シナプス可塑性 Synaptic Plasticity
P1-2-1 アセチルコリン作用によるSTDPに対する抑制性細胞の効果 Contribution of interneurons to cholinergically regulated STDP ○杉崎えり子1, 福島康弘2, 塚田稔3, 相原威1,3 ○Eriko Sugisaki1, Yasuhiro Fukushima2, Minoru Tsukada3, Takeshi Aihara1,3 玉川大学工学部1, 川崎医療福祉大学2, 玉川大学脳科学研究所3 Tamagawa University of Engineering, Tokyo1, Kawasaki University of medical welfare, Kurashiki2, Tamagawa University Brain Science Institute, Tokyo3 Spike timing-dependent plasticity (STDP) is one of the synaptic plasticity induced by more physiological manner of information processing. The direction and extent of STDP are decided by relative timing of pre- and post-synaptic activation on pyramidal cells in CA1 region of hippocampus. Interneurons co-exist with pyramidal cells in CA1, and some of them are known as feed-forward and feed-back interneurons playing an important role on regulating synaptic plasticity. Meanwhile, cholinergic inputs are projected from medial septum to CA1, and acetylcholine (ACh) is released from those terminals. It is considered that the cholinergic inputs are related to attention. In addition, it is known that ACh receptors, muscarinic (mAChR) and nicotinic (nAChR), are distributed on pyramidal cells and highly on interneurons. In order to clarify the effect of ACh on STDP, STDP protocol was applied with eserine, cholinesterase inhibitor, to activate mAChR and nAChR not only on pyramidal cells but also on interneurons. As the result, synaptic plasticity was facilitated depending on the concentration of eserine. To identify which receptors are sensitively contributing to the STDP, atropine and mecamylamine, mAChR and nAChR antagonist respectively, were applied. Activation of pyramidal cells and interneurons, STDP was increased by atopine and decreased by mecamylamine. These results suggest that, synaptic plasticity is regulated depending on the amount of ACh. In addition, STDP regulation not only by mAChR, but also by nAChR activation may indicate that endogenous ACh is an important regulator for bottom-up information in hippocampal CA1 neurons.	P1-2-2 GluN2B発現量の調節による臨界期の操作 Manipulating critical period by regulating the synaptic GluN2B expression ○大野孝恵1, 礒脇睦美1, 磯尾紀子1, 福田諭1, 前田仁士1, 三品昌美2, 桜井正樹1 ○Takae Ohno1, Mutsumi Isowaki1, Noriko Isoo1, Satoshi Fukuda1, Hitoshi Maeda1, Masayoshi Mishina2, Masaki Sakurai1 帝京大・医・生理学1, 東京大院・薬・分子神経生物2 Dept Physiol, Teikyo Univ Sch Med, Tokyo1, Dept Mol Neurobiol & Pharmacol, Grad Sch Med, Univ Tokyo, Tokyo2 Neuronal plasticity is generally active only in young age during a short time window so called critical period, after which is closed, loss of plasticity limits major remodeling of neuronal circuits and will never be re-opened throughout life. Molecules that may alter such CNS plasticity, however, still remains poorly understood. Because GluN2B-subunit containing NMDA receptors (2B) show much longer time course with larger Ca influx than GluN2A-subunit (2A), shift of dominant NMDAR subunit from 2B to 2A during development is hypothesized to be essential for regulating this time window. In this study, using in vitro model of corticospinal projection system, co-cultured the slices of sensorimotor cortex and cervical cord, we tried to identify mechanism that closes the critical period. In order to selectively activate the corticospinal axons, we infected the cortical slices with AAV-EYFP-tagged Channelrhodopsin (ChR2) and stimulated with LED light (465 nm). 2B that is known to shift to 2A during development declined markedly toward the end of critical period in the spinal cord. In 2A knockout mice, which express 2B in high level even after the end of the critical period, showed extension of the critical period. Surprisingly, up-regulation of 2B by blocking mGluR5 using MTEP (10μM) not only elongated but also re-opened the once closed critical period in wild type mice. Partial reduction of inhibitory input by a glycine (0.2μM), which markedly enhanced Ca influx through 2B channels, also extended the critical period. Finally, the partial blockade of casein kinase 2 (CK2) by TBB (1μM) application also extended the closure of critical period by preventing the internalization of synaptic 2B. Our findings indicate that loss of 2B subunit plays an essential role in closing the critical time window and that 2B or its downstream CK2 may be the molecule that reactivate the synaptic plasticity even in more matured stage in this system.
