Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038220 (status epilepticus)
 7,272 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Antagonists of the N-methyl-D-aspartate (NMDA) subtype of glutamate (Glu) receptor have become the focus of considerable attention as potential neurotherapeutic agents in view of mounting evidence implicating NMDA receptors in acute central nervous system (CNS) injury syndromes such as stroke, trauma, and status epilepticus. In addition, NMDA receptor antagonists are of potential interest for the clinical management of neuropathic pain and preventing the development of tolerance to opiate analgesics. A potentially serious obstacle to the development of NMDA antagonists as neurotherapeutic drugs is the paradoxical fact that whereas these agents do have significant neurotherapeutic potential, they also have psychotogenic and neurotoxic properties. We have been intensively investigating the mechanisms underlying these adverse properties and have discovered several methods of suppressing or preventing their expression. In addition, we have been exploring the possibility that a common mechanism may underlie the psychotogenic and neurotoxic actions of these agents and that this mechanism may have relevance to the pathogenesis of idiopathic psychotic processes such as schizophrenia. In this chapter, we will review our findings pertaining to NMDA antagonists in the dual context of their value as tools for exploring mechanisms underlying neuropsychiatric disturbances, particularly schizophrenia, and their potential promise as therapeutic agents. For additional references and a more complete elaboration of our hypothesis pertaining to NMDA receptor dysfunction and schizophrenia, please see a recent review (Olney and Farber 1995).
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PMID:NMDA antagonists as neurotherapeutic drugs, psychotogens, neurotoxins, and research tools for studying schizophrenia. 874 58

We studied the production of tumor necrosis factor alpha (TNF alpha) and interleukin-6 (IL-6) 2 and 7 days following status epilepticus (SE), induced in rats by intra-amygdala injection of kainate. At day 2 the release of both cytokines by hippocampal slices prepared from epileptic animals was increased compared to controls, whereas at day 7 only TNF alpha secretion was enhanced. Since SE-induced neuronal damage is probably due to excitotoxicity, we investigated the effects of agonists of glutamate receptors on TNF alpha release in organotypic hippocampal cultures. A correlation was found between the damage intensity and the release of TNF alpha, suggesting production of this cytokine by macrophagic microglia. We propose a role for TNF alpha and IL-6 in the adaptive phenomena which follow severe limbic seizures.
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PMID:Release of TNF alpha in the rat hippocampus following epileptic seizures and excitotoxic neuronal damage. 881 15

Cerebrospinal fluid (CSF) concentrations of glutamate and gamma- aminobutyric acid (GABA), as estimates of levels in the extracellular compartment of brain, were determined in 7-day postnatal rats at the terminus of hypoxia-ischemia and during status epilepticus, induced with bicuculline, at 2 and 24 h of recovery. Hypoxia-ischemia was associated with increased CSF glutamate, which was not increased further during status epilepticus. In contrast, CSF GABA was increased by hypoxia-ischemia as well as by status epilepticus during recovery. CSF glutamate/GABA ratios in rat pups subjected to status epilepticus with or without prior hypoxia-ischemia were lower than control animals during recovery. The lack of any significant increase in glutamate or in the glutamate/GABA ratio during status epilepticus would preclude any neuronal injury from occurring in those immature rats sustaining seizures alone or any accentuation of brain damage in those animals subjected to prior cerebral hypoxia-ischemia.
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PMID:Cerebrospinal fluid concentrations of glutamate and GABA during perinatal cerebral hypoxia-ischemia and seizures. 883 71

Glutamate is an excitatory neurotransmitter in the mammalian central nervous system and a neurotoxin (excitotoxin) that has the potential to destroy neurones by activation of ionotropic receptors. In contrast to the well documented role of glutamate in the pathogenesis of neuronal degeneration resulting from hypoxia/ischaemia, hypoglycaemia, status epilepticus and trauma, it has been difficult to establish a link between the excitotoxicity and neuronal death that occur in chronic neurodegenerative disorders. Impairment of energy metabolism has been shown to increase neuronal vulnerability to glutamate. The cause of this phenomenon lies in the attenuation of the Mg2+ blockade of the N-methyl-D-aspartate receptors that leads to persistent activation of these receptors by physiologic extracellular glutamate concentrations. The concept of increased neuronal vulnerability to excitotoxic injury establishes a link between slow neuronal degeneration and excitotoxicity and suggests that glutamate antagonists may prove beneficial in the treatment of chronic neurodegenerative diseases that have been resistant to therapy.
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PMID:Excitotoxicity and neurodegenerative diseases. 884 37

