OBJECTIVETo examine the changes in the expression of mGluR4 after diffuse brain injury (DBI) and to determine the role of its specific agonist L-2-amino-4-phosphonobutyrate (L-AP4) in vivo.

METHODSA total of 161 male SD rats were randomized into the following groups. Group A included normal control, sham-operated control and DBI group. DBI was produced according to Marmarou's diffuse head injury model. mRNA expression of mGluR4 was detected by hybridization in situ. Group B included DBI alone, DBI treated with normal saline and DBI treated with L-AP4. All DBI rats were trained in a series of performance tests, following which they were subjected to DBI. At 1 and 12 hours, animals were injected intraventricularly with L-AP4 (100 mmol/L, 10 microl) or normal saline. Motor and cognitive performances were tested at 1, 3, 7, 14 days after injury and the damaged neurons were also detected.

RESULTSThere was no significant difference between normal control group and sham-operated group in the expression of mGluR4 (P>0.05). The animals exposed to DBI showed significantly increased expression of mRNA of mGluR4 compared with the sham-operated animals 1 h after injury (P<0.05). At 6 hours, the evolution of neuronal expression of mGluR4 in the trauma alone group was relatively static. Compared with saline-treated control animals, rats treated with L-AP4 showed an effective result of decreased number of damaged neurons and better motor and cognitive performances.

CONCLUSIONSIncreased expression of mGluR4 is important in the pathophysiological process of DBI and its specific agonist L-AP4 can provide remarkable neuroprotection against DBI not only at the histopathological level but also in the motor and cognitive performance.

Aminobutyrates ; pharmacology ; Analysis of Variance ; Animals ; Brain Injuries ; metabolism ; Excitatory Amino Acid Agonists ; pharmacology ; Male ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Receptors, Metabotropic Glutamate ; drug effects ; metabolism

Glutamate induced rapid phosphorylation of moesin, one of ERM family proteins involved in the ligation of membrane to actin cytoskeleton, in rat hippocampal cells (JBC, 277:16576-16584, 2002). However, the identity of glutamate receptor has not been explored. Here we show that a-amino- 3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor is responsible for glutamate-induced RhoA activation and phosphorylation of moesin. Glutamate induced phosphorylation at Thr-558 of moesin was still detectible upon chelation of Ca(2+), suggesting involvement of AMPA receptor instead of N-methyl D-Aspartate (NMDA) receptor in this phosphorylation of moesin. AMPA but not NMDA- induced moesin phosphorylation was independent of Ca(2+). Both AMPA and NMDA but not Kainate induced moesin phosphorylation at similar levels. However, the kinetics of phosphorylation varied greatly between AMPA and NMDA where AMPA treatment rapidly increased phosphomoesin, which reached a maximum at 10 min after treatment and returned to a basal level at 30 min. In contrast, NMDA-induced phosphorylation of moesin reached a maximum at 30 min after treatment and was remained at higher levels at 60 min. A possible involvement of RhoA and its downstream effector, Rho kinase in the AMPA receptor-triggered phosphorylation of moesin was also explored. The kinetics for the glutamate- induced membrane translocation of RhoA was similar to that of moesin phosphorylation induced by AMPA. Moreover, Y-27632, a specific Rho kinase inhibitor, completely blocked AMPA-induced moesin phosphorylation but had no effect on NMDA-induced moesin phosphorylation. These results suggest that glutamate-induced phosphorylation of moesin may be mediated through the AMPA receptor/RhoA/Rho kinase pathway.
Animals ; Calcium/metabolism ; Cell Line ; Excitatory Amino Acid Agonists/*metabolism ; Glutamic Acid/metabolism ; Kainic Acid/metabolism ; Microfilament Proteins/*metabolism ; N-Methylaspartate/*metabolism ; Phosphorylation ; Protein-Serine-Threonine Kinases/metabolism ; Rats ; Receptors, AMPA/metabolism ; Receptors, N-Methyl-D-Aspartate/metabolism ; Research Support, Non-U.S. Gov't ; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/*metabolism ; rhoA GTP-Binding Protein/*metabolism

