Glutamine synthetase (GS) is a key enzyme in the regulation of glutamate neurotransmission in the central nervous system. It is responsible for converting glutamate to glutamine, consuming one ATP and NH3 in the process. Glutamate is neurotoxic when it accumulates in extracellular fluids. We investigated the effects of GS in both a spinal cord injury (SCI) model and normal rats. 0.1-ml of low (2-microM) and high (55-microM) concentrations of GS were applied, intrathecally, to the spinal cord of rats under pentobarbital anesthesia. Immediately after an intrathecal injection into the L1-L3 space, the rats developed convulsive movements. These movements initially consisted of myoclonic twitches of the paravertebral muscles close to the injection site, repeated tonic and clonic contractions and extensions of the hind limbs (hind limb seizures) that spread to the fore limbs, and finally rotational axial movements of the body. An EMG of the paravertebral muscles, fore and hind limbs, showed the extent of the muscle activities. GS (2-microM) caused spinal seizures in the rats after the SCI, and GS (6-microM) produced seizures in the uninjured anesthetized rats. Denatured GS (70 degrees C, 1 hour) also produced spinal seizures, although higher concentrations were required. We suggest that GS may be directly blocking the release of GABA, or the receptors, in the spinal cord.
Animals ; Electromyography ; Female ; *Glutamate-Ammonia Ligase/administration & dosage ; Injections, Spinal ; Male ; Rats ; Rats, Long-Evans ; Seizures/*chemically induced/physiopathology ; Spinal Cord Diseases/*chemically induced/physiopathology

Animals ; Flunarizine ; pharmacology ; Hippocampus ; drug effects ; physiopathology ; Male ; Neurons ; drug effects ; physiology ; Penicillins ; adverse effects ; Rats ; Rats, Wistar ; Seizures ; chemically induced ; physiopathology

This study was undertaken to observe the effect of acute stress on seizure occurrence in chronic period of epileptic model rats. Lithium-pilocarpine (LiCl-PILO)-induced epileptic rat model was constructed. At the spontaneous recurrent seizure period, acute stress stimulations such as cat's urine and foot electrical shock were applied to observe the behavioral changes and seizure occurrence. The results showed that after the cat's urine stimulation, the self-directed behaviors of the epileptic model rats decreased significantly, while the risk assessment behaviors increased significantly. The seizure occurrence, however, was not observed during the 45 min after the stimulation. Applying electrical foot shocks also did not evoke seizures in epileptic model rats. On the contrast, intra-peritoneal injection of low dose of pentylenetetrazole (PTZ, 30 mg/kg) evoked seizure more efficiently, and the duration of seizure activity was extensively prolonged in epileptic model rats than that of control rats. Taken together, these results indicate that although applying stress stimulations such as cat's urine and electrical foot shock cause several behavioral changes, they are not severe enough to evoke seizure in epileptic model rats.
Animals ; Behavior, Animal ; Disease Models, Animal ; Epilepsy ; chemically induced ; physiopathology ; Lithium Chloride ; adverse effects ; Pentylenetetrazole ; adverse effects ; Pilocarpine ; adverse effects ; Rats ; Seizures ; physiopathology ; Stress, Physiological

OBJECTIVE: To determine the correlation of phosphorylated ribosomal S6 protein (P-S6) content in blood and brain tissue in mice and rats with seizure. METHODS: Seizure models were induced by intraperitoric injection of kainic acid (KA) in C57BL/mice and SD rats. Flow cytometry was used to detect the content of P-S6 in blood; Western blot was used to detect the expression of P-S6 in brain tissues. The correlation between P-S6 expression in blood and in brain tissue was examine by Pearson analysis, and the correlation between P-S6 expression in blood and the severity of seizure was also observed. RESULTS: Western blotting analysis showed that the expression of P-S6 was significantly increased in peripheral blood and brain tissue in mice 1 h after KA-induced seizure,and the expression levels increased to (1.49±0.45) times (<0.05) and (2.55±0.66) times ( <0.01) of the control group, respectively. Flow cytometry showed that the positive percentage and average fluorescence intensity of P-S6 in the blood of mice increased significantly 1 h after KA-induced seizures (<0.01), which was consistent with the expression of P-S6 in brain tissue (=0.8474, <0.01). Flow cytometry showed that the average fluorescence intensity of P-S6 in blood increased from 14.89±9.75 to 52.35±21.72 (<0.01) in rats with seizure, which was consistent with the change of P-S6 in brain tissue (=0.9385, <0.01). Rats with higher levels of seizure were of higher levels of P-S6 in peripheral blood. CONCLUSIONS Consistent correlation of P-S6 expression is demonstrated in peripheral blood and in brain tissue after KA-induced seizure, suggesting that the expression of P-S6 in blood can accurately reflect the changes of mTOR signaling pathway in brain tissue.
Animals ; Brain ; drug effects ; physiopathology ; Gene Expression Regulation ; drug effects ; Kainic Acid ; Mice ; Mice, Inbred C57BL ; Phosphorylation ; Rats ; Rats, Sprague-Dawley ; Seizures ; blood ; chemically induced ; physiopathology

OBJECTIVETo investigate the modulatory effects of morphine on the susceptibility to pentylenetetrazole-induced seizures, and the involvement of endogenous histamine in this process.

