三叉神经根慢性压迫损伤对大鼠三叉神经尾侧亚核内WDR神经元电活动的影响

目的:观察三叉神经根慢性压迫损伤对大鼠三叉神经脊束核尾侧亚核(caudal subnucleus of the spinaltrigeminal nucleus,Vc)内广动力范围(wide dynamic range neurons,WDR)神经元自发放电和诱发放电活动的影响。方法:通过慢性压迫损伤三叉神经根的方法建立三叉神经痛(TN)动物模型,采用在体细胞外记录技术观察空白对照组和TN模型组大鼠Vc内WDR神经元的自发放电和诱发的放电活动。结果:对照组和TN模型组大鼠Vc内WDR神经元自发放电频率分别为0.84±0.15 Hz和3.18±0.59 Hz;口面部感受野分别给予刷、压、夹机械刺激后,对照组大鼠Vc内WDR神经元的诱发放电频率分别为3.27±1.28 Hz、5.62±0.74 Hz和6.76±1.22 Hz,而TN组大鼠诱发放电频率则分别为7.85±1.57 Hz、10.04±0.72 Hz和12.04±1.77 Hz。结论:TN模型组大鼠Vc内WDR神经元的自发放电频率和诱发放电频率均显著高于对照组大鼠,提示三叉神经根慢性压迫损伤可诱导Vc内WDR神经元兴奋性增强。     

侧脑室注射肾上腺髓质素激活去缓冲神经大鼠最后区神经元

目的观察侧脑室注射肾上腺髓质素(AM)对去缓冲神经大鼠最后区神经元自发放电和Fos蛋白表达的影响。方法应用细胞外记录的电生理学方法,观察雄性SD大鼠神经元自发放电活动;用免疫组化方法检测Fos蛋白的表达。结果侧脑室注射AM(1,3nmol/kg)诱发最后区出现大量Fos样免疫阳性神经元(Fos-LI),最后区神经元自发放电频率明显增加;降钙素基因相关肽受体拮抗剂CGRP8-37(30nmol/kg)可明显减弱AM的效应。结论AM对最后区神经元有直接兴奋作用,降钙素基因相关肽受体介导这一效应。     

大鼠延髓呼吸神经元的类型和分布

在56只去大脑、肌松、人工通气、切断双侧颈迷走神经的成年SD大鼠细胞内记录了161个延髓呼吸神经元胞体。根据细胞内膜电位变化节律与膈神经放电周期的时相关系和关于呼吸活动的三个时相的学说,这些神经元可分为三类:吸气神经元(n=61),吸气后神经元(n=63)和呼气神经元(n=37)。用逆向激     

平行绑定多电极技术研究大鼠基底核毁损对海马自发放电的影响

目的:研究应用平行绑定多电极细胞外记录技术探讨海人藻酸(KA)注射毁损Meynert基底核(NBM)后海马CA1区自发放电活动的改变。方法:雄性SD大鼠在水合氯醛麻醉和脑立体定位仪引导下,KA注射后破坏双侧NBM,一周后用改装的平行绑定多电极记录大鼠海马CA1区自发放电活动。结果:(1)与传统的细胞外单电极或多电极记录相比,本方法电极制备简单、灵活、造价低廉,细胞损伤小,可同时记录单个核团内多个神经元或相邻脑区多个神经元的活动,便于进一步对神经元环路活动进行分析。结合锋电位分类技术,可对单一通道获得的多个神经元活动进行甑别,大大提高实验精度和效率;(2)比较NBM毁损组和对照组核团放电发现:NBM毁损组大鼠CA1区自发放电频率明显减少,其中单个放电与爆发式(burst)放电类型的平均放电频率同时降低;NBM毁损组自发放电类型发生改变,burst数量增加,但burst内发放频率下降,burst间隔延长。结论:(1)平行绑定多电极技术简便、易行、灵活,结合多通道记录技术可为开展神经元环路活动研究提供有力工具;(2)NBM毁损可致大鼠海马CA1区自发放电频率减少和放电模式改变,提示NBM胆碱能系统参与海马环路的神经活动调控,NBM损伤所致海马自发放电活动的改变可能有助于解释阿尔茨海默病认知功能的下降。     

