Blockade of synaptic transmission from hair cells to auditory afferent nerves by 6-Cyano-2,3-dihydroxy-7-nitroquinoxaline, a selective non-NMDA receptor antagonist

1990 ◽  
Vol 248 (1) ◽  
pp. 25-30 ◽  
Author(s):  
K. Doi ◽  
N. Mori ◽  
T. Matsunaga ◽  
T. Tsumoto
Keyword(s):  
Nmda Receptor ◽  
Synaptic Transmission ◽  
Receptor Antagonist ◽  
Hair Cells ◽  
Nmda Receptor Antagonist ◽  
Afferent Nerves

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.

scholarly journals Ketamine Produces a Long-Lasting Enhancement of CA1 Neuron Excitability

2021 ◽  
Vol 22 (15) ◽  
pp. 8091
Author(s):  
Grace Jang ◽  
M. Bruce MacIver
Keyword(s):  
Nmda Receptor ◽  
Potassium Channel ◽  
Receptor Antagonist ◽  
Hippocampal Slices ◽  
Nmda Receptor Antagonist ◽  
Channel Block ◽  
Mk 801 ◽  
Ca1 Region ◽  
Excitatory Transmission ◽  
Ketamine Anesthesia

Ketamine is a clinical anesthetic and antidepressant. Although ketamine is a known NMDA receptor antagonist, the mechanisms contributing to antidepression are unclear. This present study examined the loci and duration of ketamine’s actions, and the involvement of NMDA receptors. Local field potentials were recorded from the CA1 region of mouse hippocampal slices. Ketamine was tested at antidepressant and anesthetic concentrations. Effects of NMDA receptor antagonists APV and MK-801, GABA receptor antagonist bicuculline, and a potassium channel blocker TEA were also studied. Ketamine decreased population spike amplitudes during application, but a long-lasting increase in amplitudes was seen during washout. Bicuculline reversed the acute effects of ketamine, but the washout increase was not altered. This long-term increase was statistically significant, sustained for >2 h, and involved postsynaptic mechanisms. A similar effect was produced by MK-801, but was only partially evident with APV, demonstrating the importance of the NMDA receptor ion channel block. TEA also produced a lasting excitability increase, indicating a possible involvement of potassium channel block. This is this first report of a long-lasting increase in excitability following ketamine exposure. These results support a growing literature that increased GABA inhibition contributes to ketamine anesthesia, while increased excitatory transmission contributes to its antidepressant effects.

scholarly journals Reduction of food intake by cholecystokinin requires activation of hindbrain NMDA-type glutamate receptors

2011 ◽  
Vol 301 (2) ◽  
pp. R448-R455 ◽  
Author(s):  
Jason Wright ◽  
Carlos Campos ◽  
Thiebaut Herzog ◽  
Mihai Covasa ◽  
Krzysztof Czaja ◽  
...  
Keyword(s):  
Nmda Receptor ◽  
Food Intake ◽  
Nmda Receptors ◽  
Receptor Antagonist ◽  
Fourth Ventricle ◽  
Nmda Receptor Antagonist ◽  
Behavioral Pattern ◽  
Vagal Afferents ◽  
Nmda Receptor Antagonists ◽  
The Brain

Intraperitoneal injection of CCK reduces food intake and triggers a behavioral pattern similar to natural satiation. Reduction of food intake by CCK is mediated by vagal afferents that innervate the stomach and small intestine. These afferents synapse in the hindbrain nucleus of the solitary tract (NTS) where gastrointestinal satiation signals are processed. Previously, we demonstrated that intraperitoneal (IP) administration of either competitive or noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonists attenuates reduction of food intake by CCK. However, because vagal afferents themselves express NMDA receptors at both central and peripheral endings, our results did not speak to the question of whether NMDA receptors in the brain play an essential role in reduction of feeding by CCK. We hypothesized that activation of NMDA receptors in the NTS is necessary for reduction of food intake by CCK. To test this hypothesis, we measured food intake following IP CCK, subsequent to NMDA receptor antagonist injections into the fourth ventricle, directly into the NTS or subcutaneously. We found that either fourth-ventricle or NTS injection of the noncompetitive NMDA receptor antagonist MK-801 was sufficient to inhibit CCK-induced reduction of feeding, while the same antagonist doses injected subcutaneously did not. Similarly fourth ventricle injection of d-3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphoric acid (d-CPPene), a competitive NMDA receptor antagonist, also blocked reduction of food intake following IP CCK. Finally, d-CPPene injected into the fourth ventricle attenuated CCK-induced expression of nuclear c-Fos immunoreactivity in the dorsal vagal complex. We conclude that activation of NMDA receptors in the hindbrain is necessary for the reduction of food intake by CCK. Hindbrain NMDA receptors could comprise a critical avenue for control and modulation of satiation signals to influence food intake and energy balance.

MK801 impairs thermoregulation in the heat

2002 ◽  
Vol 80 (3) ◽  
pp. 226-232 ◽  
Author(s):  
Frédéric Canini ◽  
Nadine Simler ◽  
Lionel Bourdon
Keyword(s):  
Locomotor Activity ◽  
Nmda Receptor ◽  
Receptor Antagonist ◽  
Core Temperature ◽  
Exposure Duration ◽  
Heat Exposure ◽  
Nmda Receptor Antagonist ◽  
Dopamine Metabolism ◽  
Body Core Temperature ◽  
Body Core

The effects of MK801 (dizocilpine), a glutamate NMDA receptor antagonist, on thermoregulation in the heat were studied in awake rats exposed to 40°C ambient temperature until their body core temperature reached 43°C. Under these conditions, MK801-treated rats exhibited enhanced locomotor activity and a steady rise in body core temperature, which reduced the heat exposure duration required to reach 43°C. Since MK801-treated rats also showed increased striatal dopaminergic metabolism at thermoneutrality, the role of dopamine in the MK801-induced impairment of thermoregulation in the heat was determined using co-treatment with SCH23390, a dopamine D1 receptor antagonist. SCH23390 normalized the locomotor activity in the heat without any effect on the heat exposure duration. These results suggest that the MK801-induced impairment of thermoregulation in the heat is related to neither a dopamine metabolism alteration nor a locomotor activity enhancement.Key words: heatstroke, NMDA receptor, thermoregulation, dopamine, locomotion.

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