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Koleilat A, Dugdale JA, Christenson TA, Bellah JL, Lambert AM, Masino MA, Ekker SC, Schimmenti LA. L-type voltage-gated calcium channel agonists mitigate hearing loss and modify ribbon synapse morphology in the zebrafish model of Usher syndrome type 1. Dis Model Mech 2020; 13:13/11/dmm043885. [PMID: 33361086 PMCID: PMC7710014 DOI: 10.1242/dmm.043885] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 09/15/2020] [Indexed: 01/19/2023] Open
Abstract
The mariner (myo7aa−/−) mutant is a zebrafish model for Usher syndrome type 1 (USH1). To further characterize hair cell synaptic elements in myo7aa−/− mutants, we focused on the ribbon synapse and evaluated ultrastructure, number and distribution of immunolabeled ribbons, and postsynaptic densities. By transmission electron microscopy, we determined that myo7aa−/− zebrafish have fewer glutamatergic vesicles tethered to ribbon synapses, yet maintain a comparable ribbon area. In myo7aa−/− hair cells, immunolocalization of Ctbp2 showed fewer ribbon-containing cells in total and an altered distribution of Ctbp2 puncta compared to wild-type hair cells. myo7aa−/− mutants have fewer postsynaptic densities – as assessed by MAGUK immunolabeling – compared to wild-type zebrafish. We quantified the circular swimming behavior of myo7aa−/− mutant fish and measured a greater turning angle (absolute smooth orientation). It has previously been shown that L-type voltage-gated calcium channels are necessary for ribbon localization and occurrence of postsynaptic density; thus, we hypothesized and observed that L-type voltage-gated calcium channel agonists change behavioral and synaptic phenotypes in myo7aa−/− mutants in a drug-specific manner. Our results indicate that treatment with L-type voltage-gated calcium channel agonists alter hair cell synaptic elements and improve behavioral phenotypes of myo7aa−/− mutants. Our data support that L-type voltage-gated calcium channel agonists induce morphological changes at the ribbon synapse – in both the number of tethered vesicles and regarding the distribution of Ctbp2 puncta – shift swimming behavior and improve acoustic startle response. Summary: We quantified behavioral and synaptic morphology differences between wild-type zebrafish larvae and the mariner (myo7aa−/−) mutant, finding that these differences can be modified by L-type voltage-gated calcium channel agonists.
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Affiliation(s)
- Alaa Koleilat
- College of Continuing and Professional Studies, University of Minnesota, Minneapolis, MN 55108, USA.,Mayo Clinic Graduate School of Biomedical Sciences, Clinical and Translational Science Track, Rochester, MN 55905, USA.,Center for Clinical and Translational Science, Mayo Clinic, Rochester, MN 55905, USA
| | - Joseph A Dugdale
- Department of Otorhinolaryngology, Mayo Clinic, Rochester, MN 55905, USA
| | | | - Jeffrey L Bellah
- Center for Clinical and Translational Science, Mayo Clinic, Rochester, MN 55905, USA.,Department of Genetics and Development, Columbia University, New York City, NY 10032, USA
| | - Aaron M Lambert
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Mark A Masino
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Stephen C Ekker
- Center for Clinical and Translational Science, Mayo Clinic, Rochester, MN 55905, USA.,Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | - Lisa A Schimmenti
- Department of Otorhinolaryngology, Mayo Clinic, Rochester, MN 55905, USA .,Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA.,Department of Pediatrics, University of Minnesota, Minneapolis, MN 55455, USA.,Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA.,Department of Ophthalmology and Visual Neuroscience, University of Minnesota, Minneapolis, MN 55454, USA.,Department of Clinical Genomics, Mayo Clinic, Rochester, MN 55905, USA
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Kitano Y, Komiyama C, Makino M, Takasuna K, Satoh H, Aoki T, Kinoshita M, Takazawa A, Yamauchi T, Sakurada S. Anticonvulsant and neuroprotective effects of the novel nootropic agent nefiracetam on kainic acid-induced seizures in rats. Brain Res 2006; 1057:168-76. [PMID: 16122714 DOI: 10.1016/j.brainres.2005.07.052] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2005] [Revised: 07/27/2005] [Accepted: 07/27/2005] [Indexed: 11/19/2022]