吸入麻醉剂氟烷对大鼠视上核和杏仁中央核神经元自发放电频率的影响

为了探讨吸入麻醉剂对中枢神经元作用的机制 ,应用膜片钳全细胞记录技术在新生 SD大鼠脑薄片上观察了吸入麻醉剂氟烷对视上核和杏仁中央核自发放电频率的影响。结果证明 ,0 .75 %、1.5 %和 2 .5 5 %浓度的氟烷对杏仁中央核神经元的自发放电频率可产生不同程度的抑制作用 ,而对视上核神经元的自发放电频率则产生明显的增强效应。给药后用人工脑脊液冲洗 5min后 ,1.5 %浓度的氟烷对神经元的作用可恢复至给药前水平。本研究的结果提示 ,吸入麻醉剂氟烷能明显地改变中枢神经元自发放电频率 ,但对不同部位的神经元 ,氟烷的作用不同 ;视上核和杏仁中央核是麻醉剂对中枢神经系统作用的重要部位。     

吸入麻醉剂氟浣对大鼠视上核和仁中央核神经元自发放电频率的影响

为了探讨吸入麻醉剂对中枢神经元作用的机制，应用膜片钳全细胞记录技术在新生SD大鼠脑薄片上观察了吸入麻醉剂氟烷对视上核杏仁中央核自发放电频率的影响。结果证明，0.75%、1.5%和2.55%浓度的氟烷对杏仁中央核神经元的自发放电频率可产生不同程度的抑制作用，而对视上核神经元的自发放电频率则产生明显的增强效应。给药后用人工脑脊液冲洗5min后，1.5%浓度的氟烷对神经元的作用可恢复至给药前水平。本研究的结果提示，吸入麻醉剂氟烷能明显地改变中枢神经元自发放电频率，但对不同部位的神经元，氟烷的作用不同；视上核和杏仁核是麻醉剂地中枢神经系统作用的重要部位。     

腺苷对大鼠缰核神经元自发放电活动及c-fos蛋白表达的影响

目的:观察腺苷(Adenosine,Ado)对缰核(Habenula nucleus,Hb)神经元单位放电的影响及外侧缰核内c-fos蛋白表达的变化,探讨腺苷对影响睡眠的缰核神经元活动及相关基因表达的影响及可能机制。方法:脑薄片灌注、腹腔内注射、原位免疫细胞化学等。结果:脑薄片灌注腺苷,导致内侧缰核神经元自发放电活动受到抑制,而外侧缰核神经元自发放电活动明显增加;腹腔注射腺苷0.5小时后,与注射生理盐水组相比较,外侧缰核c-fos蛋白的表达量明显增加。结论:腺苷对大鼠内侧缰核神经元自发放电起抑制作用,对外侧僵核神经元自发放电则有兴奋作用,并可促进外侧缰核c-fos蛋白表达,这为腺苷在外侧缰核内可促进睡眠提供了依据。     

在新型成年大鼠纵切脊髓片上骶髓后连合核神经元的盲膜片钳全细胞 …

本文介绍了一种新型的成年大鼠（５－８周龄）纵切脊髓片模型。此模型与传统的横切脊髓片的不同之处是可带有多条长达１０ｍｍ的后根。在体视显微镜下骶髓后连合核（ＤＣＮ）为一条透明的灰质带，极易与后角其它部位区分，因此最适合于对ＤＣＮ神经元的研究。应用盲膜片钳全细胞记录法，在此模型上研究了ＤＣＮ神经元自发的和后根刺激诱发的兴奋性突触后电位（ＥＰ－ＳＰｓ）。自发的和后根刺激诱发的快ＥＰＳＰｓ主要由非ＮＭＤＡ谷     

兔颈上神经节神经元的急性分离及其通道电流记录

目的 探讨兔颈上神经节神经元分离及电生理研究的方法.方法 为了获得适用于膜片钳实验技术的单个颈上神经节神经细胞,应用酶和机械分离相结合的方法,急性分离20～30 d幼兔的单个颈上神经节神经元.通过倒置显微镜直接观察以及全细胞膜片钳技术的电压钳和电流钳分别对分离得到的颈上神经节神经元的形态学和电生理学特性进行研究.结果 急性分离所得活性较好的颈上神经节神经元胞体具有圆形和顶树突特征,立体感强,光晕明显.在全细胞膜片钳记录模式下可记录到全细胞电流、钠电流、钾电流及动作电位.结论 该方法可以得到形态和生理特性良好的单个颈上神经节神经元;该方法适用于膜片钳技术的研究,对深入探讨药物、物理因子等对神经节神经元离子通道的影响具有重要的应用价值.     