Rats treated systemically with kainate develop stereotyped epileptic seizures involving mainly limbic structures that may last for hours. This model of limbic status epilepticus has been widely studied using classical neuropathological techniques. We used in situ nick translation histochemistry to examine patterns of DNA fragmentation in this model. We found a stereotyped and reproducible pattern of neuronal populations that demonstrate evidence of DNA fragmentation from 24 h to one week after kainate treatment. Neither blockade of new protein synthesis nor blockade of the N-methyl-D-aspartate-type glutamate receptors significantly altered this response. Moreover, we saw no evidence of the regular internucleosomal cleavage of DNA that produces a characteristic laddered appearance of 180-200 bp DNA fragments after gel electrophoresis in samples obtained from microdissected affected regions. These studies suggest that DNA fragmentation after systemic kainate-induced seizures is not the result of programmed cell death. This assay may be useful for quantitative testing of both neuroprotective agents and mechanistic hypotheses.
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PMID:Anatomical studies of DNA fragmentation in rat brain after systemic kainate administration. 886 4

A novel antiepileptic drug, tiagabine ((R)-N-[4,4-di-(3-methylthien-2-yl) but-3-enyl] nipecotic acid hydrochloride), was studied in rats in order to determine its efficacy in preventing seizures, seizure-induced neuronal damage and impairment of spatial memory in the perforant pathway stimulation model of status epilepticus. In pilot experiments, administration of tiagabine (50, 100 or 200 mg/kg/day) with subcutaneously implanted Alzet osmotic pumps led to a dose-dependent increase in tiagabine concentrations in the serum and brain. Two days of tiagabine treatment at a dose range of 50-200 mg/kg/day did not change the levels of gamma-aminobutyric acid (GABA), glutamate or aspartate in cisternal cerebrospinal fluid (CSF) compared to the controls. In the pentylenetetrazol test, the maximal anticonvulsive effect of tiagabine administered via osmotic pumps was achieved already with a dose of 50 mg/kg/day. In the perforant pathway model of status epilepticus, subchronic treatment with tiagabine (Alzet pumps, 50 mg/kg/day) completely prevented the appearance of generalized clonic seizures during stimulation (P < 0.001). In the same rats, tiagabine treatment reduced the loss of pyramidal cells in the CA3c and CA1 fields of the hippocampus (P < 0.05) but not the loss of somatostatin immunoreactive neurons in the hilus. Two weeks after perforant pathway stimulation, the tiagabine-treated rats performed better in the Morris water-maze test than the vehicle-treated rats did (P < 0.001). Our results show that tiagabine treatment reduces the severity of seizures in the perforant pathway stimulation model of status epilepticus. Possibly associated with the reduction in seizure number and severity, tiagabine treatment also reduced seizure-induced damage to pyramidal cells in the hippocampus as well as the impairment of the spatial memory associated with hippocampal damage.
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PMID:Tiagabine prevents seizures, neuronal damage and memory impairment in experimental status epilepticus. 890 Oct 9

1. The main purposes of this study are to characterize the intracellular and extracellular responses of cells in superficial layers of entorhinal cortex (EC) in chronically epileptic animals, determine whether their altered physiology is dependent on being connected to hippocampus, and investigate whether there is evidence of augmented excitation and inhibitory interneuron disconnection. 2. Functional connectivity was maintained between the hippocampal area and the EC in vitro in a combined rat hippocampal-parahippocampal slice preparation by slicing with a vibratome at a 30-deg angle to the base of the brain. Three groups of animals were studied: naive animals, animals that had experienced a previous episode of (nonconvulsive) self-sustaining limbic system status epilepticus (SSLSE) induced by electrical stimulation resulting in a chronically epileptic state, and animals in an electrode control group. In chronically epileptic rats and the electrode control group, studies were done on tissue contralateral to the side of electrode implantation. 3. Extracellular and intracellular recordings were made from the superficial layers of EC. Neurons in the superficial layers of the EC were activated by stimulation of the deep layers within the EC or the angular bundle adjacent to the EC, which contains axons from EC neurons. Responses could be elicited by antidromic and synaptic mechanisms by stimulation at either site. In addition, a monosynaptic protocol was used that involved direct activation of interneurons with a stimulating electrode placed near the recording electrode in the presence of the ionotropic glutamate blockers D(-)-2-amino-5-phosphonovaleric acid (APV) and 6,7-dinitroquinoxaline-2-3-dione (DNQX). 4. Responses were collected over a range of stimulus intensities, from very low to high intensities, to construct input/output function (I/O) curves. Amplitudes and durations were measured at the lowest stimulus intensity that elicited a maximum responses. 5. Extracellular field potential responses from electrode controls did not differ from naives qualitatively with respect to morphology of field potential responses or quantitatively with respect to response duration and amplitude. Field potential responses in tissue from post-SSLSE rats differed markedly in morphology from naive and electrode controls, being more complex, significantly longer in duration, and decreased in amplitude. These epileptiform responses were shortened markedly by blockade of N-methyl-D-aspartate (NMDA) receptors with APV, but this manipulation did not convert responses to a normal morphology. These responses were abolished by blockade of non-NMDA mediated ionotropic glutamate receptors with DNQX. 6. During intracellular recordings of neurons in slices from both control and epileptic animals, neurons were quiescent under resting conditions in the absence of electrical stimulation. 7. Intracellular responses in electrode controls were identical to naive, and together were considered "controls." In control tissue, evoked intracellular responses were similar to those previously described and most commonly consisted of an excitatory postsynaptic potential (EPSP) that was blocked partially by the NMDA-receptor antagonist APV, followed by hyperpolarizing potentials, which were identified electrophysiologically and pharmacologically as gamma-aminobuturic acid-A (GABAA)- and GABAB-receptor-mediated inhibitory postsynaptic potentials (IPSPs). EPSPs were blocked completely by DNQX. 8. In chronically epileptic tissue, evoked intracellular responses differed markedly from responses in control animals, exhibiting all-or-none prolonged paroxysmal depolarizing events with multiple superimposed action potentials in response to a single shock. These depolarizing events were reduced in duration and amplitude, but not abolished, in APV. IPSPs were not seen or markedly reduced at all stimulus intensities. These intracellular responses never resembled control responses. Intracellur responss correlated precisely in morphology and duration with extracellular field potentials. (ABSTRACT TRUNCATED)
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PMID:Responses of the superficial entorhinal cortex in vitro in slices from naive and chronically epileptic rats. 893 Feb 45