METHODSBoth the wild-type (WT) mice and histidine decarboxylase (a key enzyme for histamine biosynthesis) deficient (HDC-KO) mice were subcutaneously injected with different doses of morphine, and 1 hour later the pentylenetetrazole solution (1.5 %) was infused into the tail vein at a constant rate of 0.3 ml/min. The minimal dose of pentylenetetrazole (mg/kg) needed to induce myoclonic jerks and clonus convulsion was recorded as the thresholds of seizures.

RESULTIn WT mice, morphine dose-dependently decreased the thresholds of both myoclonic jerks and clonus convulsion. In HDC-KO mice, morphine at 10 mg/kg only significantly decreased the threshold of myoclonic jerks from (38.6 +/-2.9)mg/kg to (32.5 +/-0.7)mg/kg, but had no significant effect on the threshold of clonus convulsion [from (51.8 +/-2.1)mg/kg to (47.6 +/-1.2)mg/kg]. In addition, the value of decreased myoclonic jerks (15.8 +/-1.4)% and clonus convulsion (8.3 +/-0.9)% thresholds were much lower in HDC-KO mice than in WT mice [(26.1 +/-2.5)% and (20.8 +/-2.4)%, respectively].

CONCLUSIONMorphine can decrease the thresholds of pentylenetetrazole in induction of seizure, and the endogenous histamine may be involved in this process.

Animals ; Disease Susceptibility ; chemically induced ; metabolism ; physiopathology ; Dose-Response Relationship, Drug ; Histamine ; metabolism ; physiology ; Histidine Decarboxylase ; genetics ; metabolism ; Male ; Mice ; Mice, Knockout ; Morphine ; pharmacology ; Myoclonus ; chemically induced ; metabolism ; physiopathology ; Narcotics ; pharmacology ; Pentylenetetrazole ; Random Allocation ; Seizures ; chemically induced ; genetics ; physiopathology ; Sensory Thresholds ; drug effects

OBJECTIVESeizures occur more frequently in the neonatal period than at any other time in life. A controversy which has been debated for the recent years is whether recurrent neonatal seizures can lead to long-term adverse consequences or are simply a reflection of underlying brain dysfunction and are not intrinsically harmful. Despite numerous clinical observations showed that seizures may be detrimental to the developing brain, the pathological mechanism has not yet been completely understood. The goal of this study was to investigate what effect was induced by recurrent seizures in neonatal rats on dentate granule cell neurogenesis.

METHODSSixty-four neonatal Wistar rats were randomly divided into seizure group (n = 40) and control group (n = 24). The rats of seizure group were subjected to three times of pilocarpine injections intraperitonealy at postnatal day 1 (P1), 4 (P4) and 7 (P7). Neonatal rats of the control group were given saline injection (i.p.) at the same time points. The rat were sacrificed separately at the next four time points: immediately after the third seizure (P7), the fourth day after the seizure (P11), the fourteenth day (P21) and the forty fifth day (P52), corresponding control group rats were killed accordingly. The rats in both seizure and control groups were given bromodeoxyuridine (BrdU) injection 36 hours before sacrifice to indicate newly generated cells. Brain tissue sections were prepared and subjected to Nissl staining for neuronal loss, by BrdU labeling for cell proliferation and by BrdU + NF200 (neurofilament 200) double labeling for the identification of the newly formed cells.

RESULTSThe numbers of BrdU-labeled cells were age-dependent in the control group, decreased with age, and their morphorlogy and distribution changed (P < 0.01). BrdU-labeled cells decreased significantly in the seizure group compared with the matched controls at P7 and P11 (P < 0.01), while at P21 there was no significant difficence between the two groups. On the contrary, BrdU-labeled cells increased significantly in the seizure group compared with the matched controls at P52 (P < 0.01). Most BrdU-labeled cells in granular cell layer (GCL) of both seizure group and control group coexpressed NF200.

CONCLUSIONRecurrent seizures during neonatal period lead to decreased neurogenesis at the early stage after the third seizure, and at later time points increase of neurogenesis. Most of newly generated cells can differentiate into neurons.

