坐骨神经阻滞引起成年大鼠初级体感皮层代表区的快速改变

为了探讨成年大鼠坐骨神经（ＳＣＩ）去传入后初级体感皮层是否发生快速重组,在氯胺酮麻醉下,利用微电极测定后爪代表区,然后用普鲁卡因阻滞对侧ＳＣＩ。结果表明,阻滞后１ｈ、４ｈ和８ｈ,隐神经代表区（ＳＡＲ）比对照分别增大３２．５％（ｎ＝７）、９３．０％（ｎ＝１７）和１００％（ｎ＝４）。此外,在原ＳＡＲ和新生ＳＡＲ记录的平均多单位诱发反应的峰潜伏期,后者比前者延长４．３ｍｓ。作者推测在快速出现的皮层重组机制中,皮层－皮层多突触通路的去抑制可能起重要作用     

坐有神经阻滞引起成年大鼠初级体感皮层代表区的快速改变

为了探讨成年大鼠坐骨神经去传入后初级体感皮层是否发生快速重组,在氯胺酮麻醉下,利用微电极测定后爪代表区,然后用普鲁卡因阻滞对侧ＳＣＩ。结果表明,阻滞后１ｈ,４ｈ和８ｈ,隐神经代表区比对照分别增大３２．５％,９３．０５和１００％。此上,在原ＳＡＲ和新生ＳＡＲ记录的平均多单位诱发反应的峰潜伏期,后者比前者延长４．３ｍｓ。作者推测在快速出现的皮层重组机制中,皮层－皮层多突触通路的去抑制可能起重要作用。     

去胡须对大鼠行为及桶状皮层的影响

目的:研究外周去胡须后大鼠行为及桶状皮层(barrel cortex,BC)的可塑性变化。方法:SD大鼠随机分组(n=4):正常对照(A组),出生后第2天去除双侧颊脂垫组(B组),出生后第2天去除右侧颊脂垫组(C组),出生后1～5d每天剪右侧胡须,从出生后第5天起不剪由其胡须自由生长组(D组)。出生后第30天时称体重,测量左侧D2胡须长度,观测行为学变化(如狭缝实验、自由探索行为和趋壁行为)。采用细胞色素氧化酶组织化学法研究barrel排列与发育情况。结果:A组能迅速辨别出正确狭缝并钻入,平均用时(5.6±2.3)s;B组大鼠只有当鼻尖碰到狭缝壁时才会钻入狭缝。C组大鼠当其右侧脸颊靠近狭缝时,不能辨别出狭缝,只有当其掉转身体,用左侧胡须探测时才可能迅速钻入正确的狭缝。D组的表现同C组,B、C、D组大鼠进入正确狭缝的所用时间均显著长于A组(P0.01,P0.05,P0.01)。去除双侧颊脂垫的大鼠其左趋壁时间、右趋壁时间以及总趋壁时间均较正常大鼠短。去除右侧颊脂垫组的大鼠右趋壁时间也显著短于正常(P0.05)。四组大鼠左侧D2胡须长度以及体重均无显著差异。从出生后第2天时一直剪除右侧胡须的小鼠在出生后第30天时发现其barrel变小,排列较混乱,barrel之间的界限不清,皮层细胞色素氧化酶(CO)反应的灰度明显变淡。结论:外周去传入不引起大鼠体重改变及残留胡须长度的代偿性改变,但可引起其趋触及探索行为方面的改变。外周去传入可导致barrel形状及排列的可塑性变化。     

外周损伤引起成年大鼠体感皮层的功能重组

为了了解外周神经损伤对体感皮层分域组构的影响,在成年大鼠上观察了切断坐骨神经(SC)前、即刻和切断后数周内后爪皮层代表区的改变。在盐酸氯胺酮麻醉下,用微电极记录后爪皮肤轻触刺激在对侧体感皮层工区诱发的多单位反应,得出后爪的皮层代表区图。在16例中,8例大鼠观察了切断SC的即时效应。结果表明,不但SC代表区丧失皮肤反应性,原隐神经(SA)代表区的皮肤反应性也明显下降或消失,同时神经元自发活动也明显减弱。另8例大鼠在切断后数周内做了1～3次重复测定。在最初几天,原SA代表区范围内多数记录点的皮肤反应性仍未恢复,但在原SC代表区内,一些记录点转而对SA皮肤轻触刺激起反应。在随后数周内SA代表区进行性地扩张,占领了大部分原SC代表区。这一结果说明成年大鼠外周神经损伤可导致体感皮层发生显著的重组改变。     

