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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The functional role of metabotropic glutamate receptor (mGluR) activation was investigated following intracerebral administration of 1S,3R-ACPD in mice. Injections of 1S,3R-ACPD (50-800 nmol in 5 microliters) into the thalamus produced a dose-dependent increase in limbic seizures. These effects were stereoselective since 1R,3S-ACPD, did not elicit seizure activity. Pharmacologically, limbic seizures were attenuated by the mGluR partial agonist/antagonist L-2-amino-3-phosphonopropionate (L-AP3) and dantrolene, an inhibitor of intracellular calcium mobilization, but not by D-AP3 or ionotropic glutamate receptor antagonists (MK-801 or GYKI-52466). Thus, activation of mGluRs by 1S,3R-ACPD in mice, induces limbic seizures that may involve the mobilization of intracellular calcium stores.
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PMID:Intracerebral 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) produces limbic seizures that are not blocked by ionotropic glutamate receptor antagonists. 812 13

Mice selectively bred to be Withdrawal Seizure-Prone (WSP) or Seizure-Resistant (WSR) after chronic ethanol administration have been reported to be differentially sensitive to the anticonvulsant and proconvulsant effects on alcohol withdrawal of drugs interacting with glutamate receptors. Several behavioral effects of the noncompetitive glutamate receptor antagonist, dizocilpine, were determined in WSP and WSR mice to see whether their differential sensitivity generalized to effects unrelated to seizures, and to see whether it was only apparent during ethanol withdrawal. Dizocilpine potentiated the loss of righting reflex induced by ethanol, and dose-dependently stimulated habituated and nonhabituated open field activity. WSP and WSR mice were equally sensitive to these effects of dizocilpine. Pretreatment with dizocilpine increased the transcorneal amperage necessary to produce maximal electroshock seizures: WSR mice were more sensitive than WSP to this effect. Ethanol withdrawal (i.e., testing 6 h after a 24-h exposure to ethanol vapor) and dizocilpine had several effects on mice tested in the hole-in-wall apparatus. Several differences between WSP and WSR mice were also found, but in no case did dizocilpine differentially affect ethanol-withdrawing WSP and WSR mice. Across these experiments, differences between WSP and WSR mice in response to dizocilpine were rather specific. For some responses, WSP and WSR mice were equally sensitive, but only in the seizure-related measure assessed were naive WSR mice more sensitive than WSP.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of dizocilpine in withdrawal seizure-prone (WSP) and withdrawal seizure-resistant (WSR) mice. 820 61

Expression of the immediate-early gene c-fos has been advanced as a marker of neuronal activity in the adult nervous system. We sought to test the validity of c-fos mRNA expression as a marker of neuronal activity during seizures and to elucidate specific neurotransmitter receptors whose activation was necessary for seizure-evoked c-fos mRNA expression. We correlated c-fos mRNA expression, measured with in situ hybridization, with kindled seizure-induced firing of hippocampal dentate granule cells or substantia nigra pars compacta and pars reticulata neurons. We found that the occurrence of seizure-evoked synchronous action potentials during the seizure exhibited a perfect qualitative correlation with the presence of c-fos mRNA expression in the granule cells 30 min following the seizure (Fisher's exact test, p = 0.002). However, there was no quantitative correlation between the number of seizure-induced population action potentials and the magnitude of c-fos mRNA expression in the granule cells. In the substantia nigra, where neuronal populations have previously been demonstrated to exhibit synchronous firing during kindled seizures, no induction of c-fos mRNA was detected in either pars compacta or pars reticulata. Pretreatment with antagonists of the NMDA subtype of glutamate receptor selectively and markedly decreased seizure-induced c-fos mRNA expression in the dentate granule cells, despite increasing the number of granule cell population action potentials. These findings illustrate the complexity of the relationship between c-fos induction and neuronal burst firing during kindled seizures.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Induction of c-fos mRNA by kindled seizures: complex relationship with neuronal burst firing. 838 Nov 72

