NMDA和非NMDA受体拮抗剂对伤害性辐射热引起的缩腿反射抑制的比较

我们以前的电生理工作：Ｎ－甲基－Ｄ－门冬氨酸受体主要参与介导皮肤来源的伤害性信息的传入,而非ＮＭＤＡ受体主要参与介导肌肉来源的伤害性信息的传入。为进一步证实这一发现,应用鞘内注射的方法,观察ＮＭＤＡ和非ＮＭＤＡ受体拮抗剂对大鼠伤害性辐射热刺激所引起的缩腿反射潜伏期的影响。     

微透析测试刺激皮肤和肌肉神经引起的天门冬氨酸和谷氨酸在脊髓的释放

为分析ＮＭＤＡ和非ＮＭＤＡ受体在介导脊髓不同性质疼痛的机能分化,应用微透析技术,测量刺激皮肤和肌肉神经引起的天门冬氨酸（Ａｓｐ）和谷氨酸（Ｇｌｕ）在脊髓背角的释放。电刺激皮肤神经兴奋Ｃ纤维诱发的Ａｓｐ和Ｇｌｕ的释放分别是基础值的（３２３±５５）％（Ｐ＜００１）和（１６９±１６）％（Ｐ＜００５）;电刺激肌肉神经兴奋Ｃ纤维诱发的Ａｓｐ和Ｇｌｕ的释放分别是基础值的（１５０±１６）％（Ｐ＜００１）和（２１８±４２）％（Ｐ＜００５）。兴奋皮肤传入引起的Ａｓｐ释放明显高于Ｇｌｕ的释放（约３倍）;而兴奋肌肉传入引起的Ｇｌｕ释放明显高于Ａｓｐ的释放（约２倍）。从而提示,皮肤伤害性传入主要引起Ａｓｐ的释放增加,而肌肉的伤害性传入则主要引起Ｇｌｕ的释放增加,它们分别主要作用于ＮＭＤＡ和非ＮＭＤＡ受体而介导不同的痛传入信息。     

NMDA受体与中枢神经系统发育

中枢神经系统兴奋性氨基酸离子型受体－ＮＭＤＡ受体,是由ＮＭＤＡＲ１和ＮＭＤＡＲ２两个亚单位共同构成的受体通道复合体。ＮＭＤＡ受本激活后可引起神经元细胞对Ｎａ＾＋,Ｋ＾＋和Ｃａ＾２＋通透性增强,产生兴奋性突触后电位,在中枢神经发育的过程中,ＮＭＤＡ受体通过不同亚型的选择性表达,改变自身的结构和功能,进而影响ＮＭＤＡ受体介导的Ｃａ＾２＋内流,调节神经元内Ｃａ＾２＋依赖的第二信使系统,最终实现对中枢神经     

小鼠大脑皮质N—甲基—D—天冬氨酸受体的鉴定及其的衰老时的变化

以放射性配基结合分析法对正常成年小鼠大脑皮中Ｎ－甲基－Ｄ－天冬氨酸（ＮＭＤＡ）受体作了鉴定;观察了衰老小鼠ＮＭＤＡ受体、空间辨别能力、海马突触传递长时程增强的变化及补肾中药复方对这些变化的影响。结果表明：小鼠大脑皮质含有丰富的、高亲和力的ＮＭＤＡ受体;衰老过程中小鼠ＮＭＤＡ受体的最大结合容量Ｂｍａｘ）呈渐进性降低,空间辨别能力下降,ＬＴＰ的振幅和斜率明显降低;补肾中药复方具有提高衰才小鼠ＮＭＤＡ受     

大鼠三叉神经尾侧亚核内SPR阳性神经元与初级传入和下行投射纤维之间的突触联系

用追踪和免疫电镜技术研究三叉神经尾侧亚核（Ｖｃ）内Ｐ物质受体（ＳＰＲ）阳性神经元与初级传入和下行投射之间的突触联系。光镜观察发现,在Ｖｃ浅层,ＳＰＲ阳性神经元的分布与ＲＭｇ下行投射终末的分布有重叠。电镜观察发现,三叉初级传入终末和ＳＰＲ阳性神经元树突形成非对称性轴树突触;ＲＭｇ下行投射终末与ＳＰＲ阳性神经元树突也形成非对称性轴树突触,提示ＲＭｇ下行投射纤维可能通过直接作用于丘脑投射神经元对三叉初级传入的伤害性信息进行调控。     

