阿部 和穂

モルモット気管平滑筋を弛緩させる南天実エキスの活性成分の同定を試み、それがヒゲナミンであり、β<SUB>2</SUB>受容体刺激によって気管拡張をおこすことを解明した。

We have previously found that the induction of hippocampal long-term potentiation (LTP) is modulated by neuron activities in the basolateral amygdala (BLA). However, little is known about what neurotransmitter system in the BLA contributes to modulation of hippocampal LTP. In the present study, we investigated possible involvement of BLA dopaminergic system in the induction of UP at the perforant path (PP)-dentate gyrus (DG) granule cell synapses of anesthetized rats. The induction of PP-DG LTP was significantly attenuated by intra-BLA injection of the D(1) receptor antagonist SCH23390 (2 or 6 nmol) or the D(2) receptor antagonists, chlorpromazine (30 or 100 nmol) or haloperidol (4.4 or 13.3 nmol). The effects of SCH23390 and haloperidol were abolished by concomitant intra-BLA injection of the D(1) receptor agonist SKF38393 (17 nmol) and the D(2) receptor agonist quinpirole (3 nmol), respectively. Furthermore, lesioning with 6-hydroxydopamine of the ventral tegmental area, the origin of the dopaminergic system projecting to the BLA, resulted in attenuated PP-DG LTP, which was restored by intra-BLA injection of SKF38393 or quipirole. These results suggest that the induction of PP-DG UP is promoted by the BLA dopaminergic system via both D(1) and D(2) receptors. (C) 2009 Elsevier Inc. All rights reserved.

We have previously found that the induction of long-term potentiation in the synaptic pathway from the basolateral amygdala to the dentate gyros (BLA-DG LTP) is regulated by L-type Ca2+ channels, dopamine D-2 receptors and GABAergic inhibition. In the present study, we investigated possible relations among the three mechanisms by using anesthetized rats. Blockade of GABAergic inhibition with picrotoxin abolished both the inhibitory effect of the dopamine D-2 receptor antagonist chlorpromazine and the promoting effect of the dopamine D-2 receptor agonist quinpirole on the induction of BLA-DG LTP. However, the inhibitory effect of the L-type Ca2+ channel blocker verapamil on BLA-DG LTP was not affected by picrotoxin. These results suggest that the role of dopamine D-2 receptors in the induction of BLA-DG LTP is modulatory and depends on GABAergic inhibition, whereas the role of L-type Ca2+ channels is fundamental. (C) 2009 Elsevier B.V. All rights reserved.

We have previously found that the induction of hippocampal long-term potentiation (LTP) is modulated by neuron activities in the basolateral amygdala (BLA). However, little is known about what neurotransmitter system in the BLA contributes to modulation of hippocampal LTP. In the present study, we investigated possible involvement of BLA serotonergic system in the induction of LTP at the perforant path (PP)-dentate gyrus (DG) granule cell synapses of anesthetized rats. The induction of PP-DG LTP was significantly inhibited by intra-BLA injection of the 5-HT2 receptor antagonist cinanserin (25-50 nmol), but not by intra-BLA injection of the 5-HT1.7 receptor antagonist methiothepin (50 nmol), the 5-HT3 receptor antagonist ondansetron (50 nmol) or the 5-HT4 receptor antagonist RS23597-190 (100 nmol). In addition, intra-BLA injection of the 5-HT2C receptor agonist MK212 (50 nmol) facilitated the induction of PP-DG LTP. These results suggest that the induction of PP-DG LTP is promoted by activation of 5-HT2C receptors in the BLA. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

We have previously found that synaptic pathway from the basolateral amygdala (BLA) to the dentate gyrus (DG) displays N-methyl-D-aspartate (NMDA) receptor-independent form of long-term potentiation (LTP), which should be a valuable model for elucidating neural mechanisms linking emotion and memory. To explore its cellular mechanisms, we investigated possible involvement of the beta-adrenergic, muscarinic cholinergic and dopaminergic systems on UP in this pathway of anesthetized rats. The induction of BLA-DG LTP was not affected by administration of the beta-adrenoceptor antagonist propranolol (50-150 nmol, i.c.v.), the muscarinic receptor antagonist scopolamine (2-6 mg/kg, i.p.), the cholinesterase inhibitor physostigmine (50 nmol, i.c.v.) or the dopamine D-1 receptor antagonist SCH23390 (100 nmol, i.c.v.), but Significantly inhibited by the dopamine D-2 receptor antagonists, chlorpromazine (15 nmol, i.c.v.) and haloperidol (0.15-0.5 mg/kg, i.p.), and significantly promoted by the dopamine D-2 receptor agonist quinpirole (78 nmol, i.c.v.). Furthermore, lesioning with 6-hydroxydopamine of the ventral tegmental area (VTA), the origin of mesolimbic dopaminergic neurons, resulted in attenuated BLA-DG LTP. These results Suggest that the D-2-dopaminergic system, but not the beta-adrenergic, muscarinic or D-1-dopaminergic system, is involved in the induction of BLA-DG LTR In addition, inhibition of BLA-DG UP by haloperidol or VIA lesion was abolished by blockade of GABAergic inhibition with picrotoxin. It is probable that the D-2-dopaminergic system promotes the induction of BLA-DG LTP by Suppressing GABAergic inhibition. (C) 2008 Elsevier Ltd. All rights reserved.

