Amygdaloid kindling in glutamate transporter (GLAST) knockout mice

PURPOSE: Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system. We previously reported abnormal glutamate release during seizures after kindling. GLAST and GLT-1 are astrocytic glutamate transporters, highly concentrated in the cerebellum and the telencephalon, respectively. We have investigated whether stages of amygdala kindling in knockout (KO) mice deficient in GLAST are the same as those of wild mice. METHODS: Electrodes were implanted into the basolateral amygdala, bilaterally, in C57BL/6J mice and GLAST KO mice under anesthesia. Once-daily stimulation was applied on one side through these electrodes, and bilateral EEG recordings were obtained. RESULTS: The behavioral manifestations of kindling in mice were (a) arrest of behavior, (b) head nodding, (c) forelimb clonus, (d) bilateral forelimb clonus with rearing, (e) tonic generalized convulsion with elevation of tail and falling with generalized tonic convulsion (GTC). Results of kindling: (a) Mutant mice kindled more slowly than wild-type mice (more stimulations were required to reach each stage in mutants); (b) after kindling was completed, additional stimulations induced shorter afterdischarges (ADs) in mutants than in wild-type mice; (c) Interictal epileptic spikes were more frequent in the mutants than in the wild-type mice, both in the stimulated amygdala and in the contralateral amygdala. CONCLUSIONS: GLAST KO mice, which are missing one type of astrocytic glutamate transporter, demonstrate kindling of an epileptic focus. However, the kindling is significantly slower in the GLAST mutant than in wild-type mice. These findings suggest that glutamate transport by the astrocytic GLAST transporter may have a role in normal epileptogenesis.     

An early decrease in cell proliferation after pentylenetetrazole-induced seizures

There are increasing data on the influence of seizures on neurogenesis in the adult brain. However, data on cell proliferation and differentiation during the early stages of kindling are scarce. We have used pentylenetetrazole (PTZ)-induced kindling to investigate the temporal profile of cytogenesis in the germinative zones of adult rat brain. For comparison, we also used a single PTZ-induced generalized tonic–clonic seizure. During kindling development, the density of 5-bromo-2'-deoxyuridine-positive cells demonstrated similar changes in all germinative zones: a dramatic decrease after the first subthreshold PTZ injection, and a gradual increase to the control level following repeated PTZ administration. On the contrary, a single PTZ-induced generalized tonic–clonic seizure was followed by an increase in the number of proliferating cells in both the dentate gyrus and the subventricular zone. These results may indicate the existence of global mechanisms affecting cellular proliferation in adult brain during seizures. Different temporal profiles of neuronal damage and proliferation changes suggest that neurodegeneration is unlikely to be a global proliferation-regulating factor. The data may contribute to better understanding of the initial phase of kindling development and epileptogenesis.     

Hyperthermic seizures and hyperthermia in immature rats modify the subsequent pentylenetetrazole-induced seizures

It has been described that febrile seizures during infancy increase risk of subsequent non-febrile seizures during the adulthood. However, latency period between febrile seizure and the onset of the first spontaneous seizure has not been evaluated. The present study was designed to investigate the susceptibility to subsequent seizures in immature rats that had experienced early-life hyperthermic seizures and before they achieved the adult age. The results were compared with those induced by hyperthermia alone. Pentylenetetrazol (PTZ) was applied 24 h or 20 days after hyperthermic seizures or hyperthermia were induced in 10-day-old rats by a regulated stream of moderately heated air. One day after hyperthermic seizures or hyperthermia, animals demonstrated enhanced latency to the PTZ-induced myoclonic (88% and 53%, respectively), clonic (60% and 60%, respectively) and tonic seizures (233% and 659%, respectively). The incidence of myoclonic and clonic seizures was similar to that in control group (100%). However, hyperthermic seizures reduced (50%) the incidence of tonic seizures. Twenty days after hyperthermic seizures there was an augmented latency to tonic seizures (123%) and reduced incidence for all the PTZ-induced seizures (71% myoclonic; 71% clonic seizures; 57% tonic seizures) when compared with control group (100%). In contrast, hyperthermia enhanced only the latency to myoclonic (133%) and clonic seizures (659%). Our data indicate that hyperthermic seizures or hyperthermia induces a protective effect against PTZ-induced seizures during a latency period. A possible involvement of γ-aminobutyric acid (GABA) system is discussed.     