Abstract
Nefiracetam is a novel pyrrolidone-type nootropic agent, and it has been reported to possess a potential for antiepileptic therapy as well as cognition-enhancing effects. We investigated the anticonvulsant and neuroprotective effects of nefiracetam in kainic acid-induced seizures of rats, compared with levetiracetam and standard antiepileptic drugs. Subcutaneous injection of kainic acid (10 mg/kg) induced typical behavioral seizures such as wet dog shakes and limbic seizures and histopathological changes in the hippocampus (degeneration and loss of pyramidal cells in CA1 to CA4 areas). Nefiracetam (25, 50 and 100 mg/kg po) had no effect on the behavioral seizures and dose-dependently inhibited the hippocampal damage. In contrast, levetiracetam, a pyrrolidone-type antiepileptic drug, inhibited neither. Valproic acid and ethosuximide prevented the hippocampal damage without attenuating the behavioral seizures as nefiracetam. Zonisamide and phenytoin did not inhibit the behavioral seizures, while zonisamide enhanced the hippocampal damage and phenytoin increased the lethality rate. Carbamazepine inhibited the behavioral seizures at 50 mg/kg and enhanced that at 100 mg/kg, and it completely inhibited the hippocampal damage at both doses. We have previously reported that anticonvulsant spectrum of nefiracetam paralleled that of zonisamide, phenytoin or carbamazepine in standard screening models. However, the pharmacological profile of nefiracetam was closer to valproic acid or ethosuximide than that of zonisamide, phenytoin or carbamazepine in this study. These results suggest that anticonvulsant spectrum and mechanism of nefiracetam are distinct from those of standard antiepileptic drugs, and nefiracetam possesses a neuroprotective effect that is unrelated to seizure inhibition.
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Affiliation(s)
- Yutaka Kitano
- New Product Research Laboratories II, Daiichi Pharmaceutical Co., Ltd., 1-16-13 Kita-Kasai, Edogawa-ku, Tokyo 134-8630, Japan.
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3
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Kitano Y, Komiyama C, Makino M, Kasai Y, Takasuna K, Kinoshita M, Yamazaki O, Takazawa A, Yamauchi T, Sakurada S. Effects of Nefiracetam, a novel pyrrolidone-type nootropic agent, on the amygdala-kindled seizures in rats. Epilepsia 2005; 46:1561-8. [PMID: 16190926 DOI: 10.1111/j.1528-1167.2005.00261.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE Nefiracetam (NEF) is a novel pyrrolidonetype nootropic agent, and it has been reported to possess various pharmacologic effects as well as cognition-enhancing effects. The present study focused on the effects of NEF in amygdala-kindled seizures and its potential for antiepileptic therapy. METHODS Effects of NEF on fully amygdala-kindled seizures and development of amygdala-kindled seizures were investigated in rats and compared with those of levetiracetam (LEV), a pyrrolidone-type antiepileptic drug (AED). RESULTS In fully amygdala-kindled rats, NEF (25, 50, and 100 mg/kg, p.o.) decreased afterdischarge induction, afterdischarge duration, seizure stage, and motor seizure duration in a dose-dependent manner. LEV (25, 50, and 100 mg/kg, p.o.) had no effects on afterdischarge induction and slightly decreased afterdischarge duration, whereas it markedly decreased seizure stage and motor seizure duration. In contrast to the results in fully amygdala-kindled rats, NEF (25 and 50 mg/kg/day, p.o.) had few or no effects on the development of amygdala-kindled seizures. As well as fully amygdala-kindled seizures, LEV (50 mg/kg/day, p.o.) markedly inhibited the development of behavioral seizures without reducing daily afterdischarge duration. CONCLUSIONS Although NEF possesses potent anticonvulsant effects on fully amygdala-kindled seizures, it has few or no effects on the development of amygdala-kindled seizures. LEV shows marked anticonvulsant effects on both phases of kindling. In fully amygdala-kindled rats, NEF inhibits both electroencephalographic and behavioral seizures, whereas LEV inhibits only behavioral seizures. This double dissociation suggests that NEF has a distinct anticonvulsant spectrum and mechanisms from those of LEV.
