老年人内侧膝状体形态、血供和来源动脉的病理学改变

目的 :研究老年人内侧膝状体的形态、毗邻及供血动脉来源、分支、分布和病理改变。方法 :体视及手术显微镜下观察 60～ 80岁年龄的脑内侧膝状体的形态、毗邻和血供情况 ;取内侧膝状体来源动脉 (大脑后动脉 )光镜下观察动脉壁的病理改变情况。结果 :内侧膝状体呈半球形 ,动脉来源于大脑后动脉的分支 ,即丘脑膝状体动脉 ,脉络丛后内、外动脉和丘体动脉 ,每侧有小动脉 ( 6.8± 1 .5 )支 ,大脑后动脉粥样硬化改变者占 88.3 %。结论 :内侧膝状体动脉细小 ,仅由大脑后动脉供血 ,动脉硬化可致小动脉管腔狭窄 ,供血不足 ,可能是老年人听力下降的原因之一。     

E15胎鼠内侧膝状体超微结构观察

取Ｅ１５胎鼠内侧膝状体，固定、脱水、包埋、超薄切片，透射电镜观察。神经细胞散在分布，细胞核偏位，表面呈齿状，核膜下染色质较浓密。细胞浆含大量游离核糖体，粗面内质网已出现。线粒体嵴数目少，而其基质密度高。高尔基复合体的扁平囊可达５层之多，胞浆呵见中空的大泡。神经细胞的突起较少。本文认为Ｅ１５内侧膝状体处于已分化、低发育状态。     

基于三维建模的猫内侧膝状体与听皮层的投射研究

目的研究猫内侧膝状体(medial geniculate body,MGB)的立体定位与主要亚核团的三维可视化及其与听皮层(auditory cortex,AC)的神经投射。方法在细胞构筑及采用辣根过氧化物酶(Horseradish Peroxidase,HRP)、生物素葡聚糖胺(biotinylated dextran amine,BDA)进行神经追踪基础上,建立猫内侧膝状体及听皮层冠状切片的二维数据库,通过软件Amira实现可视化及三维建模。结果1.猫内侧膝状体腹侧群(MGBv)、背侧群(MGBd)以及内侧群(MGBm)三个主要亚核团的重建模型真实、精确,再现了猫右脑半球内MGB各亚核团的自然形态及毗邻。2.内侧膝状体各亚核团的构成方式、听皮层的层状分布模式、广义听皮层内部各亚区之间的配布模式之间存在着相对应的组构格局。结论细胞构筑、神经示踪、组织化学染色和数字人图像处理技术相结合,实现了内侧膝状体主要亚核团的三维重建,对听觉通路的相关研究和小核团的数字解剖学研究具有重要意义。     

胎鼠内侧膝状体植入成年大鼠听皮质区的形态学研究

将E15-E16天胎鼠的内侧膝状体原基植入到成年Wistar大鼠听皮质区脑腔内,于移植后60天取材,Nissl、Weil、Marsland-Glees法制备光镜及透射电镜观察.光镜下移植物神经元存活且分化发育良好,有少数神经元未分化成熟.移植物的细胞构筑有一定的特征.电镜下移植物丰富的神经毡内有树突和轴突.可看到不对称型和对称型的突触,突触前膜内含有空心的圆形或椭圆形突触小泡及大颗粒小泡.结果显示移植物神经元的形态结构与正常内侧膝状体基本一致,但在发育过程上有一定的延迟.移植物内已建立了局部神经环路,血脑屏障已形成.     