Fisetin (3,3',4',7-tetrahydroxyflavone) has been found to be neuroprotective, induce neuronal differentiation, enhance memory, and inhibit the aggregation of the amyloid beta protein (A beta) that may cause the progressive neuronal loss in Alzheimer's disease. The diverse collection of biological activities of this compound may lead to a new type of therapeutic drug for Alzheimer's disease. As the first step to design even more effective drugs based upon the structure of fisetin, the present study investigated the Structural requirements for the anti-amyloidogenic activity of fisetin by comparing the effects of several structurally related flavonoids on A beta fibril formation in vitro. A beta 1-42 (20 mu M) and the flavonoids were incubated for 0-48 h at 37 degrees C, and fibril formation was quantitatively determined by the thioflavin T fluorescence assay. Among ten flavonoids tested, fisetin, 3',4',7-trihydroxylflavone, 3,3',4'-trihydroxyflavone, luteolin, quercetin and myricetin inhibited A beta fibril formation. On the other hand, 3,3',7-trihydroxyflavone, 5-deoxykaempferol, chrysin and kaempferol enhanced A beta fibril formation. These results suggest that the 3',4'-dihydroxyl group, but not the 3- or 7-hydroxyl group, is essential for the inhibitory effect of fisetin on A beta fibril formation. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

モルモット鼻粘膜の薬物反応性に部位差があることを明らかにした。

Small molecules that activate signaling pathways used by neurotrophic factors could be useful for treating CNS disorders. Here we show that the flavonoid fisetin activates ERK and induces cAMP response element-binding protein (CREB) phosphorylation in rat hippocampal slices, facilitates long-term potentiation in rat hippocampal slices, and enhances object recognition in mice. Together, these data demonstrate that the natural product fisetin can facilitate long-term memory, and therefore it may be useful for treating patients with memory disorders.

Background: Nitric oxide (NO) is produced by the action of NO synthase (NOS) isoforms and is considered an important mediator Of inflammatory response including airways. In this study, the changes in the expression levels of NOS isoforms in nasal mucosae were determined in a guinea pig model of allergic rhinitis. Methods: An allergic rhinitis model was prepared in guinea pigs by repeated challenge with aerosolized dinitrophenylated ovalbumin antigen. Twenty-four hours after the last antigen challenge, the expression levels of NOS isoforms in nasal mucosae were determined by immunoblottings. Changes in the isometrical tension of isolated mucosal tissues of nasal septa induced by histamine were measured also. Results: Although the expression levels of endothelial NOS (eNOS) and neuronal NOS (nNOS) in nasal mucosae were not affected by the repeated antigen exposure, the inducible NOS (iNOS) level was markedly and significantly increased in the challenged animals. In isolated nasal mucosal tissues, histamine induced a concentration-dependent relaxation, which was sensitive to an H-1-receptor antagonist, mepyramine, and an NOS inhibitor, L-NMMA. No significant change in the histamine responsiveness was observed between the sensitized control and repeatedly antigen-challenged groups. Conclusion: The expression of three isoforms of NOS, including eNOS, nNOS, and iNOS, was presented in guinea pig nasal mucosa. A marked increase in iNOS expression in the repeatedly antigen-challenged animals suggests an important role of iNOS in the pathogenesis of allergic rhinitis. However, the pathophysiological role(s) of NO generated by iNOS in nasal allergy is still unclear.

