The purpose of this study was to investigate the effect of glutamate and its ionotropic receptor agonists on the response to acute hypoxia in rat carotid body in vitro. Briefly, after SD rats were anesthetized and decapitated, the bilateral carotid bifurcations were rapidly isolated. Then bifurcation was placed into a recording chamber perfused with 95% O₂-5% CO₂ saturated Kreb's solution. The carotid body-sinus nerve complex was dissected, and the carotid sinus nerve discharge was recorded using a suction electrode. To detect the response of carotid body to acute hypoxia, the chamber was perfused with 5% O₂-5% CO₂-90% N₂ saturated Kreb's solution for a period of 100 s at an interval of 15 min. To observe the effect of glutamate, ionotropic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor agonist AMPA or N-methyl-D-aspartate (NMDA) receptor agonist NMDA on the response to acute hypoxia in rat carotid body, the chamber was perfused with 5% O₂-5% CO₂-90% N₂ saturated Kreb's solution containing the corresponding reagent. The results showed that glutamate (20 μmol/L), AMPA (5 μmol/L) or NMDA (10 μmol/L) inhibited the acute hypoxia-induced enhancement of carotid sinus nerve activity, and these inhibitory effects were dose-dependent. In summary, the activation of glutamate ionotropic receptors appears to exert an inhibitory effect on the response to acute hypoxia in carotid body of rats.
Rats ; Animals ; Glutamic Acid/pharmacology* ; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/pharmacology* ; N-Methylaspartate/pharmacology* ; Carotid Body ; Rats, Sprague-Dawley ; Carbon Dioxide ; Receptors, N-Methyl-D-Aspartate ; Receptors, AMPA ; Hypoxia

Ketamine (KTM), a N-methyl-D-aspartate (NMDA) receptor antagonist, was found to has an anti-inflammatory effect, but some patients suffered from exacerbated pro-inflammatory reactions after anesthesia with KTM. The present study was aimed to examine the underlying mechanism of pro-inflammatory effects of KTM. In this study, RAW264.7 cells were exposed to KTM and NMDA alone or combined for 30 min before lipopolysaccharide (LPS) stimulation. The expression levels of IL-6 and TNF-α were detected by RT-PCR and ELISA, and those of NMDA receptors by RT-PCR in RAW264.7 cells. Additionally, the TLR4 expression was determined by RT-PCR and flow cytometry, respectively. The results showed that in RAW264.7 cells, KTM alone promoted the TLR4 expression, but did not increase the expression of IL-6 or TNF-α. In the presence of LPS, KTM caused a significantly higher expression of IL-6 and TNF-α than LPS alone. NMDA could neither alter the IL-6 and TNF-α mRNA expression, nor reverse the enhanced expression of IL-6 and TNF-α mRNA by KTM in LPS-challenged cells. After TLR4-siRNA transfection, RAW264.7 cells pretreated with KTM no longer promoted the IL-6 and TNF-α expression in the presence of LPS. In conclusion, KTM accelerated LPS-induced inflammation in RAW264.7 cells by promoting TLR4 expression, independent of NMDA receptor.
Anesthetics, Dissociative ; pharmacology ; Animals ; Cell Survival ; drug effects ; Gene Expression Regulation ; Inflammation Mediators ; pharmacology ; Interleukin-6 ; genetics ; Ketamine ; pharmacology ; Lipopolysaccharides ; pharmacology ; Macrophages ; drug effects ; metabolism ; Male ; Mice ; N-Methylaspartate ; pharmacology ; RAW 264.7 Cells ; Signal Transduction ; drug effects ; Toll-Like Receptor 4 ; genetics ; metabolism ; Tumor Necrosis Factor-alpha ; genetics

OBJECTIVETo study different effects of Herba Lycopodii (HL) Alcohol Extracted Granule combined methylprednisolone on behavioral changes, brain derived neurotrophic factor (BDNF) expression levels, and N-methyl-D-aspartate (NMDA) receptor levels in rats with spinal cord injury (SCI).

