The excitotoxic effect of kainic acid on dendrites and neuronal cell bodies of hippocampus and dentate gyrus was studied with time (1, 4, 8, 16 hours, 2, 7, 14 days) light and electron microscopically by intraperitonial injection into rat. The results obtained were as follows. 1) The acute dendrotoxic effect was observed as laminar pattern of swelling along pyramidal cell body layer and dendritic fields and was most prominently at 2-4 hours after kainic acid injection. In ultractructural study, the acute change occurred in dendrites of pyramidal cells in hipocampus because the synapses between nerve terminals and swollen components were not destroyed and remained intact and, identified the swollen structures as dendrites. So, it was obvious from the results that the acute change by kainic acid was osmolysis and was continued till initial 4 hours but was finally faded out. 2) The distribution of kainic acid receptor within hippocampus was different because the prominent dendritic swelling occurred in proximal basilar dendritic field of CA 3 and 4 and the proximal and distal basilar dendritic fields of CA 1 and 2, and no change was observable in dentate granule cell. The sensitivity of hippocampal dendritic fields to kainic acid could be put in decreasing order as CA3, CA4, CA1, CA2 and dentate granule cell 3) With the elapse of time, the acute change disappeared and pyramidal cells began to degenerate by the chronic reaction about 7 days after kainic acid injury, and the pyramidal cell density in CA regions greatly decreased. Almost all pyramidal cells degenerated the dentate granule cells were not affected to kainic acid throughout the time. In conclusions, hippocampal neurons were postulated to be very sensitive to kainic acid, and in contrast to the gradual disappearance of acute change within several hours, the degeneration of pyramidal neurons by chronic change was developed within several days regardless of acute change.
Animals ; Brain* ; Dendrites ; Dentate Gyrus ; Hippocampus ; Kainic Acid* ; Neurons* ; Pyramidal Cells ; Rats* ; Receptors, Kainic Acid ; Synapses

Glutamate-induced cobalt uptake reveals that non-NMDA glutamate receptors (GluRs) are present in rat taste bud cells. Previous studies involving glutamate induced cobalt staining suggest this uptake mainly occurs via kainate type GluRs. It is not known which of the 4 types of taste bud cells express subunits of kainate GluR. Circumvallate and foliate papillae of Sprague-Dawley rats (45~60 days old) were used to search for the mRNAs of subunits of non-NMDA GluRs using RT-PCR with specific primers for GluR1-7, KA1 and KA2. We also performed RT-PCR for GluR5, KA1, PLCbeta2, and NCAM/SNAP 25 in isolated single cells from taste buds. Taste epithelium, including circumvallate or foliate papilla, express mRNAs of GluR5 and KA1. However, non-taste tongue epithelium expresses no subunits of non-NMDA GluRs. Isolated single cell RT-PCR reveals that the mRNAs of GluR5 and KA1 are preferentially expressed in Type II and Type III cells over Type I cells.
Animals ; Cobalt ; Epithelium ; Glutamic Acid ; Kainic Acid ; Rats ; Rats, Sprague-Dawley ; Receptors, Glutamate ; Receptors, Kainic Acid ; RNA, Messenger ; Taste Buds ; Tongue

To investigate the mechanism of the excitatory signal transmission, the effects of N-methyl-D-aspartate(NMDA, ionotropic glutamate agonist) and kynurenic acid(glutamate antagonist) on catfish retinal neurons were explored using conventional intracellular recording techniques. Horizontal cells were depolarized by glutamate, kainate, quisqualate, and NMDA but gyperpolarized by kynurenate. Transient components of both ON-and OFF-bipolar cells were reduced either by glutamate or by NMDA. Kynurenate suppressed sustained components of the third-order neurons or OFF-bipolar cells. Furthermore, kynurenate blocked the depolarizing actions of NMDA on horizontal cells and ON-sustained cells with large ON-transient components. The results suggest that NMDA would exert a tonic depolarization in the horizontal cells and the 3rd-order neurons, and there might be a preferential suppression on the a NMDA receptors by kynurenic acid in the catfish retina.
Catfishes ; Glutamic Acid ; Kainic Acid ; Kynurenic Acid* ; N-Methylaspartate ; Neurons* ; Quisqualic Acid ; Receptors, N-Methyl-D-Aspartate ; Retina* ; Retinal Neurons

