Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The Ca2+ permeability of non-NMDA and NMDA receptor channels was studied using a fluorometric flux measurement approach in somata and dendrites of CA1 pyramidal neurones in rat hippocampal slices. For this purpose, the Ca2+ fraction of the total cation current (named 'fractional Ca2+ current') was measured directly from the change in the Ca(2+)-sensitive fura-2 fluorescence at 380 nm excitation wavelength. 2. The fractional Ca2+ current through the somatic NMDA receptor channels was 10.69 +/- 2.13% (mean +/- S.D.) and that through dendritic receptor channels was 10.70 +/- 1.96%. The fractional Ca2+ current was not dependent on the extracellular Mg2+ concentration and its voltage dependence was in agreement with the Goldman-Hodgkin-Katz current equation. 3. AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate) or kainate applications produced small but significant Ca2+ entry. Fractional Ca2+ currents of 0.58 +/- 0.34% were measured for somatic AMPA applications, 0.68 +/- 0.20% for somatic kainate applications, 0.66 +/- 0.25% for dendritic AMPA applications and 0.61 +/- 0.16% for dendritic kainate applications. 4. The expression pattern of glutamate receptor subunits encoding messenger ribonucleic acids (mRNAs) was analysed with the single-cell reverse transcriptase-polymerase chain reaction (RT-PCR) approach applied to CA1 pyramidal neurones. The AMPA receptor subunits GluR-A, GluR-B and GluR-C, and the NMDA receptor subunits NR2A and NR2B were found to be abundantly expressed in all CA1 pyramidal neurones tested. 5. This study establishes the fractional Ca2+ current through somatic and dendritic NMDA and non-NMDA receptor channels in CA1 pyramidal neurones. The dendritic, presumably synaptic, NMDA receptor channels are highly Ca2+ permeable and have a fractional Ca2+ current closely resembling that of somatic extrasynaptic NMDA receptor channels. Both somatic and dendritic non-NMDA receptor channels are of the 'low Ca2+ permeable' type and have a fractional Ca2+ current that is about twenty times smaller than that of NMDA receptor channels.
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PMID:Fractional Ca2+ currents through somatic and dendritic glutamate receptor channels of rat hippocampal CA1 pyramidal neurones. 881 9

Excitatory amino acids can modify the tone of cerebral vessels and permeability of the blood-brain barrier (BBB) by acting directly on endothelial cells of cerebral vessels or indirectly by activating receptors expressed on other brain cells. In this study we examined whether rat or human cerebromicrovascular endothelial cells (CEC) express ionotropic and metabotropic glutamate receptors. Glutamate and the glutamate receptor agonists N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA), and kainate failed to increase [Ca2+]i in either rat or human microvascular and capillary CEC but elicited robust responses in primary rat cortical neurons, as measured by fura-2 fluorescence. The absence of NMDA and AMPA receptors in rat and human CEC was further confirmed by the lack of immunocytochemical staining of cells by antibodies specific for the AMPA receptor subunits GluR1, GluR2/3, and GluR4 and the NMDA receptor subunits NR1, NR2A, and NR2B. We failed to detect mRNA expression of the AMPA receptor subunits GluR1 to GluR4 or the NMDA receptor subunits NR1(1XX); NR1(0XX), and NR2A to NR2C in both freshly isolated rat and human microvessels and cultured CEC using reverse transcriptase polymerase chain reaction (RT-PCR). Cultured rat CEC expressed mRNA for KA1 or KA2 and GluR5 subunits. Primary rat cortical neurons were found to express GluR1 to GluR3 and NR1, NR2A, and NR2B by both immunocytochemistry and RT-PCR and KA1, KA2, GluR5, GluR6, and GluR7 by RT-PCR. Moreover, the metabotropic glutamate receptor agonist 1-amino-cyclopentyl-1S, 3R-dicorboxylate (1S,3R-trans-ACPD), while eliciting both inositol trisphosphate and [Ca2+]i increases and inhibiting forskolin-stimulated cyclic AMP in cortical neurons, was unable to induce either of these responses in rat or human CEC. These results strongly suggest that both rat and human CEC do not express functional glutamate receptors. Therefore, excitatory amino acid-induced changes in the cerebral microvascular tone and BBB permeability must be affected indirectly, most likely by mediators released from the adjacent glutamate-responsive cells.
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PMID:Evidence that functional glutamate receptors are not expressed on rat or human cerebromicrovascular endothelial cells. 953 5