Mounting evidence supports an important role of chemokines, produced by spinal cord astrocytes, in promoting central sensitization and chronic pain. In particular, CCL2 (C-C motif chemokine ligand 2) has been shown to enhance N-methyl-D-aspartate (NMDA)-induced currents in spinal outer lamina II (IIo) neurons. However, the exact molecular, synaptic, and cellular mechanisms by which CCL2 modulates central sensitization are still unclear. We found that spinal injection of the CCR2 antagonist RS504393 attenuated CCL2- and inflammation-induced hyperalgesia. Single-cell RT-PCR revealed CCR2 expression in excitatory vesicular glutamate transporter subtype 2-positive (VGLUT2) neurons. CCL2 increased NMDA-induced currents in CCR2/VGLUT2 neurons in lamina IIo; it also enhanced the synaptic NMDA currents evoked by dorsal root stimulation; and furthermore, it increased the total and synaptic NMDA currents in somatostatin-expressing excitatory neurons. Finally, intrathecal RS504393 reversed the long-term potentiation evoked in the spinal cord by C-fiber stimulation. Our findings suggest that CCL2 directly modulates synaptic plasticity in CCR2-expressing excitatory neurons in spinal lamina IIo, and this underlies the generation of central sensitization in pathological pain.
Animals ; Benzoxazines ; pharmacology ; therapeutic use ; Chemokine CCL2 ; antagonists & inhibitors ; genetics ; metabolism ; pharmacology ; Excitatory Amino Acid Agents ; pharmacology ; Excitatory Amino Acid Agonists ; pharmacology ; Female ; Freund's Adjuvant ; toxicity ; Hyperalgesia ; chemically induced ; metabolism ; prevention & control ; Long-Term Potentiation ; drug effects ; physiology ; Luminescent Proteins ; genetics ; metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Mice, Transgenic ; Myelitis ; chemically induced ; drug therapy ; metabolism ; Neurons ; drug effects ; Pain Management ; Somatostatin ; genetics ; metabolism ; Spinal Cord ; cytology ; Spiro Compounds ; pharmacology ; therapeutic use ; Vesicular Glutamate Transport Protein 2 ; genetics ; metabolism ; Vesicular Inhibitory Amino Acid Transport Proteins ; genetics ; metabolism

OBJECTIVEKetogenic diet (KD) is a high fat, low protein, low carbohydrate diet. Its antiepileptic effect is certain but the underlying mechanism is unknown. The aim of the study was to reveal the possible mechanism from the view points of synaptic reorganization and GluR(5) expression in hippocampus.

METHODSEpilepsy was induced in Sprague-Dawley rats by kainic acid at postnatal day 28, all control animals were fed with normal rodent chow, whereas experimental rats were fed with ketogenic feed for 8 weeks. Spontaneous recurrent seizures were recorded. Mossy fiber sprouting and neuron damage in hippocampus were investigated by Timm staining and Nissl staining. Western blot and RT-PCR methods were applied to detect the expression of GluR(5) and GluR(5) mRNA in hippocampus.

RESULTSKD-fed rats (1.40 +/- 1.03) had significantly fewer spontaneous recurrent seizures than control diet-fed rats (7.36 +/- 3.75). The mean A of mossy fiber sprouting in the inner molecular layer of dentate gyrus was markedly higher in KA induced animals than that in saline control animals but it was similar in different diet fed groups. No significant differences were found in the mean A of Timm staining in CA(3) area and Nissl staining of neuron in hilus, CA(3) and CA(1) area. After KA kindling, KD-fed animals [(189.38 +/- 40.03)/mg pro] had significantly higher GluR(5) expression in hippocampus than control diet-fed animals [(128.79 +/- 46.51)/mg pro] although their GluR(5) mRNA was the same.

CONCLUSIONMossy fiber sprouting may be responsible for epileptogenesis in KA induced model and KD can suppress seizures in these animals. KD may upregulate young rat GluR(5) in inhibitory interneurons of CA(1) thus lead to an increased inhibition to prevent the propagation of seizure.

