戊四氮致痫对大鼠海马星形胶质细胞的影响

目的　探讨戊四氮（ＰＴＺ）致痫对大鼠海马星形胶质细胞的影响。方法　应用免疫组织化学方法观察ＰＴＺ致痫后大鼠海马内胶原纤维酸性蛋白（ＧＦＡＰ）变化的特点,同时观察了不同强度的痫性发作与ＧＦＡＰ改变的关系。结果　ＧＦＡＰ改变于ＰＴＺ致痫后１２ｈ 开始,２４ｈ 达到高峰,７２ｈ 已开始回落,并且痫性发作的强度与ＧＦＡＰ改变有一定的联系。结论　癫痫与星形细胞之间确有一定联系。     

青霉素对体外培养鼠脑γ－氨基丁酸能神经元及胶质细胞的影响

以免疫细胞化学方法观察了分离培养４天、１０天鼠大脑皮层、海马ＧＡＢＡ能神经元以及ＧＦＡＰ免疫反应阳性星形胶质细胞对大剂量致痫剂青霉素（Ｐｅｎｉｃｉｌｉｎ，ＰＥＮ）的反应。结果大剂量ＰＥＮ（３００μ／ｍｌ培养液）可引起培养海马及皮层γ－氨基丁酸（γ－ａｍｉｎｏｂｕｔｙｒｉｃａｃｉｄ，ＧＡＢＡ）能神经元数目明显减少，星形胶质细胞显著增生，且尤以海马胶质细胞增生明显。提示：（１）脑内尤其海马区星形胶质细胞增生与癫痫发生、发展有一定的关系；（２）传统致痫剂ＰＥＮ可能是通过抑制ＧＡＢＡ能神经元功能、刺激星形胶质细胞增生，从而导致癫痫发作     

不同类型癫痫患者脑脊液中γ-氨基丁酸含量分析及抗癫痫药物对其的影响

本文采用高效液相色谱紫外检测３７例不同类型的特发性癫痫患者脑脊液（ＣＳＦ）中γ－氨基丁酸（ＧＡＢＡ）含量，特发性强直－阵挛性发作组ＣＳＦ中ＧＡＢＡ水平明显低于单纯部分性发作组和单纯部分性发作继发强直－阵挛性发作组（Ｐ＜０．０５）。服用抗癫痫药物组ＣＳＦ中ＧＡＢＡ含量明显高于未用药组（Ｐ＜０．００１），疾病组ＣＳＦ中ＧＡＢＡ含量明显低于正常对照组（Ｐ＜０．００１），初步表明特发性癫痫的发病机制与中枢神经系统内抑制性氨基酸递质水平过低有关。     

不同类型癫痫患者脑脊液中γ—氨基丁酸含量分析及抗癫痫…

本文采用高效液相色谱紫外检测３７例不同类型的特发性癫痫患者脑脊液中γ－氨基丁酸含量，特发性强直－阵挛性发作组ＣＳＦ中ＧＡＢＡ水平明显低于单纯部分性发作组和单纯部分性发作继发强直－阵挛性发作组（Ｐ〈０．０５），服用抗癫痫药物组ＣＳＦ中ＧＡＢＡ含量明显高于未用药组（Ｐ〈０．００１），疾病组ＣＳＦ中ＧＡＢＡ含量明显低于正常对照组（Ｐ〈．００１），初步表明特发性癫痫的发病机制与中枢神讷抑制性氨基酸递质水平     

