The Role of CNQX in the Different Types of Synaptic Release in Mice / 现代生物医学进展

Objective:To explore the role of 6-CYANO-2,3-DIHYDROXY-7-NITROQUIN OXALINE (CNQX) in different types of synapse secretion.Methods:The spontaneous mEPSCs and eEPSCs at different extracellular concentrations of CNQX in cultured cortical or hippocampal neurons were recorded respectively.Results:The half inhibitory concentration (IC50) of CNQX in evoked neurotransmitter release was significantly higher than that of spontaneous release,indicating that the spontaneous neurotransmitter release was more sensitive to CNQX.No apparent difference was observed between cortical and hippocampal cells,suggesting that the blocking effect of CNQX was similar in different brain regions.Conclusion:CNQX might have differential regulating mechanisms between excitatory spontaneous and evoked neurotransmitter release,but without brain regions specificity.

Involvement of AMPA receptors for Mesobuthus tamulus Pocock venom-induced depression of monosynaptic reflex in neonatal rat spinal cord in vitro.

Glutamate is a putative neurotransmitter at Ia-α motoneuron synapse in the spinal cord and mediate the action via N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors. Since NMDA receptors are not involved in M. tamulus Pocock (MBT) venom-induced depression of spinal monosynaptic reflex (MSR), the present study was undertaken to evaluate the role of AMPA receptors in mediating the depression of MSR by MBT venom. The experiments were performed on isolated hemisected spinal cord from 4-6 day old rats. Stimulation of a dorsal root with supramaximal voltage evoked MSR and polysynaptic reflex (PSR) potentials in the corresponding segmental ventral root. Superfusion of MBT venom (0.3 µg/ml) depressed the spinal reflexes in a time-dependent manner. The maximum depression of MSR(~ 66%) was seen at 10 min  and it was 25 min for PSR (~ 75%). The time to produce 50% depression of MSR and PSR was 6.7 ± 1.5 and 10.8 ± 2.6 min, respectively. Pretreatment of the cords with 6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX, 0.1 μM), an AMPA receptor antagonist, blocked the venom-induced depression of MSR but not PSR. The results indicate that venom-induced depression of MSR is mediated via AMPA receptors.

The Neuroprotective Effects of 6-cyano-7-nitroquinoxalin-2,3-dione (CNQX) Via Mediation of Nitric Oxide Synthase on Hypoxic-ischemic Brain Injury in Neonatal Rats

PURPOSE: Current studies have demonstrated the neuroprotective effects of 6-cyano-7-nitroquinoxalin-2,3-dione (CNQX) in many animal models of brain injury, including hypoxic-ischemic (HI) encephlopathy, trauma and excitotoxicity, but limited data are available for those during the neonatal periods. Here we investigated whether CNQX can protect the developing rat brain from HI injury via mediation of nitric oxide synthase. METHODS: In an in vivo model, left carotid artery ligation was done in 7-day-old Sprague-Dawley (SD) rat pups. The animals were divided into six groups; normoxia (N), hypoxia (H), hypoxia with sham-operation (HS), hypoxia with operation (HO), HO treated with vehicle (HV), and HO treated with CNQX at a dose of 10 mg/kg (HC). Hypoxia was made by exposure to a 2 hr period in the hypoxic chamber (92% N2, 8% O2). In an in vitro model, embryonic cortical neuronal cell culture of SD rats at 18-day gestation was done. The cultured cells were divided into three groups: normoxia (N), hypoxia (H), and hypoxia treated with CNQX (HC). The N group was prepared in 5% CO2 incubators and the other groups were placed in 1% O2 incubators (94% N2, 5% CO2) for 16 hr. RESULTS: In the in vitvo and in vivo models, the expressions of iNOS and eNOS were reduced in the hypoxia group when compared to the normoxia group, whereas they were increased in the CNQX-treated group compared to the hypoxia group. In contrast, the expression of nNOS was showed reversely. CONCLUSION: CNQX has neuroprotective property over perinatal HI brain injury via mediation of nitric oxide synthase.