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Affiliation(s)
- Yutaka Kitano
- New Product Research Laboratories II, Daiichi Pharmaceutical Co., Ltd., Edogawa-ku, Tokyo.
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Snyder PJ, Bednar MM, Cromer JR, Maruff P. Reversal of scopolamine‐induced deficits with a single dose of donepezil, an acetylcholinesterase inhibitor. Alzheimers Dement 2005; 1:126-35. [DOI: 10.1016/j.jalz.2005.09.004] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Revised: 09/12/2005] [Accepted: 09/14/2005] [Indexed: 10/25/2022]
Affiliation(s)
- Peter J. Snyder
- Department of PsychologyUniversity of Connecticut406 Babbidge Road, Unit 1020StorrsCT06269-1020USA
- Pfizer Global Research & DevelopmentGrotonCTUSA
| | | | - Jennifer R. Cromer
- Department of PsychologyUniversity of Connecticut406 Babbidge Road, Unit 1020StorrsCT06269-1020USA
| | - Paul Maruff
- CogState LtdMelbourneAustralia
- School of Psychological ScienceLaTrobe UniversityMelbourneAustralia
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5
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Kitano Y, Komiyama C, Makino M, Takasuna K, Takazawa A, Sakurada S. Anticonvulsant properties of the novel nootropic agent nefiracetam in seizure models of mice and rats. Epilepsia 2005; 46:811-8. [PMID: 15946322 DOI: 10.1111/j.1528-1167.2005.66504.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE Nefiracetam (NEF) is a novel pyrrolidone-type nootropic agent, and it has been reported to possess various pharmacologic effects as well as cognition-enhancing effects. The present study focused on the anticonvulsant effect of NEF and its potential for antiepileptic therapy. METHODS The anticonvulsant properties of NEF were investigated in experimental seizure models of mice and rats, compared with levetiracetam (LEV) and other standard antiepileptic drugs [AEDs; zonisamide (ZNS), phenytoin (PHT), carbamazepine (CBZ), valproic acid (VPA), diazepam (DZP), and ethosuximide (ESM)]. With reference to standard programs for evaluating potential AEDs, the study included the traditional maximal electroshock seizure and subcutaneous chemoconvulsant (pentylenetetrazole, bicuculline, picrotoxin, strychnine, or N-methyl-D-aspartate) seizure tests and two threshold models (the increasing-current electroshock seizure test and intravenous pentylenetetrazole seizure threshold test). Neurotoxic activities were examined with the rotarod test and traction test. RESULTS NEF inhibited electroshock-induced seizures at nontoxic doses, whereas it had no effect on seizures chemically induced by pentylenetetrazole, bicuculline, picrotoxin, strychnine, or N-methyl-D-aspartate. The anticonvulsant spectrum of NEF paralleled that of ZNS, PHT, and CBZ. The anticonvulsant efficacy of NEF was comparable with that of ZNS and less potent than that of PHT, CBZ, and DZP. However, the safety margin of NEF was superior to that of ZNS, CBZ, VPA, and DZP. LEV showed only slight anticonvulsant effects in threshold models, and it was not effective in conventional screening models. CONCLUSIONS These results suggest that NEF has distinct anticonvulsant spectrum and mechanisms from those of LEV. NEF is an orally active and safe AED, and it possesses a potential for antiepileptic therapy.