低钙高镁人工脑脊液对大鼠脑片臂旁外侧核神经元温度敏感性的影响

目的:探讨臂旁外侧核(Lateral parabrachial nucleus,LPBN)神经元的温度敏感性是否依赖于突触传递。方法:制备含LPBN的大鼠脑干片后,在32～40℃范围内循环改变灌流液温度,利用脑片膜片钳技术,鉴定LPBN神经元温度敏感性;然后灌流低钙高镁人工脑脊液(Ca~(2+)0.2 mmol·L-1,Mg~(2+)11.4 mmol·L-1)阻断突触传递,进一步检测大鼠LPBN热敏及温度不敏感神经元在不同温度下的胞外自发放电活动的变化,分析其温度敏感系数的变化。结果:阻断突触传递后,热敏神经元的自发放电活动及温度敏感系数均无显著变化(P0.05);阻断突触传递后,中等斜率(n=11)和低等斜率(n=11)的温度不敏感神经元的自发放电频率呈多样性改变,放电幅度无明显改变(P0.05),温度敏感系数大部分显著提高(P0.05),其中4个神经元在突触阻断后,从温度不敏感神经元变成热敏神经元,洗脱后又恢复为温度不敏感神经元。结论:LPBN热敏神经元的温度敏感性与突触传递无关,属于内在特性。     

刺激延髓背角诱发的小鼠脑干网状结构内向Vmo投射的GABA能神经元突触后反应的电生理学研究

本实验利用谷氨酸脱羧酶67-绿色荧光蛋白(GAD67-GFP)基因敲入小鼠制备离体脑片,结合TMR逆行束路追踪技术,在荧光镜和红外镜头下,利用膜片钳全细胞记录的方法对电刺激延髓背角(即三叉神经脊束核尾侧亚核,Vc)诱发的小鼠小细胞网状结构(PCRt)内GABA能和TMR逆标的运动前神经元的突触后反应及其反应类型、药理学特征进行系统的研究。结果显示:(1)高频刺激(20 Hz)Vc,在PCRt内GFP和TMR双标的运动前神经元上可记录到兴奋性的突触后电流(EP-SCs),波形显示为单突触反应;(2)电压钳记录模式下,α-氨基羟甲基恶唑丙酸受体(AMPA受体)拮抗剂氨基-2-硝基喹啉-2,3-二酮(CNQX)及N-甲基-D-天冬氨酸受体(NMDA受体)阻断剂D,L-2-氨基-5-磷酸基戊酸(AP-5)均可显著降低刺激Vc所诱发的小鼠PCRt内GFP和TMR双标神经元的EPCSs的幅值;(3)电流钳模式下,刺激Vc,在PCRt内GFP和TMR双标的神经元上记录到兴奋性突触后电位,其幅度与刺激强度在一定范围内呈正相关。以上结果提示,小鼠PCRt内向三叉神经运动核(Vmo)发出投射的GABA能运动前神经元可通过其细胞膜上AMPA受体或NMDA受体的介导,对口面部伤害性信息发挥整合和调控作用,以实现对口面部伤害性反射活动的精确调节。     

The in vitro slice preparation for combined morphological and electrophysiological studies of rat visual cortex

The morphological condition of slices of rat visual cortex, maintained in vitro in an interface-type recording chamber, was assessed. In addition, neurones in these slices were impaled with glass micropipettes for intracellular recording and horseradish peroxidase (HRP) injection. After fixation and embedding, slices were examined by light and electron microscopy. Slices sectioned orthogonally to the original plane of cutting showed a vertical zonation of tissue preservation. The upper zone contained dense and flattened neuronal somata, although the neuropil appeared normal. The central zone was well preserved, with the appearance of most somata, dendrites, axons and synapses comparing favourably with perfusion-fixed material. The lower zone contained many abnormal, vacuolated somata. The morphology of HRP-injected neurones was assessed by light microscopy. Dendrites could be visualised in great detail and spines were clearly visible. Local axon arbors were well represented. There was good correlation between electrophysiological and morphological criteria for the assessment of the condition of the slice. We conclude that, provided the extent of degeneration within the slice is monitored and appreciated, slices of visual cortex can provide both electrophysiological and morphological data of high quality.     