Prolonged seizures have long been known to be associated with cell injury and cell death in brain. Such seizure-related neuronal injury has been assumed to be mediated by glutamate, the same excitatory amino acid in the central nervous system which propagates the seizure itself. Elevated extracellular concentrations of glutamate have not been demonstrated in brain during seizures in experimental animals. However, these studies have not been performed during status of a duration adequate to induce cell injury, a time when the putative neurotoxins might be demonstrable. We therefore induced status epilepticus (recorded both with conventional surface EEG and with deep electrodes in the area of greatest vulnerability, the piriform cortex) and lengthened the time of status to the point of cell death. Seizures were induced with intravenous kainic acid, and prolonged by injecting the NMDA antagonist AP-7 into the substantia nigra. Microdialysis probes were introduced into the piriform cortex of one hemisphere to assess the presence of extracellular glutamate. In the contralateral hemisphere the degree of neuronal injury was estimated by measurement of heat shock protein (HSP) expression and cell death quantified by acid fuchsin staining. In this model, neuronal injury correlates linearly with seizure duration; however, elevation of glutamate in the extracellular space was not seen even when neuronal injury was profound.
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PMID:The role of excitatory neurotransmitters in seizure-induced neuronal injury in rats. 893 Mar 50

Systemic administration of kainic acid, a cyclic analogue of glutamate, produces many of the clinical features of human temporal lobe epilepsy and status epilepticus in rats, including the induction of motor convulsions and the degeneration of neurons in the hippocampus and piriform cortex. Differential display PCR was used to identify mRNAs that are differentially expressed between degenerating and nondegenerating tissues in the brain after kainic acid-induced seizure activity. A novel cDNA fragment expressed in the degenerating hippocampus and piriform cortex, but not in the nondegenerating parietal cortex, was identified, cloned, and sequenced. This novel cDNA fragment identified a new member of the synaptotagmin gene family that is rapidly and transiently induced in response to seizure activity. Differential expression of this synaptotagmin gene, syt X, was confirmed by Northern blot analysis and in situ hybridization. This novel, inducible synaptotagmin gene may provide a direct link between seizure-induced neuronal gene expression and subsequent modulation of synaptic structure and function.
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PMID:A novel seizure-induced synaptotagmin gene identified by differential display. 912 48

The pro- or anticonvulsant properties of propofol remain a matter of controversy. Although numerous case reports describe the appearance of abnormal movements, posturing and seizure-like activity related to the use of propofol, systematic studies in both humans and animals strongly suggest that it possesses antiepileptic properties. Propofol consistently reduces the seizure duration during electroconvulsive therapy, its use has been successful in controlling refractory status epilepticus and in animals it offers a strong protection against lignocaine- or pentylene-tetrazol-induced epilepsy. The beneficial effects of propofol may be related to its uniform depressant action on the central nervous system, to a potentialization of GABA-mediated pre- and postsynaptic inhibition, and by decreasing the release of excitatory transmitters, glutamate and aspartate.
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PMID:Propofol: pro- or anticonvulsant? 920 33


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