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1.
不同发展阶段的习得性长时程突触增强对新学习的影响 总被引:1,自引:0,他引:1
在慢性实验条件下观察到大鼠由学习训练所产生的海马CA_3区习得性长时程突触增强,它的不同发展阶段对新学习任务的习得有不同的作用:(1)在它的形成阶段及巩固阶段对新学习均有易化作用,虽然两个阶段突触效应增强的程度都处于相同的高水平,但后者的易化作用相对要大些,提示这两个发展阶段突触的可塑性变化是有差异的;还有,新学习任务的训练并没有引起突触效应的进一步增强,表明突触效应的长时程增强有“饱和”现象。(2)在它消退后,对新学习任务的习得没有影响。上述结果提示学习的组织形式不同,可从突触机制上影响学习的效果,并进一步证明习得性长时程突触增强是学习和记忆的神经基础。 相似文献
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海马齿状回突触效应的习得性长时程增强 总被引:8,自引:0,他引:8
本实验应用慢性埋植电极技术以电生理学给合行为学的方法,观察大白鼠海马齿状回在以视觉和味觉信号为条件信号的条件反应的建立、巩固和消退过程中突触效应的变化。结果表明在明暗辨别学习中出现突触效应长时程增强(LTD),其保持时间的长短与巩固性训练的多少呈正相关,LTP消退,习得行为也消退。对照实验证明它并非测试本身所引起,提示此习得性LTP与学习和记忆活动是密切相关的。但在建立条件性味觉厌恶中,却无LTP出现。这就从突触水平上进一步证明我们提出的海马在不同感觉信息的记忆活动中其作用是不同的及海马不仅在记忆的形成,而且在其保持和再现中也有重要作用的观点。 相似文献
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习得性长时程突触增强在学习各阶段中的变化 总被引:4,自引:1,他引:3
应用慢性埋植技术以电生理学结合行为学的方法,观察大鼠海马CA_3区锥体细胞在明暗辨别反应的建立、巩固、消退和再建立的连续过程中,突触效应的变化规律。结果:在条件反应的建立过程中,产生突触效应长时程增强(LTP);在条件反应的巩固过程中,LTP继续保持;在条件反应的消退过程中,LTP消退;在条件反应的再建立过程中,再次产生LTP。而这种习得性LTP的发展和变化超前于习得性行为的产生和改变。这是在同一动物身上实现了以往多项工作的连贯性观察,表明在动物学习活动的连贯的迅速改变的各个阶段,海马CA_3区有相应的对条件性行为有制约作用的习得性LTP的发生和改变。它为论证习得性LTP可能是学习和记忆的神经基础之一,提供了新的有力证据。 相似文献
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本研究探查大鼠分辨学习中海马齿状回(DG)和CA_3区突触效应的变化及其相互关系,以探讨同一学习中海马不同区突触可塑性变化的特点及其相互关系,进一步论证习得性长时程增强(LTP)是学习和记忆的神经基础。发现:(1)穿通纤维的单个刺激可在DG和CA_3同时记录到潜伏期、峰值和波形各异的群体峰电位(PS);在一定范围内PS随刺激强度的增加而增大,但DG的PS增大程度比CA_3的小;据此,检测刺激的强度应选在该范围内。(2)随着行为训练,DG和CA_3区的突触传递同时产生LTP,两者LTP的发展是显著正相关关系(P<0.01),PS峰值同时达到最高水平,且先于分辨反应达学会标准,首次表明在同一学习中大鼠海马的DG和CA_3的习得性LTP是同时产生的。本研究还表明,在慢性实验下同时记录和分析行为学习中海马两个区突触效应的变化及其相互关系是可能的,这给从神经环路角度研究学习和记忆的突触机制提供了有用的模型。 相似文献
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神经颗粒素(Neurogranin,NG)是一种新发现的脑特异性蛋白质。它分布在多个脑区,特别在对学习记忆至关重要的脑区海马。该物质自发现以来,许多学者对其生物学作用,特别是与学习记忆的关系进行了大量的研究,并取得了相当的进展。研究表明NG参与了在学习记忆功能中起核心作用的脑内几种蛋白信号传导途径、长时程增强(Long-term potentiation, LTP)和长时程抑制(Long-term depression, LTD)等突触可塑性机制。NG基因敲除后,动物出现学习记忆能力缺陷。因而它可能涉及学习记忆的形成和巩固 相似文献
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对海马突触传递长时程增强效应的研究已取得许多重要进展,其中发现很多蛋白激酶的参与,近年来由于转基因和基因打靶等分子生物学实验手术的应用,PKC,CaMKⅡ和PKA等多种蛋白激酶的同功酶或其不同亚单位在LTP中的作用已在相应的变异小鼠上得到直接证实,文章概述了这些目前被认为参与了海马突触传递长时程增强过程的蛋白激酶及其作用。 相似文献
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Almaguer-Melian W Rojas-Reyes Y Alvare A Rosillo JC Frey JU Bergado JA 《Neurobiology of learning and memory》2005,83(1):72-78
Growing evidence suggests that processes of synaptic plasticity, such as long-term potentiation (LTP) occurring in one synaptic population, can be modulated by consolidating afferents from other brain structures. We have previously shown that an early-LTP lasting less than 4 h (E-LTP) in the dentate gyrus can be prolonged by stimulating the basolateral amygdala, the septum or the locus coeruleus within a specific time window. Pharmacological experiments have suggested that noradregeneric (NE) and/or cholinergic systems might be involved in these effects. We have therefore investigated whether the direct intraventricular application of agonists for NE- or muscarinic receptors is able to modulate synaptic plasticity. E-LTP was induced at the dentate gyrus of freely moving rats using a mild tetanization protocol that induces only an E-LTP. NE or oxotremorine (OXO) were applied icv 10 min after the tetanus. Results show that low doses of NE (1.5 and 5 nM) effectively prolong LTP. A higher dose (50 nM) was not effective. None of the OXO doses employed (5, 25, and 50 nM) showed similar effects. These results stress the importance of transmitter-specific modulatory influences on the time course of synaptic plasticity, in particular NE whose application mimics the reinforcing effect of directly stimulating limbic structures on LTP. 相似文献
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Disconnection analysis of CA3 and DG in mediating encoding but not retrieval in a spatial maze learning task