P1-2-3 出生後のペリニューロナルネット形成の脳地図 The brain maps of perineuronal nets in various developmental stages ○松永渉1, 笹川誉世1, 西真弓1 ○Wataru Matsunaga1, Takayo Sasagawa1, Mayumi Nishi1 奈良県立医科大学　第一解剖学1 Dept of Anatomy and Cell Biology, Nara Medical University1 Perineuronal nets (PNNs) are unique extracelluer matrix that surrounds neuronal cell bodies and proximal neurites in a reticular structure. It is well known that PNNs correspond to the ending of the critical period. The critical period is an important stage that an enough amount of sensory experiences are required for the development of neural circuits. In the visual system, PNNs were formed at critical periods, and degradation of PNNs with chondroitinase ABC enables to reactivate ocular dominance plasticity in the adult visual cortex. On the other hand, PNNs show inhibitory effects on axonal growth, and it is major obstacle to treatment of neuronal injury and diseases. Recent works showed that infusion of chondroitinase ABC enables to regrow of severed axons. Therefore, PNNs become one of the most noteworthy subject, and studies of localization and functions of PNNs in various brain regions is important. However, topographical investigations of PNNs during postnatal development are insufficient. The aim of this study is to investigate the postnatal formation of PNNs in various brain regions, and we performed histochemical staining of PNNs using wisteria floribunda lectin (WFA) in the whole mice brains at different stages of postnatal day 3 (P3) to 21, 5 and 11-week-old. Our results showed that the density of WFA reactivity became higher with advancing age. However, developmental changes of WFA reactivity showed considerable regional specificities. In the cortex, appearance of WFA reactivity in the layer II/III was started from P7 in the primary motor and primary sensory regions, and from P14 in the visual cortex. The net-like or ring-shaped WFA reactivity was seen from P12. In the hypothalamus and hippocampus, first appearance of WFA reactivity was later than cortex. On the other hand, in the pons, net-like WFA reactivity was observed even at P3, and it seems to be the earliest formation of PNNs in the brain.	P1-2-4 障害を受けた後の平行線維シナプスはどのように再形成されるか The process in the regeneration of parallel fiber synapses after transection ○市川量一1, 辰巳治之1, 渡辺雅彦2 ○Ryoichi Ichikawa1, Haruyuki Tatsumi1, Masahiko Watanabe2 札幌医大・医・第一解剖1, 北海道大院・医・解剖発生2 Dept Anat, Sapporo medical Univ, Sapporo1, Dep Anat, Hokkaido Univ, Sapporo2 Cerebellar Purkinje cells (PCs) receive two kinds of excitatory input, numerous parallel fibers (PFs) and single climbing fiber (CF). While CF travels in sagittal plane, where PC dendrites extend, PFs run in a vertical direction to sagittal plane. To observe progressive change of synaptic organization on PC dendrites caused by PF damage, we made superficial incision almost parallel to sagittal plane to cerebellar cortex of wild-type mice. One day after PF transection (1 d), PFs were rare in molecular layer and extensive free spines newly emerged in the wild-type. At 7 d, presynaptic terminal enlarged with forming more synaptic contact with PC dendrite spines and almost free spine disappeared in the wild-type. At 30 d, PFs in molecular layer recovered losses and the PF varicosities increased in length density, whose synapse number decreased to be almost the same as the control. While PF synapses are regenerated, the expression amount of GluD2 persisted unaltered. These data suggest the deafferentiation caused by PF damage was compensated by the synaptic formation of survived PFs with PC dendritic spines within 7 days. Then, PF branches, which were elongated or divided, increased in molecular layer and PF synapses were reorganized in long-term. In such process, expression of GluD2 is static for the synapse formation.