大鼠皮层扩散性抑制过程的在体内源光信号成像

皮层扩散性抑制(cortical spreading depression,CSD)是研究偏头痛、脑梗塞等疾病的一种重要病理模型.而CSD过程中伴随发生的皮层血液动力学变化目前尚不完全清楚.利用高分辨的内源光信号成像技术,在体观测了大鼠CSD产生和发展过程中540 nm及660 nm波长皮层反射内源光信号变化的时空动力学特征,分析讨论了引起这一内源光信号变化可能的内在生理机制.实验结果显示,CSD诱发的内源光信号变化呈现多时相的特点,其传播由刺激中心以同心圆的样式向周围扩散,速度约为(3.7±0.4) mm/min.对于540 nm,CSD引起了皮层反射光强的降低［幅度(－2.1±1.2)%, 持续时程(16.2±3.8)s］,升高 ［幅度(2.9±1.6)%, 持续时程(13.8±2.2)s］,再降低 ［幅度(－14.2±4.5)%, 持续时程(40.6±8.4)s］和再升高持续时程［(146.2±40.3)s］,同时观测到软脑膜动脉的大幅度舒张,血管管径变化峰值增大了(69.2±26.1)%.而对于660 nm, 内源光信号变化的时间特性在皮质区主要表现为反射光强的增大［幅度(3.8±0.6)%, 持续时程(17.9±5.1)s］,减小［幅度(－3.0±1.7)%, 持续时程(43.3±6.4)s］和稍后持续缓慢的光强增加.     

电压敏感染料成像技术及其在神经科学中的应用

电压敏感染料成像(voltage sensitiVe dye imaging,VSDI)技术利用结合在神经细胞脂膜上的染料,将膜电位转化为荧光或光吸收信号,并用光学成像方法对神经电活动进行多点测量.VSDI在过去的50年内发展迅速,其良好的时空分辨率使它成为一种在介观(mesoscopic)时空尺度上研究神经元群体电活...     

大鼠丘脑侧后核到初级视皮层突触传递的短时程可塑性

大鼠丘脑侧后核(lateral posterior thalamic nucleus,LP nucleus)到初级视皮层的突触连接是膝体外视觉通路的重要组成部分.运用场电位记录和电泳的方法在位研究了该视觉回路突触传递的短时程可塑性.结果表明,无论是运用双脉冲刺激还是串刺激都能观察到明显的短时程抑制特性.电泳荷包牡丹碱(bicuculline)和2-hydroxy-saclofen使该抑制作用减弱,电泳钙离子使抑制加强,电泳APV对抑制作用没有明显影响.所以突触前递质释放水平的改变,和γ-氨基丁酸(GABA)能受体（尤其是GABA_B受体）的活动都会影响该回路突触传递的短时程可塑性,而N-甲基-D-天冬氨酸(NMDA)受体则几乎没有作用.该回路很强的短时程抑制特性可能与LP核在视觉注意中的作用有关.     

电刺激尾核头部对隐神经A类和C类纤维传入诱发体感皮层电反应的影响

实验用猫,在氯醛糖麻醉、三碘季铵酚制动下,用方波电脉冲刺激隐神经,配合极化电流阻断技术分别引起隐神经Ａ和Ｃ类纤维兴奋,在对侧大脑皮层ＳⅠ区和ＳⅡ区记录平均诱发电位（分别同称为Ａ－ＳⅠＥＰ、Ａ－ＳⅡＥＰ、Ｃ－ＳⅠＥＰ、Ｃ－ＳⅡＥＰ）。用双极同心圆电极刺激尾核头部不同部位。实验结果表明,只有刺激同侧尾核头部内侧浅表部位,才对Ｃ－ＳⅠＥＰ,Ｃ－ＳⅡＥＰ,Ａ－ＳⅡＥＰ有抑制作用,提示尾核头部对大脑皮层不同躯体感觉代表区有不同的调制作用,对ＳⅠ区Ｃ类纤维传入信息有独特的抑制作用。     