Ca2+ influx appears to be important for triggering myoblast fusion. It remains, however, unclear how Ca2+ influx rises prior to myoblast fusion. Recently, several studies suggested that NMDA receptors may be involved in Ca2+ mobilization of muscle, and that Ca2+ influx is mediated by NMDA receptors in C2C12 myoblasts. Here, we report that other types of ionotropic glutamate receptors, non-NMDA receptors (AMPA and KA receptors), are also involved in Ca2+ influx in myoblasts. To explore which subtypes of non-NMDA receptors are expressed in C2C12 myogenic cells, RT-PCR was performed, and the results revealed that KA receptor subunits were expressed in both myoblasts and myotubes. However, AMPA receptor was not detected in myoblasts but expressed in myotubes. Using a Ca2+ imaging system, Ca2+ influx mediated by these receptors was directly measured in a single myoblast cell. Intracellular Ca2+ level was increased by KA, but not by AMPA. These results were consistent with RT-PCR data. In addition, KA-induced intracellular Ca2+ increase was completely suppressed by treatment of nifedifine, a L-type Ca2+ channel blocker. Furthermore, KA stimulated myoblast fusion in a dose-dependent manner. CNQX inhibited not only KA-induced myoblast fusion but also spontaneous myoblast fusion. Therefore, these results suggest that KA receptors are involved in intracellular Ca2+ increase in myoblasts and then may play an important role in myoblast fusion.
6-Cyano-7-nitroquinoxaline-2,3-dione ; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid ; Kainic Acid* ; Muscle Fibers, Skeletal ; Myoblasts ; Receptors, AMPA ; Receptors, Ionotropic Glutamate ; Receptors, Kainic Acid* ; Receptors, N-Methyl-D-Aspartate

OBJECTIVETo explore the effect of up-regulation of KA1 subunit of the kainate receptor on endoplasmic reticulum stress (ERS)-induced excitotoxic neurodegeneration in mouse hippocampus.

METHODSSeventy adult male KM mice were subjected to microinjections into the hippocampus of kainic acid (KA) or 500, 1000, or 2000 µg/ml tunicamycin (TM). At 1, 2, 3, 4, 5, 8, and 12 h after the injections, the mice were assessed for Bederson scores and sacrificed for FJB staining and immunofluorescence observation of the brain slices.

RESULTSAt 3, 4, 5, and 8 h after KA injection and at 4 and 5 h after of 2000 µg/ml TM injection, the mice showed severe central nervous system dysfunction, and FJB staining revealed increased cell death in the hippocampus, where up-regulated expressions of KA1 receptor and ERS marker P-eIF2α were found by immunofluorescence staining (P<0.05).

CONCLUSIONMicroinjection of KA or TM into the hippocampus causes neuronal death and ERS with up-regulated expression of KA1. In this process of neuronal apoptosis, the membrane receptor KA1 receives the apoptosis signal and transfers it to the inside of the cells to cause cell endoplasmic reticulum dysfunction and ERS response, which ultimately leads to neuronal death.

Animals ; Apoptosis ; Endoplasmic Reticulum Stress ; Hippocampus ; pathology ; Kainic Acid ; pharmacology ; Male ; Mice ; Neurons ; pathology ; Receptors, Kainic Acid ; metabolism ; Tunicamycin ; pharmacology ; Up-Regulation

BACKGROUND: Androsterone is one of the major metabolites from testosterone whose clinical importance remains unclear. This study evaluated the effects of androsterone on seizure susceptibility in mouse models of epilepsy. METHODS: The efficacy of androsterone (10~200 mg/kg, i.p.) against seizures induced by various GABA receptor antagonists and glutamate receptor agonists was evaluated. RESULTS: Androsterone protected mice against seizures induced by PTZ (pentylenetetrazol), PCX (picrotoxin), and DMCM (methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate) in a dose-dependent manner. Androsterone did not protect against seizures induced by kainic acid, NMDA (N-methyl-D-aspartic acid), or 4-AP (4-aminopyridine) in mice. CONCLUSIONS: These results suggest that androsterone exhibits anticonvulsant activity that occurs largely via nongenomic mechanisms. Testosterone-derived androsterone might be an endogenous protective neuroactive steroid in the brain.
Androsterone ; Animals ; Carbolines ; Epilepsy ; GABA Antagonists ; gamma-Aminobutyric Acid ; Kainic Acid ; Mice ; N-Methylaspartate ; Receptors, Glutamate ; Seizures ; Testosterone

PURPOSE: c-fos is rapidly and transiently induced in the intact CNS by a wide variety of exogenous stimuli that include seizures, glutamate receptor activation, sensory stimulation and stress. In adult animals, systemic KA administration produces limbic seizures that results in c-fos protein expression, irreversible morphological changes and localized neuronal death. So we studied the pattern of c-fos protein expression and histological findings in hippocampal formation, following kainic acid-induced seizures during the postnatal period in the rat. METHODS: Sprague-Dawley rat pups ranging from 8 to 10 days of age, received kainic acid(KA, 5mg/kg) by intraperitoneal injection. Control rats were injected with normal saline. The rats were perfused and fixed with 4% buffered paraformaldehyde at varying time-intervals after KA injection, the brains were sectioned and immunohistochemically stained for c-fos protein and performed HE staining. RESULTS: In the hippocampus, immunohistochemistry showed that c-fos protein expressed at 12 hr after KA injection and disappeared thereafter. c-fos protein expressed in all sectors of the hippocampus but most densely expressed in CA1 and CA3 sectors. Rarely c-fos expression was seen in the granular cell layer of dentate gyrus. There were no histologic changes in the hippocampus at 2 weeks after KA injection. CONCLUSION: c-fos, a proapoptotic gene in adult rats, seemed to have an additive role in neuronal cell adaptation to exogenous stimuli in neonatal rats. As a result, it suggests that the roles of c-fos in neuronal cells after noxious stimuli are different between neonatal and adult rats.
Adult ; Animals ; Brain* ; Dentate Gyrus ; Hippocampus* ; Humans ; Immunohistochemistry ; Injections, Intraperitoneal ; Kainic Acid* ; Neurons ; Rats* ; Rats, Sprague-Dawley ; Receptors, Glutamate ; Seizures