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Affiliation(s)
- Yutaka Kitano
- New Product Research Laboratories II, Daiichi Pharmaceutical Co., Ltd., Tokyo, Japan.
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Ueda M, Fujita R, Koji T, Ueda H. The Cognition-Enhancer Nefiracetam Inhibits Both Necrosis and Apoptosis in Retinal Ischemic Models in Vitro and in Vivo. J Pharmacol Exp Ther 2004; 309:200-7. [PMID: 14718588 DOI: 10.1124/jpet.103.061127] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The retinal ischemic-reperfusion stress (130 mm Hg, 45 min) caused neuronal damage throughout all cell layers and reduced the thickness of retinal layer by 30% at 7 days after the stress of mouse retina. The intravitreous injection of 100 pmol of nefiracetam, a cognition-enhancer, completely prevented the damage when it was given 30 min before and 3 h after the stress. Partial prevention was observed when it was given 24 h after the stress, or low dose (10 pmol) nefiracetam was given 30 min before the stress. However, aniracetam had no effect. In the retinal cell line N18-RE-105, the ischemic-reperfusion stress by 2 h culture under the serum-free condition with low oxygen (less of 0.4% O(2)) and low glucose (1 mM) caused necrosis or apoptosis in the low-density (0.5 x 10(4) cell/cm(2))or high-density (5 x 10(4) cell/cm(2)) culture, respectively. The necrosis showed membrane disruption, loss of electron density, and mitochondrial swelling, whereas apoptosis showed nuclear fragmentation and condensation in transmission electron microscopical analyses and in experiments using specific cell death markers. Nefiracetam inhibited both necrosis and apoptosis, whereas brain-derived neurotrophic factor (BDNF) inhibited only apoptosis. The cell-protective actions of nefiracetam were abolished by nifedipine and omega-conotoxin GVIA, L-type and N-type calcium channel blocker, but not by PD98059 or wortmannin, extracellular signal-regulated kinase 1/2 or phosphoinositide 3-kinase inhibitor, respectively, whereas those of BDNF were abolished by PD98059 and wortmannin, but not by nifedipine and omega-conotoxin GVIA. All these findings suggest that nefiracetam inhibit necrosis and apoptosis occurred in the ischemic/hypoxic neuronal injury through an increase in Ca(2+) influx.
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Affiliation(s)
- Mutsumi Ueda
- Division of Molecular Pharmacology and Neuroscience, Nagasaki University Graduate School of Biomedical Sciences, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
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von Linstow Roloff E, Platt B, Riedel G. No spatial working memory deficit in beta-amyloid-exposed rats. A longitudinal study. Prog Neuropsychopharmacol Biol Psychiatry 2002; 26:955-70. [PMID: 12369272 DOI: 10.1016/s0278-5846(02)00211-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Two experiments are described assessing whether long-term intraventricular or intrahippocampal administration of beta-amyloid protein 1-40 (beta A1-40) affects spatial working memory in rats monitored in a longitudinal study using the open-field water maze. A delayed matching-to-position procedure (DMTP) was employed in which platform locations were semi-randomly altered between days but were kept constant over the four trials on each day. Intertrial intervals (ITIs) were either 30 s or 1 h between Trials 1 and 2 (all other intervals = 30 s), with Trial 2 performance being an index for spatial working memory. Animals were trained before and tested repeatedly at various intervals after application of various compounds (see below) in five successive test sessions (TSs). In Experiment 1, beta A1-40 was applied after a challenge with long-term oral exposure to aluminium (Al; as 0.1% sulfate in drinking water). This in itself did not affect spatial working memory at any delay, despite of the more than 6 months of intake. beta A1-40 administered alone via intracerebroventricular (icv) minipumps (20 micrograms in 250 microliters) led to a small increase in latencies to find the platform, which recovered to control levels 3 months after minipumps were exhausted. Application of beta A1-40 in Al-exposed animals led to a subtle and progressive decline in working memory. This deterioration was reversed by the nootropic compound nefiracetam, which had no effect on the Al only group. In Experiment 2, well-trained rats were bilaterally implanted with intra-hippocampal minipumps containing beta A1-40 or reverse sequence beta A40-1. This did not impair spatial working memory in the DMTP task, measured either directly after minipumps were exhausted, or 2 weeks later. When intraperitoneally (i.p.) injected with a low concentration of the muscarinic antagonist scopolamine (0.2 mg/kg), a dose that was not effective alone, animals in the beta A1-40 group were amnesic. These data suggest that intra-hippocampal beta A1-40 administration alters cholinergic transmission, but these alterations may be mild and thus do not lead to obvious working memory deficits in a DMTP task in well-trained animals.