Prolonged exposure to lead lowers the threshold of pentylenetetrazole-induced seizures in rats

PURPOSE: The aim of this work was to study the effects of prolonged exposure to lead on the threshold of experimental seizures induced by pentylenetetrazole (PTZ). METHODS: The 120 Wistar male rats were allocated randomly into four groups; (A) controls, and lead-treatment groups (B, C, and D) that received lead acetate in the drinking water for a period of 30 days at concentrations of 250, 500, and 1,000 ppm, respectively. After exposure, a trial of PTZ-induced seizures was conducted in all groups, and blood contents of lead were determined by atomic absorption spectrophotometry. RESULTS: Blood lead contents increased in a dose-dependent manner. Time elapsed to develop the first myoclonic jerk and the tonic-clonic seizure was less in all lead-exposed groups than in controls. This effect was greater in the groups administered 500 and 1,000 ppm of lead. The required doses of PTZ to induce myoclonic jerks and tonic-clonic seizures were lower in lead-exposed rats than in controls. CONCLUSIONS: We found a reduction in the threshold for seizures in rats whose blood contents of lead were similar to those of humans from some areas of urban centers with high levels of air pollution.     

Isobolographic and subthreshold analysis of interactions among felbamate and four conventional antiepileptic drugs in pentylenetetrazole-induced seizures in mice

PURPOSE: Despite possibility of idiosyncratic reaction development, felbamate (FBM) is recommended in Lennox-Gastaut syndrome and partial refractory epilepsy. The aim of this study was to evaluate the profile of interactions between FBM and four conventional antiepileptic drugs (AEDs): clonazepam (CZP), ethosuximide (ESM), phenobarbital (PB), and valproate (VPA), in pentylenetetrazole (PTZ)-induced convulsions in mice, a model of myoclonic seizures in humans. METHODS: Data obtained from PTZ-evoked seizures were compared by use of two basic procedures, the subthreshold method and isobolographic analysis. Results of the chimney test (evaluating motor coordination) also were elaborated isobolographically. Thus it was possible to determine both median toxic dose (TD50) and protective index (PI) for each drug combination. RESULTS: FBM reduced the clonic seizure activity [with an ED50 of 9.7 mg/kg; TD50, 439.1 mg/kg; and PI, 45.3]. FBM at the dose of 10 mg/kg, but not 7.5 mg/kg, significantly reduced PTZ-induced convulsions in mice. In the subthreshold method, FBM (7.5 mg/kg) did not affect the protective activity of conventional AEDs used in the study. However, when applied at 10 mg/kg, it enhanced the protective activity of PB and ESM, but not that of VPA or CZP. The nature of these interactions could not be precisely estimated with this method. The exact profile of drug interactions was determined with the use of isobolography. In terms of seizure inhibition, antagonism was found between FBM and VPA applied at the fixed-dose ratio of 3:1. Synergy was detected between FBM and PB (1:3). Combinations of FBM with VPA (1:3, 1:1), PB (1:1, 3:1), and ESM or CZP (1:3, 1:1, 3:1) led to additive interactions. As regards motor impairment, the combinations of FBM with VPA (1:3) or CZP (1:1, 3:1) were synergistic. Remaining combinations exhibited pure additivity. Pharmacokinetic events may influence FBM/ESM and FBM/CZP interactions, because FBM lowered the brain concentration of ESM and increased that of CZP. CONCLUSIONS: The profitable benefit index was found only for the combination of FBM with PB (1:3). Conversely, the combinations of FBM with either VPA (1:3) or CZP (1:1, 3:1) do not seem promising for the therapy of refractory myoclonic convulsions. Isobolographic analysis provides more reliable clues to be considered by the clinicians willing to introduce AED combinations for the therapy of epilepsy.     