后丘脑动脉的显微解剖及其微血管构筑

用手术显微镜观测了４８例成人后丘脑的动脉，并用墨汁明胶灌注，厚片透明，碱性磷酸酶染色示血管内皮及甲酯铸型法，在体视显微镜和扫描电镜下观察了１４例胎儿后丘脑的微血管构筑。后丘脑的动脉分为内侧膝状体丘脑动脉，外侧膝状体丘脑动脉和膝状体间丘脑动脉。     

大鼠前庭—丘脑投射——HRP法研究

用 HRP 法研究了41只大鼠的前庭—丘脑投射。在丘脑腹前核(腹外侧核)、腹内侧核、中央外侧核、腹后核、丘脑后核、内侧膝状体大细胞部及外侧膝状体腹侧核等处分别注入 HRP 后,在前庭核簇的不同亚核中观察到标记细胞。证实了大鼠和猫及猴同样也有前庭—丘脑投射。并依前庭—丘脑投射的细胞起源和终止部位不同,可将前庭—丘脑投射大致分为两大类。第一类起自前庭核簇所有四个亚核,投射到丘脑的“非特异”核群,包括腹前核(可能还有腹外侧核),腹内侧核及中央外侧核,可能与维持并改变大脑皮层的兴奋性以及完成运动功能有关。第二类仅起自前庭内侧核和降核,投射到丘脑的腹后核及后核群(包括丘脑后核、内侧膝状体大细胞部及外侧膝状体腹侧核),可能和前庭感觉的传递以及前庭感觉和其它感觉的会聚有关。     

P77PMC大鼠听源性惊厥神经回路──核团损毁研究

采用立体定位直流电损毁法,分别损毁双侧下丘、脑桥吻侧网状核、内侧膝状体、黑质,观察核团损毁对大鼠听源性惊厥行为的影响,以寻找与P77PMC大鼠听源性惊厥有关的神经核团。结果表明：双侧下丘损毁后能完全阻断强直阵挛性惊厥,脑桥吻侧网状核损毁能明显减少惊厥发生（P＜0．05）,而双侧内侧膝状体及黑质损毁对惊厥无明显影响（P＜0．05）。提示下丘是P77PMC大鼠听源性惊厥的关键核团,而脑桥吻侧网状核可能参与了惊厥回路,内侧膝状体可能并未参与惊厥回路,黑质在此惊厥中的作用尚不明确。     

猫外侧膝状体腹核至上丘和顶盖前区的定位投射——HRP法

本文采用HRP方法观察了猫外侧膝状体腹核至上丘和顶盖前区的定位投射,HRP注射在上丘深层后,可见同侧较吻端的外侧膝状体腹核内侧部腹侧半的许多细胞被标记,这些细胞成团分布,多为圆形或卵圆形。注射在吻端顶盖前区以后,二侧较尾端的外侧膝状体腹核外侧部的细胞被标记,以对侧为主。注射至尾端顶盖前区(部分扩散至上丘)后,同侧较尾端的外侧膝状体腹核外侧部腹侧半的细胞被标记。与注射于上丘者相比,细胞密度较低,亦为圆形或卵圆形,提示外侧膝状体腹核至上丘或顶盖前区的投射具有较明显的局部组构关系。     

金黄地鼠上丘和外侧膝状体之间的联系

本实验采用了顺行和逆行追踪技术,对金黄地鼠上丘与丘脑视核团的纤维联系进行了实验观察。一、用尼氏和Loyez染色法,对4只正常金黄地鼠上丘和外侧膝状体背核和腹核的正常结构做了观察。二、3~H-亮氨酸和3~H-脯氨酸注入动物上丘不同部位(4只,存活期一天)后,可见神经末梢标记于同侧的外侧膝状体背核和腹核的外侧部位。若注射部位在上丘外侧,其投射部位在外侧膝状体背核和腹核的尾外侧;注射部位移向内侧,投射部位移向吻外侧。三、将HRP注入外侧膝状体背核(4只,存活期一天)或腹核(2只,存活期一天)或后外侧核(2只,存活期一天)后,在同侧上丘浅层见有标记神经元。在上丘深层则未见。本实验说明了上丘浅层的神经元对同侧的外侧膝状体背核和腹核有局部定位的投射,并按视野和视网膜将该投射作定位排列。     