癫痫状态大鼠海马GAD67mRNA,GABA—TmRNA表达水平的动态观察

为了研究癫痫状态下大鼠海马区ＧＡＤ６７ｍＲＮＡ、ＧＡＢＡ－ＴｍＲＮＡ的表达水平，采用马桑内酯（ｃｏｒｉａｒｉａｌａｃｔｏｎｅ，ＣＬ）侧脑室注射所致大鼠癫痫状态模型，动态观察ＣＬ致痫前后大鼠海马ＧＡＤ６７ｍＲＮＡ、ＧＡＢＡ－ＴｍＲＮＡ表达水平的变化，同时观察了动物行为学改变及脑电图变化。实验结果显示，侧脑室注射ＣＬ后约１５分钟，大鼠海马及皮质ＥＥＧ出现阵发性棘慢波及高波幅慢波；ＣＬ注射后１５～３０分钟，实验鼠均出现明显的连续发作性四肢抽动、尖叫等症状，且持续６～８小时。ＣＬ侧脑室注射后３０分钟、１小时、２小时、４小时或８小时各时限点组大鼠海马ＧＡＤ６７ｍＲＮＡ表达水平均低于正常对照组。ＣＬ注射后３０分钟组大鼠海马ＧＡＢＡ－ＴｍＲＮＡ表达水平高于正常对照组，但３０分钟后各时限组ＧＡＢＡ－ＴｍＲＮＡ表达水平与正常对照组比较增加不明显。提示ＣＬ所致癫痫持续状态的后期，大鼠海马ＧＡＤ６７ｍＲＮＡ、ＧＡＢＡ－ＴｍＲＮＡ表达信号的减弱，可能与致痫因素及癫痫持续后期合并的缺血、缺氧性脑损害致使海马区ＧＡＤ、ＧＨＢＡ－Ｔ免疫反应阳性细胞死亡有关。     

实验性癫痫大鼠脑组织中ATP酶含量变化的研究

本文采用戊四氮（ＰＴＺ）诱发大鼠癫痫模型，用化学比色法测定了癫痫大鼠额叶皮层及海马中Ｎａ＋－Ｋ＋－、Ｃａ２＋－、Ｍｇ２＋－ＡＴＰａｓｅ含量的变化。结果发现：癫痫大鼠脑组织中额叶皮层及海马的诸ＡＴＰａｓｅ含量显著降低。提示额叶皮层及海马中ＡＴＰａｓｅ下降与癫痫发作有关     

实验性癫痫大鼠乳头体中P物质含量变化的研究

本文采用戊四氮（ＰＴＺ）诱发大鼠癫痫模型，动态观察了癫痫大鼠脑组织中乳头体、海马及颞叶皮层Ｐ（ＳＰ）含量的变化。结果发现，癫痫后大鼠乳头体ＳＰ含量显著下降，１击后恢复至正常水平，海马及颞叶皮层的ＳＰ含量未发现明显变化。提示乳头体中ＳＰ与癫痫发作有关。     

青霉素对体外培养鼠脑γ—氨基丁酸能神经元及胶质细胞的影响

经免疫细胞化学方法观察了分离培养４天，、１０天鼠大脑皮层、海马ＧＡＢＡ能神经元以及ＧＦＡＰ免疫反应阳性星形胶质细胞对大剂量致痫剂青霉素的反应。结果大剂量ＰＥＮ可引起培养海马及皮层γ－氨基丁酸能神经元数目明显减少，星形胶质细胞显著增生，且尤以海马胶质细胞增生明显。提示：（１）脑内尤其海马区星形胶南细胞增生与癫痫发生，发展有一定的关系。（２）传统致痫剂ＰＥＮ可能是通过抑制ＧＡＢＡ能神经元功能、刺激星形     

孕激素对癫痫大鼠大脑皮层,海马FOS蛋白表达的影响

本实验采用流式细胞免疫荧光技术对马桑内酯（ＣＬ）致痫及给予孕激素后再致痫大鼠大脑皮层、海马细胞ＦＯＳ表达进行定量检测。结果显示：ＣＬ致痫组大鼠皮层、海马ＦＯＳ表达的荧光指数（ＦＩ）和阳性细胞数较正常对照组明显增高（Ｐ＜０．０１）；给予孕酮（Ｐ）后再致痫组皮层、海马ＦＯＳ表达较单纯ＣＬ致痫组减少（Ｐ＜０．０１，Ｐ＜０．０５）。     