Sub-chronic treatment with pioglitazone exerts anti-convulsant effects in pentylenetetrazole-induced seizures of mice: The role of nitric oxide

Objectives

Pioglitazone delayed the development of seizure responses and shortened the duration of convulsion of genetically epileptic EL mice. The anti-epileptic effect of pioglitazone was attributed partly through the reduction of inflammatory responses and preventing apoptosis. There are also some reports showing that some pioglitazone effects mediate through nitric oxide. In this study we evaluated sub-chronic pioglitazone effects in two models of intravenous and intraperitoneal pentylenetetrazole-induced clonic seizures in mice.

Materials and methods

Different doses of pioglitazone were administered orally for 10 days in different groups of male mice. l-NAME, a non selective inhibitor of nitric oxide synthase, aminoguanidine, a selective inhibitor of inducible nitric oxide synthase, or l-arginine, a nitric oxide donor, was administered acutely or sub-chronically to evaluate the role of nitric oxide in pioglitazone anti-seizure effects.

Results

We demonstrated that sub-chronic administration of pioglitazone exerted anti-convulsant effects in both models of intravenous and intraperitoneal pentylenetetrazole. Acute and sub-chronic pre-administration of l-NAME prevented the anti-convulsant effect of pioglitazone in both models of intravenous and intraperitoneal pentylenetetrazole. Aminoguanidine did not alter the anti-convulsant effect of pioglitazone in two models of intravenous and intraperitoneal pentylenetetrazole. Both acute and sub-chronic pre-treatment of mice with l-arginine exerted anti-convulsant effect when administered with a non effective dose of pioglitazone in intraperitoneal method. In intravenous method, acute administration of l-arginine with a non-effective dose of pioglitazone enhanced the seizure clonic latency.

Conclusion

Taken together, sub-chronic pioglitazone treatment exerts anti-convulsant effects in intravenous and intraperitoneal pentylenetetrazole-induced seizures of mice probably through induction of constitutive nitric oxide synthase.     

Molsidomine enhances the protective activity of valproate against pentylenetetrazole-induced seizures in mice

Summary. Molsidomine (25 mg kg⁻¹), a donor of nitric oxide, commonly used in the treatment of coronary artery disease, enhanced the protective activity of valproate against the clonic phase of pentylenetetrazole-induced seizures in mice, significantly reducing the ED₅₀ of valproate from 123.5 to 78 mg kg⁻¹. Molsidomine was found to be ineffective with respect to the protective action of clonazepam, ethosuximide and phenobarbital. Alone, molsidomine in a dose of 25 mg kg⁻¹ was ineffective in this model of seizures. Since N^G-nitro-L-arginine, an inhibitor of nitric oxide synthase, failed to reverse the effect of molsidomine on valproate, an involvement of nitric oxide in the mechanism of the anticonvulsive efficacy of valproate does not seem to be probable. Molsidomine (25 mg kg⁻¹) significantly elevated the free plasma level of valproate from 33.8 to 46.2 μg ml⁻¹. Therefore, we conclude that the interaction of molsidomine with valproate is at the pharmacokinetic level. The combination of valproate with molsidomine appears beneficial because is free from adverse effects, in terms of motor impairment and long-term memory deficit. Our results suggest that the dosage of valproate in patients with coronary artery disease treated with molsidomine should be decreased. It would allow us to reduce adverse effects of valproate. Received September 4, 2001; accepted November 5, 2001     

Immunization with the glutamate receptor-derived peptide GluR3B induces neuronal death and reactive gliosis, but confers partial protection from pentylenetetrazole-induced seizures

Do autoantibodies (Ab's) against glutamate/AMPA receptor subtype 3 affect the severity of seizures? Rats immunized with the GluR3B-peptide (amino acids (aa) 372-395) or with the control GluR3A-peptide (aa 245-274) produced the respective anti-GluR3B and anti-GluR3A Ab's (both types of Ab's found in some epilepsy patients). The GluR3B-immunized rats exhibited neuronal death and reactive gliosis in the brain, but not overt spontaneous seizures. Surprisingly, in response to the chemoconvulsant pentylenetetrazole, the GluR3B-immunized rats displayed fewer jerks, a lower percentage of generalized seizures, and a lower overall seizure-severity score than GluR3A-immunized, scrambled GluR3B-immunized or non-immunized control rats. These findings, combined with the previously demonstrated ability of anti-GluR3B Ab's to bind, activate, and kill neurons and glia, suggest that if these Ab's are present in the brain they may cause neuronal death, which by itself may be pro-epileptic, but they may also decrease the excitability of seizure-related neural circuits, thereby conferring partial protection from seizures induced by other exogenously applied epileptogenic stimuli. The present results could have clinical implications for epilepsy.     