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Affiliation(s)
- Eva von Linstow Roloff
- Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
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Aihara H, Li X, Fujiwara S, Matsumura T, Okumura S, Tozaki H, Kanno T, Ohta K, Nagai K, Nishizaki T. The protective action of nefiracetam against electrophysiological and metabolic damage in the hippocampus after deprivation of glucose and oxygen. Brain Res 2001; 922:158-62. [PMID: 11730716 DOI: 10.1016/s0006-8993(01)03165-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The present study examined the effect of nefiracetam on ischemic brain damage by monitoring population spikes (PSs) in the dentate gyrus of guinea pig hippocampal slices; assaying high-energy phosphates (ATP and CrP) in guinea pig hippocampal slices; and monitoring whole-cell membrane-currents and intracellular Ca(2+) levels in cultured hippocampal neurons. Twenty-minute ischemic insult to slices, i.e., deprivation of glucose and oxygen from artificial cerebrospinal fluid, abolished PSs. As compared with only 35% recovery of the PS amplitude for control, PS amplitude reversed to 65% of basal levels 40 min after returning normal conditions by treatment with nefiracetam (0.01 microM). Ischemic insult reduced the levels of adenosine triphosphate (ATP) and creatine phosphate (CrP) in slices, and when returned to normal conditions, recovering to 70 and 85% of basal values, respectively, 30 min after returning normal conditions. Nefiracetam (0.01 microM) facilitated the recovery of ATP and CrP, reaching 110 and 140% of basal values, respectively. Nefiracetam inhibited N-methyl-D-aspartate (NMDA)-evoked currents to 35% of basal amplitudes. Likewise, nefiracetam (0.01 microM) inhibited intracellular Ca(2+) rise through NMDA receptor channels to 30% of basal levels. The results of the present study, thus, suggest that nefiracetam has the potential to protect against ischemic brain damage, possibly in part by preventing from accumulation of intracellular calcium through NMDA receptor channels.
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Affiliation(s)
- H Aihara
- Department of Physiology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya 663-8501, Japan
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Abstract
The pyrrolidone (2-oxopyrrolidine) family of chemicals has been the subject of research for more than three decades. Experimental and clinical work first focused on their so-called nootropic effects; later came the possibilities for neuroprotection after stroke and use as antiepileptic agents. Piracetam, the first of the class, was developed by pioneering research by C Giurgea in the late 1960s, and it was he who coined the term "nootropic", to mean enhancement of learning and memory. The term is sometimes extended to include other actions such as neuroprotection. These properties, together with the lack of other generally adverse psychopharmacological actions (eg, sedation, analgesia, or motor or behavioural changes), distinguish the pyrrolidones from other psychoactive drug classes. The mechanisms of action of these drugs are still not fully established; indeed, different compounds in this class may have different modes of action. Interest in this drug class has recently been reawakened by the licensing of levetiracetam as a potentially major new antiepileptic drug and of piracetam for its antimyoclonic action and effects after stroke and in mild cognitive impairment. Other drugs in this class are currently at an advanced stage of development, and the renewal of interest in this therapeutic area is likely to mean not only that more pyrrolidones will enter clinical practice in the next few years but also that the clinical indications of drugs already licensed will widen.
