猫脊髓背角双投射神经元的外周传入特性

电刺激猫颈髓背索和背外侧索可双重地逆向激动同侧腰骶髓背角神经元。该神经元对非伤害性和伤害性皮肤刺激发生反应;对电刺激其感受野的反应具有单突触性、低阈值和传导快等特征;该神经元的突触前和突触后纤维的传导速度相似,但不具正变关系。结果表明,SCT-DCPS神经元具有低阈机械感受型和广动力范围型两种生理学模型;从A_β传人接受输入并与之构成单突触联系;其突触前纤维直径与突触后纤维直径之间不具匹配关系。     

C类纤维传入诱发体感皮层电反应的脊髓上传通路

实验用猫,在氯醛糖和三碘季铵酚处理下进行。以强电脉冲刺激腓浅神经,结合极化电流阻滞A类纤维的传入后,选择性引起C类纤维传入时,在对侧大脑皮层体感Ⅰ区记录到特异的C类纤维皮层诱发电位(G-CEP)。观察到损毁脊髓胸11节段对侧腹外侧索后,C-CEP的幅值明显衰减;损毁同侧背索后,G-CEP的幅值也明显衰减;保留同侧背索,损毁脊髓其他部份后,C-CEP仍出现,但幅值变小;同时损毁上述两索后,C-CEP完全消失。提示C类纤维传入诱发C-CEP的脊髓上传通路位于同侧背索和对侧腹外侧索。     

脊髓背部电刺激对延脑内侧网状结构诱发电位抑制效应的分析

实验在46只急性麻痹清醒的猫上进行。以每秒100次的重复电脉冲刺激脊髓背部(L_1)可以抑制刺激腓肠神经在延脑内侧网状结构所引起的诱发电位,抑制后效应可持续5—10分钟。在12只动物上进行了脊髓部分横断的分析,在腰2水平切断刺激部位以下的两侧侧索靠近背角部分的纤维(简称背外侧索),上述抑制作用大大减弱。如再在刺激部位上、下(胸13及腰2)分别切割背索,则抑制效应完全消失。在刺激部位以上切断两侧背外侧索并不影响抑制效应的出现。在10只动物上将背索及背外侧索从脊髓本体上分离,以观察直接刺激的效应。结果表明,分别刺激两侧背外侧索或背索对延脑诱发电位都有抑制效应,前者的作用大于后者。如同时刺激分离的背外侧索及背索则诱发电位在整个刺激期间完全被抑制,其效应与背部电刺激相似,只是所需要的电流强度较弱。上述观察证明,脊髓背部电刺激对延脑网状结构诱发电位的抑制作用是通过背外侧索的下行通路和背索的上行及下行通路而实现的。背外侧索的作用大于背索,抑制作用主要发生在脊髓水平。     

刺激大鼠大脑脚影响脊髓伤害感受性传递的下行途径

在麻醉大鼠用部分切割脊髓的方法分析了刺激大脑脚影响脊髓背角伤害感受性神经元的下委途径。刺激ＣＰ对背角神经元伤害感受性反应（Ｃ－反应）的影响以抑制为,部分（３０．７％）神经元在抑制作用产生之前先被兴历,抑制作用主要是通过背索或背外侧索实现的,然而在多数神经元是两者共同作用的结果,其中ＤＬＦ的作用似乎更为重要。兴历作用则是通过ＤＦ实现的。由于大鼠的皮质脊髓束位于ＤＦ中,以上结果提示大脑皮层不仅可直接通     

白暨豚脊髓的解剖学和组织学研究

采用２头白暨豚的脊髓分别做成浸制标本和切片。其脊髓式为Ｃ８－Ｔ１０－Ｌｃ１２。根据Ｒｅｘｅｄ的细胞构筑原则将其灰质分为１０层,并对每层及其相关神经核的关系作了描记。在全髓白质中均发现特殊细胞群,包括侧索中的颈、胸、腰属外侧核,背索中的脊髓背索核,以及腹索中的散在细胞。还发现其软膜内陷到脊髓深部,在白质和灰质中形成腔隙和管道并充满脑脊液,神经细胞浸于脑脊液中。作者认为这些细胞应是接触脑脊液神经元（Ｃ     