海藻氨酸致癎大鼠中海马谷氨酸转运体功能的研究

目的　研究海藻氨酸(KA)致疒间大鼠海马谷氨酸转运体(GluTs)功能的变化,进一步探讨GluTs 参与癫疒间发生的机制。方法　60只Wistar大鼠随机分为KA组和对照组,每组再按点燃后4h、24h、48h、5 d、7d不同时点随机分为5个亚组,分别测定不同时点海马突触颗粒和海马组织切片对3H L 谷氨酸的摄取 量,观察GluTs于点燃后不同时点的活性。结果　KA组点燃后海马突触颗粒GluTs功能在各时点均降低(均 P<0.01),海马组织切片GluTs功能在点燃后初期上升而后下降(P<0.05)。结论　KA可引起海马GluTs 功能的变化,其可能与癫疒间的发生及易感性的形成有关。     

Administration of lithium and magnesium chloride inhibited tolerance to the anticonvulsant effect of morphine on pentylenetetrazole-induced seizures in mice

Although morphine has an anticonvulsant effect in several animal models of seizures, its potential clinical application in epilepsy may be hindered by its adverse effects like opioid tolerance. The present study evaluated the development of tolerance to the anticonvulsant effect of morphine in a model of clonic seizures induced with pentylenetetrazole (PTZ) in male Swiss mice. We also examined whether administration of either lithium chloride (LiCl) or magnesium chloride (MgCl(2)) was able to prevent the probable tolerance. Our data demonstrated that the anticonvulsant effect of a potent dose of morphine (1mg/kg) was abolished in chronic morphine-treated mice (mice administered the same dose of morphine intraperitoneally twice daily for 4 days). Four days of pretreatment with low and noneffective doses of MgCl(2) (2 and 5mg/kg) and LiCl (5mg/kg) inhibited the development of tolerance to the anticonvulsant effect of morphine (1mg/kg, ip). Moreover, a single acute injection of the aforementioned agents at the same doses reversed the expression of tolerance to the anticonvulsant effects of morphine (1mg/kg, ip). Chronic 17-day treatment with LiCl (600 mg/L in drinking water) also inhibited the development of tolerance to the anticonvulsant effects of 1mg/kg morphine. These results demonstrate that the anticonvulsant effect of morphine is subject to tolerance after repeated administration. Both development and expression of tolerance are inhibited by either LiCl or MgCl(2). As both LiCl and MgCl(2) can modulate the function of N-methyl-d-aspartate (NMDA) receptors, we discuss how NMDA receptor functioning might be involved in the effects of LiCl and MgCl(2) on the development of tolerance to the anticonvulsant effect of morphine.     

Investigation of the effects of tianeptine and fluoxetine on pentylenetetrazole-induced seizures in rats

The effects of tianeptine and fluoxetine on pentylenetetrazole (PTZ)-induced seizures in rats were investigated. Female Wistar rats (172-278 g) were used in the study. Tianeptine (1.25, 2.5, 5, 10 and 20 mg/kg) and fluoxetine (2.5, 5, 10 and 20 mg/kg) or saline were injected to rats intraperitoneally 30 min before PTZ (50 mg/kg) injections. Immediately after PTZ administrations, latency and intensity of the PTZ-induced seizures was recorded and scored, respectively. Fluoxetine (2.5-20 mg/kg) did not produce any significant difference in latency and intensity of the PTZ-induced seizures. Although tianeptine (1.25-20 mg/kg) also did not affect the latency time, it produced significant attenuations in the intensity of the seizures. Tianeptine did not cause any significant change in the locomotor activity of the rats. The results of this preliminary study suggest that tianeptine but not fluoxetine has some inhibitory effects on PTZ-induced seizures in rats.     