N-methyl-D-aspartate (NMDA) receptor subunit expression changes during development and following injury in several brain regions. These changes may be mediated by neurotrophic factors, such as brain derived neurotrophic factor (BDNF). Exposure of cultured cortical neurons to BDNF (100 ng/ml) for 24 h produced a significant decrease in the NMDA-induced whole-cell currents sensitive to the NR2B subunit selective NMDA receptor antagonist, CP-101,606, suggesting a relative decrease in NR2B subunit expression. There was a significant increase in NR2A by Western blot analysis. Consistent with the electrophysiology and Western blot analysis, reverse transcriptase-polymerase chain reaction (RT-PCR) amplification revealed that BDNF caused a significant increase in relative NR2A subunit expression, a significant decrease in relative NR2B subunit expression and no change in relative NR2C subunit expression. These results suggest that BDNF enhances NMDA receptor maturation, warranting further study of the mechanism of BDNF effects on NMDA receptor subunit expression and the role these effects play in development and neuronal injury.
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PMID:Brain derived neurotrophic factor induction of N-methyl-D-aspartate receptor subunit NR2A expression in cultured rat cortical neurons. 973 98

Activation of glutamate receptors has been shown to mediate a large number of neuronal processes such as long-term potentiation and ischemic damage. In addition to neurons and glia, glutamate receptors may occur on cerebral endothelial cells (CECs). The aim of the present study was to determine which glutamate receptors are expressed in CECs and to demonstrate the functional presence of such channels. By using reverse transcriptase-polymerase chain reaction, we showed that primary cultures of rat CECs express N-methyl-D-aspartate (NMDA) receptors (NR1 subunit, which is necessary for the formation of functional NMDA receptors, and NR2A-C subunits), 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl-propionate (AMPA) receptors (GLUR1-4 subunits), and metabotropic receptors (mGLUR). Exposure of the cultures to 2 mM glutamate, a well-established mediator of ischemic damage, for 30 min increased significantly the phosphorylation of calcium/calmodulin-dependent protein kinase II even after 10- and 60-min recovery times. This effect could be prevented by the NMDA blocker MK-801. The presence of multiple glutamate receptor types may confer a finely tuned responsiveness of the cerebral endothelium to glutamate in physiological and pathological conditions.
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PMID:Expression of glutamate receptors on cultured cerebral endothelial cells. 985 65

Quantitative reverse transcriptase - polymerase chain reaction was used to analyze the relative expressions of NR1, NR2A, NR2B, NR2C, NR2D, and NR3 subunits of the NMDA receptor in the piriform, entorhinal, visual, and motor cortices as well as in the olfactory bulb of adult rat. The analysis detected clear differences in the relative proportions of the NMDA receptor subunits between the five forebrain regions examined. These differences were particularly striking when the piriform and motor cortices were compared. In the piriform cortex, NR1 was the predominant transcript. The expression of NR2A was only slightly higher than half of that of NR1. NR2B was expressed even at lower levels ( approximately 30% of NR1). NR2C and NR3 were expressed at levels which were approximately 15% of those of NR1. NR2D had the lowest levels of expression ( approximately 3% of NR1). In contrast, NR2B was the predominant transcript in the motor cortical region, where it was expressed at the levels close to 135% of those of NR1 message. NR2A had the levels of expression of approximately 50% of those of NR1. The NR2C expression was close to 25% that of NR1, and the NR2D and NR3 transcripts were totally absent from this cortical area. These findings suggest a significant regional variability of the NMDA receptors in the adult rat forebrain.
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PMID:Expression of NR1, NR2A-D, and NR3 subunits of the NMDA receptor in the cerebral cortex and olfactory bulb of adult rat. 1065 28