Ethanol, acutely, is a potent and selective inhibitor of the function of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor in primary cultures of cerebellar granule cells. The effect of ethanol can be reversed by high concentrations of glycine, and nonequilibrium ligand binding studies in brain membrane preparations suggest that ethanol may act by decreasing the frequency of ion channel opening. After chronic consumption of ethanol by animals, the number of NMDA receptors (measured by ligand binding) is increased in many brain areas. Similarly, NMDA receptor function is increased in cerebellar granule cells exposed chronically to ethanol. In the intact animal, this receptor up-regulation may be associated with ethanol withdrawal seizures, which are attenuated by uncompetitive antagonists at the NMDA receptor. In contrast to ethanol, barbiturates have a greater inhibitory effect at the kainate subtype of glutamate receptor than at the NMDA receptor. After chronic barbiturate ingestion, kainate binding is decreased in certain brain areas, while ligand binding to the NMDA receptor is increased. Overall, the pattern of brain area-specific effects of barbiturates on NMDA and kainate receptor function is quite distinct from that of ethanol.
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PMID:Ethanol, sedative hypnotics, and glutamate receptor function in brain and cultured cells. 839 Feb 39

Repeated administration of a subconvulsant dose of a local anesthetic will eventually induce seizures, a phenomenon similar to electrical kindling. We have investigated the effect of repeated lidocaine and cocaine administration on the phosphoinositide (PI) hydrolysis induced by batrachotoxin (BTX), a specific Na channel activator. Rats were injected with cocaine or saline daily for 6 days and PI hydrolysis was assayed in sliced frontal cortex. Cocaine treatment had no effect on BTX-induced PI hydrolysis while in vitro cocaine blocked the BTX effect. In a second experiment, rats received daily injections of lidocaine or saline. After a rat developed at least two seizures, it was sacrificed together with a rat receiving lidocaine injections which had never seized and a rat receiving saline injections. Basal, BTX and ibotenic acid (IBO; a glutamate receptor agonist)-stimulated PI hydrolysis did not differ among the three groups in slices of either hippocampus (HC) or piriform cortex (PC) though IBO-stimulated PI hydrolysis was much greater in the HC than in the PC. Neither in vitro nor in vivo carbamazepine altered the effect of cocaine on BTX-induced PI hydrolysis. These results demonstrate that local anesthetic kindling does not alter PI hydrolysis coupled to Na channel or IBO activation.
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PMID:Effect of cocaine, lidocaine kindling and carbamazepine on batrachotoxin-induced phosphoinositide hydrolysis in rat brain slices. 839 85

To address the question of whether the mode of seizure induction contributes to the effects of seizures on glutamate receptor gene expression, we examined rat dorsal hippocampal slides by in situ hybridization after kindling by electrical stimulation of the amygdala, or after electrically induced tonic-clonic seizures. Levels of a glutamate receptor subtype (GluR1) mRNA were analyzed at three periods post kindled seizures and found to be decreased only in brains that were obtained 24 h after the last kindled seizure. This downregulation of GluR1 mRNA was transient and was observed only in animals that had behavioral manifestations after being electrically stimulated. It is probable that maintenance of the kindled state cannot be explained by a long-lasting change in GluR1 gene expression. Repeated electroshock-induced seizures increased GluR1 mRNA levels in the hippocampus. Our results show that mode of induction is an important determinant of the effects of seizures on the levels of expression of a glutamate receptor gene.
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PMID:Differential effects of kindled and electrically induced seizures on a glutamate receptor (GluR1) gene expression. 850 92

5-Chloro-7-trifluoromethyl-1,4-dihydro-2,3-quinoxalinedione (ACEA-1011) has analgesic properties in animal models of tonic pain. To investigate the mechanisms underlying this effect we used electrical recording techniques to characterize the in vitro pharmacology of ACEA-1011 at mammalian glutamate receptors. Two preparations were used: Xenopus oocytes expressing rat brain receptors and cultured rat cortical neurons. Results showed that ACEA-1011 is a competitive antagonist at NMDA receptor glycine sites. Apparent antagonist affinities (Kb values) were 0.4 to 0.8 microM in oocytes and approximately 0.6 microM in neurons. IC50 values for ACEA-1011 against four binary subunit combinations of cloned rat NMDA receptors (NR1A/NR2A, 2B, 2C or 2D) ranged from 0.4 to 8 microM (1 microM glycine). The 20-fold variation in sensitivity was due to a combination of subunit-dependent differences in glycine and antagonist affinities; EC50 values for glycine ranged between 0.08 to 0.8 microM and Kb values for ACEA-1011 between 0.2 to 0.8 microM. In addition, ACEA-1011 inhibited AMPA-preferring non-NMDA receptors by competitive antagonism at glutamate binding sites. Kb values were 4 to 9 microM in oocytes and 9 to 10 microM in neurons. The ED50 for ACEA-1011 in a mouse maximum electroshock-induced seizure model was approximately 12 mg/kg i.v.. Our results indicate that ACEA-1011 is a systemically active broad selectivity ionotropic glutamate receptor antagonist.
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PMID:Pharmacology of 5-chloro-7-trifluoromethyl-1,4-dihydro-2,3-quinoxalinedione: a novel systemically active ionotropic glutamate receptor antagonist. 853 Oct 83