大鼠上丘的传出投射——ARG法和WGA-HRP法研究

本实验将~3H-Leucine 或 WGA-HRP 定位注(导)入大鼠一侧上丘内,观察了上丘传出纤维的终止部位。上丘浅层的传出纤维下行终止于二叠体旁核(以同侧核的背、腹群为主)、同侧桥核的背外侧部;其上行投射终止于内侧膝状体、膝上核、顶盖前区后核、丘脑外侧后核(以上均为两侧性,以同侧为主)、同侧的内及外侧视束核和外侧膝状体的背侧及腹侧核。另外,在两侧视束和视束交叉处均有标记颗粒。上丘中、深层的传出纤维终止于同侧中央灰质、Darkschewitsch 核、Cajal 中介核、楔形核以及对侧上丘;上行终止于内测膝状体,膝上核、顶盖前区前核、丘脑外侧后核(以上均为两侧性,以同侧为主)、束旁核、未定带、丘脑腹侧核(以上均为同侧);下行终止于同侧的有二叠体旁区和二叠体旁核,桥核的背外侧部、下丘外侧部、桥脑和延髓网状结构、下橄榄核的外侧部;终止于对侧的有二叠体旁核、桥脑和延髓网状结构内侧部、下橄榄核的内侧副核、脊髓颈段前角。     

The distribution of calbindin, calretinin and parvalbumin immunoreactivity in the human thalamus

Calcium-binding proteins show a heterogeneous distribution in the mammalian central nervous system and are useful markers for identifying neuronal populations. The distribution of the three major calcium-binding proteins - calbindin-D28k (calbindin), calretinin and parvalbumin - has been investigated in eight neurologically normal human thalami using standard immunohistochemical techniques. Most thalamic nuclei show immunoreactive cell bodies for at least two of the three calcium-binding proteins; the only nucleus showing immunoreactivity for one calcium-binding protein is the centre médian nucleus (CM) which is parvalbumin-positive. Overall, the calcium-binding proteins show a complementary staining pattern in the human thalamus. In general terms, the highest density of parvalbumin staining is in the component nuclei of the ventral nuclear group (i.e. in the ventral anterior, ventral lateral and ventral posterior nuclear complexes) and in the medial and lateral geniculate nuclear groups. Moderate densities of parvalbumin staining are also present in regions of the mediodorsal nucleus (MD). By contrast, calbindin and calretinin immunoreactivity both show a similar distribution of dense staining in the thalamus which appears to complement the pattern of intense parvalbumin staining. That is, calbindin and calretinin staining is most dense in the rostral intralaminar nuclear group and in the patchy regions of the MD which show very low levels of parvalbumin staining. However, calbindin and calretinin also show low levels of staining in the ventral nuclear complex and in the medial and lateral geniculate bodies which overlaps with the intense parvalbumin staining in these regions. These results show that the calcium-binding proteins are heterogeneously distributed in a complementary fashion within the nuclei of the human thalamus. They provide further support for the concept recently proposed by Jones (Jones, E.G., 1998. Viewpoint: the core and matrix of thalamic organization. Neuroscience 85, 331-345) that the primate thalamus comprises of a matrix of calbindin immunoreactive cells and a superimposed core of parvalbumin immunoreactive cells which may have differential patterns of cortical projections.     

Localization of N-acetylaspartylglutamate-like immunoreactivity in selected areas of the rat brain

N-acetylaspartylglutamate (NAAG) was detected immunohistochemically in the rat brain using an antiserum which recognizes carbodiimide-fixed NAAG. NAAG-like immunoreactivity is described in 5 areas of the brain; olfactory bulb, septal nuclear area, lateral geniculate nucleus, superior colliculus and the entorhinal cortex/hippocampal formation. Mitral cells of the olfactory bulb and neurons concentrated in the medial septum were densely immunostained. A dense population of immunoreactive puncta was found in the superior colliculus and lateral geniculate nucleus (LGN). The LGN also contained immunoreactive neurons. The entorhinal cortex contained numerous immunoreactive cells in layers II-III while the hippocampus had few neurons that were NAAG-positive.     