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Affiliation(s)
- S Shorvon
- Department of Clinical Neurology, Institute of Neurology, National Hospital for Neurology and Neurosurgery, Queen Square, University College London, WC1, London, UK.
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DeFord SM, Wilson MS, Gibson CJ, Baranova A, Hamm RJ. Nefiracetam improves Morris water maze performance following traumatic brain injury in rats. Pharmacol Biochem Behav 2001; 69:611-6. [PMID: 11509223 DOI: 10.1016/s0091-3057(01)00559-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Nefiracetam, a pyrrolidone derivative, is a nootropic agent that has facilitated cognitive function in a wide variety of animal models of cognitive dysfunction. The purpose of this study was to investigate the efficacy of the chronic postinjury administration of nefiracetam (DM-9384) in improving cognitive performance following central fluid percussion brain injury in rats. Twenty-four hours following surgical preparation, a sham injury or a moderate fluid percussive injury (2.1 atm) was delivered. Nefiracetam was administered chronically (0 or 9 mg/kg, po, for sham animals and 0, 3, or 9 mg/kg for injured animals) on postinjury days 1-15. Cognitive performance was assessed using the Morris water maze (MWM) on postinjury days 11-15. Chronic administration of 3 and 9 mg/kg nefiracetam attenuated MWM deficits produced by central fluid percussive brain injury. Importantly, the MWM performance of the injured animals treated with 9 mg/kg did not significantly differ from uninjured, sham animals. The 9-mg/kg dose of nefiracetam did not have a positive or negative effect on MWM performance of uninjured animals. The results of the present experiment suggest that a nootropic such as nefiracetam may be an appropriate treatment for trauma-induced cognitive dysfunction.
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Affiliation(s)
- S M DeFord
- Department of Psychology, Virginia Commonwealth University, P.O. Box 842018, 808 West Franklin Street, Richmond, VA 23284-2018, USA.
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11
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Zhao X, Kuryatov A, Lindstrom JM, Yeh JZ, Narahashi T. Nootropic drug modulation of neuronal nicotinic acetylcholine receptors in rat cortical neurons. Mol Pharmacol 2001; 59:674-83. [PMID: 11259610 DOI: 10.1124/mol.59.4.674] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nefiracetam (DM-9384) is a new pyrrolidone nootropic drug being developed for the treatment of Alzheimer's type and poststroke vascular-type dementia. Because the cholinergic system plays an important role in cognitive functions and Alzheimer's disease dementia, the present study was conducted to elucidate the mechanism of action of nefiracetam and aniracetam on neuronal nicotinic acetylcholine receptors (nnAChRs). Currents were recorded from rat cortical neurons in long-term primary culture using the whole-cell, patch-clamp technique. Two types of currents were evoked by acetylcholine (ACh): alpha-bungarotoxin-sensitive, alpha 7-type currents and alpha-bungarotoxin-insensitive, alpha 4 beta 2-type currents. Although nefiracetam and aniracetam inhibited alpha 7-type currents only weakly, these nootropic agents potentiated alpha 4 beta 2-type currents in a very potent and efficacious manner. Nefiracetam at 1 nM and aniracetam at 0.1 nM reversibly potentiated alpha 4 beta 2-type currents to 200 to 300% of control. Nefiracetam at very high concentrations (approximately 10 microM) also potentiated alpha 4 beta 2-type currents but to a lesser extent, indicative of a bell-shaped dose-response relationship. Nefiracetam markedly increased the saturating responses induced by high concentrations of ACh. However, human alpha 4 beta 2 subunits expressed in human embryonic kidney cells were inhibited rather than potentiated by nefiracetam. The specific protein kinase A inhibitors (H-89, KT5720, and peptide 5-24) and protein kinase C inhibitors (chelerythrine, calphostin C, and peptide 19--63) did not prevent nefiracetam from potentiating alpha 4 beta 2-type currents, indicating that these protein kinases are not involved in nefiracetam action. The nefiracetam potentiating action was not affected by 24-h pretreatment of neurons with pertussis toxin, but was abolished by cholera toxin. Therefore, G(s) proteins, but not G(i)/G(o) proteins, are involved in nefiracetam potentiation. These results indicate that nnAChRs are an important site of action of nefiracetam and G(s) proteins may be its crucial target.