The KA1 kainate receptor (KAR) subunit in the substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) has been implicated in the processing of nociceptive information from the orofacial region. This study compared the expression of the KA1 KAR subunit in the SG of the Vc in juvenile, prepubescent and adult mice. RT-PCR, Western blot and immunohistochemistry analyses were used to examine the expression level in SG area. The expression levels of the KA1 KAR subunit mRNA and protein were higher in juvenile mice than in prepubescent or adult mice. Quantitative data revealed that the KA1 KAR subunit mRNA and protein were expressed at levels approximately two and three times higher, respectively, in juvenile mice than in adult mice. A similar expression pattern of the KA1 KAR subunit was observed in an immunohistochemical study that showed higher expression in the juvenile (59%) than those of adult (35%) mice. These results show that the KA1 KAR subunits are expressed in the SG of the Vc in mice and that the expression level of the KA1 KAR subunit decreases gradually with postnatal development. These findings suggest that age-dependent KA1 KAR subunit expression can be a potential mechanism of age-dependent pain perception.
Age Factors ; Animals ; Gene Expression Profiling ; *Gene Expression Regulation, Developmental ; Mice ; Receptors, Kainic Acid/*metabolism ; Substantia Gelatinosa/*metabolism

We examined excitotoxicity, putatively a major mechanism of ischemic neuronal death, in primary rat retinal cultures. Retinal cultures were prepared from newborn rats (day 1 or 2). Exposure of these cultures (DIV8-10)to NMDA or kainate induced neuronal death. Furthermore, MK-801 or CNQX each partially attenuated glutamateinduced neuronal death, suggesting that both NMDA and kainate receptors mediate it. Thy-1(+) retinal ganglion neurons, like neurons as a whole, were equally injured by NMDA and by kainate. However, GABA(+) or calbindin (+) neurons of the inner nuclear layer were resistant to NMDA, but highly vulnerable to kainate. These neurons may have AMPA/kainate receptors that are highly permeable to Ca2+, as they take up cobalt with kainate stimulation. These results suggest that the AMPA/kainate receptor, rater than the NMDA receptor, may mediate this pattern of selective neurnonal death.
6-Cyano-7-nitroquinoxaline-2,3-dione ; Animals ; Calbindins ; Cell Death* ; Cobalt ; Dizocilpine Maleate ; GABAergic Neurons ; Ganglion Cysts ; Humans ; Infant, Newborn ; Kainic Acid ; N-Methylaspartate ; Neurons ; Rats ; Receptors, Kainic Acid ; Retinal Neurons* ; Retinaldehyde*

OBJECTIVE: We studied the expression of pain-related molecules such as substance P involved in chronic pain of fibromyalgia syndrome (FMS) patients using rat cortical cells in hypoxia. METHODS: We sacrificed pregnant Sprague-Dawley rat and got embryo. We cultured the cortical cells and compared the expression of pain-related molecules in 1st, 3rd, 5th day cortical cells exposed to hypoxia (37 degrees C, 5% CO2, 98% N2) to control by immunohistochemistry. We measured the density at soma using softwear 'Scion image'. RESULTS: The expression of substance P was increased in hypoxic cortical cell group than control (control mean: 49.9 vs. hypoxia 1st day: 75.4 (p<0.001), 3rd day: 65.6 (p<0.001), 5th day: 79.9 (p<0.001)). The expression of kainate receptor was increased in hypoxic cortical cell group than control (control mean: 58.4 vs. hypoxia 1st day: 64.9 (p<0.001), 3rd day: 63.3 (p<0.001), 5th day: 62.9 (p<0.001)). The expression of N-methyl-D-aspartate receptor 2B was increased in hypoxic cortical cell group than control (control mean : 59.4 vs. hypoxia 1st day: 60.8 (p<0.001), 3rd day: 62.6 (p<0.001), 5th day: 67.1 (p<0.001)). But, the expression of calcitonin gene related peptide was decreased in hypoxic cortical cell group than control (control mean: 76.8 vs. hypoxia 1st day: 76.4 (p<0.001), 3rd day: 71.5 (p<0.001), 5th day: 61.3 (p<0.001)). CONCLUSION: Hypoxia during night could increase the expression of some pain-related molecules, which might be the cause of chronic pain in FMS patients.
Animals ; Anoxia ; Calcitonin Gene-Related Peptide ; Carisoprodol ; Chronic Pain ; Embryonic Structures ; Fibromyalgia* ; Glutamic Acid ; Humans ; Immunohistochemistry ; N-Methylaspartate ; Rats ; Rats, Sprague-Dawley ; Receptors, Kainic Acid ; Substance P