METHODSMale adult SD rats were randomly divided into five groups, i.e., the sham-operation group, the model group, the HL treatment group, the methylprednisolone treatment group, the HL + methylprednisolone treatment group. Rats in the HL treatment group were intragastrically administered with HL at the daily dose of 50 mg/kg for 5 successive days. Rats in the methylprednisolone treatment group were intramuscularly injected with 50 mg/kg methylprednisolone within 8 h after spinal cord contusion, and then the dose of methylprednisolone was reduced for 10 mg/kg for 5 successive days. Rats in the HL + methylprednisolone treatment group received the two methods used for the aforesaid two groups. Basso Beattie and Bresnahan (BBB) score (for hindlimb motor functions) were assessed at day 0, 3, 7, and 28 after operation. At day 13 after SCI, injured spinal T8-10 was taken from 8 rats of each group and stored in liquid nitrogen. The N-methyl-D-aspartate (NMDA) receptor affinity (Kd) and the maximal binding capacity (Bmax) were determined using [3H]MK-801 radioactive ligand assay. Rats' injured spinal cords were taken for immunohistochemical assay at day 28 after SCI. Expression levels of BDNF in the ventral and dorsal horn of the spinal cord were observed.

RESULTSCompared with the sham-operation group, the number of BDNF positive neurons in the ventral and dorsal horn of the spinal cord increased in the model group, Bmax increased (470 ± 34), Kd decreased, and BBB scores decreased at day 3 -28 (all P <0. 05). Compared with the SCI model group, the number of BDNF positive neurons and Kd increased, BBB scores at day 3 -28 increased (P <0. 05) in each medicated group. Bmax was (660 ± 15) in the methylprednisolone treatment group, (646 ± 25) in the HL treatment group, and (510 ± 21) in the HL +methylprednisolone treatment group (P <0. 05). Compared with the methylprednisolone treatment group, the number of BDNF positive neurons and Kd increased, BBB scores at day 7 -28 increased, and Bmax decreased in the HL treatment group and the HL + methylprednisolone treatment group (all P <0. 05). Compard with the HL treatment group, the number of BDNF positive neurons and Kd increased, and Bmax decreased (all P < 0.05).

CONCLUSIONSHL could effectively improve motor functions of handlimbs, increase expression levels of BDNF in the spinal cord, and lessen secondary injury by affecting spinal levels of NMDA receptors. It showed certain therapeutic and protective roles in treating SCI. Its effect was better than that of methylprednisolone with synergism.

Animals ; Brain-Derived Neurotrophic Factor ; metabolism ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Ethanol ; Male ; Methylprednisolone ; pharmacology ; therapeutic use ; Models, Animal ; N-Methylaspartate ; metabolism ; Neurons ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; Spinal Cord Injuries ; drug therapy ; metabolism

NMDA-induced excitotoxicity cause severe neuronal damage including apoptosis and necrosis. The present study was aimed to evaluate the proportion of NMDA-induced apoptosis of rat cortical neurons and discover signal transduction mechanism. Caspase inhibitor and lactate dehydrogenase (LDH) assay were used to study the NMDA-induced apoptosis. To explore the involved signal pathways, the primary culture of rat cortical neurons were pretreated by the inhibitors of three MAPK pathways, extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK. With 2 h of NMDA treatment, cellular apoptosis was measured by caspase-3 activity, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) and Annexin V staining. The results showed that: (1) Caspase-dependent apoptosis accounted for 22.49% in NMDA-induced neuronal death; (2) Pretreatment with p38 MAPK inhibitor SB203580 (10 μmol/L) significantly decreased NMDA-mediated caspase-3 activity by 30.43% (P < 0.05). However, ERK inhibitor PD98059 (20 μmol/L) or JNK inhibitor SP600125 (20 μmol/L) did not influence caspase-3 activity; (3) Pretreatment with SB203580 significantly reduced the number of NMDA-induced TUNEL-positive cells by 33.10% (P < 0.05). PD98059 (20 μmol/L) or SP600125 (20 μmol/L) did not show obvious effect; (4) Pretreatment with SB203580 (10 μmol/L) significantly reduced the number of NMDA-induced early apoptotic neurons by 55.56% (P < 0.05). Also, SP600125 (20 μmol/L) significantly decreased the amount of late apoptotic/dead cells by 67.59% (P < 0.05). There was no effect of PD98059 (20 μmol/L). These results indicate that: (1) NMDA induces neuronal apoptosis besides necrosis; (2) p38 MAPK, but not JNK and ERK, is involved in NMDA-induced neuronal apoptosis, and inhibition of the apoptotic signaling pathway contributes to neuroprotection; (3) JNK activation might contribute to NMDA-induced neuronal necrosis rather than apoptosis.
Animals ; Anthracenes ; pharmacology ; Apoptosis ; Caspase 3 ; metabolism ; Cells, Cultured ; Extracellular Signal-Regulated MAP Kinases ; antagonists & inhibitors ; Imidazoles ; pharmacology ; JNK Mitogen-Activated Protein Kinases ; antagonists & inhibitors ; MAP Kinase Signaling System ; N-Methylaspartate ; pharmacology ; Neurons ; cytology ; Primary Cell Culture ; Pyridines ; pharmacology ; Rats ; p38 Mitogen-Activated Protein Kinases ; antagonists & inhibitors