Seizure generation: The role of nodes and networks

The longstanding dichotomy between the concepts of "focal" and "primary generalized" epilepsy has become increasingly blurred, raising fundamental questions about the nature of ictal onset in localized brain regions versus large-scale brain networks. We hypothesize that whether an EEG discharge appears focal or generalized is driven by the pattern of connections in brain networks, irrespective of the presence of focal brain abnormality. Using a computational model of a simple "brain" consisting of four regions and the connections between them, we explored the effects of altering connectivity structure versus the effects of introducing an "abnormal" brain region, and the interactions between these factors. Computer simulations demonstrated that electroencephalography (EEG) discharges representing either generalized or focal seizures arose purely as a consequence of subtle changes in network structure, without the requirement for any localized pathologic brain region. Furthermore we found that introducing a pathologic region gave rise to focal, secondary generalized, or primary generalized seizures depending on the network structure. Counterintuitively, we found that decreasing connectivity between regions of the brain increased the frequency of seizure-like activity. Our findings may enlighten current controversies surrounding the concepts of focal and generalized epilepsy, and help to explain recent observations in genetic animal models and human epilepsies, where loss of white matter pathways was associated with the occurrence of seizures.     

Long-term reduction of benzodiazepine receptor density in the rat cerebellum by acute seizures and kindling and its recovery 6 months later by a pentylenetetrazole challenge

Seizures induced by an acute pentylenetetrazole (50 mg/kg) injection were accompanied by a long-term (at 1-48 h, but not on day 7) decrease in the density (B(max)) of [3H]-diazepam binding to benzodiazepine receptors in rat cerebellar cortex with no change in affinity (K(d)). Kindling for 24 days by daily administrations of pentylenetetrazole (20 mg/kg) led to the same decrease in benzodiazepine receptor density (at 1-48 h, but not on day 7) as that observed after a single dose of pentylenetetrazole (50 mg/kg). This suggests a common mechanism for both acute and kindling-induced seizures, dependent on the long-term receptor changes. The increased susceptibility to seizures persisted for 6 months after the termination of kindling, with BDZ receptor density in cerebellar cortex reduced almost by half. In age-matched controls, an acute dose of PTZ (30 mg/kg) induced seizures and decrease in both B(max) and K(d) of [3H]-diazepam binding. In kindled rats, at 6 months post-kindling, the same dose of PTZ (30 mg/kg) restored the benzodiazepine receptor density to the level found 6 months before, at the time of termination of kindling. Also, the severity of seizures was enhanced in the kindled rats. The results are discussed in terms of a balance of inhibitory and excitatory processes, in which the reduced BDZ receptor density at 6 months post-kindling may represent a compensatory reaction to outbalance some alterations in excitatory systems that have been reported to be induced by kindling.     

Pharmacodynamic and/or pharmacokinetic characteristics of interactions between loreclezole and four conventional antiepileptic drugs in pentylenetetrazole-induced seizures in mice: an isobolographic analysis