Whole-cell patch-clamp recordings were performed on 12- to 15-day-old rat locus coeruleus neurones in a midpontine slice preparation. Application of noradrenaline (100 microM) and N-methyl-D-aspartate (NMDA; 100 microM) induced a small outward current and a distinct inward current, respectively. Single-cell reverse transcriptase-polymerase chain reaction (scRT-PCR), used to analyse the expression pattern of NMDA receptor subunits 2A, 2B, and 2C (NR2A-C) subsequent to electrophysiological characterization, demonstrated differences in the capacity of individual locus coeruleus neurones to express NR2A-C mRNA. NR2C mRNA expression predominated over those of NR2A and NR2B mRNA in most neurones. In addition, in neurones containing NR2C mRNA NMDA induced significantly larger currents than in cells lacking expression of this gene. RT-PCR studies performed on tissue preparations of adult rats also revealed a distinct expression of NR2C mRNA. In conclusion, the present data demonstrate differences in the mRNA expression pattern of NR2A-C of individual locus coeruleus neurones with a predominant NR2C mRNA expression in the majority of the cells.
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PMID:Single-cell RT-PCR analysis of N-methyl-D-aspartate receptor subunit expression in rat locus coeruleus neurones. 1119 30

N-methyl-D-aspartate receptors (NRs) are a group of ionotropic glutamate receptors in the brain and they are composed of heteromeric subunits (NR1, NR2A-D and NR3). In the neostriatum, a brain region that is associated with movement in animals, NMDA channels are known to involve in the motor control. Our previous report (Lai et al., 2000, Neuroscience 98, 493-500) has shown that a single dose of antisense oligodeoxynucleotides that are specific to NR1 subunit results in blockage of the gene expression of NR1 as well as NR2A subunits in the neostriatum. In the present study, antisense oligodeoxynucleotides that are specific to NR2B (ANR2B) were then employed as molecular tools to further investigate the molecular interactions of NMDA receptor subunits in the neostriatum. A single dose of ANR2B was injected unilaterally into the rat neostriatum. After one day of injection, no modification of motor behavior was found in the ANR2B-injected rats. The mRNA level of NR2B in the ANR2B-injected neostriatum was found to be decreased (-20.4%) by reverse transcriptase polymerase chain reaction (RT-PCR). However, the mRNA levels of NR1, NR2A, NR2C and NR2D in the ANR2B-treated neostriatum were found to be unchanged. After two days of injection, NR2B immunoreactivity was found to decrease in the ANR2B-treated neostriatum by immunofluorescence (-35.1%). At higher magnification, NR2B immunoreactivity was found to decrease in presumed spiny neurons of the neostriatum (-23.4%). No change in NR1 immunoreactivity was observed. These results indicate that a single dose of ANR2B can successfully block the gene expression of NR2B in neurons of the neostriatum and there is less effect on NR1 and other NR2 subunits. The blockage of the gene expression of NR2B is therefore specific and the present results may provide important implications in applications of antisense in research and in clinical therapy of neurological diseases.
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PMID:Modulation of the gene expression of N-methyl-D-aspartate receptor NR2B subunit in the rat neostriatum by a single dose of specific antisense oligodeoxynucleotide. 1155 72

The N-methyl-D-aspartate (NMDA) receptor is a subtype of ionotropic glutamate receptor that is involved in synaptic mechanisms of learning and memory, and mediates excitotoxic neuronal injury. In this study, we tested the hypothesis that NMDA receptor subunit gene expression is altered in Alzheimer's disease (AD), especially in brain regions known to be important in memory. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was used to determine the messenger RNA (mRNA) levels of the NMDA receptor subunits NR1, NR2A, and NR2B in the hippocampus and entorhinal cortex of postmortem brain samples from nine clinically well-characterized AD patients and nine aged controls. Cerebellum, a site minimally affected by AD, was also chosen for comparison assessment. Results showed decreased levels of the NR2 mRNAs in AD brains compared to controls. Reductions of NR2A (46.2%, p<0.01) and NR2B (43.2%, p<0.0001) mRNA levels were identified in the entorhinal cortex. Reductions of NR2A (41.4%, p<0.05) and NR2B (40.6%, p=0.058) mRNA levels were found in the hippocampus. NR1 mRNA levels were similar in all three brain regions in both AD and controls. No significant changes of subunit NR2A and NR2B mRNA levels were identified in the cerebellum. Postmortem delay (PMD), tissue storage time, brain weight, or age of the subjects did not affect these changes. These data suggest that alterations in NMDA receptor subunits, especially the NR2A and NR2B, may be important in AD, particularly in neuronal populations that underlie impaired learning and memory.
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PMID:N-methyl-D-aspartate receptor subunit NR2A and NR2B messenger RNA levels are altered in the hippocampus and entorhinal cortex in Alzheimer's disease. 1212 70