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The dentate gyrus (DG) subregion of the hippocampus has been shown to be involved in encoding but not retrieval in a spatial maze task (modified Hebb-Williams maze). The first experiment in this study examined whether a lesion to the CA3 would contribute to a similar encoding deficit. A DG group was included in order to replicate previous results. Relative to controls, animals receiving CA3 lesions were impaired in encoding, not retrieval, on the modified Hebb-Williams maze--similar to a group that received DG lesions. This suggests the possibility that CA3 and DG are working together to mediate encoding processes. The second experiment in this study was designed to test the interaction between CA3 and DG using a disconnection paradigm. Animals with contralateral lesions (CA3 lesioned in one hemisphere, DG lesioned in the other hemisphere) showed a significant disruption effect on encoding, but not retrieval, when compared with animals with ipsilateral lesions (CA3 and DG lesioned in the same hemisphere, leaving the other hemisphere intact). This suggests an interaction between CA3 and DG in supporting encoding but not retrieval processes in a spatial maze learning task. 相似文献
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The mitogen-activated protein kinase (MAPK) pathway is an evolutionarily conserved signaling cascade involved in both synaptic plasticity and memory formation. Following our recent observation of translation regulation in taste learning and memory, we aimed to study MAPK-dependent translation regulation in long-term potentiation (LTP), a cellular model of learning and memory. We first analyzed ERK1/2 activation following high-frequency stimulation in the dentate gyrus (DG) of the hippocampus, in vivo. Surprisingly, our results indicate that the activation of both ERK2 and p38 was strongly affected by the order in which the DG was dissected out, but not by other experimental parameters. Specifically, we found that ERK2 and p38 phosphorylation were higher in the second than in the first dentate gyrus removed (up to 30s apart). Similar results were obtained when we isolated the 'order of removal' factor by looking at MAPK phosphorylation in rats that had not undergone any electrophysiological procedure (i.e., na?ve rats). This effect is so robust, that it probably masks the effect of LTP induction on MAPK activation. We suggest that some of the correlations found between MAPK activation and brain function in vivo may be due to cellular stress. In addition, careful experimental procedures and control are indispensable in the analysis of biochemical correlations of post-translation modifications that subserve both general neuronal function and synaptic plasticity. 相似文献
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The effectiveness of tetraethylammonium (TEA) and high-frequency stimulation (HFS) in inducing long-term synaptic modification is compared in CA1 and dentate gyrus (DG) in vitro. High-frequency stimulation induces long-term potentiation (LTP) at synapses of both perforant path-DG granule cell and Schaffer collateral-CA1 pyramidal cell pathways. By contrast, TEA (25 mM) induces long-term depression in DG while inducing LTP in CA1. The mechanisms underlying the differential effect of TEA in CA1 and DG were investigated. It was observed that T-type voltage-dependent calcium channel (VDCC) blocker, Ni2+ (50 microM), partially blocked TEA-induced LTP in CA1. A complete blockade of the TEA-induced LTP occurred when Ni2+ was applied together with the NMDA receptor antagonist, D-APV. The L-type VDCC blocker, nifidipine (20 microM), had no effect on CA1 TEA-induced LTP. In DG of the same slice, TEA actually induced long-term