NMDA Receptor-Mediated Differential Laminar Susceptibility to the Intracellular Ca2+ Accumulation Induced by Oxygen-Glucose Deprivation in Rat Neocortical Slices

1998 ◽  
Vol 79 (1) ◽  
pp. 430-438 ◽  
Author(s):  
Atsuo Fukuda ◽  
Kanji Muramatsu ◽  
Akihito Okabe ◽  
Yasunobu Shimano ◽  
Hideki Hida ◽  
...  
Keyword(s):  
Nmda Receptor ◽  
Receptor Antagonist ◽  
Kynurenic Acid ◽  
Pyramidal Cells ◽  
Glucose Deprivation ◽  
Nmda Receptor Antagonist ◽  
Oxygen Glucose Deprivation ◽  
Glutamate Receptor Antagonist ◽  
Intracellular Ca ◽  
Cellular Ca

Fukuda, Atsuo, Kanji Muramatsu, Akihito Okabe, Yasunobu Shimano, Hideki Hida, Ichiro Fujimoto, and Hitoo Nishino. NMDA receptor-mediated differential laminar susceptibility to the intracellular Ca2+ accumulation induced by oxygen-glucose deprivation in rat neocortical slices. J. Neurophysiol. 79: 430–438, 1998. Slices of somatosensory cortex taken from immature rats on postnatal day (P)7–14 were labeled with fura-2. Intracellular Ca2+ concentration ([Ca2+]i) was monitored in identified pyramidal cells as the ratio of fluorescence intensities (RF340/F380) during oxygen-glucose deprivation. The RF340/F380 ([Ca2+]i) of individual pyramidal cells was monitored in each of the cortical layers II–VI simultaneously. Neurons in all neocortical layers exhibited significant increases in [Ca2+]i that varied with the duration of oxygen-glucose deprivation. Individual neurons responded to oxygen-glucose deprivation with abrupt increases in [Ca2+]i after various latencies. The ceiling level of the [Ca2+]i increase differed from cell to cell. Neurons in layer II/III showed significantly greater increases in [Ca2+]i than those in layers IV, V, or VI. Kynurenic acid, a nonselective glutamate receptor antagonist, and bicuculline, a selective γ-aminobutyric acid (GABA)A receptor antagonist, suppressed the intracellular Ca2+ accumulation induced by oxygen-glucose deprivation in all neocortical layers examined. After kynurenic acid, but not after bicuculline, there was no longer a differential [Ca2+]i increases in layer II/III. Both 2-amino-5-phosphonopentanoic acid (AP5), a selective N-methyl-d-aspartate (NMDA) receptor antagonist, and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-NMDA receptor antagonist, strongly suppressed the intracellular Ca2+ accumulation induced by oxygen-glucose deprivation in all layers. The laminar difference in terms of the [Ca2+]i increases was abolished by AP5, but not by CNQX. These results indicate that layer II/III cells are the most prone to oxygen-glucose deprivation-induced intracellular Ca2+ accumulation, and that this is primarily mediated by NMDA receptors. Thus, layer II/III neurons would be more likely to suffer cellular Ca2+ overload and excitotoxicity during ischemia than layer IV–VI cells. Such a differential laminar vulnerability might play an important role in determining the pathological characteristics of the immature cortex and its sequelae later in life.

Retrotrapezoid nucleus glutamate receptors: control of CO2-sensitive phrenic and sympathetic output

1993 ◽  
Vol 74 (6) ◽  
pp. 2958-2968 ◽  
Author(s):  
E. E. Nattie ◽  
M. Gdovin ◽  
A. Li
Keyword(s):  
Nmda Receptor ◽  
Receptor Antagonist ◽  
Glutamate Receptor ◽  
Kynurenic Acid ◽  
Nmda Receptor Antagonist ◽  
Initial Slope ◽  
Xanthurenic Acid ◽  
Retrotrapezoid Nucleus ◽  
Nerve Signal ◽  
Kynurenic Acid Analogue

