6-methyl-2-(phenylethynyl)pyridine and Status-Epilepticus

The present study examined whether a single or multiple episode(s) of status epilepticus induced with kainic acid (KA) during the first 3 weeks of postnatal (P) development would aberrantly stimulate proliferation zones that alters migration to potentially injured areas and whether they would be blocked by selective Group I mGluR antagonists. mGluR1α (LY367385) and mGluR5 (MPEP) antagonists were administered 2h following KA-induced status epilepticus and animals were examined after 7days. Proliferating cells of the subventricular zone (SVZ), third ventricle, hippocampus, amygdala cortical complex were analyzed with the proliferative marker, Ki67; and two complementary retrograde dye tracers. Proliferation increased in extrahippocampal limbic structures when KA was administered on P13 or P20 which correlated with number of injured cells at the older age. LY367385 post-treatment caused striking decreases in proliferation in all limbic structures in the presence and absence of injury, whereas a reduction with MPEP was observed only within the amygdala cortical complex (Amg/ERcx) in the presence of multiple seizures (3×KA). After 3×KA and LY367385 post-treatments, diminished co-staining of dye tracers with Ki67 was observed within the Amg/ERcx despite high levels of progenitors marked by the retrograde tracers in this region. This indicates that not only was local proliferation within the SVZ and distant structures inhibited, but also that migration itself was reduced indirectly since there were less cells to migrate from the SVZ. Co-labeling with biomarkers provided evidence for neuronal differentiation suggesting potential aberrant integration may occur in distant locations, and that targeting of mGluR1α receptors may be a potential therapeutic strategy for future development.

Topics: Age Factors; Animals; Animals, Newborn; Benzoates; Brain; Cell Cycle; Cell Movement; Cell Proliferation; Disease Models, Animal; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Female; Gene Expression Regulation, Developmental; Glycine; Kainic Acid; Lateral Ventricles; Male; Pregnancy; Pyridines; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate; Rhodamines; Status Epilepticus; Time Factors

Recently, we demonstrated that mRNA for the neuronal glutamate transporter, excitatory amino acid carrier 1 (EAAC1), is found in dendrites of hippocampal neurons in culture and in dendrites of hippocampal pyramidal cells after pilocarpine-induced status epilepticus (SE). We also showed that SE increased the levels of EAAC1 mRNA ~15-fold in synaptoneurosomes. In this study, the effects of SE on the distribution EAAC1 protein in hippocampus were examined. In addition, the effects of Group 1 mGluR receptor activation on the levels of EAAC1 protein were examined in synaptoneurosomes prepared from sham control animals and from animals that experience pilocarpine-induced SE. We find that EAAC1 immunoreactivity increases in pyramidal cells of the hippocampus after 3 h of SE. In addition, the group I mGluR agonist, (S)-3,5-dihydroxyphenylglycine (DHPG), caused an increase in EAAC1 protein levels in hippocampal synaptoneurosomes; this effect of DHPG was much larger (~3- to 5-fold) after 3 h of SE. The DHPG-induced increases in EAAC1 protein were blocked by two different inhibitors of translation but not by inhibitors of transcription. mGluR1 or mGluR5 antagonists completely blocked the DHPG-induced increases in EAAC1 protein. DHPG also increased the levels of glutamate receptor 2/3 protein, but this effect was not altered by SE. The DHPG-induced increase in EAAC1 protein was blocked by an inhibitor of the mammalian target of rapamycin or an inhibitor of extracellular signal-regulated kinase. These studies provide the first evidence EAAC1 translation can be regulated, and they show that regulated translation of EAAC1 is up-regulated after SE.

Topics: Animals; Blotting, Western; Convulsants; Dendrites; Dose-Response Relationship, Drug; Excitatory Amino Acid Transporter 3; Extracellular Signal-Regulated MAP Kinases; Fluorescent Antibody Technique; Hippocampus; Male; Methoxyhydroxyphenylglycol; Neurons; Pilocarpine; Pyridines; Rats; Rats, Sprague-Dawley; Receptor, Metabotropic Glutamate 5; Receptors, Metabotropic Glutamate; RNA, Messenger; Status Epilepticus; Synaptosomes; TOR Serine-Threonine Kinases

By intravenous administration of group I metabotropic glutamate receptor antagonists at 1 or 2h during pilocarpine induced status epilepticus (PISE), we showed that mGluR1 antagonists AIDA or LY367385 (at dosages ranging from 25 to 200mg/kg), mGluR5 antagonists SIB1757 (at dosages ranging from 25 to 200mg/kg), SIB1893 (from 25 to 100mg/kg), MPEP (from 25 to 100mg/kg) injected at 1 or 2h during PISE were ineffective in controlling status epilepticus (SE). However, when administered at 1h during PISE, MPEP at 200mg/kg, combination of MPEP (200mg/kg) with MK801 (0.1mg/kg) or with MK801 (0.1mg/kg) and diazepam (0.5mg/kg), combination of SIB1893 (200mg/kg) with MK801 (0.1mg/kg) could effectively control behavioral SE, and were neuroprotective. In particular, the combination of MPEP with MK801 and diazepam could stop both behavioral SE and electrical SE (under EEG monitoring) within a few minutes after the administration. HPLC study showed that a high level of MPEP was maintained in the blood and its metabolism rate was slow in experimental mice with PISE. We therefore concluded that the combination of MPEP (200mg/kg) with MK801 (0.1mg/kg) and diazepam (0.5mg/kg) could effectively stop SE and its subsequent neuronal loss in the hippocampus when administered 1h during PISE. It may provide a new approach to effectively control intractable SE.

Topics: Animals; Behavior, Animal; Chromatography, High Pressure Liquid; Diazepam; Disease Models, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Therapy, Combination; Electroencephalography; Excitatory Amino Acid Antagonists; GABA Modulators; Male; Mice; Oxazines; Pilocarpine; Pyridines; Status Epilepticus