Effect of gap junction blockers on hippocampal ripple energy expression in rats with status epilepticus. / ç¼éš™è¿žæŽ¥é˜»æ–­å‰‚å¯¹å¤§é¼ ç™«ç—«åŽæµ·é©¬æ¶Ÿæ³¢æŒ¯è¡èƒ½é‡å˜åŒ–çš„å½±å“.

OBJECTIVES: To study the effect of gap junction blockers, quinine (QUIN) and carbenoxolone (CBX), on hippocampal ripple energy expression in rats with status epilepticus (SE). METHODS: A total of 24 rats were randomly divided into four groups: model, QUIN, valproic acid (VPA), and CBX (n=6 each). A rat model of SE induced by lithium-pilocarpine (PILO) was prepared. The QUIN, VPA, and CBX groups were given intraperitoneal injection of QUIN (50 mg/kg), VPA by gavage (200 mg/kg), and intraperitoneal injection of CBX (50 mg/kg) respectively, at 3 days before PILO injection. Electroencephalography was used to analyze the change in hippocampal ripple energy before and after modeling, as well as before and after chloral hydrate injection to control seizures. RESULTS: Ripple expression was observed in the hippocampal CA1, CA3, and dentate gyrus regions of normal rats. After 10 minutes of PILO injection, all groups had a gradual increase in mean ripple energy expression compared with 1 day before modeling, with the highest expression level before chloral hydrate injection in the model, VPA and CBX groups (P<0.05). The QUIN group had the highest expression level of mean ripple energy 60 minutes after PILO injection. The mean ripple energy returned to normal levels in the three intervention groups immediately after chloral hydrate injection, while in the model group, the mean ripple energy returned to normal levels 1 hour after chloral hydrate injection. The mean ripple energy remained normal till to day 3 after SE in the four groups. The changing trend of maximum ripple energy was similar to that of mean ripple energy. CONCLUSIONS: The change in ripple energy can be used as a quantitative indicator for early warning of seizures, while it cannot predict seizures in the interictal period. Gap junction blockers can reduce ripple energy during seizures.

[Effect of advanced maternal age on development of hippocampal neural stem cells in offspring rats].

OBJECTIVE: To study the effect of advanced maternal age (AMA) on the development of hippocampal neural stem cells in offspring rats. METHODS: Ten 3-month-old and ten 12-month-old female Sprague-Dawley rats were housed individually with 3-month-old male rats (1:1, n=20), whose offspring rats were assigned to a control group and an AMA group. A total of 40 rats were randomly selected from each group. Immunofluorescence assay and Western blot were used to localize and determine the levels of protein expression of Nestin and doublecortin (DCX) on day 7 as well as neuronal nuclear antigen (NeuN) and glial fibrillary acidic protein (GFAP) on day 28 (n=8 for each marker). Immunofluorescence assay was also used to localize the hippocampal expression of polysialylated isoforms of neural cell adhesion molecule (PSA-NCAM) on day 14 (n=8 for each marker). RESULTS: According to the Western blot results, the AMA group had significantly lower protein expression of DCX than the control group (P<0.05), while there were no significant differences in the protein expression of Nestin, NeuN, and GFAP between the two groups (P>0.05). According to the results of immunofluorescence assay, the AMA group had significantly lower protein expression of Nestin, DCX, and PSA-NCAM in the hippocampal dentate gyrus (DG) region than the control group (P<0.05), while there were no significant differences in the above indices in the hippocampal CA1 and CA3 regions between the two groups (P>0.05). The AMA group had significantly higher expression of NeuN in the hippocampal CA1 region than the control group (P<0.01), while there were no significant differences in the expression of NeuN in the hippocampal DG and CA3 regions between the two groups (P>0.05). The AMA group had significantly lower expression of GFAP in the hippocampal CA1, CA3, and DG regions than the control group (P<0.05). CONCLUSIONS: AMA may cause inhibition of proliferation, survival, and migration of hippocampal neural stem cells. AMA may also affect their differentiation into neurons and astrocytes, which will eventually lead to developmental disorders of hippocampal neural stem cells in offspring rats.

Levetiracetam Protects Against Cognitive Impairment of Subthreshold Convulsant Discharge Model Rats by Activating Protein Kinase C (PKC)-Growth-Associated Protein 43 (GAP-43)-Calmodulin-Dependent Protein Kinase (CaMK) Signal Transduction Pathway.

