Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The glutamatergic synapses between inner hair cells and afferent neurons seem to be involved in pathophysiological conditions of the cochlea. The excessive release of glutamate from inner hair cells during noise trauma and ischemia affects the afferent neurons. It is possible that in tinnitus outer hair cell or inner hair cell dysfunction or damage leads to an altered spontaneous release of glutamate from inner hair cells. Thus, the pharmacological modulation of glutamatergic neurotransmission could be of great value in the therapy of certain inner ear diseases. Recently, it has been discovered that the spasmolytic drug memantine has antiglutamatergic properties. As a possible drug for inner ear diseases, we were interested in the action of memantine on the neurotransmission of inner hair cells. With the aid of microiontophoretic techniques we were able to show a strong depressing effect on spontaneous activity as well as on glutamate-induced activity. This effect seems to be mediated by a blockade of N-methyl-D-aspartate (NMDA) receptors as memantine showed a strong inhibiting effect on NMDA-induced activity but not on AMPA-induced activity. These results recommend memantine for the treatment of inner ear diseases, e.g. especially tinnitus.
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PMID:Memantine suppresses the glutamatergic neurotransmission of mammalian inner hair cells. 951 76

Tumor necrosis factor-alpha (TNF alpha) is a cytokine rapidly produced in the brain in response to vigorous neuronal activity and tissue injury. TNF alpha may protect neurons against excitotoxic and oxidative insults by a mechanism involving activation of the transcription factor NF-kappaB. Whole-cell perforated patch clamp recordings in cultured rat hippocampal neurons showed that long-term treatment (24-48 h) with TNF alpha increases Ca2+ current density; pharmacological analysis indicated a major increase in current through L-type voltage-dependent calcium channels. Long-term treatment with TNF alpha caused a decrease in currents induced by glutamate, NMDA, AMPA, and kainate. Shorter exposures to TNF alpha (acute; 2 h) did not alter Ca2+ current or glutamate receptor agonist-induced currents. Ceramide, an intracellular messenger that activates the transcription factor NF-kappaB, mimicked the actions of TNFs on Ca2+ current density and currents induced by glutamate receptor agonists. Cotreatment with kappaB decoy DNA abolished the effects of TNF alpha on Ca2+ current and excitatory amino acid-induced currents, demonstrating a requirement for NF-kappaB activation in the actions of TNF alpha. Neurons pretreated with TNF alpha exhibited increased intracellular Ca2+ concentrations following membrane depolarization but reduced intracellular Ca2+ concentration responses to excitatory amino acids, compared with neurons in untreated control cultures or cultures cotreated with kappaB decoy DNA. These findings suggest important roles for the transcription factor NF-kappaB in modulation of voltage-dependent calcium channels and glutamate receptors and the many physiological and pathophysiological processes in which these ion channels are involved. Such signaling mechanisms may be particularly important in injury settings such as ischemia or trauma, where TNF alpha expression is increased and NF-kappaB is activated.
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PMID:The transcription factor NF-kappaB mediates increases in calcium currents and decreases in NMDA- and AMPA/kainate-induced currents induced by tumor necrosis factor-alpha in hippocampal neurons. 957 71

Striatal spiny neurons are selectively vulnerable in Huntington's disease (HD) and ischemia, whereas large aspiny (LA) cholinergic interneurons of the striatum are spared in these pathological conditions. We have investigated whether a different sensitivity to ionotropic glutamatergic agonists might account for this differential vulnerability. Intracellular recordings were obtained from morphologically identified striatal spiny neurons and LA cholinergic interneurons by using a rat brain slice preparation. The two striatal neuronal subtypes had strikingly different intrinsic membrane properties. Both subtypes responded to cortical stimulation with excitatory postsynaptic potentials: these potentials, however, had a different time course and pharmacology in the two classes of cells. Interestingly, membrane depolarizations and inward currents produced by exogenous glutamate receptor agonists (AMPA, kainate, and NMDA) were remarkably larger in spiny neurons than in LA interneurons. Moreover, concentrations of agonists producing reversible membrane changes in LA interneurons caused irreversible depolarizations in spiny cells. Our data suggest that the different physiological responses induced by the activation of ionotropic glutamate receptors may account for the cell type-specific vulnerability of striatal neurons in ischemia and HD.
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PMID:Striatal spiny neurons and cholinergic interneurons express differential ionotropic glutamatergic responses and vulnerability: implications for ischemia and Huntington's disease. 958 52