AVP_(4-8)增加海马组织内NGF mRNA和蛋白含量

本文采用了Ｎｏｒｔｈｅｒｎ杂交和ＥＬＩＳＡ法，观察了神经肽ＡＶＰ４－８对大鼠海马组织中神经生长因子（ＮＧＦ）ｍＲＮＡ和蛋白水平的影响，结果显示：给大鼠皮下注射ＡＶＰ４－８１２ｈ后，海马组织中ＮＧＦｍＲＮＡ的水平明显高于生理盐水对照组。而给大鼠皮下注射精氨酸加压素（ＡＶＰ）和催产素（ＯＴ）对ＮＧＦｍＲＮＡ的水平均无显著影响。另外，用ＡＶＰ４－８孵育离体大鼠海马组织切片，能使ＮＧＦ蛋白表达量升高，且在４．５ｈ左右达到高峰。     

Dynamic changes in CA1 dendritic spines associated with ischemic tolerance

Hippocampal CA1 neurons are particularly vulnerable to 5-10 min durations of global ischemia. These cells can develop tolerance to ischemia through prior exposure to brief episodes of ischemia (ischemic preconditioning, IP). Dendritic spines are implicated in various forms of neuroplasticity including memory and recovery of function. Here we characterized the changes in hippocampal CA1 dendritic spines during the development of ischemic tolerance and the subsequent postischemic recovery period. Gerbils received 5 min, bilateral carotid artery occlusions preceded by two 1.5 min occlusions each of which were 24 h apart (tolerance groups). Spine densities were calculated from CA1 apical and basilar dendrites in tolerant animals that survived 3 (IP3), 10 (IP10) or 30 (IP30) days as well as sham-operated animals and those that received only the two preconditioning episodes (PO). Habituation to a novel open-field was assessed 3, 7, 10 and 30 days after ischemia to gauge CA1 functional integrity. Dendritic spines were quantified from Golgi-Cox stained sections of the CA1 subfield. IP10, IP30 and PO animals had significantly higher CA1 basilar and apical spine densities than all other groups. Tolerant animals initially displayed open-field habituation impairments at a time when spine densities were reduced. Behavioral impairments gradually subsided over time in coincidence with an increase in CA1 spine densities. These findings suggest that dendritic spines may play a role in recovery of function associated with ischemic tolerance and stroke.     

Bilateral lesions of CA1 and CA2 fields of the hippocampus are sufficient to cause a severe amnesic syndrome in humans.

A patient is reported in whom a classic amnesic syndrome developed as a result of repeated episodes of cerebral ischaemia, accompanied by seizures. The amnesia was very severe for both old and newly acquired memories and the critical lesions defined by MRI were circumscribed areas confined to CA1 and CA2 fields of both hippocampi.     

Hippocampal damage following repeated brief hypotensive episodes in the rat

We examined the brain damage following repeated hypotensive episodes in the rat. Severe hypotension was induced by withdrawal of arterial blood. The MABP was maintained at about 25 mm Hg with isoelectric EEG and the shed blood was retransfused. After 1 week of recovery, histopathological changes were examined. No brain damage was observed after 1 min of isoelectric EEG. Mild neuronal damage to the hippocampal CA1 subfield was seen in some animals after two episodes of 1-min isoelectric EEG at a 1-h interval. Significant and consistent neuronal loss in the hippocampal CA1 subfield was observed after three episodes of 1-min isoelectric EEG. Scattered neuronal damage in the thalamus was additionally seen in some animals. The present study indicates that repeated brief hypotensive episodes produce brain damage depending on the number of episodes, even though no brain damage results when induced as a single insult. This animal model may reproduce hemodynamic transient ischemic attacks in humans.     

Dissociation of the IPSP and response to GABA during spreading depression-like depolarizations in hippocampal slices

We have compared the sensitivity of CA1 and CA3 hippocampal pyramidal cells, in mature and immature tissue, to spreading depression-like depolarization episodes. Using hippocampal slices from rabbit, we have found that mature and immature tissue, and CA1 and CA3 neurons, were differentially prone to depolarization episodes, depending on the method used to produce the depolarization. CA1 region was generally more sensitive than CA3. Spontaneous and stimulus-evoked depolarizations were seen more frequently in immature tissue than in mature slices, but anoxia-induced depolarizations were much more likely to occur in mature tissue. Synaptic transmission and responses to somatic gamma-aminobutyric acid (GABA) ejection were compared during anoxia-induced depolarizations in mature slices. The early component of the inhibitory postsynaptic potential (IPSP) normally had the same reversal potential as the GABA response. During anoxia-induced depolarization, both the drug response and the PSPs were lost. Synaptic transmission generally disappeared before the response to exogenous GABA application; the GABA response reappeared before synaptic function was restored. During the recovery of resting potential (RMP) following depolarization, the reversal potential of the early IPSP differed significantly from that of the GABA response; when the cell had recovered to RMP, the IPSP was depolarizing, whereas GABA application produced a 'normal' cell hyperpolarization. IPSPs and GABA-mediated responses attained their pre-depolarization form within a few minutes of RMP recovery. These observations suggest that, at least under special circumstances, the early component of the IPSP and GABA-mediated hyperpolarizations can be dissociated. Therefore, the early IPSP may be mediated by more complex mechanisms than a simple alteration in chloride conductance due to GABA-receptor interactions.     