Animals ; Blotting, Western ; CA1 Region, Hippocampal ; metabolism ; pathology ; CA3 Region, Hippocampal ; metabolism ; pathology ; Chromosome Pairing ; drug effects ; Dentate Gyrus ; metabolism ; pathology ; Diet, Ketogenic ; methods ; Disease Models, Animal ; Epilepsy ; chemically induced ; diet therapy ; genetics ; metabolism ; pathology ; Excitatory Amino Acid Agonists ; Hippocampus ; drug effects ; metabolism ; pathology ; Kainic Acid ; Male ; Mossy Fibers, Hippocampal ; metabolism ; pathology ; Pyramidal Cells ; metabolism ; pathology ; RNA, Messenger ; metabolism ; Rats ; Receptors, Kainic Acid ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction

Estrogen replacement therapy in postmenopausal women may reduce the risk of Alzheimer's disease, possibly by ameliorating neuronal degeneration. In the present study, we examined the neuroprotective spectrum of estrogen against excitotoxicity, oxidative stress, and serum-deprivation-induced apoptosis of neurons in mouse cortical cultures. 17beta-estradiol as well as 17alpha-estradiol and estrone attenuated oxidative neuronal death induced by 24 hr exposure to 100 microM FeCl2, excitotoxic neuronal death induced by 24 hr of exposure to 30 microM N-methyl-D-aspartate (NMDA) and serum-deprivation induced neuronal apoptosis. Furthermore, estradiol attenuated neuronal death induced by Abeta25-35. However, all these neuroprotective effects were mediated by the anti-oxidative action of estrogens. When oxidative stress was blocked by an antioxidant trolox, estrogens did not show any additional protection. Addition of a specific estrogen receptor antagonist ICI182,780 did not reverse the protection offered by estrogens. These findings suggest that high concentrations of estrogen protect against various neuronal injuries mainly by its anti-oxidative effects as previously shown by Behl et al. Our results do not support the view that classical estrogen receptors mediate neuroprotection.
Amyloid beta-Protein/pharmacology ; Animal ; Antioxidants/pharmacology* ; Antioxidants/metabolism ; Apoptosis/drug effects* ; Cells, Cultured ; Chelating Agents/pharmacology ; Chromans/pharmacology ; Estradiol/pharmacology ; Estrogens/pharmacology* ; Estrogens/metabolism ; Estrone/pharmacology ; Ethylenediamines/pharmacology ; Excitatory Amino Acid Agonists/pharmacology ; Ferric Compounds/pharmacology ; Lactate Dehydrogenase/analysis ; Mice ; N-Methylaspartate/pharmacology ; Neurons/metabolism ; Neurons/drug effects* ; Neurons/cytology ; Organ of Corti/cytology ; Peptide Fragments/pharmacology ; Staurosporine/pharmacology

Estrogen replacement therapy in postmenopausal women may reduce the risk of Alzheimer's disease, possibly by ameliorating neuronal degeneration. In the present study, we examined the neuroprotective spectrum of estrogen against excitotoxicity, oxidative stress, and serum-deprivation-induced apoptosis of neurons in mouse cortical cultures. 17beta-estradiol as well as 17alpha-estradiol and estrone attenuated oxidative neuronal death induced by 24 hr exposure to 100 microM FeCl2, excitotoxic neuronal death induced by 24 hr of exposure to 30 microM N-methyl-D-aspartate (NMDA) and serum-deprivation induced neuronal apoptosis. Furthermore, estradiol attenuated neuronal death induced by Abeta25-35. However, all these neuroprotective effects were mediated by the anti-oxidative action of estrogens. When oxidative stress was blocked by an antioxidant trolox, estrogens did not show any additional protection. Addition of a specific estrogen receptor antagonist ICI182,780 did not reverse the protection offered by estrogens. These findings suggest that high concentrations of estrogen protect against various neuronal injuries mainly by its anti-oxidative effects as previously shown by Behl et al. Our results do not support the view that classical estrogen receptors mediate neuroprotection.
Amyloid beta-Protein/pharmacology ; Animal ; Antioxidants/pharmacology* ; Antioxidants/metabolism ; Apoptosis/drug effects* ; Cells, Cultured ; Chelating Agents/pharmacology ; Chromans/pharmacology ; Estradiol/pharmacology ; Estrogens/pharmacology* ; Estrogens/metabolism ; Estrone/pharmacology ; Ethylenediamines/pharmacology ; Excitatory Amino Acid Agonists/pharmacology ; Ferric Compounds/pharmacology ; Lactate Dehydrogenase/analysis ; Mice ; N-Methylaspartate/pharmacology ; Neurons/metabolism ; Neurons/drug effects* ; Neurons/cytology ; Organ of Corti/cytology ; Peptide Fragments/pharmacology ; Staurosporine/pharmacology