BACKGROUND Subclinical epileptiform discharges (SEDs) are defined as epileptiform electroencephalographic (EEG) discharges without clinical signs of seizure in patients. The subthreshold convulsant discharge (SCD) is a frequently used model for SEDs. This study aimed to investigate the effect of levetiracetam (LEV), an anti-convulsant drug, on cognitive impairment of SCD model rats and to assess the associated mechanisms. MATERIAL AND METHODS A SCD rat model was established. Rats were divided into an SCD group, an SCD+ sodium valproate (VPA) group, and an SCD+ levetiracetam (LEV) group. The Morris water maze was used to evaluate the capacity of positioning navigation and space exploration. The field excitatory post-synaptic potentials (fEPSPs) were evaluated using a bipolar stimulation electrode. NCAM, GAP43, PS95, and CaMK II levels were detected using Western blot and RT-PCR, respectively. PKC activity was examined by a non-radioactive method. RESULTS LEV shortens the latency of platform seeking in SCD rats in positioning navigation. fEPSP slopes were significantly lower in the SCD group, and LEV treatment significantly enhanced the fEPSP slopes compared to the SCD group (P<0.05). The NCAM and GAP-43 levels were increased and PSD-95 levels were increased in SCD rats (P<0.05), which were improved by LEV treatment. The PKC activity and CaMK II levels were decreased in SCD rats and LEV treatment significantly enhanced PKC activity and increased CaMK II levels. CONCLUSIONS Cognitive impairment in of SCD model rats may be caused by decreased PKC activity, low expression of CaMK II, and inhibition of LTP formation. LEV can improve cognitive function by activating the PKC-GAP-43-CaMK signal transduction pathway.

Alterations of Hippocampal Myelin Sheath and Axon Sprouting by Status Convulsion and Regulating Lingo-1 Expression with RNA Interference in Immature and Adult Rats.

Seizure-induced brain damage is age-dependent, as evidenced by the different alterations of neural physiopathology in developing and mature brains. However, little is known about the age-dependent characteristics of myelinated fiber injury induced by seizures. Considering the critical functions of oligodendrocyte progenitor cells (OPCs) in myelination and Lingo-1 signaling in regulating OPCs' differentiation, the present study aimed to explore the effects of Lingo-1 on myelin and axon in immature and adult rats after status convulsion (SC) induced by lithium-pilocarpine, and the differences between immature and adult brains. Dynamic variations in electrophysiological activity and spontaneous recurrent seizures were recorded by electroencephalogram monitoring after SC. The impaired microstructures of myelin sheaths and decrease in myelin basic protein caused by SC were observed through transmission electron microscopy and western blot analysis respectively, which became more severe in adult rats, but improved gradually in immature rats. Aberrant axon sprouting occurred in adult rats, which was more prominent than in immature rats, as shown by a Timm stain. This damage was improved or negatively affected after down or upregulating Lingo-1 expression. These results demonstrated that in both immature and adult brains, Lingo-1 signaling plays important roles in seizure-induced damage to myelin sheaths and axon growth. The plasticity of the developing brain may provide a potential window of opportunity to prevent the brain from damage.

[Level of brain-derived neurotrophic factor in the microenvironment of the neuron-astrocyte co-culture system by Mg2+-free-induced seizure-like discharge].

OBJECTIVE: To study the level of brain-derived neurotrophic factor (BDNF) in the microenvironment of the neuron-astrocyte co-culture system by Mg2+-free-induced seizure-like discharge and analyze the source of BDNF. METHODS: Hippocampal neurons (N) of fetal rats and astrocytes (AST) of neonatal rats were purified and divided into four groups, included control N (Con N) group, Mg2+-free treated N (Mg2+-free N) group, control N+AST co-culture (Con N+AST) group and Mg2+-free treated N+AST co-culture (Mg2+-free N+AST) group. The Mg2+-free treated groups were exposed to Mg2+-free media for 3 hrs to induce a repeated spontaneous seizure-like discharge. The level of BDNF in each group at different time points was measured using ELISA. RESULTS: The cellular morphous of AST changed in the Mg2+-free N+AST group at 48 hrs. Neuronal epileptiform activity was observed in the Mg2+-free media at 3 hrs, and continued to exist until the microenvironment returned to normal for 72 hrs. The BDNF level increased at 24 hrs and 48 hrs in the Con N+AST group compared with the control N group (P<0.05). Compared with Con N+AST group, BDNF level increased at 12, 24 and 48 hrs in the Mg2+-free N+AST group, especially at 12 and 24 hrs (P<0.01). There were no significant differences in the level of BDNF between the Con and Mg2+-free N groups. Compared with Mg2+-free N group, BDNF level increased at 24 hrs in the Mg2+-free N+AST group (P<0.05). CONCLUSIONS: The results of the experiment suggest that BDNF in the Con N+AST group might be excreted from both N and AST, but chiefly from N. Activated AST may be the main source for increasing BDNF in the Mg2+-free N+AST group.

[Establishment of animal model of myoclonus originating from axis of cortex-thalamus].

OBJECTIVE: To develop a series of experimental animal models of myoclonus with different origins consistent with myoclonus seizure in clinic setting. METHODS: GABA(A) antagonist SR95531 was microinjected into the primary motor cortex (PMC), corpus striatum, nucleus reticular of the thalamus (NRT) to induce myoclonus (EMG burst of myoclonus

[Changes in electroencephalograph and somatosensory evoked potential and their relationship with neuron apoptosis in rat after ischemic insult to brain].