We have recently found that synaptic pathway from the basolateral amygdala (BLA) to the dentate gyrus (DG) displays N-methyl-D-aspartate (NMDA) receptor-in dependent form of long-term potentiation (LTP), which should be a valuable model for elucidating neural mechanisms linking emotion and memory. To explore its cellular mechanisms, we investigated the effects of L-type Ca2+ channel blockers on LTP in this pathway of anesthetized rats. Intraperitoneal administration of verapamil (3-30 mg/kg) or diltiazem (6-20 mg/kg) significantly impaired the induction of UP following high-frequency stimulation. When verapamil was administered after high-frequency stimulation, it did not affect the pre-established LTP. These results suggest that activation of L-type Ca2+ channels is necessary for the induction of UP in the BLA-DG pathway. (C) 2004 Elsevier B.V. All rights reserved.

While nonspecific airway hyperresponsiveness (AHR) is a central feature of allergic bronchial asthma, the mechanism underlying the development of AHR is not clearly understood. We have previously demonstrated in vitro hyperresponsiveness of bronchial smooth muscle to acetylcholine (ACh) in rats that were actively sensitized and repeatedly challenged with aerosolized antigen. It has also been demonstrated that the ACh-induced, RhoA-mediated Ca(2+) sensitization is markedly augmented concomitantly with an increased expression and activation of RhoA protein in the bronchial smooth muscle of the antigen-treated rats. In the present study, we have investigated whether TNF-alpha, a proinflammatory cytokine which is involved in bronchial asthma, causes upregulation of RhoA mRNA and protein in the rat bronchus. Treatment of rat bronchial smooth muscle preparations with TNF-alpha (300 ng/ml for 24 hr) significantly shifted the concentration-response curve to ACh upwards, but did not alter the response to high K(+), when compared to that of control tissues. Levels of RhoA mRNA and protein in the TNF-alpha-treated bronchus were significantly greater than those in the control group. In conclusion, it is suggested that the augmentation of the ACh-induced contractile response evoked by TNF-alpha might be mediated by an upregulation of RhoA in rat bronchial smooth muscle.

Although ethanol has been reported to inhibit the induction of long-term potentiation in hippocampal CA1 and dentate gyrus synapses of rats, very little is known about the effect of ethanol on synaptic plasticity in other brain regions. Therefore, in the present study, we investigated the effect of ethanol on long-term potentiation in synaptic pathway from the basolateral amygdala to the dentate gyrus by using anesthetized rats in vivo. I.v. (20-40%x2 ml/kg) or i.c.v. (30-40%x5 mul) administration of ethanol did not affect the basal amplitude of dentate gyrus field potential evoked by basolateral amygdala stimulation, but significantly inhibited the induction of long-term potentiation following application of tetanic stimulation. Since long-term potentiation in this pathway was independent of N-methyl-D-aspartate receptors, the inhibitory effect of ethanol is unlikely to be caused by suppression of N-methyl-D-aspartate receptor function. Alternatively, long-term potentiation in this pathway was significantly suppressed by the benzodiazepine agonist diazepam (2 mg/kg, i.p.), and the inhibitory effect of ethanol was abolished by the GABA(A) receptor channel blocker picrotoxin (1 mg/kg, i.p.). The present study demonstrates that ethanol inhibits the induction of long-term potentiation in the basolateral amygdala-dentate gyrus pathway by enhancing GABAA receptormediated neurotransmission. (C) 2004 IBRO. Published by Elsevier Ltd. All rights reserved.

We investigated the effect of agmatine on cell viability of rat cerebellar granule neurons in a high-K+ (27.5 mM) medium. Exposure of cultured rat cerebellar granule neurons to agmatine (200-800 muM) resulted in a significant decrease in cell viability. Agmatine-induced neuronal death began to occur 6-12 h after addition, and gradually progressed. The agmatine neurotoxicity was attenuated by N-methyl-D-aspartate (NMDA) receptor antagonists and by enzymatic degradation Of L-glutamate with glutamic pyruvic transaminase. Furthermore, a significant increase in extracellular L-glutamate concentration was detected before cell death occurred. In addition, agmatine-induced glutamate release and cell death were both blocked by pretreatment with botulinum toxin C, which is known to specifically inhibit the exocytosis. The agmatine neurotoxicity was not observed when extracellular K+ concentration was lower (10 mM). These results suggest that agmatine induces glutamate release through the exocytosis and thereby causes NMDA receptor-mediated neuronal death in conditions in which extracellular K+ concentrations are elevated. (C) 2003 Elsevier B.V. All rights reserved.

