In addition to classical synaptic transmission, information is transmitted between cells via the activation of extrasynaptic receptors that generate persistent tonic current in the brain. While growing evidence supports the presence of tonic NMDA current (INMDA) generated by extrasynaptic NMDA receptors (eNMDARs), the functional significance of tonic I(NMDA) in various brain regions remains poorly understood. Here, we demonstrate that activation of eNMDARs that generate I(NMDA) facilitates the α-amino-3-hydroxy-5-methylisoxazole-4-proprionate receptor (AMPAR)-mediated steady-state current in supraoptic nucleus (SON) magnocellular neurosecretory cells (MNCs). In low-Mg2+ artificial cerebrospinal fluid (aCSF), glutamate induced an inward shift in I(holding) (I(GLU)) at a holding potential (V(holding)) of -70 mV which was partly blocked by an AMPAR antagonist, NBQX. NBQX-sensitive I(GLU) was observed even in normal aCSF at V(holding) of -40 mV or -20 mV. I(GLU) was completely abolished by pretreatment with an NMDAR blocker, AP5, under all tested conditions. AMPA induced a reproducible inward shift in I(holding) (I(AMPA)) in SON MNCs. Pretreatment with AP5 attenuated I(AMPA) amplitudes to ~60% of the control levels in low-Mg2+ aCSF, but not in normal aCSF at V(holding) of -70 mV. I(AMPA) attenuation by AP5 was also prominent in normal aCSF at depolarized holding potentials. Memantine, an eNMDAR blocker, mimicked the AP5-induced I(AMPA) attenuation in SON MNCs. Finally, chronic dehydration did not affect I(AMPA) attenuation by AP5 in the neurons. These results suggest that tonic I(NMDA), mediated by eNMDAR, facilitates AMPAR function, changing the postsynaptic response to its agonists in normal and osmotically challenged SON MNCs.
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid* ; Brain ; Cerebrospinal Fluid ; Dehydration ; Glutamic Acid ; Memantine ; N-Methylaspartate* ; Neurons ; Receptors, AMPA ; Receptors, N-Methyl-D-Aspartate* ; Supraoptic Nucleus ; Synaptic Transmission

OBJECTIVETo study the protective effect of cerebrospinal fluid containing Qingxin Kaiqiao recipe on PC12 cell injury induced by glutamate (Glu), in order to provide basis for the conical application of the recipe.

METHODSD rats were orally administered with decoction of Qingxin Kaiqiao recipe (7.9 g x kg(-1)) for three and a half days, 2 times a day, in order to prepare cerebrospinal fluid containing Qingxin Kaiqiao recipe. PC cells were divided into the normal group, the model group, the nimodipine group, the 10% normal CSF group, the 10% medicated CSF group, the 20% normal CSF group, the 20% medicated CSF group. Except for the normal group, other groups were cultured with PC12 cells and Glu with the final concentration of 20 mmol x L(-1) to establish the nerve cell injury model. Apart from the model group and the normal group, other groups were intervened with nimodipine, normal cerebrospinal fluid, and 10% and 20% medicated CSF. RT-PCR was used to detect the expression level of Bax mRNA, Bcl-2 mRNA and Caspase-3 mRNA, and MTT method was used to detect the activity of PC12 cells.

RESULTThe activity of PC12 cells of all of medicated CSF groups was higher than that of the model group, with the decrease in the expression of Bax mRNA and Caspase-3 mRNA and the increase in the expression of Bcl-2 mRNA. They showed a significant different with the model group (P < 0.01). The 20% medicated CSF group was superior than the 10% medicated CSF group (P < 0.01).

CONCLUSIONQingxin Kaiqiao recipe shows an apparent protective effect on PC12 cells injured by Glu.

Animals ; Apoptosis ; drug effects ; Caspase 3 ; genetics ; Cerebrospinal Fluid ; Glutamic Acid ; toxicity ; Male ; Medicine, Chinese Traditional ; Neuroprotective Agents ; pharmacology ; PC12 Cells ; Proto-Oncogene Proteins c-bcl-2 ; genetics ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo observe the effects of polydatin on dynamic changes of excitatory amino acids in cerebrospinal fluid and water content of brain tissue of cerebral hemorrhage rats. And to discuss the therapeutic action and mechanisms of polydatin on brain hemorrhagic injured rats.

