Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Enzymatic production of prostaglandins (PGs) from exogenous arachidonic acid was studied in brain microsomal fractions prepared from mice following pentylenetetrazol (PTZ)-induced convulsions. Prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) measured either by radioimmunoassay or after incubation with [1-14C]arachidonic acid (AA) was significantly increased in microsomes from the convulsed animals. Pretreatment of the mice with the anticonvulsant ethosuximide prevented the enhanced PG production. The increased PG synthesis could not be attributed to an increased substrate availability nor to an activated phospholipase nor to a direct effect of the convulsant on the fatty acid cyclooxygenase. Evidence that a modification of the cyclooxygenase had occurred with seizure activity was obtained from kinetic analysis; the apparent Km for the AA was lowered from 30 +/- 3 microM in the controls to 12 +/- 1 microM in the PTZ-treated mice. Further evidence for a modification of the fatty acid cyclooxygenase was obtained from incubations of the microsomes with catalase to reduce peroxide formation. Limiting peroxide levels did not decrease the microsomal cyclooxygenase activity in the PTZ-treated mice to control levels. Seizure activity induced by picrotoxin and strychnine also increased the microsomal capacity of the convulsed animals to synthesize PGs. The increased brain fatty acid cyclooxygenase activity may result from a biochemical modification of the enzyme induced by seizure activity.
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PMID:Evidence for increased activity of mouse brain fatty acid cyclooxygenase following drug-induced convulsions. 310 89

The effects of five nonsteriodal prostaglandin (PG) synthetase inhibitors on the electrocorticogram were studied in rats with chronically implanted supracortical electrodes. All of PG synthetase inhibitors produced high voltage activity in the electrocorticogram. However, behavior and spectral analysis of the electrocortical activity suggests that these drugs could be divided into two groups. Meclofenamic acid and mefenamic acid produced dose-related increases in excitation (to seizure) while ibuprofen, paracetamol and indomethacin produced dose-related increases in sedation.
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PMID:Differential effects of prostaglandin synthetase inhibitors on EEG in rat. 392 13

Release of prostaglandins (PGs) from brain tissue increases during experimentally-induced and spontaneous seizures. However, whether PGs or other arachidonic acid metabolites have a role in induction of seizures is still unclear. The effectiveness of pretreatment with PG synthetase inhibitors on pentylenetetrazol (PTZ)-induced models of epilepsy was investigated in free-moving rats with chronically-implanted supracortical electrodes. The effects on the electrocortical and motor manifestations of both a subconvulsive (30 mg.kg-1) and a convulsive (60 mg.kg-1) dose of PTZ were examined. Mefenamic acid (15 or 50 mg.kg-1), meclofenamic acid (15 or 50 mg.kg-1), ibuprofen (30 or 90 mg.kg-1) and paracetamol (300 or 450 mg.kg-1) delayed the onset of PTZ-induced convulsions. But mefenamic acid and meclofenamic acid also potentiated the excitatory effects of both subconvulsive and convulsive doses of PTZ. Indomethacin (3, 10 or 30 mg.kg-1) had no significant effect. The results suggest that the differential effects were produced by actions not related to the cyclo-oxygenase inhibition although the more consistent decrease of convulsive behavior may have resulted from inhibition of PG synthesis.
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PMID:Differential effect of prostaglandin synthetase inhibitor pretreatment on pentylenetetrazol-induced seizures in rat. 392 64

To investigate the relationship of prostaglandins (PGs) to seizure induction, the effects of six PG synthetase inhibitors on convulsions induced by flurothyl, picrotoxin, pentetrazol (PTZ), electroshock or bicuculline were evaluated. Ibuprofen, sulindac, mefenamic acid, and low dose meclofenamic acid increased the latency-to-onset in the flurothyl and/or PTZ models; the electroshock, picrotoxin and bicuculline models were not significantly affected by any of the pretreatment agents. These results suggest that PGs are involved in the mechanism(s) underlying fluorthyl- and PTZ-induced convulsions, but not picrotoxin-, electroshock-, or bicuculline-induced convulsions.
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PMID:Effect of prostaglandin synthetase inhibitors on experimentally induced convulsions in rats. 643 67