Isobolographic analysis was used to characterize the interactions between loreclezole (LCZ) and clonazepam (CZP), ethosuximide (ETS), phenobarbital (PB), and valproate (VPA) in suppressing pentylenetetrazole (PTZ)-induced seizures and in producing acute neurotoxic adverse effects in the chimney test in mice so as to identify optimum combinations. Moreover, protective indices (PIs) and benefit indices (BIs) were calculated so that a ranking in relation to advantageous combination could be established. Any pharmacokinetic contribution was ascertained by measurement of brain antiepileptic drug (AED) concentrations. All AED combinations comprising LCZ and CZP, ETS, PB, and VPA (at the fixed ratios of 1:3, 1:1, and 3:1) were additive in their seizure suppression. However, these interactions were complicated by changes in brain AED concentrations consequent to pharmacokinetic interactions. Thus, LCZ significantly increased total brain ETS concentrations (VPA, CZP, and PB concentrations were unaffected), and ETS decreased, and VPA increased, total brain LCZ concentrations. Only combinations of LCZ with CZP and PB were completely free of any pharmacokinetic interaction. Furthermore, in the chimney test, isobolographic analysis showed that the combination of LCZ and CZP, at the fixed ratio of 1:1, was supra-additive (synergistic, P<0.05), whereas LCZ and ETS at fixed ratios of 1:3 and 1:1 were subadditive (antagonistic, P<0.05). The remaining combinations of LCZ with CZP (1:3 and 3:1), ETS (3:1), PB (all fixed ratios of 1:3, 1:1, and 3:1), and VPA (at the fixed ratios of 1:3, 1:1, and 3:1) barely displayed additivity. In conclusion, BI, which is a measure of the margin of safety and tolerability of drugs in combination and comprises anticonvulsant and neurotoxic measures, was favorable for only one combination (LCZ and ETS at a fixed ratio of 1:3) with a value of 1.39. In contrast, LCZ and CZP constitute an unfavorable combination (BI=0.61-1.01). The combinations of LCZ with PB or VPA do not offer any advantage as assessed by the parameters (BI range: 0.75-0.91) used in this study. However, these conclusions are confounded by the fact that LCZ is associated with significant pharmacokinetic interactions.     

Region‐specific deletions of the glutamate transporter GLT1 differentially affect seizure activity and neurodegeneration in mice

Glial glutamate transporter GLT1 plays a key role in the maintenance of extracellular glutamate homeostasis. Recent human genetic studies have suggested that de novo mutations in GLT1 (EAAT2) cause early‐onset epilepsy with multiple seizure types. Consistent with these findings, global GLT1 null mice show lethal spontaneous seizures. The consequences of GLT1 dysfunction vary between different brain regions, suggesting that the role of GLT1 dysfunction in epilepsy may also vary with brain regions. In this study, we generated region‐specific GLT1 knockout mice by crossing floxed‐GLT1 mice with mice that express the Cre recombinase in a particular domain of the ventricular zone. Selective deletion of GLT1 in the diencephalon, brainstem and spinal cord is sufficient to reproduce the phenotypes (excess mortality, decreased body weight, and lethal spontaneous seizure) of the global GLT1 null mice. By contrast, dorsal forebrain‐specific GLT1 knockout mice showed nonlethal complex seizures including myoclonic jerks, hyperkinetic running, spasm and clonic convulsion via the activation of NMDA receptors during a limited period from P12 to P14 and selective neuronal death in cortical layer II/III and the hippocampus. Thus, GLT1 dysfunction in the dorsal forebrain is involved in the pathogenesis of infantile epilepsy and GLT1 in the diencephalon, brainstem and spinal cord may play a critical role in preventing seizure‐induced sudden death.     

瘤周谷氨酸、天门冬氨酸水平与胶质瘤继发性 癫痫的相关性

目的 探讨瘤周谷氨酸、天门冬氨酸浓度与胶质瘤继发性癫痫的相关性。方法 收集2012年5月2015年1月手术治疗的胶质瘤瘤周组织标本47例,其中继发癫痫28例（癫痫组）,未继发癫痫19例（无癫痫组）。利用全自动L-8900高速氨基酸分析仪检测标本的谷氨酸、天门冬氨酸水平。结果 癫痫组瘤周谷氨酸、天冬氨酸含量分别为（117.54±8.63）mg/100 g、（70.79±4.70）mg/100 g,均明显高于无癫痫组[分别为（91.76±7.36）mg/100 g、（59.70±5.50）mg/100 g;P <0.05]。瘤周谷氨酸、天冬氨酸含量与癫痫均具有显著相关性,相关系数分别为0.96、0.95（P <0.05）。结论 瘤周组织谷氨酸、天门冬氨酸浓度增加可能与胶质瘤继发性癫痫有关。     

依达拉奉对癫痫大鼠脑内谷氨酸的影响

目的 探讨依达拉奉对戊四氮致痫大鼠脑中谷氨酸的影响.方法 30只成年SD大鼠随机分为对照组、癫痫组和治疗组,癫痫组和治疗组大鼠腹腔注射戊四氮60mg/kg,诱导癫痫发作.治疗组于注射戊四氮之前1h经腹腔注射依达拉奉30mg,并观察1h.然后处死大鼠取脑,应用柱前衍生HPLC-荧光法测定大鼠脑皮质谷氨酸(Glu)的含量.结果 治疗组痫性发作潜伏期、平均痫性发作等级及脑内谷氨酸含量与癫痫组相比差异均有显著性(P<0.01).结论 依达拉奉可以通过拮抗氧自由基并抑制谷氨酸的释放,在癫痫发作中发挥保护作用.     