P1-2-5 シナプス長期抑圧時におけるAMPA型グルタミン酸受容体の動態解析 Subtype-specific trafficking of AMPA receptors during hippocampal LTD ○藤井俊平1, 田中洋光1, 平野丈夫1 ○Shunpei Fujii1, Hiromitsu Tanaka1, Tomoo Hirano1 京都大院・理・生物物理1 Dept.Biophys., Grad. Sch. Sci., Kyoto Univ.1 Long-term potentiation (LTP) and long-term depression (LTD) at hippocampal synapses are regarded as basal mechanisms of learning and memory. AMPA-type glutamate receptors (AMPARs) show substantial mobility such as lateral diffusion, exocytosis and endocytosis in neurons, which seem to change during LTP or LTD. It has been reported that the decrease in number of AMPARs at postsynaptic membrane is involved in the expression of hippocampal LTD. However, when and how each subtype of AMPAR is removed from postsynaptic membrane remain unclear. Here, we induced formation of postsynaptic-like membrane (PSLM) on a glass surface to precisely visualize the location and movement of AMPARs using dual-color total internal reflection microscopy. Fluorescence-labeled AMPAR subunits (GluA1, GluA2 or GluA3) was expressed in cultured hippocampal neurons, and their changes during LTD induced by application of NMDA were studied. After induction of LTD, GluA2 and GluA3 decreased more than GluA1 in both PSLM and non-PSLM, but almost returned to the baseline level by 30 minutes after NMDA application. In contrast, the decrease of GluA1 after NMDA application was relatively weak, but it was sustained. We also noticed that GluA1-3 showed slower decrease in PSLM than in non-PSLM. Next, we addressed how GluA1-3 decreased after NMDA application. First, a possibility that the frequency of exocytosis decreases during LTD was examined. However, changes of exocytosis after LTD induction failed to explain the decrease of GluA1-3 signal, suggesting that LTD is primarily caused by the enhancement of endocytosis. To examine this point further, we have attempted to identify individual endocytotic event using clathrin and/or dynamin fused to fluorescent proteins. Effects of NMDA application to endocytosis will be presented.	P1-2-6 神経活動依存的Rabaptin-5の制御がLTP発現時のAMPA受容体の表面発現を調整する Synaptic activity controls a level of rabaptin-5, leading to alternate AMPA receptor surface expression in response to LTP induction stimulus ○清末和之1, 亀山仁彦2,3 ○Kazuyuki Kiyosue1, Kimihiko Kameyama2,3 産業技術総合研究所　健康工学研究部門1, 産業技術総合研究所　バイオメディカル研究部門2, 東京大学・医・超高齢社会感覚認知運動機能医学3 Health Research Institute, AIST1, Biomedical Research Institute, Tsukuba2, Dept. of Sensory-recording and Locomotive-function Science in super-aged Society, Tokyo, Japan3 The control of glutamate receptor delivery to the synapse is a mechanism that is critical for defining synaptic strength and potential of plasticity. To date, it remains unclear whether synaptic activation history controls receptor trafficking at the synapse. We previously reported that rabaptin-5, which participates in endosome function, was down-regulated by substantial synaptic activity. In addition, over-expression of rabaptin-5 promoted GluA1 surface expression at spines. We further explored the role of rabaptin-5 in metaplasticity, that he synapse's previous history of activity determines its current plasticity. Neurons in the inactive condition exhibited a drastic increase in GluA1 surface expression by LTP stimulus. On the other hand, Neurons having an adequate synaptic activty showed GluA2 increase in response to LTP stimulus. The GluA1 increases were prevented by shRNA expression of rabaptin-5. These results demonstrate that synaptic activity controls rabaptin-5 level and suggest that rabaptin-5 is a critical mediator for metaplasticity. A part of this work was supported by KAKENHI (20500304)