Membrane lipid-derived second messengers are generated by phospholipase A2 (PLA2) during synaptic activity. Overstimulation of this enzyme during neurotrauma results in the accumulation of bioactive metabolites such as arachidonic acid, oxygenated derivatives of arachidonic acid, and platelet-activating factor (PAF). Several of these bioactive lipids participate in cell damage, cell death, or repair-regenerative neural plasticity. Neurotransmitters may activate PLA2 directly when linked to receptors coupled to G proteins and/or indirectly as calcium influx or mobilization from intracellular stores is stimulated. The release of arachidonic acid and its subsequent metabolism to prostaglandins are early responses linked to neuronal signal transduction. Free arachidonic acid may interact with membrane proteins, i.e., receptors, ion channels, and enzymes, modifying their activity. It can also be acted upon by prostaglandin synthase isoenzymes (the constitutive prostaglandin synthase PGS-1 or the inducible PGS-2) and by lipoxygenases, with the resulting formation of different prostaglandins and leukotrienes. Glutamatergic synaptic activity and activation of postsynaptic NMDA receptors are examples of neuronal activity, linked to memory and learning processes, which activate PLA2 with the consequent release of arachidonic acid and platelet-activating factor (PAF), another lipid mediator. Both mediators may exert presynaptic and postsynaptic effects contributing to long-lasting changes in glutamate synaptic efficacy or long-term potentiation (LTP), PAF, a potential retrograde messenger in LTP, stimulates glutamate release. The PAF antagonist BN 52021 competes for receptors in presynaptic membranes and blocks this effect. PAF may also be involved in plasticity responses because PAF leads to the expression of early response genes and subsequent gene cascades. The PAF antagonist BN 50730, selective for PAF intracellular binding, blocks PAF-mediated induction of gene expression. A consequence of neural injury induced by ischemia, trauma, or seizures is an increased release of neurotransmitters, that in turn generates an overproduction of second messengers. Glutamate, a key player in excitotoxic neuronal damage, triggers increased permeation of calcium mediated by NMDA receptors and activation of PLA2 in postsynaptic neurons. NMDA receptor antagonists reduce the accumulation of free fatty acids and elicit neuroprotection in ischemic damage. Increased production of free arachidonic acid and PAF converges to exacerbate glutamate-mediated neurotransmission. These neurotoxic actions may be brought about by arachidonic acid-induced potentiation of NMDA receptor activity and decreased glutamate reuptake. On the other hand, PAF stimulates the further release of glutamate at presynaptic endings. The neuroprotective effects of the PAF antagonist BN 52021 in ischemia-reperfusion are due, at least in part, to an inhibition of presynaptic glutamate release. PAF also induces expression of the inducible prostaglandin synthase gene, and PAF antagonists selective for the intracellular sites inhibit this effect. The PAF antagonist also inhibits the enhanced abundance, due to vasogenic cerebral edema and ischemia-reperfusion damage, of inducible prostaglandin synthase mRNA in vivo. Therefore, PAF, an injury-generated mediator, may favor the formation of other cell injury and inflammation mediators by turning on the expression of the gene that encodes prostaglandin synthase.
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PMID:Mediators of injury in neurotrauma: intracellular signal transduction and gene expression. 859 8

Prostaglandin G/H synthase-2 and zif-268 mRNA expression is transiently induced in rat brain by kainic acid (KA)-induced seizures and by a single electroconvulsive shock. Induction of both genes by KA shows neuroanatomical specificity in the order hippocampus > cerebral cortex > striatum > brain stem > cerebellum. Nuclear run-on and Western blotting shows that both genes are transcriptionally activated, and that kainic acid up-regulation of prostaglandin G/H synthase-2 mRNA expression in hippocampus matches increased protein levels. Whereas the magnitude of hippocampal zif-268 mRNA induction is similar in both seizure models, peak induction of prostaglandin G/H synthase-2 mRNA is 7-fold greater in the kainic acid model than in the electroconvulsive shock model and is much more prolonged. Pretreatment of animals by intracerebroventricular injection with the intracellular platelet-activating factor receptor antagonist BN 50730 strongly attenuates kainic acid and electroconvulsive shock induction of prostaglandin G/H synthase-2 expression. The drug partially inhibits electroconvulsive shock induction of zif-268, but is relatively ineffective against kainic acid-induced zif-268 expression. Seizure-induced expression of both genes involves platelet-activating factor, but the mechanisms of induction must be otherwise distinct. The selectively elevated induction of hippocampal prostaglandin G/H synthase-2 by kainic acid correlates with a neuroanatomical region in which the agonist induces neuronal damage.
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PMID:Sustained induction of prostaglandin endoperoxide synthase-2 by seizures in hippocampus. Inhibition by a platelet-activating factor antagonist. 879 51