The diazoxide derivative IDRA 21 and other positive modulators of (AMPA)-type glutamate receptors are considered potential memory-enhancing agents. However, AMPA receptor activation contributes to CA1 hippocampal neuron damage from global ischemia in rodents, raising the possibility that 7-chloro-3-methyl-3-4-dihydro-2H-1,2,4 benzothiadiazine S,S-dioxide (IDRA 21) or drugs with similar actions may worsen ischemic neuronal injury. Here we demonstrate that glutamate plus IDRA 21 kills cultured rat hippocampal neurons by AMPA receptor activation, and, in vivo, 12 and 24 mg/kg of IDRA 21 given orally increases CA1 neuron loss produced by 10 minutes of global ischemia. Treating patients with drugs that potentiate AMPA receptor activation will have to consider these potential effects, particularly when coexistent with conditions in which excessive activation of AMPA receptors may occur (eg, stroke, seizures).
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PMID:The diazoxide derivative IDRA 21 enhances ischemic hippocampal neuron injury. 958 63

NBQX, a specific and potent AMPA receptor antagonist has been found to be neuroprotective in various models of ischemia and to have anticonvulsant properties in different models of epilepsy. In this experiment, the neurobehavioral effects of NBQX were studied. In an open field, an important ataxia was emphasized at a dose of 60 mg/kg. In a swimming task, an increase of the escape latencies was noted on the third day at a dose of 40 mg/kg. In a Morris water maze task, doses devoid of effects on locomotion were used (10, 20, and 30 mg/kg). There was no effect on the acquisition of the task at 10 mg/kg and a slight impairment at 20 mg/kg, but the rats did not learn the task at 30 mg/kg. This impairment was reversible, as shown by the increasing performance of this group without treatment. No impairment was noted in the retention phase of the Morris water maze task. The results are discussed relative to the role of the AMPA receptor in memory processes.
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PMID:Behavioral effects of NBQX, a competitive antagonist of the AMPA receptors. 958 71

It has been well established that alterations in polyamine metabolism are associated with animal models of global ischemia. Recently, this has been extended to include models of focal ischemia and traumatic brain injury. There is much evidence to support the idea that polyamines may play a multifaceted detrimental role following ischemia reperfusion. Due to the deficit of knowledge about their physiology in the CNS, the link between ischemia-induced alterations in polyamine metabolism and neuronal injury remains to be substantiated. With the recent revelation that polyamines are major intracellular modulators of inward rectifier potassium channels and certain types of NMDA and AMPA receptors, the long wait for the physiologic relevance of these ubiquitous compounds may be in sight. Therefore, it is now conceivable that the alterations in polyamines could have major effects on ion homeostasis in the CNS, especially potassium, and thus account for the observed injury after cerebral ischemia.
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PMID:Polyamines and cerebral ischemia. 967 Jul 80

The extracellular acidity that accompanies brain hypoxia-ischemia is known to reduce both NMDA and AMPA-kainate receptor-mediated currents and NMDA receptor-mediated neurotoxicity. Although a protective effect of acidic pH on AMPA-kainate receptor-mediated excitotoxicity has been assumed, such has not been demonstrated. Paradoxically, we found that lowering extracellular pH selectively increased AMPA-kainate receptor-mediated neurotoxicity in neocortical cell cultures, despite reducing peak elevations in intracellular free Ca2+. This injury potentiation may, at least in part, be related to a slowed recovery of intracellular Ca2+ homeostasis, observed after AMPA-kainate receptor activation, but not after NMDA receptor activation or exposure to high K+. The ability of acidic pH to selectively augment AMPA-kainate receptor-mediated excitotoxicity may contribute to the prominent role that these receptors play in selective neuronal death after transient global ischemia.
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PMID:Extracellular acidity potentiates AMPA receptor-mediated cortical neuronal death. 969 21