depression (LTD) instead of LTP, an effect that was blocked by D-APV. Neither T-type nor L-type VDCC blockade could prevent this LTD. When the calcium concentration in the perfusion medium was increased, TEA induced a weak LTP in DG that was blocked by Ni2+. During exposure to TEA, the magnitude of field EPSPs was increased in both CA1 and DG, but the increase was substantially greater in CA1. Tetraethylammonium application also was associated with a large, late EPSP component in CA1 that persisted even after severing the connections between CA3 and CA1. All of the TEA effects in CA1, however, were dramatically reduced by Ni2+. The results of this study indicate that TEA indirectly acts via both T-type VDCCs and NMDA receptors in CA1 and, as a consequence, induces LTP. By contrast, TEA indirectly acts via only NMDA receptors in DG and results in LTD. The results raise the possibility of a major synaptic difference in the density and/or distribution of T-type VDCCs and NMDA receptors in CA1 and DG of the rat hippocampus. 相似文献
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NT-3 facilitates hippocampal plasticity and learning and memory by regulating neurogenesis 总被引:5,自引:0,他引:5
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Shimazu K Zhao M Sakata K Akbarian S Bates B Jaenisch R Lu B 《Learning & memory (Cold Spring Harbor, N.Y.)》2006,13(3):307-315
In the adult brain, the expression of NT-3 is largely confined to the hippocampal dentate gyrus (DG), an area exhibiting significant neurogenesis. Using a conditional mutant line in which the NT-3 gene is deleted in the brain, we investigated the role of NT-3 in adult neurogenesis, hippocampal plasticity, and memory. Bromodeoxyuridine (BrdU)-labeling experiments demonstrated that differentiation, rather than proliferation, of the neuronal precursor cells (NPCs) was significantly impaired in DG lacking NT-3. Triple labeling for BrdU, the neuronal marker NeuN, and the glial marker GFAP indicated that NT-3 affects the number of newly differentiated neurons, but not glia, in DG. Field recordings revealed a selective impairment in long-term potentiation (LTP) in the lateral, but not medial perforant path-granule neuron synapses. In parallel, the NT-3 mutant mice exhibited deficits in spatial memory tasks. In addition to identifying a novel role for NT-3 in adult NPC differentiation in vivo, our study provides a potential link between neurogenesis, dentate LTP, and spatial memory. 相似文献
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Segal SK Stark SM Kattan D Stark CE Yassa MA 《Neurobiology of learning and memory》2012,97(4):465-469
Pattern separation, the process by which similar experiences can be stored as distinct memories, has been ascribed to the dentate gyrus (DG) of the hippocampus. The DG is the target of noradrenergic modulation directly and indirectly via the basolateral amygdala. We tested the hypothesis that noradrenergic activation (tested using salivary alpha-amylase) potentiates DG function, enhancing pattern separation, by showing participants fearful stimuli in a pre-training task and then testing their capacity for pattern separation in a later test. Consistent with our hypothesis, we found that increased levels of salivary alpha-amylase were positively correlated with enhanced pattern separation performance even after accounting for general enhancements in recognition. 相似文献
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Dong Song Xiaping Xie Zhuo Wang Theodore W. Berger 《Neurobiology of learning and memory》2001,76(3):375
