing order (context vs. auditory cue tests) and were not due to state-dependent learning. The inactive stereoisomers, (-)-MK-801 and (-)-HA-966, were incapable of increasing contextual freezing in DBA mice. In DBA mice, the effects of 30 mg/kg oxiracetam and 100 mg/kg aniracetam were inhibited by the (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor antagonists, NBQX, and GYKI-52466. The combined administration of 30 mg/kg oxiracetam and 1 microg/kg (+)-MK-801 produced an additive response. None of the pharmacological treatments altered performance in C57 mice at doses that were effective in DBA mice. These results suggest that DBA mice may be learning impaired due to altered glutamatergic receptor function.

Zinc changes AMPA receptor properties: results of binding studies and patch clamp recordings

The influence of zinc ions on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors was investigated using binding studies with [3H]AMPA to rat cortical membranes and patch clamp recordings from cultured superior colliculus neurones. In Tris-HCl buffer, zinc (1-10 mM) significantly increased the specific binding of [3H]AMPA whereas this increase was negligible in the presence of CaCl2 (2.5 mM) and KSCN (100 mM). This effect was associated with a dramatic increase in Bmax but a decrease in both agonist and antagonist affinity. Association and dissociation experiments showed that equilibrium [3H]AMPA binding is reached with faster kinetics in the presence of zinc. At low concentrations (0.3 mM) zinc also concentration-dependently potentiated both peak and plateau components of whole cell current responses to AMPA (100 microM). This effect was accompanied by a reduction of the degree, and slowing of the rate, of AMPA receptor desensitisation. In contrast, higher concentrations of zinc (1-3.0 mM) inhibited AMPA responses to some degree, but slowed desensitisation further. This ability of zinc to change AMPA receptor properties may be relevant to neurotoxicity associated with AMPA receptor activation.

Modulating effect of the nootropic drug, piracetam on stress- and subsequent morphine-induced prolactin secretion in male rats

1. The effect of the nootropic drug, piracetam on stress- and subsequent morphine-induced prolactin (PRL) secretion was investigated in vivo in male rats, by use of a stress-free blood sampling and drug administration method by means of a permanent indwelling catheter in the right jugular vein. 2. Four doses of piracetam were tested (20, 100, 200 and 400 mg kg-1), being given intraperitoneally 1 h before blood sampling; control rats received saline instead. After a first blood sample, rats were subjected to immobilization stress and received morphine, 6 mg kg-1, 90 min later. 3. Piracetam had no effect on basal plasma PRL concentration. 4. While in the non-piracetam-treated rats, stress produced a significant rise in plasma PRL concentration, in the piracetam-pretreated rats PRL peaks were attenuated, especially in the group given 100 mg kg-1 piracetam, where plasma PRL concentration was not significantly different from basal values. The dose-response relationship showed a U-shaped curve; the smallest dose had a minor inhibitory effect and the highest dose had no further effect on the PRL rise. 5. In unrestrained rats, morphine led to a significant elevation of plasma PRL concentration. After the application of immobilization stress it lost its ability to raise plasma PRL concentration in the control rats, but not in the piracetam-treated rats. This tolerance was overcome by piracetam in a significant manner but with a reversed dose-response curve; i.e. the smaller the dose of piracetam, the higher the subsequent morphine-induced PRL peak. 6. There is no simple explanation for the mechanism by which piracetam induces these contradictory effects. Interference with the excitatory amino acid system, which is also involved in opiate action, is proposed speculatively as a possible mediator of the effects of piracetam.

Aniracetam restores object recognition impaired by age, scopolamine, and nucleus basalis lesions

Object recognition was investigated in adult and aging male rats in a two-trials, unrewarded, test that assessed a form of working-episodic memory. Exploration time in the first trial, in which two copies of the same object were presented, was recorded. In the second trial, in which one of the familiar objects and a new object were presented, the time spent exploring the two objects was separately recorded and a discrimination index was calculated. Adult rats explored the new object longer than the familiar object when the intertrial time ranged from 1 to 60 min. Rats older than 20 months of age did not discriminate between familiar and new objects. Object discrimination was lost in adult rats after scopolamine (0.2 mg/kg SC) administration and with lesions of the nucleus basalis, resulting in a 40% decrease in cortical ChAT activity. Both aniracetam (25, 50, 100 mg/kg os) and oxiracetam (50 mg/kg os) restored object recognition in aging rats, in rats treated with scopolamine, and with lesions of the nucleus basalis. In the rat, object discrimination appears to depend on the integrity of the cholinergic system, and nootropic drugs can correct its disruption.

Effects of the nootropic drug nefiracetam on the GABAA receptor-channel complex in dorsal root ganglion neurons

The effects of nefiracetam on GABA-induced chloride currents were studied with rat dorsal root ganglion neurons in primary culture using the whole-cell patch-clamp technique. The dose-response curve for GABA-induced currents was shifted by 16 microM to lower concentrations by 10 microM nefiracetam while the maximal response was reduced by 22.84 +/- 0.68%. Thus at a low concentration (10 microM) of GABA, the chloride currents were potentiated by nefiracetam in a concentration-dependent manner. With 10 microM nefiracetam, the potentiation occurred slowly and the recovery after washout was also slow. The desensitization of the GABAA receptor at high concentration (100 microM) of GABA was accelerated by nefiracetam. The recovery process of chloride currents from desensitization was not affected by nefiracetam. KT 5720 (0.56 microm), a specific protein kinase A (PKA) inhibitor, blocked the transient potentiation of GABA-activated currents by nefiracetam, but did not affect the acceleration of desensitization. Nefiracetam suppression of GABA-induced currents was also abolished by KT 5720 or the pertussis toxin. Thus, nefiracetam may inhibit Gi/G(o) proteins leading to a cascade of events that increase the intracellular cAMP level, activate the PKA system, and suppress GABA-induced currents. Nefiracetam-induced transient potentiation and acceleration of desensitization of GABA-induced currents may involve other pathways. The nefiracetam modulation of the GABAA receptor function will result in a nootropic effect on the central nervous system through modification of synaptic transmission.