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Affiliation(s)
- X Zhao
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, Illinois 60611, USA
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12
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Nishizaki T, Matsuoka T, Nomura T, Kondoh T, Watabe S, Shiotani T, Yoshii M. Presynaptic nicotinic acetylcholine receptors as a functional target of nefiracetam in inducing a long-lasting facilitation of hippocampal neurotransmission. Alzheimer Dis Assoc Disord 2000; 14 Suppl 1:S82-94. [PMID: 10850735 DOI: 10.1097/00002093-200000001-00013] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Nefiracetam (1-10 microM), a nootropic (or cognition-enhancing) agent, persistently potentiated currents through Torpedo acetylcholine (ACh) receptors expressed in Xenopus oocytes as a result of interacting with a protein kinase C pathway and the ensuing protein kinase C phosphorylation of the receptors. A similar effect was found in neuronal nicotinic ACh receptors (alpha4beta2 and alpha7). In contrast, the other nootropic agents such as piracetam and aniracetam had no potentiating action on the receptors. A sustained enhancement in the activity of nicotinic ACh receptors induced by nefiracetam caused a marked increase in the glutamate release, leading to a long-term potentiation-like facilitation of hippocampal synaptic transmissions. One of the consistent neuropathologic features of the Alzheimer brain is a loss of nicotinic ACh receptors. This fact, together with the results of our study, raises the possibility that the loss of nicotinic ACh receptors may be a key factor in the decline of cognitive function observed in Alzheimer disease and that agents targeting neuronal nicotinic ACh receptors like nefiracetam could, therefore, be of great therapeutic importance.
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Affiliation(s)
- T Nishizaki
- Department of Physiology, Kobe University School of Medicine, Japan
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13
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Nishizaki T, Nomura T, Matuoka T, Kondoh T, Enikolopov G, Enikolopo G, Sumikawa K, Watabe S, Shiotani T, Yoshii M. The anti-dementia drug nefiracetam facilitates hippocampal synaptic transmission by functionally targeting presynaptic nicotinic ACh receptors. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 80:53-62. [PMID: 11039729 DOI: 10.1016/s0169-328x(00)00117-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Nefiracetam, a pyrrolidone derivative developed as an anti-dementia drug, persistently potentiated currents through neuronal nicotinic acetylcholine (ACh) receptors (alpha7, alpha4beta2) expressed in Xenopus oocytes, and the potentiation was blocked by either the selective protein kinase C (PKC) inhibitors, GF109203X and staurosporine, or co-expressed active PKC inhibitor peptide. In primary cultures of rat hippocampal neurons, nefiracetam increased the rate of nicotine-sensitive miniature excitatory postsynaptic currents, without affecting the amplitude, and the increase was inhibited by GF109203X. In addition, the drug caused a marked increase in the glutamate release from electrically stimulated guinea pig hippocampal slices, and the effect was abolished by the nicotinic ACh receptor antagonists, alpha-bungarotoxin and mecamylamine. Nefiracetam induced a long-lasting facilitation of synaptic transmission in both the CA1 area and the dentate gyrus of rat hippocampal slices, and the facilitation was inhibited by alpha-bungarotoxin and mecamylamine. Such facilitatory action was still found in the hippocampus with selective cholinergic denervation. The results of the present study, thus, suggest that nefiracetam enhances activity of nicotinic ACh receptors by interacting with a PKC pathway, thereby increasing glutamate release from presynaptic terminals, and then leading to a sustained facilitation of hippocampal neurotransmission. This may represent a cellular mechanism underlying the cognition-enhancing action of nefiracetam. The results also provide the possibility that nefiracetam could be developed as a promising therapeutic drug for senile dementia or Alzheimer's disease.