Developmental change of GABA(A) receptor-mediated current in rat hippocampus

Developmental change of GABA(A)ergic inhibitory postsynaptic current in rat hippocampal CA3 region was examined using patch-clamp recording method. Spontaneous and evoked inhibitory postsynaptic currents were recorded from acute hippocampal slices of neonates (postnatal days 2-4) and adults (days 18-38). Decay kinetics of the spontaneous inhibitory postsynaptic current was slower in neonates than in adults. Application of 500 nM zolpidem increased decay time-constants of the inhibitory postsynaptic currents in both groups with a stronger effect on adults. Zinc (50 microM) inhibited the neonatal inhibitory postsynaptic currents but the inhibition was weaker in adults. Modification of the GABA(A)ergic inhibitory postsynaptic currents by furosemide (0.6 mM) or diazepam (100 nM) did not cause marked differences between the neonate and adult groups. These results demonstrate that GABA(A)ergic inhibitory postsynaptic currents in hippocampal CA3 pyramidal cells change developmentally and indicate that different receptor isoforms are functionally expressed between neonates and adults.     

Optical recording of spontaneous respiratory neuron activity in the rat brain stem.

We report on the optical imaging of spontaneous respiratory neuron bursts in the ventrolateral medulla (VLM) of medullary slices or brain stem-spinal cord preparations. A medullary slice with a thickness of 1.0-1.4 mm or brain stem-spinal cord from 0- to 4-d-old rats was stained with fluorescent voltage-sensitive dye, RH795. Optical signals were recorded as a fluorescence change by using an optical recording apparatus with a 128 x 128 photodiode array and a maximum time resolution of 0.6 ms. Motoneuronal activity was simultaneously recorded at the hypoglossal nerve roots or fourth cervical ventral roots. Fluorescence changes corresponding to the spontaneous inspiratory burst activity were detected in the hypoglossal nucleus and VLM in slice preparations, and in a limited area extending rostrocaudally in the VLM of the brain stem-spinal cord preparation. These measurements did not require signal averaging by multiple trials. Results suggest that inspiratory neurons are localized in more compact form at the level of the nucleus ambiguous than at the more rostral VLM, and that peak activity during the inspiratory phase propagates from the caudal to the rostral VLM. In 60% of brain stem-spinal cord preparations, weak and scattered fluorescence changes preceding the inspiratory burst activity were detected more predominantly in the rostral part of the VLM. The present findings show the feasibility of optical recordings for the in vitro analysis of spontaneous respiratory neuron activity in the medulla.     

Patch-clamp recording in brain slices with improved slicer technology

The use of advanced patch-clamp recording techniques in brain slices, such as simultaneous recording from multiple neurons and recording from dendrites or presynaptic terminals, demands slices of the highest quality. In this context the mechanics of the tissue slicer are an important factor. Ideally, a tissue slicer should generate large-amplitude and high-frequency movements of the cutting blade in a horizontal axis, with minimal vibrations in the vertical axis. We developed a vibroslicer that fulfils these in part conflicting requirements. The oscillator is a permanent-magnet-coil-leaf-spring system. Using an auto-resonant mechano-electrical feedback circuit, large horizontal oscillations (up to 3 mm peak-to-peak) with high frequency ( approximately 90 Hz) are generated. To minimize vertical vibrations, an adjustment mechanism was employed that allowed alignment of the cutting edge of the blade with the major axis of the oscillation. A vibroprobe device was used to monitor vertical vibrations during adjustment. The system is based on the shading of the light path between a light-emitting diode (LED) and a photodiode. Vibroprobe monitoring revealed that the vibroslicer, after appropriate adjustment, generated vertical vibrations of <1 microm, significantly less than many commercial tissue slicers. Light- and electron-microscopic analysis of surface layers of slices cut with the vibroslicer showed that cellular elements, dendritic processes and presynaptic terminals are well preserved under these conditions, as required for patch-clamp recording from these structures.     

Silent NMDA receptor-mediated synapses are developmentally regulated in the dorsal horn of the rat spinal cord

In vitro whole cell patch-clamp recording techniques were utilized to study silent pure-N-methyl-D-aspartate (NMDA) receptor-mediated synaptic responses in lamina II (substantia gelatinosa, SG) and lamina III of the spinal dorsal horn. To clarify whether these synapses are present in the adult and contribute to neuropathic pain, transverse lumbar spinal cord slices were prepared from neonatal, naive adult and adult sciatic nerve transected rats. In neonatal rats, pure-NMDA receptor-mediated excitatory postsynaptic currents (EPSCs) were elicited in SG neurons either by focal intraspinal stimulation (n = 15 of 20 neurons) or focal stimulation of the dorsal root (n = 2 of 7 neurons). In contrast, in slices from naive adult rats, no silent pure-NMDA EPSCs were recorded in SG neurons following focal intraspinal stimulation (n = 27), and only one pure-NMDA EPSC was observed in lamina III (n = 23). Furthermore, in rats with chronic sciatic nerve transection, pure-NMDA EPSCs were elicited by focal intraspinal stimulation in only 2 of 45 SG neurons. Although a large increase in Abeta fiber evoked mixed alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and NMDA receptor-mediated synapses was detected after sciatic nerve injury, Abeta fiber-mediated pure-NMDA EPSCs were not evoked in SG neurons by dorsal root stimulation. Pure-NMDA receptor-mediated EPSCs are therefore a transient, developmentally regulated phenomenon, and, although they may have a role in synaptic refinement in the immature dorsal horn, they are unlikely to be involved in receptive field plasticity in the adult.     