Anti-inflammatory cytokines, TGF-β1 and IL-10, exert anti-hypoxic action and abolish posthypoxic hyperexcitability in hippocampal slice neurons: comparative aspects

The aim of this study was to investigate the comparative effects of transforming growth factor β1 (TGF-β1) and interleukin-10 (IL-10) on the repeated brief hypoxia-induced alterations in the activity of hippocampal slice CA1 pyramidal neurons. The method of field potentials measurement in CA1 region of hippocampal slices was used. The principal results of our work are summarized as follow. 1. TGF-β1 reduces the depressive effect of brief hypoxia on the population spike amplitude more effectively than IL-10. 2. During TGF-β1 exposure (in contrast to IL-10), three 3-min hypoxic episodes do not induce the rapid hypoxic preconditioning. 3. TGF-β1 and IL-10 equally abolish posthypoxic hyperexcitability induced by repeated brief episodes of hypoxia in CA1 pyramidal neurons. These findings indicated that TGF-β1 and IL-10 are able to evoke anti-hypoxic effect and abolish the development of posthypoxic hyperexcitability induced by repeated brief hypoxic episodes in hippocampal CA1 pyramidal neurons. Our results also demonstrated that TGF-β1 reduced the effectiveness of hypoxia to depress neuronal activity more effectively than IL-10. We suggest that the present findings allow to explain the certain neuroprotective mechanisms of IL-10 and TGF-beta1 in the early phase of hypoxia and indicate that a therapeutic anti-inflammatory approach using these substances can provide neuroprotection in the brain hypoxic conditions.     

The relationship between interictal and ictal paroxysms in an in vitro model of focal hippocampal epilepsy

In studies of focal epilepsy it is frequently assumed that the interictal spike is the elementary form of epileptic activity and that seizure, or ictal, episodes evolve by temporal summation and spatial expansion of interictal paroxysms. We examined this hypothesis in an in vitro model of acute focal epilepsy produced by perfusing rat hippocampal slices with solutions containing moderately elevated concentrations of K+. Some of the preparations treated in this way displayed recurring electrical seizures in the CA1 field. Each seizure episode typically evolved by a seemingly smooth progression of brief interictal bursts into sustained ictal discharge. However, exposure of preparations showing electrical seizures to blockers of synaptic transmission or to cholinergic agonists abolished interictal spiking in all hippocampal fields but did not impede the initiation of ictal episodes in area CA1. Likewise, severing the connections between areas CA3 and CA1 abolished interictal spiking in area CA1 without disrupting the initiation of seizures in this region. These data clearly show that in this model, focal seizures arise independent of interictal spikes and through different cellular mechanisms. While interictal electrogenesis requires chemical synaptic excitation, ictal episodes can be initiated and maintained by nonsynaptic neuronal interactions.     

Ischemic preconditioning in 18- to 20-month-old gerbils: long-term survival with functional outcome measures.