METHODA quantitative determination method of Asp and Glu was established by microdialysis-HPLC. The cerebral hemorrhage model in rats was induced by local injection of type VII collagenase. The dynamic changes of Asp and Glu in cerebrospinal fluid were observed on 0, 6, 12, 24, 36, 48, 60, 72, 84, 96, 108 h of cerebral hemorrhage rats, and then the water content of brain tissue was detected.

RESULTThe content of Asp and Glu increased rapidly within 24 h after cerebral hemorrhage, and to the highest in 24 h, then decreased gradually. Compared with the cerebral hemorrhage model group, the content of Asp and Glu increased slowly in polydatin group, and there were significant differences in 12-72 h and 6-84 h (P < 0.01, P < 0.05), but there was no significant difference after 84 h and 96 h. Compared with sham group, water content of brain tissue significantly higher in model group, while significantly lower (P < 0.01) in polydatin group.

CONCLUSIONPolydatin can inhibit increasing content of Asp and Glu in cerebrospinal fluid dynamics, and significantly inhibit cerebral edema of cerebral hemorrhage rats. It shows that the mechanisms of anti-cerebral hemorrhage injury of polydatin may be related to increasing of excitatory amino acids after cerebral hemorrhage.

Animals ; Aspartic Acid ; cerebrospinal fluid ; Cerebral Hemorrhage ; cerebrospinal fluid ; drug therapy ; Disease Models, Animal ; Drugs, Chinese Herbal ; therapeutic use ; Excitatory Amino Acids ; cerebrospinal fluid ; Glucosides ; therapeutic use ; Glutamic Acid ; cerebrospinal fluid ; Humans ; Male ; Rats ; Rats, Sprague-Dawley ; Stilbenes ; therapeutic use

The aim of this study is to investigate the effect of (S)-4-carboxy-3-hydroxy-phenylglycine [(S)-4C3HPG], a mixed group I glutamate metabotropic receptor antagonist and a group II agonist, on impairment in a cortical impact model of traumatic brain injury (TBI) in mice and to elucidate the possible mechanisms. Mice were injected (i.p.) with saline, 1 mg/kg (S)-4C3HPG, 5 mg/kg (S)-4C3HPG and 10 mg/kg (S)-4C3HPG (n=10 per group), respectively, at 30 min before moderate TBI. Neurological deficit scores, water content in injured brain and glutamate concentration in cerebral spinal fluid (CSF) were detected at 24 h after TBI. The expressions of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) mRNA in injured cortex were also detected by real-time RT-PCR. The results showed that the neurological deficits and cerebral edema were significantly attenuated in mice pretreated with (S)-4C3HPG (5 and 10 mg/kg respectively) compared with those in mice pretreated with saline. Furthermore, (S)-4C3HPG treatment also decreased the glutamate concentration in CSF and the expressions of TNF-α and IL-1β mRNA remarkably in a dose-dependent manner. These results suggest that (S)-4C3HPG treatment attenuates cortical impact-induced brain injury possibly via suppression of glutamate release and inhibition of excessive inflammatory cytokine production. These findings highlight the potential benefit of glutamate metabotropic receptor ligand for preventing TBI.
Animals ; Brain Injuries ; drug therapy ; metabolism ; physiopathology ; Cytokines ; metabolism ; Glutamic Acid ; cerebrospinal fluid ; Glycine ; analogs & derivatives ; therapeutic use ; Male ; Mice ; Mice, Inbred C57BL ; Receptors, Metabotropic Glutamate ; agonists ; antagonists & inhibitors