OBJECTIVETo investigate the role of N-Methyl-D-aspartic acid (NMDA)-type glutamate receptors in the central nucleus of the amygdale (CeA) in food and water intake.

METHODSMale Sprague-Dawley rats with stainless steel cannulae implanted unilaterally into the CeA were used. The prototypic NMDA receptor agonist NMDA, or the selective NMDA receptor antagonist D(-)-2-amino-5-phosphonopentanoic acid (D-AP-5) was microinjected into the CeA of satiated and euhydrated rats.

RESULTSIntra-CeA injection of 8.50, 17.00, or 34.00 nmol NMDA did not alter food intake but significantly increased water intake 0-1 h after the injection (F(3,32)=3.191, P=0.037) independent of food intake. Without affecting the food intake, injection of 6.34, 12.70, or 25.40 nmol D-AP-5 into the CeA significantly decreased water intake 0-1 h after the injection (F(3,28)=3.118, P=0.042) independent of food intake.

CONCLUSIONNMDA receptors in the CeA may participate in the control of water intake rather than food intake.

2-Amino-5-phosphonovalerate ; pharmacology ; Amygdala ; drug effects ; Animals ; Drinking ; drug effects ; Eating ; drug effects ; Excitatory Amino Acid Agonists ; pharmacology ; Excitatory Amino Acid Antagonists ; pharmacology ; Injections, Intraventricular ; Male ; N-Methylaspartate ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; agonists ; antagonists & inhibitors

In normal rat forebrain, the NR1/NR2A and NR1/NR2B dimmers are the main constitutional forms of NMDA receptors. The present study was carried out to determine the functional properties of the heteromeric NMDA receptor subunits and their inhibition by bis(7)-tacrine (B7T). Rat NR1, NR2A and NR2B cDNAs were transfected into human embryonic kidney 293 cells (HEK-293). The inhibition of NMDA-activated currents by B7T was detected in HEK-293 cell expressing NR1/NR2A or NR1/NR2B receptors by using whole-cell patch-clamp techniques. The results showed that in HEK-293 cells expressing NR1/NR2A receptor, 1 μmol/L B7T inhibited 30 μmol/L NMDA- and 1000 μmol/L NMDA-activated steady-state currents by 46% and 40%, respectively (P>0.05; n=5), suggesting that the inhibition of B7T on NR1/NR2A receptor doesn't depend on NMDA concentration, which is consistent with a non-competitive mechanism of inhibition. But for the NR1/NR2B receptor, 1 μmol/L B7T inhibited 30 μmol/L NMDA- and 1000 μmol/L NMDA-activated steady-state currents by 61% and 13%, respectively (P<0.05; n=6), showing that B7T appears to be competitive with NMDA. In addition, simultaneous application of 1 μmol/L B7T and 1000 μmol/L NMDA produced a moderate inhibition of peak NMDA-activated current, followed by a gradual decline of the current to a steady state. However, the gradual onset of inhibition produced by B7T applied simultaneously with NMDA was eliminated when B7T was given 5 s before NMDA. These results suggested that B7T inhibition of NMDA current mediated by NR1/NR2B receptor was slow onset, and it did not depend on the presence of the agonist. With holding potentials ranging from -50 to +50 mV, the B7T inhibition rate of NMDA currents didn't change significantly, and neither did the reversal potential. We are led to conclude that the NR1/NR2B recombinant receptor can serve as a very useful model for studying the molecular mechanism of NMDA receptor inhibition by B7T.
Cell Line ; HEK293 Cells ; Humans ; N-Methylaspartate ; pharmacology ; Receptors, N-Methyl-D-Aspartate ; genetics ; Tacrine ; analogs & derivatives ; pharmacology