外周炎性刺激条件下大鼠脊髓背角PPE mRNA及L-ENK样品和μ阿片受体样阳性结构的变化

以鹿角菜胶（ＣＡＲ）注射到大鼠一侧后爪的足底皮下作为伤害性刺激模型,分别于ＣＡＲ刺激后６、１２ｈ和１、３ｄ处死动物,对照组动物仅将盐水注入一侧后爪足底皮下,用原位杂交法和免疫组织化学法观察前原脑啡肽（ＰＰＥ）ｍＲＮＡ阳性神经元、亮氨酸脑啡肽（Ｌ－ＥＮＫ）和μ阿片受体（ＭＯＲ）样阳性结构在大鼠脊髓背角（ＳＤＨ）的分布和变化。对照组大鼠ＳＤＨ内可见到大量ＰＰＥｍＲＮＡ阳性神经元,这些阳性神经元主要分布于Ⅰ、Ⅱ层和Ⅴ、Ⅵ层,ＣＡＲ刺激后６ｈ,刺激侧ＳＤＨ中ＰＰＥｍＲＮＡ阳性神经元的数量明显增多,１２ｈ和１ｄ达到最高水平,３ｄ时略有下降,但仍高于正常水平。Ｌ－ＥＮＫ样阳性纤维和终末主要分布于正常大鼠ＳＤＨ的Ⅰ、Ⅱ层,ＣＡＲ刺激后１ｄ,Ｌ－ＥＮＫ样阳性结构在刺激侧ＳＤＨ中的密度略有升高,３ｄ后下降直至低于正常水平。ＭＯＲ阳性胞体和纤维主要分布于ＳＤＨ的Ⅱ层,ＣＡＲ刺激后１ｄ,刺激侧Ⅱ层中ＭＯＲ阳性结构明显增加,并持续到刺激后３ｄ。上述结果提示阿片类物质在伤害性信息调控中具有重要作用。     

电压门控钠通道与背根神经元伤害性传入

背根神经节（ＤＲＧ）神经元伤害性传入涉及到多层面复杂的神经递质与其相关靶受体的分子参与和调控。本文侧重结合ＤＲＧ神经元中钠电流的表达分布规律,简要地论及了电压门控钠通道与ＤＲＧ神经元伤害性性感觉传入及其调制的一些关系。     

小鼠大脑皮质N─甲基－D－天冬氨酸受体的鉴定及其在衰老时的变化

以放射性配基结合分析法对正常成年小鼠大脑皮质中Ｎ─甲基－Ｄ－天冬氨酸（ＮＭＤＡ）受体作了鉴定;观察了衰老小鼠ＮＭＤＡ受体、空间辨别能力、海马突触传递长时程增强（ｌｏｎｇｔｅｒｍｐｏｔｅｎｔｉａｔｉｏｎ,ＬＴＰ）的变化及补肾中药复方对这些变化的影响。结果表明：小鼠大脑皮质含有丰富的、高亲和力的ＮＭＤＡ受体;衰老过程中小鼠ＮＭＤＡ受体的最大结合容量（Ｂｍａｘ）呈渐进性降低,空间辨别能力下降,ＬＴＰ的振幅和斜率明显降低;补肾中药复方具有提高衰老小鼠ＮＭＤＡ全体Ｂｍａｘ值和维持ＬＴＰ于较高水平的作用。     

AMPA受体失敏和快速兴奋性突触传递

ＡＭＰＡ受体是离子型谷氨酸受体中重要的一类亚型,在中枢神经系统内主要介导快速的兴奋性突触传递。近年来,ＡＭＰＡ受体独特的失敏特性逐渐被阐明,已经确定了一些特异调节ＡＭＰＡ受体失敏的化合物。大量的生理学和药理学证据表明,ＡＭＰＡ受体失敏在快速兴奋性突触传递中起着重要的作用,对单个突触的传递效率、神经元的整合功能和突触的可塑性均有影响。     

大脑皮层神经元NMDA受体的单通道特性

本文用膜片箝技术对机械分离培养的大鼠大脑皮层神经元胞体上的ＮＭＤＡ受体的单通道特性进行了研究,实验用细胞贴附和内面向外两种形式记录单离子通道的活动。电极液内含有ＮＭＤＡ或Ｌ－门冬氨酸时,在皮层神经元上常见电导为３５ｐＳ的离子通道。通道对Ｎａ＋,Ｋ＋非选择性通透,对Ｃｌ－不通透,其平均开放时间和开放概率随超极化程度增大而降低。开放、关闭时间及ｂｕｒｓｔ时程的分布直方图均需双指数拟合。Ｍｇ２＋以电压和浓度依赖性的方式减小通道开放时间,ＡＰＶ能阻断通道活动,温度降低使通道开放时间延长及电流幅度减小。本文结果表明大脑皮层神经元上ＮＭＤＡ受体通道活动自身具有电压依赖性,因此提示ＮＭＤＡ受体通道的正常功能活动可能依赖于某些细胞内调控过程的存在。     