The present study was to investigate the role of dopamine D1 receptors and its relationship with glutamate, N-methyl-D-aspartic acid (NMDA) receptor and α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor in depression induced by chronic unpredictable mild stress (CUMS). CUMS-induced depression model was established in Sprague-Dawley rats, and intrahippocampal microinjections of D1 dopamine receptor agonist SKF38393, non-competitive NMDA receptor antagonist MK-801 and AMPA receptor antagonist NBQX were respectively adopted by rat brain stereotaxic coordinates. The behavioral observations were conducted by measurement of weight changes, sucrose preference test, open-field test and tail suspension test. The concentration of glutamic acid and the expression of its receptors' subunits were detected by HPLC and Western blot, respectively. The results showed that, compared with control group, CUMS rats showed depression-like behavioral changes, higher concentration of glutamic acid, lower expressions of NMDA receptor (NR1) and AMPA receptor (GluR2/3) in hippocampus. Pretreatment with injection of SKF38393 could rescue such depression effect of CUMS, decrease the concentration of glutamic acid, and increase the expressions of NMDA receptor (NR1), AMPA receptor (GluR2/3) in hippocampus. Pretreatment with MK-801 could enhance the antidepressant effect of SKF38393, while NBQX weakened. These results suggest that agonists of D1 dopamine receptor could reduce the concentration of glutamic acid in hippocampus, and its antidepressant effect may be mediated by AMPA receptor partially.
2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine ; pharmacology ; Animals ; Depression ; etiology ; physiopathology ; Dizocilpine Maleate ; pharmacology ; Excitatory Amino Acid Antagonists ; Glutamates ; metabolism ; Hippocampus ; metabolism ; Male ; Rats ; Rats, Sprague-Dawley ; Receptors, AMPA ; metabolism ; Receptors, Dopamine D1 ; agonists ; physiology ; Stress, Physiological ; physiology

OBJECTIVETo investigate possible protective effect of maternal immunoglobulin G (IgG) against N-methyl-D-aspartate-mediated neurotoxicity on primary-cultured rat hippocampal neurons and the mechanism of the effect.

METHODSAn in vitro system had been developed for the study of hippocampal neurons. Intracellular lactic dehydrogenase (LDH) release was used as a marker to measure the rates of neuronal damage. The cells were stained with Trypan blue to measure the rate of neuronal death.

RESULTSN-methyl-D-aspartate (NMDA) at a concentration of 50 micromol/L resulted in increased release of LDH and the cell mortality (P < 0.01, respectively). Maternal IgG of different concentration (10 mg/L, 100 mg/L) inhibited NMDA-induced intracellular LDH release (P < 0.01, respectively) and cell mortality (P < 0.05, 0.01, respectively), and larger dose had stronger effect (P < 0.05).

CONCLUSIONSMaternal IgG had protective effect on primary-cultured rat hippocampal neurons injured by NMDA and the effect was dose-dependent.

Animals ; Animals, Newborn ; Cell Death ; drug effects ; Cell Survival ; drug effects ; Cells, Cultured ; Excitatory Amino Acid Agonists ; Female ; Hippocampus ; cytology ; drug effects ; metabolism ; pathology ; Immunity, Maternally-Acquired ; immunology ; Immunoglobulin G ; biosynthesis ; isolation & purification ; pharmacology ; Immunologic Factors ; biosynthesis ; isolation & purification ; pharmacology ; L-Lactate Dehydrogenase ; analysis ; biosynthesis ; Male ; N-Methylaspartate ; Neurons ; drug effects ; metabolism ; pathology ; Organ Culture Techniques ; Pregnancy ; Rats ; Rats, Wistar