OBJECTIVETo investigate the protective mechanism of neuroactive steroid allopregnanolone on N-methyl-D-aspartate (NMDA) induced toxicity in primary mouse cortical neurons.

METHODSPrimary cultured mouse cortical neurons were subjected to allopregnanolone, the expression of beta-aminobutyric acid receptor beta2 subunit (beta2-GABA-R) mRNAs was detected by RT-PCR and Akt phosphorylation was assayed by Western blot using Akt-phosphoserine 473-specific antibody. After the cultured mouse cortical neurons were pretreated with or without allopregnanolone prior to treatment with NMDA , DNA isolated was analyzed by agarose gel electrophoresis and proteins collected were analyzed by Western blot with anti-cleaved-PARP, anti-cleaved caspase-3, and anti-cleaved caspase-9 antibodies.

RESULTSWhen cultured mouse cortical neurons were exposed to allopregnanolone both the expression of beta2-GABA-R mRNAs and Akt phosphorylation increased. Allopregnanolone inhibited the NMDA-induced apoptosis and decreased the level of active-PARP, active-caspase-3 and active-caspase-9 notably at a final concentration of 5 x 10(6) mol/L.

CONCLUSIONPretreatment with allopregnanolone may be neuroprotective on NMDA-induced neuronal cells apoptosis by increasing beta2-GABA-R expression and Akt phosphorylation.

Animals ; Animals, Newborn ; Apoptosis ; drug effects ; Caspase 3 ; metabolism ; Caspase 9 ; metabolism ; Cerebral Cortex ; cytology ; Mice ; N-Methylaspartate ; antagonists & inhibitors ; toxicity ; Neurons ; cytology ; Neuroprotective Agents ; pharmacology ; Poly (ADP-Ribose) Polymerase-1 ; Poly(ADP-ribose) Polymerases ; metabolism ; Pregnanolone ; pharmacology ; Primary Cell Culture ; RNA, Messenger ; genetics ; metabolism ; Receptors, GABA-B ; genetics ; metabolism

OBJECTIVETo study the effect and the possible mechanism of IL-6 on NMDA-excited neuronal discharges of rats in vitro.

METHODSThe cerebellar slices were prepared and spontaneous discharges of single cerebellar interposed nuclear (IN) neurons were recorded by extracellular recordings. The cerebellar slices were perfused with artificial cerebral spinal fluid (ACSF) containing N-methyl-D-aspartate (NMDA), IL-6, JAK inhibitor AG490. The changes in firing activities of the neurons treated with the drugs were recorded. The levels of phosphorylation at serine 897 site of NMDA receptor subunit 1 (NR1) in the neurons treated with various drugs mentioned above were detected by Western blot.

RESULTSThe discharge rates of the neurons that were treated with IL-6 together with NMDA were significantly lower than those of the neurons treated with NMDA alone. AG490 partially blocked the inhibitory effect of IL-6 on the NMDA-stimulated neuronal firing activity. The treatment of the neurons with IL6 and NMDA led to a concentration-dependent suppression of the phospho-NR1 expression relative to those neurons treated with NMDA alone. AG490 blocked the effect of the IL-6-induced depression of phospho-NR1 expression.

CONCLUSIONIL-6 inhibits NMDA-stimulated neuronal firing activity, and simultaneously down-regulates the phosphorylation of NR1 at serine 897 site.