Effect of Potassium, Bicuculline and CNQX on Epileptiform Activity Induced by Pilocarpine in the Rat Visual Cortex Slice

BACKGROUND: The purpose of this study was to investigate the effect of potassium, bicuculline (BIC) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) on epileptiform activity induced by pilocarpine in the rat visual cortex slices. METHODS: In the rat visual cortex slices, we observed the change of pilocarpine-induced epileptiform discharges using extracellular recordings during perfusion of artificial cerebro-spinal fluid (ACSF) with various potassium concentrations ([K+], 2.5, 5, 7.5 and 10 mM) and ACSF with 10 micrometer BIC and 20 micrometer CNQX under 7.5 mM [K+]. RESULTS: Spontaneous interictal epileptiform activity induced by pilocarpine was observed in 5 mM or higher [K+] and ictal discharge was only detected in 7.5 mM [K+]. Increase of [K+] from 2.5 to 7.5 mM not only resulted in the increase of frequency and amplitude of epileptiform activity but also favored the transformation of pilocarpine-induced interictal activity into ictal activity in the rat visual cortex. However, in 10 mM [K+], the ictal discharge was unprovoked and interictal activity was provoked with decreased frequency and amplitude. The spontaneous ictal discharge was blocked but interictal activity was maintained with increased frequency and amplitude by BIC. Interictal and ictal activities were completely blocked by CNQX. CONCLUSIONS: These results suggested that the extracellular potassium concentration, GABA system, and non-NMDA mechanism seemed to be involved in the development and maintenance of pilocarpine-induced epileptiform activity in the rat visual cortex.

Possible regulation channel of Xiaoyao San in treating rats of syndrome of liver invading the spleen by immunohistochemistry / 中华中医药杂志

Objective: Pervious RT-PCR results revealed the possibility of effective regulation channel of Xiaoyao San in treating rats of syndrome of liver invading the spleen. This experiment was designed to explore CIS rats’ immunohistochemistry findings in hippocampal subregion CA1 and amygdaloid subregion BLA after suppressing both amygdaloid AMPA receptors by microinjection of CNQX. To compare Xiaoyao San group with CNQX group, and to analysis of these findings may prove the possibility of effective regulation channel of Xiaoyao san treating this syndrome. Methods: 75 male SD rats were randomly divided into 5 equal groups: normal group, CIS group, sham-operation group, CNQX group and Xiaoyao San group. The number of GluR2 positive cells in hippocampal subregion CA1 and amygdaloid subregion BLA in these 5 groups were examined by immunohistochemistry test. Results: Compared with control group, the number of GluR2 positive cells decreased in hippocampal subregion CA1. Statistical analysis showed that no difference existed in control, CNQX and Xiaoyao San groups in CA1 region. Except CNQX group, tendency of changes were contradictory in BLA and CA1 region. In addition, the least in BLA in CNQX group. This finding revealed that Xiaoyao San may act the same as CNQX, thus Xiaoyao San afforded effective protection against this depression syndrome through suppression of both amygdaloid excitability. Conclusion: The balance coordination between hippocampus and amygdala may be the key in transformation from adaption to damage in a state of stress, was one of the central mechanisms of liver governing smoothing qi flow (LGSQF) on regulating the stress. Xiaoyao San may effectively regulate the balance of the excitability of hippocampus and amygdala. This hypothesis may reveal the regulation channel on Xiaoyao San affording effective protection against liver invading the spleen syndrome.

THE EFFECT OF CORIARIA LECTON-ACTIVITED ASTROCYTE-CONDITIONED MEDIUM AND CNQX ON NSF OF THE CEREBRAL OF NORMAL RATS AND CULTURED NEURONS / 解剖学报

Objective To explore the effects of astrocytes on the N-ethylmaleimide-sensitive fusion protin,(NSF) and AMPA receptor of the neurons as well as their function in epileptogenesis. Methods ACM was injected into lateral ventricle of SD rats and the behaviour changes were observed; Immunohistochemical method was used to assess the changes of the expression of NSF in the cerebral cortex and hippocampus; The cultured neurons were divided into control group, ACM group and CNQX+ACM group at random, immunocytochemistry was used to assess the changes of the expression of NSF, Western blotting was used to assess the changes of the content of NSF of the cultured neurons. Results Seizure was observed in ACM group 30 min after injecting ACM. the immunoreaction of NSF in hippocampus and cerebral cortex of rats were depressed than those of the control group 2h, 4h after injecting ACM (P