BACKGROUND AND PURPOSE: In young animals, ischemic preconditioning protects CA1 hippocampal neurons against global ischemia. However, cerebral ischemia occurs most frequently in individuals aged >/=65 years. This study examined the protection provided by ischemic preconditioning in a population of aged (18- to 20-month-old) gerbils. METHODS: One group of animals was exposed to two 1.5-minute episodes of global ischemia separated by 24 hours and followed 72 hours later by a 5-minute occlusion of both carotid arteries. A second group was given 2 episodes of preconditioning only. Two other groups were exposed to 5 minutes of ischemia or sham surgery. The animals survived 10, 30, or 60 days. Functional and histological assessments were used to determine the extent of protection. RESULTS: Ten days after ischemia there was >80% protection of CA1 neurons in ischemic preconditioned animals compared with 6% in ischemic gerbils. Nevertheless, these preconditioned animals were impaired in open-field tests of habituation. In addition, CA1 dendritic field potentials were smaller in amplitude compared with those in sham animals. While there was a complete loss of staining for CA1 microtubule-associated protein-2 in ischemic animals, staining in ischemic preconditioned animals was normal. This suggests that dendritic abnormalities per se were not responsible for the observed functional deficits. CA1 cell survival declined to approximately 75% of sham values (P<0.05) at 60 days after ischemia. CONCLUSIONS: Ischemic preconditioning provided substantial neuroprotection in aged gerbils. Nonetheless, the striking dissociation between histological and functional protection provided by ischemic preconditioning in aged animals emphasizes the need to use functional end points and long-term survival when assessing neuroprotection. Although functional recovery was evident with increasing survival time, CA1 cell death continued, thereby raising the possibility that the level of neuroprotection attained was not permanent.     

Cooperativity among afferents for the induction of long-term potentiation in the CA1 region of the hippocampus

Long-term potentiation of synaptic responses in the hippocampus is a unique form of physiological plasticity which can be induced by brief episodes of repetitive afferent activity and which can persist for days or months. The present study describes cooperative (or associative) interactions among afferents to the stratum radiatum of CA1 for the induction and maintenance of this phenomenon. A greater degree of long-term potentiation was obtained when adjacent afferents to the stratum radiatum were co-actively conditioned, as compared to that observed with activation of a single pathway alone. This cooperativity was not the result of increased postsynaptic discharge during conditioning, as shown by the absence of greater long-term potentiation following orthodromic and antidromic co-activation of the postsynaptic CA1 pyramidal cells.     

Propagation of specific network patterns through the mouse hippocampus

Network oscillations bind neurons into transient assemblies with coherent activity, enabling temporal coding. In the mammalian hippocampus, spatial relationships are represented by sequences of action potentials of place cells. Such patterns are established during memory acquisition and are re-played during sharp wave-ripple complexes in CA1 in subsequent sleep episodes. These events originate in CA3 and travel towards CA1 and downstream cortical areas. It is unclear, however, whether specific sequences of ripple-associated firing are solely defined within the CA1 network or whether these patterns are directly entrained by preceding activities of neurons within CA3. Using a model of sharp wave-ripple oscillations (SPW-R) in mouse hippocampal slices we analyzed the propagation of these signals between CA3 and CA1. We found tight coupling between high-frequency network activity in CA3 and CA1. Propagation of ripples through the hippocampal loop maintained precise temporal relationships at the network and cellular level, as indicated by coupling of field potentials, multiunit and single cell activity between major portions of CA3 and CA1. Moreover, SPW-R-like activity in CA1 could be elicited by electrical stimulation within area CA3 while antidromic activation of CA1 failed to induce organized high-frequency oscillations. Our data show that the specificity of neuronal assemblies is maintained with cell-to-cell precision while SPW-R propagate along the hippocampal loop.     

Developmental regulation of gene expression and astrocytic processes may explain selective hippocampal vulnerability

The hippocampus plays a central role in the brain network that is essential for memory function. Paradoxically, the hippocampus is also the brain structure that is most sensitive to hypoxic‐ischemic episodes. Here, we show that the expression of genes associated with glycolysis and glutamate metabolism in astrocytes and the coverage of excitatory synapses by astrocytic processes undergo significant decreases in the CA1 field of the monkey hippocampus during postnatal development. Given the established role of astrocytes in the regulation of glutamate concentration in the synaptic cleft, our findings suggest that a developmental decrease in astrocytic processes could underlie the selective vulnerability of CA1 during hypoxic‐ischemic episodes in adulthood, its decreased susceptibility to febrile seizures with age, as well as contribute to the emergence of selective, adultlike memory function. © 2009 Wiley‐Liss, Inc.