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Affiliation(s)
- T Nishizaki
- Department of Physiology, Kobe University School of Medicine, Japan.
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Nomura T, Nishizaki T. Nefiracetam facilitates hippocampal neurotransmission by a mechanism independent of the piracetam and aniracetam action. Brain Res 2000; 870:157-62. [PMID: 10869513 DOI: 10.1016/s0006-8993(00)02417-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nefiracetam, a nootropic (cognition-enhancing) agent, facilitated neurotransmission in the dentate gyrus of rat hippocampal slices in a dose-dependent manner at concentrations ranged from 1 nM to 1 microM, being evident at 60-min washing-out of the drug. The facilitatory action was blocked by the nicotinic acetylcholine (ACh) receptor antagonists, alpha-bungarotoxin and mecamylamine. A similar facilitation was induced by the other nootropic agents, piracetam and aniracetam, but the facilitation was not inhibited by nicotinic ACh receptor antagonists and it did not occlude the potentiation induced by nefiracetam. In the Xenopus oocyte expression systems, nefiracetam potentiated currents through a variety of neuronal nicotinic ACh receptors (alpha 3beta 2, alpha 3beta 4, alpha 4 beta 2, alpha 4 beta 4, and alpha 7) to a different extent. In contrast, neither piracetam nor aniracetam had any potentiating action on alpha 7 receptor currents. While aniracetam delayed the decay time of currents through the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor, GluR1, -2, -3, expressed in oocytes, nefiracetam or piracetam had no effect on the currents. Nefiracetam, thus, appears to facilitate hippocampal neurotransmission by functionally targeting nicotinic ACh receptors, independently of the action of piracetam and aniracetam.
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Affiliation(s)
- T Nomura
- Department of Physiology, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, 650-0017, Kobe, Japan
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Nishizaki T, Matsuoka T, Nomura T, Matsuyama S, Watabe S, Shiotani T, Yoshii M. A 'long-term-potentiation-like' facilitation of hippocampal synaptic transmission induced by the nootropic nefiracetam. Brain Res 1999; 826:281-8. [PMID: 10224305 DOI: 10.1016/s0006-8993(99)01312-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Nefiracetam, a nootropic agent, enhanced the slope of field excitatory postsynaptic potentials in the CA1 region of rat hippocampal slices to about 170% of basal levels, being evident still at 4-h washing-out of the drug. A similar sustained enhancement (>/=16 h after i.m. injection with nefiracetam) was observed in the population spikes recorded from the granular cell layer of the intact mouse hippocampus. Saturation of the enhancement in the synaptic strength occluded potentiation obtained with long-term potentiation (LTP) induced by high-frequency (tetanic) stimulation, and vice versa. Interestingly, the facilitatory action of nefiracetam was blocked by either the nicotinic acetylcholine (ACh) receptor antagonists, alpha-bungarotoxin and mecamylamine, or the selective protein kinase C (PKC) inhibitor, GF109203X, but in contrast, it was not affected by D-2-amino-5-phosphonovaleric acid (APV), a selective N-methyl-D-aspartate (NMDA) receptor antagonist. The results of the present study suggest that nefiracetam, whereas the action is independent of NMDA receptors, induces an 'LTP-like' facilitation of hippocampal synaptic transmission as a consequence of modulation of nicotinic ACh receptors and PKC. This may represent a likely mechanism underlying the cognition-enhancing actions of nefiracetam.
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Affiliation(s)
- T Nishizaki
- Department of Physiology, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
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