P1-2-7 BDNFとその前駆体分子の作用による対照的な長期シナプス可塑性 Two opposite forms of long-lasting synaptic plasticity explained by the effects of BDNF and its precursor ○櫻木繁雄1, 冨永-吉野恵子1, 小倉明彦1 ○Shigeo Sakuragi1, Keiko Tominaga-Yoshino1, Akihiko Ogura1 大阪大院・生命機能1 Frontier Biosciences, Osaka Univ, Osaka1 Long-lasting memory is assumed to be required for the repetition-dependent consolidation of memory (RdC). However, the cellular mechanism of RdC is far from clear. We found previously in stable cultures of hippocampal slices that the repetitive inductions of long-term potentiation (LTP) led to a slowly developing long-lasting (>3w) enhancement in synaptic strength coupled with new synapse formation (Tominaga-Yoshino et al., 2002, 2008). We named this novel plasticity phenomenon RISE (Repetitive LTP-Induced Synaptic Enhancement) and propose it as a model for analyzing the cellular process of RdC. Since our separate study (Kawaai et al., 2010) showed that the expression of brain-derived neurotrophic factor (BDNF) after repetitive inductions of LTP was increased, we shut off BDNF signaling by scavenging BDNF during the RISE-evoking stimulus. RISE failed to develop, as expected. We also found another form of long-lasting synaptic plasticity named LOSS (LTD-repetition-Operated Synaptic Suppression), a long-lasting synaptic weakening coupled with synapse elimination after repetitive inductions of long-term depression (LTD). Since BDNF and BDNF precursor (proBDNF) are known to exert opposite biological effects (Lu et al., 2005), we hypothesized that LOSS would be mediated by proBDNF (Egashira et al., 2010). To test this hypothesis, we applied a function-blocking antibody to BDNF receptor (TrkB) during the RISE-evoking stimulus and a function-blocking antibody to proBDNF receptor (p75NTR) during the LOSS-evoking stimulus. Under these conditions, BDNF should eventually activate p75NTR and proBDNF should activate TrkB, leading to production of LOSS and RISE, respectively. The results were actually the case. The "untoward" activation of TrkB by LOSS-evoking stimulus under p75NTR-masking was confirmed by a western blot analysis. Thus, the hypotheses that RISE and LOSS would be mediated by BDNF-TrkB and proBDNF- p75NTR pathways, respectively, were strengthened.	P1-2-8 小脳機能とシナプス可塑性におけるCdk5/p35の役割 A role of Cdk5/p35 in cerebellar function and synaptic plasticity ○石関誠人1, , 三田直輝1, 阿部学2, 山崎真弥2, 崎村健司2, 御子柴克彦3, 井上貴文1, 大島登志男1 ○Masato Ishizeki1, Xiaojuan He1, Naoki Mita1, Manabu Abe2, Maya Yamazaki2, Kenji Sakimura2, Katsuhiko Mikoshiba3, Takafumi Inoue1, Toshio Ohshima1 早稲田大院・先進理工・生医1, 新潟大　脳研　細胞神経生物学2, 理研・脳研3 Dept Life Sci Med Biosci, Waseda Univ, Tokyo, Japan1, Brain Research Ins, Niigata Univ, Niigata, Japan2, RIKEN Brain Research Ins, Saitama, Japan3 p35 acts as one of the activators of cyclin-dependent kinase 5 (Cdk5), which plays a pivotal role in neuronal migration, neuronal differentiation, and axonal elongation. A previous study showed that p35-/- (p35KO) mice exhibited a subtle abnormality in brain structure and had impaired spatial learning and memory. Through serial behavioral analyses, we found that p35KO mice had a motor coordination defect, as shown by the rotarod test. To exclude the possible contribution of the histological abnormality to the motor coordination defect, we generated Purkinje cell-specific p35 conditional knockout (L7-p35cKO) mice, which exhibited impaired cerebellar coordination, but alignment of Purkinje cells in the cerebellum was normal. Electrophysiological analyses revealed defective induction of LTD at the parallel fiber-Purkinje cell synapses in L7-p35cKO mice without affecting paired pulse facilitation. Thus we conclude that the motor coordination defect is not due to the subtle abnormality in brain structure, but to the lack of Cdk5/p35 function, and that Cdk5/p35 is required for cerebellar functions and synaptic plasticity.