格列本脲对大鼠皮层扩散性抑制中脑血管的调节作用

皮层扩散性抑制(corticalspreadingdepression,CSD)是研究偏头痛、脑梗塞等疾病的重要病理模型.已有研究表明,在普遍被观察到的CSD过程中软脑膜动脉血管大幅度舒张之前,还存在一个较小幅度的软脑膜动脉扩张和收缩.但其中的脑血管调节机制尚不清楚.采用550nm的内源信号光学成像(opticalintrinsicsignalimaging,OISI)监测ATP敏感钾离子通道(ATP-sensitivepotassiumchannels,KATP)的阻断剂格列本脲(glibenclamide,glyb),对针刺诱导的大鼠CSD过程中软脑膜动脉血管舒缩过程的影响.实验中观测到软脑膜血管的初始小收缩(initialslightconstriction,ISC)相对于对照组显著减弱,其中应用10μmol/Lglyb时,74.5%的ISC被完全抑制,100μmol/Lglyb时则有96.2%的ISC完全消失.相对于CSD发生前,软脑膜动脉血管大幅舒张(largedilation,LD)的峰值也分别显著增强了(53.8±19.3)%和(59.8±19.6)%.结果表明,可能是神经元上的KATP在CSD过程中被glyb阻断从而抑制了软脑膜动脉血管的收缩.     

大鼠局灶性脑缺血后KCl诱导皮层扩散性抑制的体光学成像

采用线栓法制备大鼠大脑中动脉栓塞(middle cerebral artery occlusion,MCAO)模型,在额叶皮层用KCl诱导产生皮层扩散性抑制(cortical spreadingdepression,CSD).MCA04 h后,利用550 nm内源信号光学成像(optical intrinsic signalimaging,OISI)监测局灶性脑缺血后大鼠顶-枕叶皮层内源光信号变化.成像1 h内观测到一系列诱导CSD波(14±3次),CSD波局限于顶-枕叶皮层中央区域扩展,以光强的显著下降为特征;而旁侧区域光强无明显改变,不具备CSD波特征,表明CSD波未传播到该区域.随后TIC染色证明上述旁侧区域已经梗死.实验表明:MCAO后4h,皮层区域旁侧部分会梗死;CSD波的0IS变化可用来区分缺血梗死区和外周供血较为完整区域(未梗死区).     

Supra-barrel Distribution of Directional Tuning for Global Motion in the Mouse Somatosensory Cortex

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刺激大脑皮层体感Ⅱ区对C类纤维传入诱发体感Ⅰ区电反应的影响

电刺激猫大脑皮层体感Ⅱ区(SⅡ)隐神经投射点对隐神经C类纤维传入引起的体感Ⅰ区(SⅠ)诱发电位(C-CEP)有明显的抑制和易化两种影响。前者使C-CEP幅值降低、潜伏期延长;后者使C-CEP幅值升高、时程延长。抑制影响的持续时间较长,而易化持续时间则较短。弱刺激SⅡ区时,易化程度和出现机率较高;而强刺激时,则抑制程度和出现机率较高。弱刺激SⅡ区浅层时,有抑制和易化两种作用;而刺激深层时则只有抑制作用,同样强度刺激深层的抑制效应比刺激浅层大。提示SⅡ区可能对SⅠ区C-CEP有调制作用。     

Evidence for Synchronous Activation of Neurons Located in Different Layers of Primary Somatosensory Cortex

Although many studies have examined the columnar organization of primary somatosensory (SI) cortex, the functional relationship among neurons in different layers remains unclear. To understand how activity is coordinated among different cortical layers, the present investigation tested the hypothesis that the initial part of a peripheral stimulus produces a serial pattern of laminar activation in SI cortex. Extracellular discharges of 334 histologically recovered neurons were recorded from the medial bank of the coronal sulcus in nine anesthetized cats during electrical or cutaneous stimulation of the distal forelimb. Mean responses during the initial 50-msec period following stimulus onset were largest in layers IIIb or IV for both types of stimulation, but laminar differences in the magnitude of onset responses were not statistically significant. Among 175 neurons with responses exceeding 0.5 spikes per stimulus, electrical Stimulation consistently produced shorter response latencies than mechanical indentation in the extragranular (II, IIIa, V, VI), but not in the middle (IIIb, IV), cortical layers. The average minimum latencies for different cortical layers ranged from 7.4 to 10.1 msec for responses to electrical stimulation and from 10.3 to 11.6 msec for responses to mechanical indentations, but these laminar differences were not statistically significant. In some experiments, neurons in different layers of a cortical column were recorded simultaneously with dual-electrode assemblies; among 37 neuron pairs in which both neurons responded with more than 0.5 spikes per stimulus, response latencies were similar, even though the neurons were separated by several hundred microns. Cross-correlation analysis of the onset responses for neurons recorded simultaneously from different layers also indicated that many cells throughout a cortical column were activated nearly simultaneously by the initial phase of a peripheral stimulus. Results from the present study are compared with previous reports examining laminar patterns of activation.     