Animals ; Cerebellum ; drug effects ; metabolism ; In Vitro Techniques ; Interleukin-6 ; pharmacology ; N-Methylaspartate ; pharmacology ; Nerve Growth Factors ; metabolism ; Neurons ; drug effects ; metabolism ; physiology ; Phosphorylation ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; metabolism

OBJECTIVETo evaluate the translocation of 5-lipoxygenase (5-LOX)) after injuries by transfection with green fluorescence protein (GFP)/5-LOX in PC12 cells.

METHODSPC12 cells were stably transfected with pEGFP-C2/5-LOX (GFP/5-LOX) or pEGFP-C2 vectors (control). After treatment with oxygen-glucose deprivation (OGD), H(2)O(2) or NMDA, GFP/5-LOX localization in the cells was observed under a fluorescence microscope. Wild-type 5-LOX was determined by immunostaining after the treatment.

RESULTIn the GFP/5-LOX-transfected cells, GFP/5-LOX was primarily localized in the nucleus; while in the GFP-transfected cells, GFP was localized in both the cytoplasm and nucleus. After OGD and H(2)O(2) treatments, GFP/5-LOX was translocated to the nuclear membrane in 50.6 % and 57.7% cells respectively. However, after NMDA treatment or in GFP-transfected cells, no translocation was observed. Wild-type 5-LOX was distributed in the nuclei and cytoplasm, and all the 3 treatments induced 5-LOX translocation to the nuclear membrane.

CONCLUSIONIn the PC12 cells stably transfected with GFP/5-LOX, GFP/5-LOX is primarily distributed in the nuclei; the OGD-, H(2)O(2)- and NMDA-induced 5-LOX translocation exhibits different properties.

Animals ; Arachidonate 5-Lipoxygenase ; genetics ; metabolism ; Cell Nucleus ; metabolism ; Glucose ; pharmacology ; Green Fluorescent Proteins ; genetics ; metabolism ; Hydrogen Peroxide ; pharmacology ; Microscopy, Fluorescence ; N-Methylaspartate ; pharmacology ; Nuclear Envelope ; metabolism ; PC12 Cells ; Protein Transport ; drug effects ; Rats ; Recombinant Fusion Proteins ; genetics ; metabolism ; Transfection

AIMTo investigate effect of ginkgo biloba extract (GBE) on N-methyl-D-aspartate (NMDA)-activated currents (I(NMDA)) and evaluate further the modulatory effects of Micro-GBE/Nano-GBE.

METHODSBy means of whole-cell patch clamp technique, NMDA-activated currents from acutely isolated rat hippocampal neurons were recored.

RESULTSThe majority of the neurons examined (81.8%, 90/110) were sensitive to NMDA (1 mmol/L) and its co-agonist Gly (10 micromol/L). NMDA activated an inward current, which manifested apparent desensitization and could be blocked by its specific antagonist MK-801. After the neurons were treated with Micro/Nano GBE (0.1 mg/ml) followed by the application of NMDA (1 mmol/L) and Gly (10 micromol/L) for 30 s, it was show that NMDA-activated currents were obviously inhibited (P < 0.01, n = 8). The inhibitory rate were 40% +/- 17% and 64% +/- 15% respectively. It showed that the modulatory effect of Nano-GBE (dissolved in the stander extracellular solution) on NMDA-activated current was significantly higher than that of Micro-GBE (dissolved in DMSO) (P < 0.05).

CONCLUSIONThe inward currents activated by NMDA could be depressed by Micro-GBE and Nano-GBE. The modulatory effects of GBE on NMDA-activated current are expected to contribute to the neuroprotective effects of ginkgo biloba extracts. In addition, at the same concentration, the modulatory effect of Nano-GBE on NMDA-activated current is better than that of Micro-GBE.

Animals ; Cells, Cultured ; Ginkgo biloba ; Hippocampus ; drug effects ; physiology ; N-Methylaspartate ; pharmacology ; Neurons ; drug effects ; physiology ; Patch-Clamp Techniques ; Plant Extracts ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; drug effects