Autoantibodies to GluR3, an AMPA glutamate receptor subtype, may be a cause of chronic unilateral encephalitis (Rasmussen's syndrome). We report a woman with chronic left hemisphere encephalitis whose partial seizures, aphasia, and motor weakness are highly responsive to intermittent steroids and cyclophosphamide. Her serum and CSF were negative for antibodies to GluR3 by both immunoblot and immunocytochemical analysis of cells transfected with GluR3 cDNA, indicating that separate immune-mediated processes may be involved in some cases of chronic encephalitis.
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PMID:Chronic steroid-responsive encephalitis without autoantibodies to glutamate receptor GluR3. 855 86

In this study we have shown, by in situ hybridization and RNase protection assay, a significant trkC mRNA increase confined to the dentate gyrus of hippocampus, both after seizures induced by intracerebroventricular injection of kainic acid and bicuculline. Moreover, after bicuculline treatment we observed an earlier increase of trkC mRNA level, which peaked after 3 h and returned back to normal levels by 12 h. In contrast, the kainic acid treatment produced a delayed increase of trkC mRNA, which initiated after 6 h, peaked at 12 h, and returned to normal levels at 24 h. This increase, which involves also trkC mRNA receptor with tyrosine kinase activity, was mediated by non-NMDA receptors and counteracted by GABA potentiating agent diazepam. Using embryonic neuronal cultures from cerebral hemispheres, including hippocampus, we found that glutamate receptor agonists, including glutamate, kainate, NMDA, and t-ACPD, increase trkC mRNA levels with the following rank order of efficacy: NMDA > t-ACPD > kainic acid > glutamate. In conclusion, our data show that trkC mRNA expression in granule cells of the hippocampus dentate gyrus is increased during seizure activity and that it is mediated by non-NMDA receptors.
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PMID:Seizures increase trkC mRNA expression in the dentate gyrus of rat hippocampus. Role of glutamate receptor activation. 856 16

The influence of intracerebrally focally administered doses of a presynaptic metabotropic glutamate receptor agonist, (1S,3S)-ACPD, and of the post-synaptically targeted competitive NMDA receptor antagonist, D-CPPene (SDZ EAA 494), was tested on the development of amygdaloid kindling. The actions of these drugs, compared to that of D-CPP, was also tested on fully developed stage 5 amygdala kindled seizures. Both (1S,3S)-ACPD and D-CPPene dose-dependently increased the generalised seizure threshold in fully kindled animals. They showed a similar potency, with (1S,3S)-ACPD acting presynaptically and D-CPPene postsynaptically. Both drugs reversibly inhibited epileptogenesis at 10 nmol in 0.5 microliter of injection vehicle, keeping the kindling stage at or below stage 2. All animals reached stage 5 after withdrawal of the 2 drugs. Whereas (1S,3S)-ACPD inhibited depolarisation-induced release of [3H]L-glutamate and [3H]D-aspartate from cortical synaptosomes (IC50 63 microM and 50 microM, respectively), D-CPPene (postsynaptically active) was without effect. These findings suggest a new approach to the development of clinically effective anticonvulsants through the development of presynaptic glutamate receptor agonists which could be administered systemically to control the extent of synaptic release of glutamate.
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PMID:Blockade of both epileptogenesis and glutamate release by (1S,3S)-ACPD, a presynaptic glutamate receptor agonist. 858 75


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