白鱀豚脊髓的解剖学和组织学研究

采用２头白豚的脊髓分别做成浸制标本和切片。其脊髓式为Ｃ＿Ｒ－Ｔ＿（１０）－Ｌ＿（Ｌｃ１２）．根据Ｒｅｘｅｄ的细胞构筑原则将其灰质分为１０层,并对每层及其相关神经核的关系作了描记。在全髓白质中均发现特殊细胞群,包括侧索中的颈、胸、腰尾外侧核,背索中的脊髓背索核,以及腹索中的散在细胞。还发现其软膜内陷到脊髓深部,在白质和灰质中形成腔隙和管道并充满脑脊液,神经细胞浸于脑脊液中。作者认为这些细胞应是接触脑脊液神经元（ＣＳＦ－ＣＮ）。     

中华白海豚的解剖学和C_6、T_8、Lc_2的组织学研究

对１头雌成体中华白海豚的脊髓从宏观到微观研究其形态结构。光镜观察标本取自Ｃ６、Ｔ８和Ｌｃ２,冰切２０～４０μｍ,硫堇及镀银两法染色。脊髓式为Ｃ８Ｔ１２Ｌ１０Ｃａ４（或Ｌｃ１４）。脊髓长占体长的２７４８％,脊髓重占脑重的３８８％。蛛网膜小梁异常发达呈薄丝绵状,软脊膜携血管随沟、裂内陷入脊髓实质。灰、白质具不规则血管周隙,含淋巴细胞及脑脊液。神经细胞与微血管浸于脑脊液中,故神经细胞为ＣＳＦ－ＣＮ。根据Ｒｅｘｅｄ的细胞构筑原则,可将Ｃ６、Ｔ８、Ｌｃ２灰质分为１０层,并对每层及其相关神经核关系作了描述。在上述３节白质侧索、背索和腹索中均发现特殊细胞群,即：颈外侧核、胸外侧核和腰尾外侧核;背索核和腹索中的弥散性细胞。     

刺激中缝背核对大鼠脊髓背角神经元伤害性反应的影响及其传出途径的分析

大量资料表明,中缝背核(DR)在痛觉调节中具有重要作用。本实验用电生理学方法研究DR在痛觉调制中的下行性抑制作用,主要观察刺激DR对清醒制动大鼠脊髓背角神经元伤害性放电的影响。其主要结果是:①刺激DR或电针可以抑制脊髓背角神经元的伤害性反应,吗啡可加强这种抑制效应;②损毁中缝大核(NRM)、纳洛酮、麦角酰二乙胺(LSD)、赛庚啶及对氯苯丙氨酸(PCPA)均能部分阻断DR对脊髓背角神经元伤害性反应的抑制,实验结果表明:刺激DR抑制脊髓背角神经元的伤害性反应,部分是通过NRM间接控制背角神经元的伤害性传入;还有一部分是不通过NRM,可能是DR直接对脊髓背角伤害性信息的调制。在这种下行性抑制通路中有5-HT和阿片样物质的参与。     

中华白海豚脊髓的解剖学和C6、T8、Lc2的组织学研究

对1头雌成体中华白海豚的脊髓从宏观到微观研究其形态结构。光镜观察标本取自C₆ 、T₈ 和 Lc₂, 冰切20～40μm, 硫堇及镀银两法染色。脊髓式为 C₈-T₁₂-L₁₀-Ca₄ (或 Lc₁₄)。脊髓长占体长的27.48 %, 脊髓重占脑重的3.88%。蛛网膜小梁异常发达呈薄丝绵状, 软脊膜携血管随沟、裂内陷入脊髓实质。灰、白质具不规则血管周隙, 含淋巴细胞及脑脊液。神经细胞与微血管浸于脑脊液中, 故神经细胞为CSF-CN。根据 Rexed 的细胞构筑原则, 可将C₆、T₈、Lc₂灰质分为10层, 并对每层及其相关神经核关系作了描述。在上述3节白质侧索、背索和腹索中均发现特殊细胞群, 即: 颈外侧核、胸外侧核和腰尾外侧核; 背索核和腹索中的弥散性细胞。
     