Recently, activation of the adenosine A2A receptors has been shown to exert protection against peripheral tissue injuries but aggravation in the central nervous system (CNS) injuries. To explore the different effects of adenosine A2A receptors and try to perform some new treatment strategies for peripheral tissue and CNS traumas, we constructed the mouse models of skin trauma, skin combined radiation-impaired wound and traumatic brain injury (TBI), respectively. Wild type mice and A2A receptor gene knockout mice were both used in the experiments. In skin trauma and combined radiation-impaired wound models, the time of wound healing was observed, while in TBI model, neurological deficit scores, water content in injured brain and glutamate concentration in cerebral spinal fluid (CSF) were detected at 24 h after TBI. The results showed that in skin trauma and combined radiation-impaired wound models, CGS21680 (an agonist of the A2A receptors) promoted while A2A receptor gene knockout delayed the course of skin wound healing. On the contrary, in TBI model, A2A receptor gene knockout, not CGS21680, showed a protective role by inhibition of glutamate release. These data further indicate that promoting glutamate release may account for the different effects of A2A receptor activation in CNS injury and peripheral tissue injury models. These findings may provide some experimental evidence and a new strategy for clinical treatment of peripheral tissue damages by agonists of A2A receptors, while treatment of CNS injuries by antagonists of A2A receptors.
Adenosine ; analogs & derivatives ; pharmacology ; Animals ; Brain ; pathology ; Brain Injuries ; physiopathology ; Disease Models, Animal ; Glutamic Acid ; cerebrospinal fluid ; Mice ; Mice, Knockout ; Phenethylamines ; pharmacology ; Receptor, Adenosine A2A ; genetics ; physiology ; Wound Healing

BACKGROUNDThe mechanisms underlying postoperative pain remain unclear. Neurotransmitters of excitatory and inhibitory amino acids play an important role in the transmission and modulation of pain in the spinal dorsal horn. This study aimed to investigate the changes of release of excitatory and inhibitory amino acids in the spinal cord during postoperative pain and to provide a novel theoretical basis for postoperative pain management.

METHODSLoop microdialysis catheters were implanted subarachnoidally via the atlanto-occipital membrane in 16 healthy Sprague-Dawley rats. All rats without neural deficits were divided into two groups, Group A and Group B, following 5 days of recovery. The tubes for microdialysis were connected and 25 microl microdialysate sample for baseline value was collected after one-hour washout in each rat. A plantar incision in the right hind paws of rats in Group A were performed under 1.2% isoflurane. All rats in Group B were only anesthetized by 1.2% isoflurane for the same duration. The microdialysate samples were collected at 3 hours, 1 day, 2 days and 3 days after the incision (or isoflurane anesthesia in Group B) in both groups. The cumulative pain scores were also assessed at the above time-points. The amino acids in the microdialysate samples were tested using high performance liquid chromatography.

RESULTSWithin Group A, the release of aspartate and glutamate at 3 hours after the incision was significantly higher than the baseline values and the release of glycine at 1 day after the incision significantly increased compared with the baseline values (P < 0.01). Within Group B, the release of neurotransmitters at each time point had no significant difference compared with the baseline values (P > 0.05). The release of aspartate and glutamate at 3 hours after the incision in Group A was significantly higher than that in Group B (P < 0.01). The release of glycine at 1 day after the incision in Group A significantly increased compared with Group B (P < 0.01). The cumulative pain scores at 3 hours, 1 day and 2 days after the incision in Group A were significantly higher than those in Group B (P < 0.01).

CONCLUSIONSThe release of the excitatory amino acids occurs in the early phase of postoperative pain and might not be involved in the maintenance of pain in a rat model of incision pain. The release of inhibitory glycine lagged behind the excitatory amino acids. The implication of inhibitory glycine release remained to be established further.

Animals ; Aspartic Acid ; secretion ; Excitatory Amino Acids ; cerebrospinal fluid ; secretion ; Glutamic Acid ; secretion ; Glycine ; secretion ; Male ; Microdialysis ; Neurotransmitter Agents ; secretion ; Pain, Postoperative ; metabolism ; Rats ; Rats, Sprague-Dawley ; Spinal Cord ; secretion