The Role of Peripheral N-Methyl-D-Aspartate (NMDA) Receptors in Freund's Complete Adjuvant Induced Mechanical Hyperalgesia in Rats / 대한마취과학회지

BACKGROUND: While the effects of excitatory amino acids have been characterized in the central nervous system, relatively little is known about their possible modulation of elements responsible for hyperalgesia within peripheral tissue. The purpose of this study was to investigate the role of excitatory amino acid receptors in mechanical hyperalgesia induced by a subcutaneous injection of Freund's complete adjuvant (FCA) into the rat hind paw. METHODS: Inflammations were induced by injecting FCA on the dorsal surface of the right hind paw of rats. Effects of excitatory aminoacid agonists or antagonists on mechanical hyperalgesia were investigated by a subcutaneous injection of a drug to the inflamed paw. Mechanical hyperalgesia was expressed as percent change in paw withdrawal threshold compared to baseline value that was measured before drug injection after inflammation was induced with FCA. RESULTS: In normal rats, an intraplantar (i.pl.) injection of L-glutamate, but not of D-glutamate (3 pmol/0.1 ml each) produced a mechanical hyperalgesia in the hind paw with a lowered paw paw-withdrawal threshold to pressure. In rats that developed the mechanical hyperalgesia associated with inflammation in the hind paw following an i.pl. injection of FCA (0.15 ml), the injection of a N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801 (1 pmol/0.1 ml) into the inflamed paw increased the paw pressure threshold (24.24.6% increase from baseline, P < 0.05). On the other hand, the injection of a non-NMDA receptor antagonist, 6-cyano-7-nitroqiunoxaline-2,3-dione (CNQX, 10 pmol/0.1 ml) into the inflamed paw had no effect on the FCA-induced lowering of the paw pressure threshold. CONCLUSIONS: The results suggest that NMDA, but not non-NMDA receptors play a substantial role in mediating the development of mechanical hyperalgesia induced in the inflamed paw following an i.pl. FCA injection.

Effect of MK801 and CNQX on Retinal Injury Induced by Ischemia, NMDA, or Kainate

To examine the protection of retinal cell death by glutamate antagonists in vivo, this study was carried out in pressure-induced ischemia model. Firstly, we observed that ischemia resulted in the similar retinaldamage to the injuries caused by NMAD and Kainate toxicity. Secondly, the retinal cell death caused by ischemia was prevented by MK801 and CNQX, glutamate antagonists for NMDA and Kainate excitotoxicity, respectively at 24hr after ischemia. MK801 was shown to prevent the cell death in ganglion cell layer and CNQX in inner unclear layer. In addition, the combination of CNQX and MK801 protected the retina neuronal cell from ischemic injury better than when they were applied separately. The partial protection of retinal cell death by glutamate antagonists in ischemia model indicates that glutamate eoxicity as well as other cell death mechanism such as apoptosis mediates ischemia induced retinal cell death. Thus, cell death by other mechanism must be also blocked in order to prevent retinal cell death, completely.

The Effect of Intrathecal NMDA and non-NMDA Receptor Antagonist on the Hyperalgesia Observed after Thermal Injury in the Rat / 대한마취과학회지

BACKGROUND: Previous reports have described NMDA antagonist reduced the nerve injury induced or inflammatory thermal hyperalgesia. This study evaluated the effects of spinally administered excitatory amino acid antagonists on the thermal hyperalgesia state induced by mild burn. METHODS: The measured response was the latency to paw withdrawal of each hindpaw after application of a focused heat lamp on the plantar surface of the paw through a glass plate upon which the animal stood. In this work, MK801, non-competitive NMDA receptor antagonist, AP5, competitive NMDA receptor antagonist, CNQX, non-NMDA receptor antagonist were injected through chronically implanted lumbar intrathecal catheters in rats with mild burn injury on the right hindpaw. RESULTS: In the normal left hindpaw, MK801, AP5 and CNQX had little effect upon paw withdrawal latency (PWL) at intrathecal doses which do not produce readily detectable motor weakness. In the right hyperalgesic hindpaw, AP5 significantly reduced PWL at a dose-dependent fashion, MK801 reduced PWL to some extent, and CNQX did not reduced PWL. CONCLUSIONS: These results suggested that spinal NMDA receptors play an important role in the hyperalgesia induced by mild burn injury.