In decerebrate cats, we asked whether endogenous glutamate in the region of the retrotrapezoid nucleus (RTN) was involved in the control of CO2-sensitive phrenic and phrenic-related sympathetic output and, if so, which type of glutamate receptor was predominant. We made unilateral 10-nl injections into the RTN of the nonspecific glutamate receptor antagonist kynurenic acid (100 and 250 mM), the N-methyl-D-aspartic acid (NMDA) receptor antagonist 2-amino-5-phosphonopentanoic acid (AP5; 1 and 10 mM), the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX; 1 and 10 mM), and the inactive kynurenic acid analogue xanthurenic acid (100 mM). Each antagonist resulted in a significant dose-dependent decrease in the amplitude of the integrated phrenic nerve signal (PNA) over 30 min (CNQX > AP5 > kynurenic acid). The duration of the phrenic cycle was also decreased because of a shortening of expiratory time (CNQX > kynurenic acid > AP5). All three antagonists significantly decreased the initial slope of the PNA response to increased CO2 by 70–80% with no clear distinction in efficacy. The amplitude of the respiratory-related integrated cervical sympathetic nerve signal (SNA) was significantly decreased after kynurenic acid and CNQX but not AP5. In each case, the decrease in respiratory-related SNA accompanied a decrease in PNA and, at high levels of CO2, the decrease in respiratory-related SNA was greater than that of PNA. Endogenous glutaminergic input to neurons in the RTN via both NMDA and non-NMDA receptors is involved in the control of eucapneic PNA and timing, PNA-related SNA, and the response to increased CO2.

Changes in Intracellular Ca2+ Induced by GABAA Receptor Activation and Reduction in Cl− Gradient in Neonatal Rat Neocortex

1998 ◽  
Vol 79 (1) ◽  
pp. 439-446 ◽  
Author(s):  
Atsuo Fukuda ◽  
Kanji Muramatsu ◽  
Akihito Okabe ◽  
Yasunobu Shimano ◽  
Hideki Hida ◽  
...  
Keyword(s):  
Nmda Receptor ◽  
Receptor Antagonist ◽  
Pyramidal Neurons ◽  
Glucose Deprivation ◽  
Receptor Activation ◽  
Neonatal Rat ◽  
Equilibrium Potential ◽  
Oxygen Glucose Deprivation ◽  
Rat Neocortex ◽  
Initial Peak

Fukuda, Atsuo, Kanji Muramatsu, Akihito Okabe, Yasunobu Shimano, Hideki Hida, Ichiro Fujimoto, and Hitoo Nishino. Changes in intracellular Ca2+ induced by GABAA receptor activation and reduction in Cl− gradient in neonatal rat neocortex. J. Neurophysiol. 79: 439–446, 1998. We have studied the effects of γ-aminobutyric acid (GABA) and of reducing the Cl− gradient on the [Ca2+]i in pyramidal neurons of rat somatosensory cortex. The Cl− gradient was reduced either with furosemide or by oxygen-glucose deprivation. Immature slices taken at postnatal day (P)7–14 were labeled with fura-2, and [Ca2+]i was monitored in identified pyramidal cells in layer II/III as the ratio of fluorescence intensities (RF340/F380). The magnitude of the [Ca2+]i increases induced by oxygen-glucose deprivation was significantly reduced (by 44%) by bicuculline (10 μM), a GABAA receptor antagonist. Under normal conditions, GABA generally did not raise [Ca2+]i, although in some neurons a small and transient [Ca2+]i increase was observed. These transient [Ca2+]i increases were blocked by Ni2+ (1 mM), a blocker of voltage-dependent Ca2+ channels (VDCCs). Continuous perfusion with GABA did not cause a sustained elevation of [Ca2+]i but bicuculline caused [Ca2+]i oscillations. After inhibition of Cl− extrusion with furosemide (1.5 mM), GABA induced a large [Ca2+]i increase consisting of an initial peak followed by a sustained phase. Both the initial and the sustained phases were eliminated by bicuculline (10 μM). The initial but not the sustained phase was abolished by Ni2+. In the presence of Ni2+, the remaining sustained response was inhibited by the addition of 2-amino-5-phosphonopentanoic acid (AP5, 20 μM), a selective N-methyl-d-aspartate (NMDA) receptor antagonist. Thus the initial peak and the sustained phase of the GABA-evoked [Ca2+]i increase were mediated by Ca2+ influx through VDCCs and NMDA receptor channels, respectively, and both phases were initiated via the GABAA receptor. These results indicate that, in neocortical pyramidal neurons, a reduction in the Cl− gradient converts the GABAA receptor-mediated action from nothing or virtually nothing to a large and sustained accumulation of cellular Ca2+. This accumulation is the result of Ca2+ influx mainly through the NMDA receptor channel. Thus GABA, normally an inhibitory transmitter, may play an aggravating role in excitotoxicity if a shift in the Cl− equilibrium potential occurs, as reported previously, during cerebral ischemia.