PURPOSE: Topiramate is a novel antiepileptic drug, and is known to act as a glutamate receptor antagonist. Excitotoxicity by glutamate is also advocated as an arm of brain injury in bacterial meningitis. We sought to delineate whether topiramate could attenuate brain energy depletion during bacterial meningitis by near infrared spectroscopy monitoring. METHODS: Meningitis was induced by intracisternal injection of 108 colony forming units of Escherichia coli. Topiramate at a dose of 50 or 100 mg/kg was given to the piglets 30 minutes before the induction of meningitis. The piglets in the meningitis control group were not given topiramate. Cerebral blood volume, cerebral blood flow, and brain cell energy state were monitored for 6 hours by near infrared spectroscopy. RESULTS: 100 mg/kg of topiramate significantly attenuated the increase in intracranial pressure and leukocyte count in the cerebrospinal fluid during study period. Although statistically insignificant, there was a trend of decrease in cerebral blood volume as indicated by total hemoglobin and cerebral blood flow as indicated by oxidized hemoglobin. Deduced hemoglobin in the meningitis was attenuated by topiramate. Topiramate did not significantly affect the brain energy state as indicated by cytochrome aa3 during the 6 hours after the induction of meningitis. CONCLUSION: 100 mg/kg of topiramate significantly attenuated the inflammatory response in experimentally induced bacterial meningitis. However, there was no significant effect of topiramate on the brain cell energy metabolism during the early phase of experimental bacterial meningitis.
Arm ; Blood Volume ; Brain Injuries ; Brain* ; Cerebrospinal Fluid ; Electron Transport Complex IV ; Energy Metabolism* ; Escherichia coli* ; Escherichia* ; Glutamic Acid ; Intracranial Pressure ; Leukocyte Count ; Meningitis ; Meningitis, Bacterial ; Meningitis, Escherichia coli* ; Receptors, Glutamate ; Spectrum Analysis ; Stem Cells

We evaluated the efficacy of non-competitive N-methyl-D-aspartate receptor antagonist MK-801 (dizocilpine) as an adjuvant therapy in experimental neonal bacterial meningitis. Meningitis was induced by injecting 10(6) colony forming units of Escherichia coli into the cisterna magna. MK-801 3 mg/kg was given as a bolus intravenous injection, 30 min before the induction of meningitis. MK-801 did not down-modulate the inflammatory parameters, such as increased intracranial pressure, cerebrospinal fluid (CSF) leukocytosis, increased lactate and TNF-alpha levels in the CSF, and hypoglycorrhachia observed in the meningitis group. MK-801 did not significantly attenuate the elevated glutamate concentration in the CSF. However, MK-801 showed some neuroprotective effects as evidenced by significant attenuation of cerebral lipid peroxidation products (conjugated dienes) and increase of brain high-energy phosphate compounds (ATP and PCr). Improvement in cerebral cortical cell membrane Na+, K+ -ATPase activity did not reach a statistical significance. These results suggest that MK-801 was effective in ameliorating brain injury in neonatal bacterial meningitis, although it failed to attenuate the inflammatory responses.
Animals ; Animals, Newborn ; Blood Glucose/metabolism ; Brain/cytology ; Brain/drug effects* ; Brain/metabolism ; Cell Membrane/drug effects* ; Cell Membrane/metabolism ; Cerebral Cortex/metabolism ; Dizocilpine Maleate/pharmacology* ; Energy Metabolism* ; Excitatory Amino Acid Antagonists/pharmacology ; Glutamic Acid/cerebrospinal fluid ; Lactic Acid/blood ; Leukocytes/metabolism ; Meningitis, Escherichia coli/drug therapy ; Meningitis, Escherichia coli/metabolism* ; Neurons/drug effects* ; Neurons/metabolism ; Neuroprotective Agents/pharmacology* ; Random Allocation ; Swine ; Tumor Necrosis Factor/cerebrospinal fluid