The effectiveness of tetraethylammonium (TEA) and high-frequency stimulation (HFS) in inducing long-term synaptic modification is compared in CA1 and dentate gyrus (DG) in vitro. High-frequency stimulation induces long-term potentiation (LTP) at synapses of both perforant path-DG granule cell and Schaffer collateral-CA1 pyramidal cell pathways. By contrast, TEA (25 mM) induces long-term depression in DG while inducing LTP in CA1. The mechanisms underlying the differential effect of TEA in CA1 and DG were investigated. It was observed that T-type voltage-dependent calcium channel (VDCC) blocker, Ni2+ (50 μM), partially blocked TEA-induced LTP in CA1. A complete blockade of the TEA-induced LTP occurred when Ni2+ was applied together with the NMDA receptor antagonist, D-APV. The L-type VDCC blocker, nifidipine (20 μM), had no effect on CA1 TEA-induced LTP. In DG of the same slice, TEA actually induced long-term depression (LTD) instead of LTP, an effect that was blocked by D-APV. Neither T-type nor L-type VDCC blockade could prevent this LTD. When the calcium concentration in the perfusion medium was increased, TEA induced a weak LTP in DG that was blocked by Ni2+. During exposure to TEA, the magnitude of field EPSPs was increased in both CA1 and DG, but the increase was substantially greater in CA1. Tetraethylammonium application also was associated with a large, late EPSP component in CA1 that persisted even after severing the connections between CA3 and CA1. All of the TEA effects in CA1, however, were dramatically reduced by Ni2+. The results of this study indicate that TEA indirectly acts via both T-type VDCCs and NMDA receptors in CA1 and, as a consequence, induces LTP. By contrast, TEA indirectly acts via only NMDA receptors in DG and results in LTD. The results raise the possibility of a major synaptic difference in the density and/or distribution of T-type VDCCs and NMDA receptors in CA1 and DG of the rat hippocampus. 相似文献
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Bergado JA Frey S López J Almaguer-Melian W Frey JU 《Neurobiology of learning and memory》2007,88(3):331-341
Transient long-term potentiation (E-LTP) can be transformed into a long-lasting LTP (L-LTP) in the dentate gyrus (DG) by behavioral stimuli with high motivational content. Previous research from our group has identified several brain structures, such as the basolateral amygdala (BLA), the locus coeruleus (LC), the medial septum (MS) and transmitters as noradrenaline (NA) and acetylcholine (ACh) that are involved in these processes. Here we have investigated the functional interplay among brain structures and systems which result in the conversion of a E-LTP into a L-LTP (reinforcement) by stimulation of the BLA (BLA-R). We used topical application of specific drugs into DG, and other targets, while following the time course of LTP induced by stimulation of the perforant pathway (PP) to study their specific contribution to BLA-R. One injection cannula, a recording electrode in the DG and stimulating electrodes in the PP and the BLA were stereotactically implanted one week before electrophysiological experiments. Topical application of atropine or propranolol into the DG blocked BLA-R in both cases, but the effect of propranolol occurred earlier, suggesting a role of NA within the DG during an intermediate stage of LTP maintenance. The injection of lidocaine into the LC abolished BLA-R indicating that the LC is part of the functional neural reinforcing system. The effect on the LC is mediated by cholinergic afferents because application of atropine into the LC produced the same effect. Injection of lidocaine inactivating the MS also abolished BLA-R. This effect was mediated by noradrenergic afferents (probably from the LC) because the application of propranolol into the MS prevented BLA-R. These findings suggest a functional loop for BLA-R involving cholinergic afferents to the LC, a noradrenergic projection from the LC to the DG and the MS, and finally, the cholinergic projection from the MS to the DG. 相似文献