Traumatic brain injury (TBI) is a major cause of disability in the pediatric population and can result in abnormal development. Experimental studies conducted in animals have revealed impaired plasticity following developmental TBI, even in the absence of significant anatomical damage. The N-methyl-D-aspartate receptor (NMDAR) is clearly involved in both normal development and in the pathophysiology of TBI. Following lateral fluid percussion injury in postnatal day (PND) 19 rats, we tested the hypothesis that TBI sustained at an early age would result in impaired NMDAR expression. Using immunoblotting and reverse transcriptase-polymerase chain reaction (RT-PCR), protein and RNA levels of NMDAR subunits were measured in the cerebral cortex and hippocampus on post-injury days (PID) 1, 2, 4, and 7 (though the PID7 analysis was only for protein) and compared with age-matched shams. Significant effects of hemisphere (analysis of variance [ANOVA], p<0.01), and interactions between hemisphere and injury (ANOVA, p<0.05) and hemisphere and PID (ANOVA, p<0.05) were found for synaptic protein levels of the NR2A subunit in hippocampus. Specifically, within the ipsilateral hippocampus, NR2A was reduced by 9.9%, 47.9%, 40.8%, and 6.3% on PID1, PID2, PID4, and PID7, respectively. Within the cortex, there was a significant effect of injury (ANOVA, p<0.05) without any hemispheric differences. These bilateral cortical reductions measured 30.5%, 3.2%, 5.7%, and 13.4% at the same timepoints after injury. Injury had no significant main effect on NR1 or NR2B protein levels. RT-PCR analysis showed no significant changes in NR1, NR2A, or NR2B gene expression; however, as a positive control, hsp70 was induced more than twofold in ipsilateral cortex and hippocampus on PID1. It is known that NR2A expression levels increase during normal development, and in response to environmental stimuli. Our data suggest that injury-induced reduction in the expression of NR2A is one likely mechanism for the impaired experience-dependent neuroplasticity seen following traumatic injury to the immature brain.
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PMID:N-methyl-D-aspartate receptor subunit changes after traumatic injury to the developing brain. 1677 79

Peripheral inflammation causes production of central cytokines that alter transmission at the N-methyl-D-aspartate receptor (NR). During development, NRs are important for synaptic plasticity and network connectivity. We therefore asked if neonatal inflammation would alter expression of NRs in the brain and behavioural performance in adulthood. We gave lipopolysaccharide (LPS) (100 microg/kg, i.p.) or saline to male rats on postnatal day (P)5, P14, P30 or P77. Subsequently we assessed mRNA levels of the NR1, NR2A, B, C and D subunits in the hippocampus and cortex either acutely (2 h) or in adulthood using real-time reverse transcriptase-polymerase chain reaction. We explored learning and memory behaviours in adult rats using the Morris water maze and contextual fear conditioning paradigms. Hippocampal NR1 mRNA was acutely increased in the P5- and P77-treated rats but was reduced in adults treated with LPS at P5, P30 and P77. P14 LPS-treated rats showed few acute changes but showed pronounced increases in NR2A, B, C and D subunit mRNA later in adulthood. The cortex displayed relatively few acute changes in expression in the neonatal-treated rats; however, it showed robust changes in NR2B, C and D mRNA in all groups given LPS in adulthood. Behavioural deficits were observed specifically in the P5 and P30 LPS-treated groups in the water maze probe trial and fear conditioning tests, consistent with hippocampal NR1 mRNA down-regulation. Thus, a single bout of inflammation during development can programme specific and persistent differences in NR mRNA subunit expression in the hippocampus, which could be associated with behavioural and cognitive deficits in adulthood.
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PMID:Neonatal inflammation produces selective behavioural deficits and alters N-methyl-D-aspartate receptor subunit mRNA in the adult rat brain. 1827 17


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