Age Factors ; Animals ; Animals, Newborn ; Bromodeoxyuridine ; Hippocampus ; physiology ; Neurogenesis ; physiology ; Pilocarpine ; Random Allocation ; Rats ; Rats, Wistar ; Recurrence ; Seizures ; chemically induced ; physiopathology ; Staining and Labeling ; methods

The purpose of the present study was to explore the relation between the modulation of cerebral blood flow and the latency of hyperbaric oxygen-induced convulsion. There were two parts in this study. First, the effect of acetazolamide on the latency of hyperbaric oxygen-induced convulsion was observed. 32 Sprague-Dawley (SD) rats were randomly divided into four groups: the acetazolamide 200, 20, 2 mg/kg body weight and normal saline (NS) group. The animals were given intraperitoneally acetazolamide or NS, respectively, before being exposed to the pressure of 6 ATA (absolute atmosphere) of pure oxygen. The time from exposure to the onset of seizure (clonic-tonic convulsion) was recorded for each animal according to behavioral observation. Second, the changes in maleic dialdehyde (MDA) and the activity of glutathione peroxidase (GSH-PX) were measured after acetazolamide treatment. 40 SD rats were randomly divided into five groups: NS group, 6 min with NS group, 6 min with acetazolamide group, 16 min with NS group, and 16 min with acetazolamide group. The dose of acetazolamide was 20 mg/kg body weight. After injection of NS or acetazolamide, the animals were subjected to the pressure of 6 ATA of pure oxygen in respect to its time course group. The rats were decapitated and the cortex, hippocampus, and striatum of brains were dissected and homogenized. The content of MDA and the activity of GSH-PX in these tissues were determined. We found that (1) there was a significant difference in the latency of hyperbaric oxygen-induced convulsion between the acetazolamide 200 mg/kg group and the NS control group, as well as between the acetazolamide 20 mg/kg group and the NS control group (P<0.01), whereas there was no significant difference between the NS group and the acetazolamide 2 mg/kg weight group (P>0.05). The latency of these groups were listed as follows: 9.78+/-1.94 min for 200 mg/kg body weight group, 10.92+/-1.68 min for 20 mg/kg body weight group, 24.32+/-4.33 min for 2 mg/kg body weight group and 22.02+/-4.32 min for NS control group. (2) there was no significant difference between all groups in the activity of GSH-PX, though it varied with the oxidation levels. In the cortex and hippocampus, the activity of GSH-PX boosted up at first, but with the progress of the oxidation it was impaired. In the striatum, the activity of GSH-PX increased stepwise with the aggravation of the oxidation. The MDA content in the cortex increased significantly in the group of 6 min with acetazolamide (P<0.01), as well as the group of 16 min with acetazolamide group both in cortex and hippocampus (P<0.01, P<0.05). The MDA content of all groups is correlated with the dose of acetazolamide and the exposure time. These results suggest that acetazolamide which dilates the brain arteriolar obviously shortens the latency of hyperbaric oxygen-induced convulsion, and that acetazolamide dilates the vessels and increases the supply of the oxygen breaking into the brain tissues and aggravates the oxidation. The hyperbaric oxygen-induced convulsion correlates closely with the oxidation injury.
Acetazolamide ; pharmacology ; Animals ; Brain ; pathology ; Hyperbaric Oxygenation ; Male ; Oxidative Stress ; Oxygen ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Seizures ; chemically induced ; physiopathology ; Vasodilator Agents ; pharmacology

OBJECTIVEData accumulated over the past years have led to widespread recognition that neurogenesis, the emergence of new neurons, persists in the hippocampal dentate gyrus of the adult mammalian brain, and can be increased by seizures in multiple models. Also, aberrant reorganization of dentate granule cell axons, the mossy fiber sprouting, occurs in human temporal lobe epilepsy and rodent epilepsy models. However a number of studies suggest that the immature brain is less vulnerable to the morphologic alteration of hippocampus after seizures. The goal of this study was to determine whether the seizures can induce dentate granule cell neurogenesis and mossy fiber sprouting in the immature rat.

METHODSSeizures was elicited by unilateral microinfusion of kainic acid (KA, 1 micro g) into the amygdula at postnatal day 15 (P15). Rat pups were given bromodeoxyuridine (BrdU) intraperitoneally on day 5 after KA administration and killed 7 d or 21 d later. The brains were processed for BrdU mitotic labeling combined with double-label immunohistochemistry using neuron-specific, early differentiation marker TuJ1 (betaIII tubulin) or granule-specific marker CaBP (calcium-binding protein calbindin D28k) as well as glia-specific marker GFAP (glial fibrillary acidic protein). Mossy fiber sprouting in intermolecular layer and CA3 subfield was assessed in Timm-stained sections both 1 month and 3 months after KA administration by using a rating scale and density measurement.