P1-2-9 側坐核においてスパイン形態可塑性をドーパミンが増強できる狭い時間枠 A narrow time window for dopaminergic enhancement of spine structural plasticity in the nucleus accumbens ○柳下祥1, 林-高木朗子1, 渡邉惠1, 河西春郎1 ○Sho Yagishita1, Akiko Hayashi-Takagi1, Satoshi Watanabe1, Haruo Kasai1 東京大学大学院　医学系研究科　構造生理学1 Laboratory of Structural Physiology, Graduagte School of Medicine, The University of Tokyo, Tokyo1 The nucleus accumbens plays a key role in reward-related learning. The principle neurons in this region, the medium spiny neurons (MSNs), receive glutamatergic inputs from various brain regions, including the prefrontal cortex, and dopaminergic (DA) inputs from the ventral tegmental area. It has been considered that a brief burst of activity of DA neurons sends a reward-related signal, which reinforces the action preceding the reward, presumably by modulating the plasticity of glutamatergic inputs on MSNs. However, it has not been clarified whether dopamine can regulate the structural plasticity of glutamatergic synapses and whether such plasticity occurs at a particular time after glutamate stimulation. Therefore, we examined the temporal profile of DA modulation on the structural plasticity at the single spine level using optogenetic control of DA neurons and two-photon uncaging of caged glutamates. In acute slice preparations from young adult mice where the direct-pathway MSNs expressing D1 receptors were virally labeled, the robust spine enlargement could be induced by two-photon uncaging of glutamate in the continuous presence of dopamine. Subsequently, we examined whether brief DA signaling was sufficient to enhance the structural plasticity by the optogenetic stimulation of dopaminergic presynaptic fibers. We observed that the optogenetic stimulation of DA fibers shortly after glutamate uncaging enhanced structural plasticity, as seen in the continuous presence of dopamine, whereas the stimulation of DA fibers either before or a few seconds after glutamate uncaging did not. Thus, there is a narrow sensitive period when dopamine can effectively modulate the structural plasticity of dendritic spines in the nucleus accumbens. Such a narrow time window enables the detection of sequential activation of the synapses by glutamate and dopamine and may provide a new basis for reinforcement learning mediated by dopamine.	P1-2-10 Cdk5によるマウス皮質ニューロンにおけるスパイン密度の制御 Cyclin-dependent kinase 5 regulates spine density of cortical neurons in mouse brain ○三田直輝1, , 大島登志男1 ○Naoki Mita1, Xiaojuan He1, Toshio Ohshima1 早学院　先理　生医1 Dept. Life Sci. Med. BioSci., Grad Sch. Adv. Eng. Sci., Waseda Univ., Tokyo1 Cyclin-dependent kinase 5 (Cdk5) activity is dependent upon association with one of two neuron-specific activators, p35 or p39. Cdk5 and its activators have been implicated in not only brain development but also higher brain functions such as synaptic plasticity, learning and memory. We previously demonstrated that p35 KO mice which have reduced Cdk5 activity exhibit impairment of hippocampal long-term depression and defective spatial learning and memory. It is not clear whether these defects are depend on histological abnormalities or reduced Cdk5 kinase activity. The aim of this study is to make clear the function of Cdk5 by using of p35 conditional knockout (p35 cKO) mice which have specific deletion of p35 in CA1 region of hippocampus (CA1-specific p35 cKO) and in whole neurons (Inducible p35 cKO).We checked the reduction of p35 in CA1-specific p35 cKO mice by Western blotting and lowered Cdk5 activity by immunostaining. We found that the reduction of spine densities in CA1 pyramidal neuron of CA1-specific p35 cKO mice as well as those in Inducible p35 cKO mice by Golgi staining. Reduction of spine density is more prominent in p35 cKO; p39 KO mice compared to that in p35 cKO mice. These result indicate that the maintenance of spine is dependent upon Cdk5 activity.