Imaging NMDA- and kainate-induced intrinsic optical signals from the hippocampal slice

1996 ◽  
Vol 76 (4) ◽  
pp. 2707-2717 ◽  
Author(s):  
R. D. Andrew ◽  
J. R. Adams ◽  
T. M. Polischuk
Keyword(s):  
Nmda Receptor ◽  
Receptor Antagonist ◽  
Ampa Receptors ◽  
Hippocampal Slice ◽  
Field Potential ◽  
Nmda Receptor Antagonist ◽  
Light Transmittance ◽  
Stratum Radiatum ◽  
Cell Swelling ◽  
Tissue Resistance

1. Brain ischemia causes excess release and accumulation of glutamate that binds to postsynaptic receptors. This opens ionotropic channels that mediate neuronal depolarization and ionic fluxes that can lead to neuronal death. 2. The CA1 pyramidal cell region of the hippocampus is particularly susceptible to this neurotoxic process. Brain cell swelling is considered an early excitotoxic event, but remains poorly under stood and documented. As cells swell, light transmittance (LT) increases through brain tissue, so we hypothesized that brief exposure to glutamate agonists would elicit cell swelling that could be imaged in real time in the hippocampal slice. 3. A 1-min bath application of 100 microM N-methyl-D-aspartate (NMDA) or 100 microM kainate at 22 degrees C greatly increased LT, particularly in the dendritic regions of CA1. The response peaked by 2-3 min and slowly reversed over the subsequent 20 min following exposure. Peak LT increases were > 50% in CA1 stratum radiatum and > 20% in both CA1 stratum oriens and the dendritic region of the dentate gyrus, all areas with a high concentration of NMDA and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors. The CA3 stratum radiatum, which contains fewer of these receptors, showed a comparatively small LT increase. 4. The NMDA receptor antagonist 2-amino-5-phosphonovalerate (AP-5) [but not 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)] blocked the CA1 response to NMDA, whereas the non-NMDA receptor antagonist CNQX (but not AP-5) blocked the response to kainate. The relative tissue resistance measured across CA1 stratum radiatum increased after NMDA or kainate exposure with a time course similar to the LT change described above. The increase in relative tissue resistance was blocked by kynurenate, a nonspecific glutamate antagonist. Increases in both LT and tissue resistance provide two independent lines of evidence that cell swelling rapidly developed in CA1 dendritic areas after activation of NMDA or AMPA receptors. 5. This swelling at 22 degrees C was accompanied by a temporary loss of the evoked CA1 field potential. However, at 37 degrees C the dendritic swelling rapidly progressed to an irreversible LT increase (swelling) of the CA1 cell bodies accompanied by a permanent loss of the evoked field. 6. We propose that dendritic swelling mediated by NMDA and AMPA receptors is an early excitotoxic event that can herald permanent damage to CA1 neurons, those cells most vulnerable to ischemic insult.

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