RESULTSThe dentate BrdU-immunoreactive cells of the KA-treated rats increased significantly compared with those of control rats on day 7 and 21 after BrdU administration (7 d: 244 +/- 15 vs. 190 +/- 10; 21 d: 218 +/- 19 vs. 133 +/- 12, P < 0.05). Approximately 80.2% and 78.7% of BrdU-labeled cells coexpressed TuJ1 in KA-treated rats and control rats on day 7 after BrdU respectively (P > 0.05). On 21 d after BrdU, 60.2% and 58.2% of dentate BrdU-labeled cells coexpressed GaBP in KA-treated rats and control rats respectively (P > 0.05). GFAP colocalized with 3%-5% dentate BrdU-labeled cells in the rats of both groups on day 7 and 21 after BrdU. It was also demonstrated that status epilepticus at P15 did not result in any detectable mossy fiber sprouting within the hippocampus both 1 month and 3 months after KA administration.

CONCLUSIONSKA induced seizures can increase granule cell neurogenesis in the immature rat. Most of newly appeared cells migrate from subgranular proliferation zone (SGZ) into granule cell layer, the hilus as well as the molecular layer, and there they can differentiate into granule neurons. These observations also indicate that there is an early developmental resistance to seizure-induced mossy fiber sprouting in the immature brain.

Animals ; Cell Differentiation ; Cell Proliferation ; Dentate Gyrus ; cytology ; physiopathology ; Disease Models, Animal ; Excitatory Amino Acid Agonists ; adverse effects ; Kainic Acid ; adverse effects ; Mossy Fibers, Hippocampal ; physiopathology ; Neurogenesis ; physiology ; Rats ; Seizures ; chemically induced ; physiopathology

OBJECTIVEOur previous work suggested that sensitivity of hippocampal neurons is changed in process of epileptic activities, and closely parallel to the dynamic characteristic of epileptic activity of the neurons. This study investigated the sensitivity of epileptic brain to vagal nerve stimulation (VNS) in epileptic process.

METHODSEpileptic model was evoked by penicillin. Left vagal nerves were stimulated to inhibit the seizures induced by penicillin. The electrocorticography (ECoG) and electromyography (EMG) were recorded to analyze inhibiting effect of VNS in epileptic process.

RESULTSIt was found that VNS could inhibit the seizures caused by penicillin, and the inhibiting effect of VNS to seizures increased as the vagal nerve stimulating time prolonged. It was also found that the inhibiting effect of VNS to seizures decreased in epileptic process.

CONCLUSIONThe results suggested that the sensitivity of epileptic brain to VNS was different in epileptic process. The inhibiting effect of VNS to seizure decreased as the development of seizures.

Action Potentials ; physiology ; Animals ; Electric Stimulation ; Electroencephalography ; Electromyography ; Epilepsy ; chemically induced ; prevention & control ; Frontal Lobe ; physiopathology ; Male ; Motor Cortex ; drug effects ; physiopathology ; Neural Inhibition ; physiology ; Nonlinear Dynamics ; Parietal Lobe ; physiopathology ; Penicillins ; Rats ; Rats, Sprague-Dawley ; Seizures ; chemically induced ; prevention & control ; Vagus Nerve ; physiology

To investigate the effect of crocin on the progression and generalized seizure of temporal lobe epilepsy in mice.Hippocampus rapid kindling model was established in C57BL/6J mice. The effects of crocin on seizure stage, afterdischarge duration (ADD), number of stimulation in each stage and final state, the incidence of generalized seizure (GS), average seizure stage and ADD were observed.Crocin (20 mg/kg) significantly retarded behavioral seizure stages (<0.05) and shortened cumulative ADD (<0.01) during hippocampus rapid kindling acquisition in mice compared with vehicle group. Meanwhile, number of stimulations in stage 1-2 was significantly increased (<0.05) and the incidence of fully kindled animals was significantly decreased (<0.01). However, 10 or 50 mg/kg crocin showed no significant effect on the above indexes (all>0.05). Crocin (100 or 200 mg/kg) significantly decreased the incidence of GS (all<0.01) and reduced average seizure stages (all<0.01) in fully-kindled mice compared with vehicle group; Fifty mg/kg crocin only reduced average seizure stages (<0.05).Low-dose crocin can retard the progression in hippocampus rapid kindling acquisition in mice, while high-dose crocin relieves the GS in fully-kindled mice, which suggests that crocin may be a potential anti-epileptic compound.
Animals ; Anticonvulsants ; pharmacology ; Carotenoids ; pharmacology ; therapeutic use ; Dose-Response Relationship, Drug ; Electric Stimulation ; Epilepsy, Temporal Lobe ; chemically induced ; drug therapy ; Hippocampus ; drug effects ; physiopathology ; Kindling, Neurologic ; drug effects ; physiology ; Mice ; Mice, Inbred C57BL ; Seizures ; classification ; drug therapy