Synaptic activation leads to the formation of arachidonic acid, platelet-activating factor (PAF, 1-O-alkyl-2-acyl-sn-3-phosphocholine) and other lipid messengers. PAF is a potent bioactive phospholipid in synaptic plasticity. PAF enhances presynaptic glutamate release, is a retrograde messenger in long-term potentiation and enhances memory formation. PAF also couples synaptic events with gene expression by stimulating a FOS/JUN/AP-1 transcriptional signaling system, as well as transcription of COX-2 (inducible prostaglandin synthase). Since the COX-2 gene is also involved in synaptic plasticity, the PAF-COX-2 pathway may have physiological significance. Seizures, ischemia and other forms of brain injury promote phospholipase A2 (PLA2) overactivation, resulting in the accumulation of bioactive lipids at the synapse. PAF, under these pathological conditions, behaves as a neuronal injury messenger by at least two mechanisms: (a) enhancing glutamate release; and, (b) by sustained augmentation of COX-2 transcription. These events link PAF with neurodegeneration. The upstream intracellular pathways of signal transduction involved in neuronal or photoreceptor cell apoptosis are not well understood and involve stress sensitive kinases. PAF is a transcriptional activator of the COX-2 gene. BN 50730, a potent intracellular PAF antagonist, blocks COX-2 induction. COX-2 transcription and protein expression are upregulated in the hippocampus in kainic acid induced epileptogenesis. There is a selectively elevated induction of COX-2 (72-fold) by kainic acid preceding neuronal cell death. BN 50730 administered by i.c.v. injection blocks seizure-induced COX-2 induction. Overall, PAF is a dual modulator of neural function and becomes an endogenous neurotoxin when over produced.
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PMID:The neuromessenger platelet-activating factor in plasticity and neurodegeneration. 993 49

Excitotoxicity involves over activation of brain excitatory glutamate receptors and has been implicated in neurological, neurodegenerative and neuropsychiatric diseases. Metabolism of arachidonic acid (AA) through the phospholipase A(2) (PLA(2))/prostaglandin-endoperoxide synthase (PTGS) pathway is increased after excitotoxic stimulation. However, the individual roles of the PTGS isoforms in this process are not well established. We assessed the role of the PTGS isoforms in the process of excitotoxicity by exposing mice deficient in either PTGS-1 (PTGS-1(-/-)) or PTGS-2 (PTGS-2(-/-)) to the prototypic excitotoxin, kainic acid (KA). Seizure intensity and neuronal damage were significantly elevated in KA-exposed PTGS-2(-/-), but not in PTGS-1(-/-), mice. The increased susceptibility was not associated with an alteration in KA receptor binding activity or mediated through the CB1 endocannabinoid receptor. The frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) was decreased in the CA1 pyramidal neurons of PTGS-2(-/-) mice, suggesting an alteration of GABAergic function. In wild-type mice, six weeks treatment with the PTGS-2 selective inhibitor celecoxib recapitulated the increased susceptibility to KA-induced excitotoxicity observed in PTGS-2(-/-) mice, further supporting the role of PTGS-2 in the excitotoxic process. The increased susceptibility to KA was also associated with decreased brain levels of PGE(2), a biomarker of PTGS-2 activity. Our results suggest that PTGS-2 activity and its specific products may modulate neuronal excitability by affecting GABAergic neurotransmission. Further, inhibition of PTGS-2, but not PTGS-1, may increase the susceptibility to seizures.
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PMID:Altered GABAergic neurotransmission is associated with increased kainate-induced seizure in prostaglandin-endoperoxide synthase-2 deficient mice. 1835 36