微透析测试刺激皮肤和肌肉神经引起的天门冬氨酸和谷氨酸在脊髓的 …

To investigate the possible mechanisms underlying the difference of NMDA and non-NMDA receptors in spinal nociception originating in skin and muscle, release of aspartate (Asp) and glutamate (Glu) in the spinal dorsal horn was detected by stimulation of cutaneous and muscular nerves in cats using microdialysis technique. Asp and Glu were increased respectively by (323 +/- 55)% and (169 +/- 16)% following stimulation of cutaneous nerve, but by (150 +/- 16)% and (218 +/- 42)% respectively following stimulation of muscular nerve. Asp increase was approximately three times higher than that of Glu following cutaneous nerve-stimulation (P < 0.01), while Glu increase was approximately twice as high as that of Asp following muscular nerve-stimulation (P < 0.05). It is likely that nociceptive cutaneous and muscular inputs preferentially elicite release of Asp and Glu respectively, resulting in a functional differentiation of NMDA and non-NMDA receptor in the mediation of different nociceptive information.     

内源性下行抑制/易化系统与5-羟色胺对脊髓伤害感受性信息的调制

内源性下行抑制系统在痛传递与调制中具有重要作用。近年来,与这一系统相对的下行易化系统开始引起人们的关注。中枢神经系统通过下行抑制易化系统对外周伤害性信息进行双向调制。５－羟色胺（５－ＨＴ）是痛上行调制系统的主要神经递质,电刺激或微量注射兴奋性氨基酸于中缝大核（ＮＭＲ）或巨细胞网状核（ＮＧＣ）内,既可兴奋也可抑制脊髓伤害性反应。这种相互矛盾遥效应可能与脊髓内的多种５－ＨＴ受体亚型有关。     

Cortical Presynaptic Control of Dorsal Horn C–Afferents in the Rat

Lamina 5 sensorimotor cortex pyramidal neurons project to the spinal cord, participating in the modulation of several modalities of information transmission. A well-studied mechanism by which the corticospinal projection modulates sensory information is primary afferent depolarization, which has been characterized in fast muscular and cutaneous, but not in slow-conducting nociceptive skin afferents. Here we investigated whether the inhibition of nociceptive sensory information, produced by activation of the sensorimotor cortex, involves a direct presynaptic modulation of C primary afferents. In anaesthetized male Wistar rats, we analyzed the effects of sensorimotor cortex activation on post tetanic potentiation (PTP) and the paired pulse ratio (PPR) of dorsal horn field potentials evoked by C–fiber stimulation in the sural (SU) and sciatic (SC) nerves. We also explored the time course of the excitability changes in nociceptive afferents produced by cortical stimulation. We observed that the development of PTP was completely blocked when C-fiber tetanic stimulation was paired with cortex stimulation. In addition, sensorimotor cortex activation by topical administration of bicuculline (BIC) produced a reduction in the amplitude of C–fiber responses, as well as an increase in the PPR. Furthermore, increases in the intraspinal excitability of slow-conducting fiber terminals, produced by sensorimotor cortex stimulation, were indicative of primary afferent depolarization. Topical administration of BIC in the spinal cord blocked the inhibition of C–fiber neuronal responses produced by cortical stimulation. Dorsal horn neurons responding to sensorimotor cortex stimulation also exhibited a peripheral receptive field and responded to stimulation of fast cutaneous myelinated fibers. Our results suggest that corticospinal inhibition of nociceptive responses is due in part to a modulation of the excitability of primary C–fibers by means of GABAergic inhibitory interneurons.     

Adenosine receptor-mediated modulation of dopamine release in the nucleus accumbens depends on glutamate neurotransmission and N-methyl-D-aspartate receptor stimulation

Adenosine, by acting on adenosine A(1) and A(2A) receptors, exerts opposite modulatory roles on striatal extracellular levels of glutamate and dopamine, with activation of A(1) inhibiting and activation of A(2A) receptors stimulating glutamate and dopamine release. Adenosine-mediated modulation of striatal dopaminergic neurotransmission could be secondary to changes in glutamate neurotransmission, in view of evidence for a preferential colocalization of A(1) and A(2A) receptors in glutamatergic nerve terminals. By using in vivo microdialysis techniques, local perfusion of NMDA (3, 10 microm), the selective A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680; 3, 10 microm), the selective A(1) receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT; 300, 1000 microm), or the non-selective A(1)-A(2A) receptor antagonist in vitro caffeine (300, 1000 microm) elicited significant increases in extracellular levels of dopamine in the shell of the nucleus accumbens (NAc). Significant glutamate release was also observed with local perfusion of CGS 21680, CPT and caffeine, but not NMDA. Co-perfusion with the competitive NMDA receptor antagonist dl-2-amino-5-phosphonovaleric acid (APV; 100 microm) counteracted dopamine release induced by NMDA, CGS 21680, CPT and caffeine. Co-perfusion with the selective A(2A) receptor antagonist MSX-3 (1 microm) counteracted dopamine and glutamate release induced by CGS 21680, CPT and caffeine and did not modify dopamine release induced by NMDA. These results indicate that modulation of dopamine release in the shell of the NAc by A(1) and A(2A) receptors is mostly secondary to their opposite modulatory role on glutamatergic neurotransmission and depends on stimulation of NMDA receptors. Furthermore, these results underscore the role of A(1) vs. A(2A) receptor antagonism in the central effects of caffeine.     