Amygdala-kindled seizures increase the expression of corticotropin-releasing factor (CRF) and CRF-binding protein in GABAergic interneurons of the dentate hilus

Kindling, a model of temporal lobe epilepsy, induces a number of neuropeptides including corticotropin-releasing factor (CRF). CRF itself can produce limbic seizures which resemble kindling in some aspects. However, tolerance to the convulsant effects of CRF develops rapidly. Hypothetically, this could be explained should seizures also induce the CRF-binding protein (CRF-BP), which has been postulated to restrict the actions of CRF. Therefore, in the present study, we used in situ hybridization to examine the effects of amygdala-kindled seizures on the mRNA levels of CRF and CRF-BP. Kindled seizures markedly elevated CRF and CRF-BP in the dentate gyrus of rats. CRF and CRF-BP were induced almost exclusively in GABAergic interneurons of the dentate hilus. The CRF and CRF-BP interneurons also expressed neuropeptide Y but not cholecystokinin. CRF appeared to have an excitatory role in the dentate gyrus as it decreased the afterhyperpolarization of dentate granule neurons. These results suggest that CRF may contribute to the development of amygdala kindling. However, the compensatory induction of CRF-BP may serve to limit the excitatory effects of CRF in the dentate gyrus.     

Glial glutamate transporter expression patterns in brains from multiple mammalian species

It is generally assumed that rodent brains can be used as representative models of neurochemical function in other species, such as humans. We have compared the distributions of the predominant glial glutamate transporters in rodents, rabbits, cats, pigs, monkeys, and humans. We identify similarities but also significant differences between species. GLT-1v, which is abundantly expressed by rodent astrocytes, is expressed only in a rare subset of astrocytes of cats and humans, and appears to be absent from brains of rabbits and monkeys. Conversely, in the pig brain GLT-1v is expressed only by oligodendrocytes. GLAST and GLT-1alpha expression differed significantly between species; while rodents and rabbits exhibited uniform expression patterns in cortex, higher species, including cats, pigs, monkeys, and humans, exhibited heterogeneities in cortical and hippocampal expression. Patches devoid of labeling intermingling with patches of strong labeling were evident in areas such as temporal cortex and frontal cortex. In addition, we noted that in human motor cortex, there were inconsistencies in labeling for the C-terminal of GLT-1alpha and common domains of GLT-1, suggesting that the C-terminal region may be missing or that an unidentified splicing is present in many human astrocytes. Collectively our data suggest that assumptions as to the roles of glutamate transporters in any species may need to be tested empirically.     

戊四氮点燃大鼠中海马谷氨酸转运体的作用研究

目的 研究点燃形成过程中和点燃后谷氨酸转运体的变化,进一步探讨慢性癫痫的点燃机制。方法 将78只雄性成年Wistar 大鼠随机分为对照组（I组）和戊四氮（PTZ）组（Ⅱ组）。Ⅱ组腹腔注射阈下剂量的PTZ（35mg/kg),每日1次,直至达到点燃标准;Ⅰ组腹腔注射等量生理盐水。采用逆转录聚合酶链式反应（RT－PCR）方法检测海马区谷氨酸转运体－1（GLT－1）mRNA和兴奋性氨基酸载体－1（EAAC1）mRNA的表达。结果 GLT－1mRNA的表达在0h、48h时显著升高,随后下降;EAAC1mRNA的表达呈上升趋势。点燃后第60d时,基本恢复至对照组水平。结论 海马区GLT－1的下降和EAAC1的升高可能与癫痫敏感性的形成与维持有关。