OBJECTIVE: To study the changes in electroencephalograph (EEG) and somatosensory evoked potential (SEP) and their relationship with neuron apoptosis in rat after ischemic insult to the brain. METHODS: Thirty-five SD rats were randomly divided into normal, sham operated and 3, 12, 24, 48, 72 hours after ischemia/reperfusion (I/R) groups with 5 rats in each group. The ischemia of brain was produced by clamping 4 vessels to the brain for various periods of time. Changes in EEG and SEP were recorded at different time after I/R, and the amounts of apoptotic neurons in hippocampus and cortex after I/R were assessed with terminal deoxynucleotidyl transferase mediated dUTP biotin nick end labeling (TUNEL) and acridine orange ethidium bromide (AO/EB) fluorescence examination techniques. RESULTS: Compared with sham operated group, EEG amplitude decreased significantly (all P<0.05), and the proportion of Delta wave increased significantly after ischemia of the brain (all P<0.05). The latent period of P1 wave crest extended markedly (all P<0.05), and P1-N1 amplitude decreased significantly after I/R (all P<0.05). EEG and SEP changes were correlated with the apoptosis and loss of neurons, which started in the hippocampus and extended to frontal cortex and parietal cortex. CONCLUSION: The combined analysis of EEG and SEP can reflect the process of neuron apoptosis, which is helpful for the diagnosis and evaluation of prognosis of patients suffering from cerebral ischemia.

Dynamic Changes in Spectral and Spatial Signatures of High Frequency Oscillations in Rat Hippocampi during Epileptogenesis in Acute and Chronic Stages.

OBJECTIVE: To analyze spectral and spatial signatures of high frequency oscillations (HFOs), which include ripples and fast ripples (FRs, >200 Hz) by quantitatively assessing average and peak spectral power in a rat model of different stages of epileptogenesis. METHODS: The lithium-pilocarpine model of temporal lobe epilepsy was used. The acute phase of epilepsy was assessed by recording intracranial electroencephalography (EEG) activity for 1 day after status epilepticus (SE). The chronic phase of epilepsy, including spontaneous recurrent seizures (SRSs), was assessed by recording EEG activity for 28 days after SE. Average and peak spectral power of five frequency bands of EEG signals in CA1, CA3, and DG regions of the hippocampus were analyzed with wavelet and digital filter. RESULTS: FRs occurred in the hippocampus in the animal model. Significant dynamic changes in the spectral power of FRS were identified in CA1 and CA3. The average spectral power of ripples increased at 20 min before SE (p < 0.05), peaked at 10 min before diazepam injection. It decreased at 10 min after diazepam (p < 0.05) and returned to baseline after 1 h. The average spectral power of FRs increased at 30 min before SE (p < 0.05) and peaked at 10 min before diazepam. It decreased at 10 min after diazepam (p < 0.05) and returned to baseline at 2 h after injection. The dynamic changes were similar between average and peak spectral power of FRs. Average and peak spectral power of both ripples and FRs in the chronic phase showed a gradual downward trend compared with normal rats 14 days after SE. SIGNIFICANCE: The spectral power of HFOs may be utilized to distinguish between normal and pathologic HFOs. Ictal average and peak spectral power of FRs were two parameters for predicting acute epileptic seizures, which could be used as a new quantitative biomarker and early warning marker of seizure. Changes in interictal HFOs power in the hippocampus at the chronic stage may be not related to seizure occurrence.

Neurotoxicity of dibutyl phthalate in brain development following perinatal exposure: a study in rats.

Dibutyl-phthalate (DBP) is a ubiquitous environmental contaminant. However, its neurotoxic effects on neonatal, immature or mature brains remain unclear. Here, we aimed to investigate the neurotoxicity of perinatal exposure of DBP on rodent offspring animals. Pregnant rats received intragastric DBP (500mg/kg body weight) daily from gestational day (GD) 6 to postnatal day (PND) 21. Animals in the control group received the same volume of edible corn oil. Brain sections or tissues from offspring rats on PND5, PND21 and PND60 were collected for analysis. Histological examination demonstrated that perinatal exposure of DBP resulted in hippocampal neuron loss and structural alternation in neonatal and immature offspring rats (PND5 and PND21), while no significant change was found in mature rats (PND60). DBP exposure induced cell apoptosis in hippocampal neurons of these neonatal and immature animals, as evidenced by the increased number of TUNEL-positive and Annexin V-propidium iodide (PI) positive cells and up-regulated caspase-3 activity. Moreover, DBP exposure decreased the expression of synaptophysin in the hippocampus and reduced both the slope and amplitude of field excitatory postsynaptic potentials (fEPSPs). DBP also impaired the spatial learning and memory of offspring rats. However, no significant difference in the susceptibility to DBP-induced neurotoxicity was found between male and female offspring rats. Our findings indicated that perinatal exposure of DBP could induce neurotoxicity in neonatal and immature offspring animals, but had no influence on mature animals after DBP withdrawal. These results may provide basic experimental evidence for better understanding the neurotoxic effects of DBP on neonatal, immature and mature brains.