BACKGROUND: Cerebral ischemia causes an increase in extracellular potassium ([K+]e) through activation of the KATP channel. This increase in [K+]e could result in neuronal depolarization and a reversal of the glutamate uptake system in glia. This may further contribute to the excessive concentrations of glutamate and asparate in the extracellular space during ischemia. If the early rise in [K+]e during ischemia could be attenuated, less excitotoxic neuronal damage may be the result. However, activation of KATP channels has been shown to attenuate the anoxia induced depolarization in the hippocampus and may reduce the release of excitatory neurotransmitters during cerebral ischemia. In this study, we address the question of whether KATP channel modulation affects [K+]e and whether it is related with extracellular glutamate concentrations. METHODS: After approval by the Animal Care and Use Committee, 18 New Zealand white rabbits were anesthetized with halothane and mechanically ventilated to maintain normocarbia. Microdialysis catheters were inserted into the left dorsal hippocampus and perfused with artificial cerebrospinal fluid at 2 ml/min. K+ sensitive microelectrodes were inserted into the contralateral hippocampus. A pneumatic tourniquet was placed loosely around the neck. Animals were randomized to receive glibenclamide (n=5, KATP blocker, 3.7 mg/kg) or cromakalim (n=5, KATP opener, 0.5 mg/kg). The control group (n=6) had neither drug. Ten-minute period of global cerebral ischemia was produced by inflation of the tourniquet combined with induced hypotension. Hippocampal [K+]e was measured throughout the periischemic period and glutamate concentrations in dialysate were determined by high-performance liquid chromatography. Peak levels were compared by ANOVA. RESULTS: Glutamate concentration significantly increased during ischemia period for all groups (p<0.05). In glibenclamide treated animals, brain glutamate concentration increased markedly during early reperfusion (t=I+15) compared to other groups (p<0.05). There were no statistical differences on ischemia-induced increases in [K+]e among the three groups. CONCLUSIONS: Although it was not possible to demonstrate an effect of modulators of the ATP sensitive K+ channel on [K+]e, glibenclamide increased glutamate during reperfusion. This paradoxical increase in glutamate after administration of a K+ channel blocker suggests that the mechanism of glutamate release is not related to [K+]e change.
Adenosine Triphosphate ; Animals ; Anoxia ; Brain ; Brain Ischemia ; Catheters ; Cerebrospinal Fluid ; Chromatography, Liquid ; Cromakalim ; Extracellular Space ; Glutamic Acid* ; Glyburide ; Halothane ; Hippocampus* ; Hypotension ; Inflation, Economic ; Ischemia* ; KATP Channels ; Microdialysis ; Microelectrodes ; Neck ; Neuroglia ; Neurons ; Neurotransmitter Agents ; Potassium ; Rabbits ; Reperfusion ; Tourniquets

In present study, the mechanism for oxygen-glucose deprivation -induced [3H]gamma-aminobutyric acid (GABA) from cerebral cortex slices of the rat was examined. Deprivation of oxygen and glucose(OGD) from Mg2+-free artificial cerebrospinal fluid, induced significant release of [3H]GABA (7.4+/-0.6% of total tissue content) from cerebral cortex slices. OGD-induced release of [3H]GABA was significantly attenuated by tetrodotoxin(TTX)(1 micrometer), Mg2+(1.2 mM), MK-801(10 micrometer), ketamine(10 micrometer), N-methyl-D-aspartate(NMDA) receptor antagonists, (DNQX)(30 micrometer), and 6-cyano-7-nitroquinoxaline-2,3-dione(CNQX)(30 micrometer), kainate/AMPA receptor antagonists, or 6-nitro-7-sulphamoyl-benzo[f]quinoxaline-2, 3-dione(NBQX)(10 micrometer), a selective AMPA receptor blocker. OGD-evoked [3H]GABA release was attenuated by (NG-nitro-L-arginine methyl ester(L-NAME) and 7-nitronidazole, nitric oxide synthase inhibitors, and methylene blue, potentiated by zaprinast, a cGMP phosphodiesterase inhibitor. OGD-induced release of [3H]GABA was inhibited by nipecotic acid, a selective neuronal GABA transporter blocker, and potentiated by DL-2.4-diamino-n-butyric acid(DABA), a neuronal and glial GABA transporter blocker. Dantrolene (30 micrometer) and 1,2-bis (2-aminophenoxy)-ethane-N, N, N', N'-tetraacetic acid tetrakis (acetoxymethyl) ester(BAPTA-AM)(30 micrometer), inhibitors of intracellular Ca2+ release, verapamil(5 micrometer), omega-conotoxinGVIA(100 nM) and omega-agatoxinIVA(100 nM), inhibitors of voltage-dependent Ca2+ channels, significantly attenuated the OGD-induced release of [3H]GABA. These results suggest that glutamate is involved in OGD-evoked [3H]GABA release, and this release is achieved by Ca2+-dependent exocytosis and reversal of transporters, and can be modulated by various neuronal mechanisms.
Animals ; Cerebral Cortex* ; Cerebrospinal Fluid ; Dantrolene ; Exocytosis ; gamma-Aminobutyric Acid ; Glutamic Acid ; Methylene Blue ; Neurons ; Nitric Oxide Synthase ; Oxygen ; Rats* ; Receptors, AMPA