The mouse cerebellar cortex in organotypic slice cultures: an in vitro model to analyze the consequences of mutations and pathologies on neuronal survival, development, and function

Thin acute slices and dissociated cell cultures taken from different parts of the brain have been widely used to examine the function of the nervous system, neuron-specific interactions, and neuronal development (specifically, neurobiology, neuropharmacology, and neurotoxicology studies). Here, we focus on an alternative in vitro model: brain-slice cultures in roller tubes, initially introduced by Beat G?hwiler for studies with rats, that we have recently adapted for studies of mouse cerebellum. Cultured cerebellar slices afford many of the advantages of dissociated cultures of neurons and thin acute slices. Organotypic slice cultures were established from newborn or 10-15-day-old mice. After 3-4 weeks in culture, the slices flattened to form a cell monolayer. The main types of cerebellar neurons could be identified with immunostaining techniques, while their electrophysiological properties could be easily characterized with the patch-clamp recording technique. When slices were taken from newborn mice and cultured for 3 weeks, aspects of the cerebellar development were displayed. A functional neuronal network was established despite the absence of mossy and climbing fibers, which are the two excitatory afferent projections to the cerebellum. When slices were made from 10-15-day-old mice, which are at a developmental stage when cerebellum organization is almost established, the structure and neuronal pathways were intact after 3-4 weeks in culture. These unique characteristics make organotypic slice cultures of mouse cerebellar cortex a valuable model for analyzing the consequences of gene mutations that profoundly alter neuronal function and compromise postnatal survival.     

Contribution of BK(Ca) channels of neurons in rostral ventrolateral medulla to CO-mediated central regulation of respiratory rhythm in medullary slices of neonatal rats

We recently described that carbon monoxide (CO) participated in the regulation of rhythmic respiration in medullary slices. The present study was undertaken to further assess whether the large-conductance calcium-activated potassium channels (BK(Ca) channels) are involved in the CO-mediated central regulation of respiratory rhythm in medullary slices. The rhythmic discharge of hypoglossal rootlets of medullary slices of neonatal rats was recorded. We observed that blocking BK(Ca) channels could partially abolish the effects of CO on the rhythmic bursts of hypoglossal rootlets. With whole-cell patch-clamp recording technique, we further observed that CO could reversibly augment potassium current density of the neurons in the rostral ventrolateral medulla. The CO-induced increase in potassium current was entirely blocked by the pretreatment of slices with BK(Ca) channels blocker; whereas blockade of CO generation with zinc protoporphyrin-IX produced an opposite response. Altogether, these data indicate that BK(Ca) channels of the neurons in neonatal rostral ventrolateral medulla could be activated by CO and involved in CO-mediated central regulation of respiratory rhythm in medullary slices.     

Size does matter: generation of intrinsic network rhythms in thick mouse hippocampal slices

Rodent hippocampal slices of < or = 0.5 mm thickness have been widely used as a convenient in vitro model since the 1970s. However, spontaneous population rhythmic activities do not consistently occur in this preparation due to limited network connectivity. To overcome this limitation, we develop a novel slice preparation of 1 mm thickness from adult mouse hippocampus by separating dentate gyrus from CA3/CA1 areas but preserving dentate-CA3-CA1 connectivity. While superfused in vitro at 32 or 37 degrees C, the thick slice exhibits robust spontaneous network rhythms of 1-4 Hz that originate from the CA3 area. Via assessing tissue O2, K+, pH, synaptic, and single-cell activities of superfused thick slices, we verify that these spontaneous rhythms are not a consequence of hypoxia and nonspecific experimental artifacts. We suggest that the thick slice contains a unitary circuitry sufficient to generate intrinsic hippocampal network rhythms and this preparation is suitable for exploring the fundamental properties and plasticity of a functionally defined hippocampal "lamella" in vitro.