大鼠脊髓诱发电位与脊髓损伤的关系——Ⅲ.脊髓局部损毁后电位的变化及电位来源分析

本文描述了大鼠脊髓L_1节段后柱、后索、侧索和前角的诱发电位及其损伤后的变化,并观察了切断L_4、L_5脊神经背、腹根与横断高位颈髓对电位的影响,以进行行电位来源分析。结果可见,上述四个区域的诱发电位基本由早反应三相波和晚反应组成。分别电解损毁这些部位后,电位波幅均普遍降低,晚期反应较早反应降低明显。后柱或后索受损对电位影响最大。局部损毁后可见L_1及T_(13)水平的硬膜上电位改变明显,尤其晚反应减弱、波峰平坦。反应时值与潜伏时未见明显改变。切断L_4脊神经背、腹根后、电位基本消失。去大脑对电位未见明显影响。结果表明,刺激坐骨神经诱发的脊髓电位起源于低位腰段传入神经和脊髓内多通路的兴奋传导,在一定程度上受腹根逆行活动的影响,与大脑及脊髓下行传导束活动无直接联系。脊髓诱发电位的幅度与波形改变可作为脊髓损伤的判断指标之一。     

Sensory responses of dorsal cells in the lamprey brain

Summary Sensory responses were evoked in 17/33 dorsal cells in the brain of the lampreyIchthyomyzon unicuspis by mechanical stimulation of the dorsolateral skin of the sucker and head. Fifteen of the responsive cells tested were classified as pressuresensitive and two as nociceptive. Thus, some of the dorsal cells which are situated in the medulla of the lamprey and which project into the branches of the trigeminal nerves have sensory functions similar to those of dorsal cells in the spinal cord.     

Effectiveness of ascending synaptic influences from various spinal funiculi on reticulospinal neurons in cats

Activity of reticulospinal neurons evoked by stimulation of the ventral, ventrolateral, dorsolateral, and dorsal funiculi of the spinal cord was recorded extracellularly in cats anesthetized with chloralose. Responses of 57 reticulospinal neurons, of which 22 projected into the ventral funiculus, 20 into the ventrolateral, and 15 into the dorsolateral, were studied. The functional properties (conduction velocity and refractory period) and the location of the neurons of the above-mentioned groups in the medulla did not differ appreciably. The most effective synaptic activation of all neurons was observed during stimulation of the dorsal and dorsolateral funiculi. Responses to stimulation of the dorsal funiculus had the lowest threshold. These responses arose in reticulospinal neurons of the ventral and ventrolateral funiculi after the shortest latent period. The effectiveness of synaptic influences from the dorsal and dorsolateral funiculi was identical in the group of neurons of the dorsolateral funiculus. Correlation between activity evoked by stimulation of the dorsal funiculus in reticulospinal neurons and peripheral nerves indicated that the responses appeared in these cells to stimulation of muscular (groups I and II) and cutaneous (group II) afferent fibers. The results indicate that impulses from low-threshold muscular and cutaneous afferents, which effectively activate reticulospinal neurons, are transmitted along ascending pathways of the dorsal funiculi.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 3, pp. 254–263, May–June, 1979.     

Peripheral and Spinal Inputs to Physiologically Identified Thalamic and Nonthalamic Relay Neurons in Cat Cuneate Nucleus

A single-unit population study of the feline cuneate nucleus was carried out to identify principal neuron types, their distribution within the nucleus, pattern of peripheral activation, and receptive field characteristics. Units were also tested for response to isolated dorsal column or dorsolateral funicular electrical stimulation. The nucleus was explored in a uniform pattern, and sample size was optimized by applying the search stimulus shocks to the dorsal spinal cord. Single units were defined as spinal afferents, cuneothalamic-relay (CTR) neurons, and non-cuneothalamic-relay (non-CTR) neurons. The following features were observed: (1) The distribution within the nucleus of specific cell types agreed with cytoarchitectural studies: Spinal afferent fibers were superficial and caudal; 22% of neurons were CTR neurons; CTR neurons were most dense in the middle of the nucleus and were largely separate from non-CTR neurons. (2) Of the 58 neurons tested for response to isolated dorsal column and dorsolateral funicular stimulation, 24% were activated from both tracts. (3) Convergent input from the off-focus periphery (defined as other than the ipsilateral forelimb) was detected in both CTR and non-CTR neurons, most commonly from the contralateral forepaw. Several neurons were activated from three limbs. (4) Thirty-seven percent of units were unresponsive to hair movement, touch, muscle palpation, or movement of joints. Compared to spinal fibers and non-CTR neurons, CTR neurons were most likely to have an identifiable input.     