NMDA与非NMDA受体激动剂对新生大鼠延髓脑片呼吸节律性放电的作用

目的：探讨N－甲基－D－天门冬氨酸（NMDA）和非NMDA类受体在基本呼吸节律发生和调节中的可能作用。方法：以改良的Kerb's液灌流新生SD大鼠离体延髓脑片,记录片与之相连的舌下神经的呼吸节律性放电活动（respiratory rhythmical discharge activity,RRDA),在灌流中给予兴奋性氨式酸类递质及相应的拮抗剂,观察其对RRDA的影响。结果：使用非NMDA受体激动剂海人酸（KA）后,可见呼吸周期及呼吸时间有所延长,NMDA受体激动剂NMDA对呼吸活动则没有明显影响;相应的拮抗剂6－氰基－7－硝基喹恶啉土卫四（DNAX）和2－氨基酸戊酸（AP5）均可使放电频率和积分幅值明显降低,吸气时间显著缩短,但DNQX同时可致呼吸周期和呼气时间明显缩短。结论：在哺乳动物基本呼吸节律的产生和调节中,NMDA类受体主要对呼吸活动的强度产生调节作用;而非NMDA类受体不仅可以影响呼吸的强度,同时对呼吸的频率也发挥调节作用。     

Modulation of NMDA receptor function by cyclic AMP in cerebellar neurones in culture

The signal transduction pathways involved in NMDA receptor modulation by other receptors remain unclear. cAMP could be involved in this modulation. The aim of this work was to analyse the contribution of cAMP to NMDA receptor modulation in cerebellar neurones in culture. Forskolin increases cAMP and results in increased intracellular calcium and cGMP that are prevented by blocking NMDA receptors. Similar effects were induced by two cAMP analogues, indicating that cAMP leads to NMDA receptor activation. It has been reported that phosphorylation of Ser897 of the NR1 subunit of NMDA receptors by cAMP-dependent protein kinase (PKA) activates the receptors. Forskolin increases Ser897 phosphorylation. Neither Ser897 phosphorylation nor cGMP increase induced by forskolin are prevented by four inhibitors of PKA, suggesting that NMDA receptor activation is dependent on cAMP but not on PKA. Inhibition of Akt prevents forskolin-induced phosphorylation of Ser897, suggesting a role for Akt in the mediation of the modulation of NMDA receptors by cAMP. Pituitary adenylate cyclase-activating polypeptide (PACAP) activates its receptors, increasing cAMP and also leading to phosphorylation of Ser897 of NR1 and activation of NMDA receptors. These results indicate that cAMP modulates NMDA receptor in cerebellar neurones and may play a role in NMDA receptor modulation by other receptors.     

Role of astrocytes and altered regulation of spinal glutamatergic neurotransmission in stress-induced visceral hyperalgesia in rats

Glutamate (Glu) is the primary excitatory neurotransmitter in the central nervous system and plays a critical role in the neuroplasticity of nociceptive networks. We aimed to examine the role of spinal astroglia in the modulation of glutamatergic neurotransmission in a model of chronic psychological stress-induced visceral hyperalgesia in male Wistar rats. We assessed the effect of chronic stress on different glial Glu control mechanisms in the spinal cord including N-methyl-d-aspartate receptors (NMDARs), glial Glu transporters (GLT1 and GLAST), the Glu conversion enzyme glutamine synthetase (GS), and glial fibrillary acidic protein (GFAP). We also tested the effect of pharmacological inhibition of NMDAR activation, of extracellular Glu reuptake, and of astrocyte function on visceral nociceptive response in naive and stressed rats. We observed stress-induced decreased expression of spinal GLT1, GFAP, and GS, whereas GLAST expression was upregulated. Although visceral hyperalgesia was blocked by pharmacological inhibition of spinal NMDARs, we observed no stress effects on NMDAR subunit expression or phosphorylation. The glial modulating agent propentofylline blocked stress-induced visceral hyperalgesia, and blockade of GLT1 function in control rats resulted in enhanced visceral nociceptive response. These findings provide evidence for stress-induced modulation of glia-controlled spinal Glu-ergic neurotransmission and its involvement in chronic stress-induced visceral hyperalgesia. The findings reported in this study demonstrate a unique pattern of stress-induced changes in spinal Glu signaling and metabolism associated with enhanced responses to visceral distension.