P1-2-11 発達期バレル皮質における視床皮質投射のスパイクタイミング依存性可塑性の性質 Characterization of spike timing-dependent plasticity at thalamocortical transmission in the developing mouse barrel cortex ○伊丹千晶1, 木村文隆3 ○Chiaki Itami1, J-Y Edna Huang2, Hui-Chen Lu2, Fumitaka Kimura3 埼玉医科大学・医・生理1, ベイラー医科大学2, 大阪大・院・分子神経科学3 Dept Physiol., Saitama Med Univ1, Baylor Coll Med, Houston, USA2, Dept Mol Neurosci, Osaka Univ Grad Sch Med, Suita3 Mammalian sensory cortex shows remarkable plasticity during critical period, in which sensory experiences shape cortical circuits in an input dependent manner. Recent studies have indicated that synapses between layers 4 - 2/3 (L4-L2/3) cells are critically important, and these synapses exhibit spike timing-dependent plasticity (STDP), in which the temporal order and precise timing of pre- and postsynaptic activation determines the direction and magnitude of plasticity. We previously reported that during the 2nd postnatal week, L4-L2/3 synapses showed a distinct form of STDP; both pre-post and post-pre timing produced LTP, with the largest effect at the shortest delay between pre- and postsynaptic activation (Itami, J. Neurosci., 2012). We also found that during the 2nd postnatal week thalamic inputs to L2/3 pyramidal cells exhibit opposite type of STDP: both pre-post and post-pre timing causes LTD, with the largest effect at the shortest delay, which we call anti-Hebbian STDP. Here we report the characterization of this type of STDP, focusing of its layer-specific effect, and the localization of involving CB1Rs using global as well as cortex-specific CB1R-KO mice. Physiological significance of two STDPs converging onto L2/3 neurons during the 2nd postnatal week will be discussed.	P1-2-12 眼優位可塑性調節機構におけるノルアドレナリンとセロトニンの異なる効果 Differential effects of noradrenaline and serotonin on the regulation of ocular dominance plasticity in rats ○中舘和彦1, 今村一之2 ○Kazuhiko Nakadate1, Kazuyuki Imamura2 明治薬科大学・薬学教育研究センター・基礎生物学部門1, 前橋工科大学・システム生体工学科2 Department of Basic Biology, Educational and Research Center for Pharmacy, Meiji Pharmaceutical University, Tokyo1, Department of Systems Life Engineering, Maebashi Institute of Technology, Gunma2 The roles of the central noradrenergic (NA) and serotonergic (5HT) system in the activity-dependent regulation of ocular dominance plasticity have been a contentious issue. We recently reported that the number of c-Fos immunopositive cells in layer IV of Oc1B ipsilateral to the stimulated eye was found to be the most sensitive index of the effects of monocular deprivation during the sensitive period of ocular dominance (OD) plasticity. Then, we studied how reduction of endogenous NA or 5HT modified OD plasticity, by examining the degree of c-Fos expression induced in visual cortex. Intraperitoneal injections of specific pharmacological agents, DSP4 and pCPA selectively impair NA- and 5HT-containing nerve terminals and fibers, respectively. In visual cortex with strongly reduced NA, the number of c-Fos-immunopositive cells was significantly decreased in response to stimulation of the deprived eye, while by open eye stimulation the expected increase in c-Fos-immunoreactivity was strongly suppressed, showing no difference from those obtained by monocular stimulation in the normal rats. In contrast, in visual cortex of 5HT reduction, no expected decrease was found in response to stimulation of the deprived eye, while a significant increase was still induced in response to open eye stimulation. These results indicate that the NA and 5HT system differentially regulate OD plasticity: the NA increases open eye response, whereas the 5HT reduces deprived eye response, following monocular deprivation during the sensitive period of OD plasticity.

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