Spinal gabapentin has been known to show the antinociceptive effect. Although several assumptions have been suggested, mechanisms of action of gabapentin have not been clearly established. The present study was undertaken to examine the action mechanisms of gabapentin at the spinal level. Male SD rats were prepared for intrathecal catheterization. The effect of gabapentin was assessed in the formalin test. After pretreatment with many classes of drugs, changes of effect of gabapentin were examined. General behaviors were also observed. Intrathecal gabapentin produced a suppression of the phase 2 flinching, but not phase 1 in the formalin test. The antinociceptive action of intrathecal gabapentin was reversed by intrathecal NMDA, AMPA, D-serine, CGS 15943, atropine, and naloxone. No antagonism was seen following administration of bicuculline, saclofen, prazosin, yohimbine, mecamylamine, L-leucine, dihydroergocristine, or thapsigargin. Taken together, intrathecal gabapentin attenuated only the facilitated state. At the spinal level, NMDA receptor, AMPA receptor, nonstrychnine site of NMDA receptor, adenosine receptor, muscarinic receptor, and opioid receptor may be involved in the antinociception of gabapentin, but GABA receptor, L-amino acid transporter, adrenergic receptor, nicotinic receptor, serotonin receptor, or calcium may not be involved.
Acetic Acids/administration & dosage ; Acetic Acids/metabolism ; Acetic Acids/pharmacology* ; Adrenergic Antagonists/metabolism ; Adrenergic alpha-Antagonists/metabolism ; Analgesics/administration & dosage ; Analgesics/metabolism ; Analgesics/pharmacology* ; Animals ; Atropine/metabolism ; Dihydroergocristine/metabolism ; Enzyme Inhibitors/metabolism ; Excitatory Amino Acid Agonists/metabolism ; GABA Antagonists/metabolism ; Injections, Spinal ; Leucine/metabolism ; Male ; Mecamylamine/metabolism ; Muscarinic Antagonists/metabolism ; N-Methylaspartate/metabolism ; Naloxone/metabolism ; Narcotic Antagonists/metabolism ; Nicotinic Antagonists/metabolism ; Pain Measurement ; Quinazolines/metabolism ; Rats ; Rats, Sprague-Dawley ; Serine/metabolism ; Spinal Cord/drug effects* ; Thapsigargin/metabolism ; Triazoles/metabolism ; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/metabolism

Neural stem cells (NSCs) have mainly been applied to neurodegeneration in some medically intractable neurologic diseases. In this study, we established a novel NSC line and investigated the cytotoxic responses of NSCs to exogenous neurotoxicants, glutamates and reactive oxygen species (ROS). A multipotent NSC line, B2A1 cells, was established from long-term primary cultures of oligodendrocyte-enriched cells from an adult BALB/c mouse brain. B2A1 cells could be differentiated into neuronal, astrocytic and oligodendroglial lineages. The cells also expressed genotypic mRNA messages for both neural progenitor cells and differentiated neuronoglial cells. B2A1 cells treated with hydrogen peroxide and L-buthionine-(S,R)-sulfoximine underwent 30-40% cell death, while B2A1 cells treated with glutamate and kainate showed 25-35% cell death. Cytopathologic changes consisting of swollen cell bodies, loss of cytoplasmic processes, and nuclear chromatin disintegration, developed after exposure to both ROS and excitotoxic chemicals. These results suggest that B2A1 cells may be useful in the study of NSC biology and may constitute an effective neurotoxicity screening system for ROS and excitotoxic chemicals.
Animals ; Brain/*cytology ; Buthionine Sulfoximine/pharmacology ; Cell Differentiation ; Cell Line ; Cell Lineage ; Cytokines/pharmacology ; Enzyme Inhibitors/pharmacology ; Excitatory Amino Acid Agonists/pharmacology ; Glutamic Acid/pharmacology ; Humans ; Hydrogen Peroxide/pharmacology ; Intercellular Signaling Peptides and Proteins/pharmacology ; Kainic Acid/pharmacology ; Mice ; Mice, Inbred BALB C ; Multipotent Stem Cells/cytology/*drug effects/physiology ; Neuroglia/cytology/drug effects/physiology ; Neurons/cytology/*drug effects/physiology ; Neurotoxins/*pharmacology ; Oxidants/pharmacology ; Phenotype ; Reactive Oxygen Species/metabolism