Spinal tracts producing slow components of spinal cord potentials evoked by descending volleys in man

Slow negative (N) and slow positive (P) waves are frequently produced in the posterior epidural space at the lumbosacral enlargement by epidural stimulation of the rostral part of human spinal cord. The production of these slow potentials are thought to be responsible for analgesia at the stimulated segment as well as below that level. In order to define the spinal tract which mediates these slow potentials, we stimulated directly or from the epidural space the dorsal, dorsolateral, lateral and ventral columns at the cervical or thoracic level, and epidurally recorded spinal cord potentials (des.SCPs) at the lumbosacral enlargement in 7 patients who underwent spine or spinal cord surgery. The des.SCPs recorded in the lumbosacral enlargement consisted of polyphasic spike potentials followed by slow N and P waves. At a near threshold level of stimulus intensity the slow N and P potentials were consistently elicited only by stimulation of the dorsal column. The slow waves were also produced by intense stimulation of other tracts, but remained significantly (P < 0.05−P <0.01) smaller than those evoked by dorsal column stimulation when compared at the same stimulus intensity. Moreover, the slow P wave could not be elicited even by intense stimulation (10 times the threshold strength for the initial spike potentials) of the ventral column. Thus, the results suggest that the slow N and P waves are mostly mediated by the antidromic impulses descending through the dorsal column.     

Intracranial Somatosensory Responses with Direct Spinal Cord Stimulation in Anesthetized Sheep

The efficacy of spinal cord stimulators is dependent on the ability of the device to functionally activate targeted structures within the spinal cord, while avoiding activation of near-by non-targeted structures. In theory, these objectives can best be achieved by delivering electrical stimuli directly to the surface of the spinal cord. The current experiments were performed to study the influence of different stimulating electrode positions on patterns of spinal cord electrophysiological activation. A custom-designed spinal cord neurostimulator was used to investigate the effects of lead position and stimulus amplitude on cortical electrophysiological responses to spinal cord stimulation. Brain recordings were obtained from subdural grids placed in four adult sheep. We systematically varied the position of the stimulating lead relative to the spinal cord and the voltage delivered by the device at each position, and then examined how these variables influenced cortical responses. A clear relationship was observed between voltage and electrode position, and the magnitude of high gamma-band oscillations. Direct stimulation of the dorsal column contralateral to the grid required the lowest voltage to evoke brain responses to spinal cord stimulation. Given the lower voltage thresholds associated with direct stimulation of the dorsal column, and its possible impact on the therapeutic window, this intradural modality may have particular clinical advantages over standard epidural techniques now in routine use.     

Specific effects of alpha-D,L-aminoadipic acid on synaptic transmission in frog spinal cord

The sucrose gap technique was employed to investigate both synaptic and amino acid evoked responses from motoneurones or primary afferents of frog spinal cord. alpha-D,L-Aminoadipic acid (alpha-D,L-AAD) selectively antagonized responses to acidic amino acids, especially aspartate. The drug was most effective in antagonizing the polysynaptic components of synaptic potentials evoked by dorsal root or lateral column stimulation but had little effect on their monosynaptic components. The ventral root dorsal root potential which is thought to be mediated by a pathway that does not involve acidic amino acids was insensitive to alpha-D,L-AAD. These data, which were confirmed by intracellular recording from motoneurones, provided further evidence for the role of acidic amino acids in polysynaptic pathways in frog spinal cord.     

Long-range afferents in the rat spinal cord. II. Arborizations that penetrate grey matter.

1. The caudal extent of the collateral arborizations of entering sensory fibres in rat spinal cord was investigated by two methods: bulk labelling of peripheral nerves by injection of horseradish peroxidase conjugated to cholera toxin (B-HRP) and by antidromic stimulation using small currents from microelectrodes in the spinal cord while recording from single units in peripheral nerve or dorsal root. 2. The results show that injection of B-HRP into the sural or sciatic nerve labelled sural afferents in the grey matter three to four segments caudal to their root entry and sciatic nerve fibres were located in S4, the most caudal segment examined, four to six segments caudal to their root entry. 3. Detailed mapping with microelectrode stimulation showed that the parent descending fibres from filaments dissected from the L1 dorsal root coursed more than 20 mm, seven to eight segments caudal to the entry point in the dorsal columns and sent branches into the grey matter. Single units from the sural nerve were also followed caudally into the S2 and S3 spinal cord segments and also issued collateral branches into the grey matter. 4. The present results suggest that there is close agreement in the caudal penetration of long-ranging afferents by using complementary anatomical and electrophysiological methods.