Localization and Central Projections of Primary Afferent Neurons That Innervate the Temporomandibular Joint in Cats

Primary afferent neurons that innervate the temporomandibular joint (TMJ) in cats were labeled by injecting a 2-5% solution of wheatgerm agglutinin bound to horseradish peroxidase into the joint capsule and capsular tissues in 14 cats and processing the brain stem and trigeminal ganglia using the tetramethylbenzidine method described by Mesulam (1978). The perikarya of ganglion cells that innervate the TMJ ranged in diameter from 15 to 109 μm and were primarily located in the posterolateral portion of the trigeminal ganglion. The central processes of these neurons entered the brain stem in middle pons and were distributed to all portions of the sensory trigeminal nuclei. However, the majority of labeled fibers and greatest density of terminal labeling were observed in the dorsal part of the main sensory nucleus and the subnucleus oralis of the spinal trigeminal nucleus. Very few labeled fibers were observed in the spinal tract of the trigeminal nerve below the obex. However, evidence for axon terminals was consistently observed in laminae I, II, and III of the medullary dorsal horn. These findings concur with physiological evidence showing that information from the TMJ influences neurons in rostral (Kawamura et al, 1967) and in caudal (Broton et al, 1985) portions of the trigeminal sensory nuclei.     

乙酰胆碱在刺激SⅡ区影响C类纤维传入诱发的SI区电反应中的作用

电刺激猫大脑皮层体感Ⅱ区(SⅡ)对隐神经C类纤维传入引起的体感Ⅰ区(SⅠ)诱发电位(C—CEP)有抑制和易化作用。在SⅠ区局部用阿托品能部分地阻断电刺激SⅡ区对C—CEP的抑制作用,但对易化作用的影响不明显;而用六烃季铵(C_6)能阻断易化作用,但对抑制作用的影响却不明显。在SⅠ区局部应用0.01％乙酰胆碱(ACh)对C—CEP有易化作用,用0.1％ACh则有抑制作用。结果提示,ACh可能参与SⅡ区对SⅠ区C—CEP的影响,通过SⅠ区的胆碱能M受体起抑制作用,通过N受体起易化作用。     

Acute Effects of Total or Partial Digit Denervation on Raccoon Somatosensory Cortex

The immediate effects of total or partial denervation of single digits (0-16 hr after nerve transection) on primary somatosensory cortex were studied electrophysiologically. Comparisons of response properties and cortical somatotopy were made between intact raccoons and four groups of raccoons with transection of some or all of the nerves innervating the fourth or fifth digit. Animals with all four digital nerves cut (amputation of the digit) were most different from normal. Approximately half of the penetrations in the affected cortical region showed inhibitory responses to stimulation of adjacent skin regions. These consisted of a strong response to stimulus offset and/or a suppression of spontaneous activity during indentation. Since these responses were substantially different from those recorded several months after digit amputation, additional changes in connectivity and synaptic strength must occur with chronic denervation. These inhibitory responses were not seen in animals with one, two, or three nerves cut per digit.

In the animals with partial denervation of a digit, the greatest disruption occurred when both ventral nerves to the glabrous skin were transected. This yielded cell clusters with abnormally large receptive fields, disruptions in somatotopic organization, and a decreased occurrence of low-threshold responses. If only one nerve to glabrous skin was transected, there was less change, even if it was combined with transection of both nerves to hairy skin. These results suggest that the release of inhibitory responses in a cortical digital region by amputation is prevented by the retention of even one ventral nerve. None of the denervation conditions produced large nonresponsive areas of cortex, which would have indicated a loss of all inputs.