培養アストロサイトにおけるAβによるグルタミン酸取込みの促進がMAP kinaseによって抑制的に制御されていることを明らかにした。

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90）と関連した続報。アストログリア細胞の重要な機能のひとつは、興奮性神経伝達物質グルタミン酸を取り込んで処理することである。神経細胞が神経伝達のために放出したグルタミン酸が蓄積したままでは、神経細胞は機能しなくなる。アストログリア細胞は、必要無くなったグルタミン酸を取り込んで処理することにより神経伝達を正常に保っている。本論文では、ラット脳より調製した培養アストログリア細胞にA・を与え、グルタミン酸取り込みの変化を調べた。その結果、A・に曝されたアストログリア細胞には、グルタミン酸取り込みを担う輸送分子が増え、たくさんのグルタミン酸を処理できるように機能亢進することが判明した。A・に曝された神経系において、アストログリア細胞は、神経細胞を守るように代償的役割を果たすことが示された。

培養アストロサイトにおいて、AβがMAP kinaseのリン酸化と核移行を特異的に促進することを見い出した。

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56）と関連した論文。感情を司る脳部位として、扁桃体の他に、視床下部がある。コルサコフ症候群患者で見られる記憶障害は、視床下部の異常に原因があるとも言われる。本論文では、２）と同様に、ラットの海馬神経の電気活動を測定しながら、視床下部を実験的に操作した時の影響を調べた。その結果、視床下部を活性化すると海馬神経の働きが促進されることを発見した。さらに、その効果には抑制性神経伝達物質GABAの機能変化が必要であることを明らかにした。

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私達は、脳が未発達な状態で誕生する。これは、生前から脳の神経回路を固定せず、生後の外界環境に適応できる最適の神経回路を柔軟に作り上げて行くために役立っていると思われる。生後の脳の発達過程の研究は、記憶のメカニズムを解き明かす重要な課題のひとつである。本論文では、様々な週齢のラット新生児の大脳皮質視覚領における神経伝達を比較・検討した。その結果、生後決まった期間で神経伝達が完成されて行く過程を解析することに成功し、さらにその発達過程を左右している脳内物質として、セロトニンを同定した。

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アルツハイマー病の原因物質のひとつと考えられているA・は神経細胞に対して毒性を示すことがわかっているが、脳内には神経細胞の他にアストログリア細胞が存在する。その数は神経細胞より多く、神経細胞を助ける重要な役割を果たしているにも関わらずA・のアストログリア細胞に対する作用はあまり研究されていない。本論文では、ラット脳から調製した培養アストログリア細胞に対するA・の効果を調べた。その結果、神経細胞とは異なり、アストログリア細胞はA・に曝されても死なず、その代わりに星状化と呼ばれる形態変化が見られた。この形態変化は、アストログリア細胞が障害を修復しようとする時に現れると考えられた。また、この形態変化は、興奮性神経伝達物質グルタミン酸によって抑制されることがわかった。脳内におけるA・の作用の全容を理解するためには、神経細胞に対する作用だけでなく、アストログリア細胞に対する作用も解明しなければならないこと

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培養神経細胞に対するAβの毒性作用にMAPキナーゼが関与するという仮説が他の研究グループより報告されていたが、再検討の結果、関与しないことが証明された。

飲酒時に摂取したエタノールはアセトアルデヒドに代謝される。アセトアルデヒドが体内に蓄積すると、気分が悪い、赤面などの所謂「悪酔い」になる。エタノール代謝物のアセトアルデヒドが、飲酒時の記憶障害に関与するかどうかは不明であった。本論文では、ラットに人為的処置を施し、エタノール摂取時に血中アセトアルデヒド蓄積が起こりやすいモデルを作り、海馬神経の電気活動への影響を調べた。その結果、アセトアルデヒドの蓄積しやすいラットでは、エタノールを与えた時に生じる海馬神経の機能低下が、増悪されることが判明した。飲酒時には、エタノールそのものだけでなく、代謝物アセトアルデヒドも、記憶障害の原因となっていることを、世界で初めて報告した。

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Aβの神経毒性がコレステロールによって軽減されるというデータが他の研究グループより報告されていたが、培養ラット海馬神経細胞を用いて再検討した結果、コレステロールにはAβ神経毒性を軽減する効果は無く、以前に報告されていた作用はコレステロール溶液に含まれる添加物のシクロデキストリンに由来するものであることを証明した。

培養神経細胞を用いてAβの作用を詳細に解析し、MTTアッセイによりAβの異なる2つの作用が検出されることを明らかにした。ひとつは酸化的ストレスによる細胞死、ひとつは酸化的ストレスとは無関係のMTTホルマザン漏出の促進であった。