Excitatory neurotransmission at many CNS synapses depends upon AMPA-type glutamate receptors. Derangements in AMPA receptor-mediated synaptic transmission may be a contributing factor in neurological and neurodegenerative diseases and could be a target for therapeutic intervention. Drugs that positively modulate AMPA receptors by reducing AMPA receptor desensitization and/or slowing AMPA receptor deactivation, such as thiazide derivative (cyclothiazide, diazoxide, IDRA 21) and benzoylpiperidine derivatives (1-BCP, CX516, aniracetam), facilitate AMPA receptor-mediated processes and may have beneficial therapeutic effects. For example, AMPA modulators facilitate long-term potentiation, which may be important for memory storage, and facilitate memory encoding in behavioral experiments. Thus, AMPA modulators might ameliorate memory deficits that occur in dementia, such as Alzheimer's disease. However, AMPA receptor-mediated excitotoxicity may occur with excessive AMPA receptor activation such as in seizures or ischemia, and positive AMPA modulators would promote neuronal injury under those conditions. Regardless of the ultimate clinical utility of positive AMPA modulators, their discovery and study have already provided significant insight into the physiology and structural determinants of important AMPA receptor properties. This review attempts to synthesize a variety of studies that have utilized these AMPA modulators to gain insight into fundamental as well as clinically relevant AMPA receptor-mediated processes.
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PMID:Modulating excitatory synaptic neurotransmission: potential treatment for neurological disease? 974 4

We have recently shown that galactocerebroside (Gal-C)-expressing oligodendrocytes are highly vulnerable to (AMPA)/kainate receptor-mediated death. Here we examined the vulnerability of cells at different developmental stages of the oligodendrocyte lineage to AMPA/kainate receptor-mediated excitotoxicity. Oligodendrocyte precursor cells, pre-oligodendrocytes and mature oligodendrocytes were killed by 24 h exposures to low concentrations of kainate (30-100 microM). Death was attenuated by the AMPA/kainate receptor antagonist 6-nitro-7-sulfamoylbenzo(f)quinoxaline-2,3-dione (NBQX). The high vulnerability of oligodendrocytes and their precursors to AMPA/kainate receptor excitotoxicity may represent an important mechanism of white matter damage resulting from trauma or ischemia in the perinatal and adult central nervous system (CNS).
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PMID:Multiple classes of the oligodendrocyte lineage are highly vulnerable to excitotoxicity. 976 Jan 16

The neuroprotective effect of YM90K, a potent AMPA receptor antagonist, was examined in rats with permanent and transient occlusion of middle cerebral artery (MCA) using intraluminal suture occlusion method. In rats with permanent MCA occlusions, two types of occluders were used to compare the efficacy of YM90K. When a 4-0 (diameter: 0.19 mm) suture was used, YM90K (20 mg kg(-1) h(-1) i.v. infusion for 4 h) significantly reduced infarct volume (P<0.05) and neurologic deficits (P<0.05) 24 h after MCA occlusion. Infarct volume was also reduced by YM90K at the same dose (P<0.01) when severe ischemia was induced by a 3-0 (diameter: 0.23 mm) suture. In rats with transient (3 h) MCA occlusions, a 10-mg kg(-1) h(-1) dose of YM90K that did not show significant protection in rats with permanent MCA occlusion offered neuroprotective effects. These data demonstrate that YM90K provides cerebral neuroprotection against a wide range of ischemic insults.
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PMID:YM90K, an AMPA receptor antagonist, protects against ischemic damage caused by permanent and transient middle cerebral artery occlusion in rats. 984 Apr 29


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