Interruption of projections from the medial geniculate body to an archi-neostriatal field disrupts the classical conditioning of emotional responses to acoustic stimuli

We have previously found that the coupling of changes in autonomic activity and emotional behavior to acoustic stimuli through classical fear conditioning survives bilateral ablation of auditory cortex but is disrupted by bilateral lesions of the medial geniculate nucleus or inferior colliculus in rats. Auditory fear conditioning thus appears to be mediated by the relay of acoustic input from the medial geniculate nucleus to subcortical rather than cortical targets. Since the medial geniculate nucleus projects, in addition to auditory cortex, to a striatal field, involving portions of the posterior neostriatum and underlying archistriatum (amygdala), we have sought to determine whether interruption of connections linking the medial geniculate nucleus to this subcortical field also disrupts conditioning. The conditioned emotional response model studied included the measurement of increases in mean arterial pressure and heart rate and the suppression of exploratory activity and drinking by the acoustic conditioned stimulus following delayed classical conditioning, where the footshock unconditioned stimulus appeared at the end of the conditioned stimulus. The peak increase in arterial pressure and the duration of activity and drinking suppression were greater in unoperated animals subjected to delayed conditioning than in pseudoconditioned controls, where the footshock was randomly rather than systematically related to the acoustic stimulus. Increases in heart rate, however, did not differ in conditioned and pseudoconditioned groups. While the arterial pressure and behavioral responses therefore reflect associative conditioning, the heart rate response does not. Rats were prepared with bilateral lesions of the medial geniculate nucleus, bilateral lesions of the striatal field or asymmetrical unilateral lesions destroying the medial geniculate nucleus on one side and the striatal field on the contralateral side. The latter preparation leaves one medial geniculate nucleus and one striatal field intact but disconnected and thus produces a selective auditory deafferentation of the intact striatal field. Control groups included animals with unilateral lesion of the medial geniculate nucleus, with unilateral lesion of the medial geniculate nucleus combined with lesion of the ipsilateral striatal field, unilateral lesion of the medial geniculate combined with lesion of the contralateral anterior neostriatum (a striatal area outside of the medial geniculate nucleus projection field).(ABSTRACT TRUNCATED AT 400 WORDS)     

Histometric changes and cell death in the thalamus after neonatal neocortical injury in the rat

Freezing injury to the developing cortical plate results in a neocortical malformation resembling four-layered microgyria. Previous work has demonstrated that following freezing injury to the somatosensory cortex, males (but not females) have more small and fewer large cells in the medial geniculate nucleus. In the first experiment, we examined the effects of induced microgyria to the somatosensory cortex on neuronal numbers, neuronal size, and nuclear volume of three sensory nuclei: ventrobasal complex, dorsal lateral geniculate nucleus, and medial geniculate nucleus. We found that there was a decrease in neuronal number and nuclear volume in ventrobasal complex of microgyric rats when compared with shams, whereas there were no differences in these variables in the dorsal lateral geniculate nucleus or medial geniculate nucleus. We also found that there were more small and fewer large neurons in both ventrobasal complex and medial geniculate nucleus. In experiment 2, we attempted to determine the role of cell death in the thalamus on these histometric measures. We found that cell death peaked within 24 h of the freezing injury and was concentrated mostly in ventrobasal complex. In addition, there was evidence of greater cell death in males at this age. Taken together, these results support the notion that males are more severely affected by early injury to the cerebral cortex than females.     

The organization of the crossed geniculogeniculate pathway of the rat: a Phaseolus vulgaris-leucoagglutinin study.

The intergeniculate leaflet of the thalamus is known to give rise to neuronal projections to the suprachiasmatic nuclei and the rostral part of the pineal gland. Via these projections the intergeniculate leaflet is considered to play a role in regulation of circadian rhythms. Iontophoretic injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin were placed in various subnuclei of the lateral geniculate nucleus in order to study the topographical organization of the crossed geniculogeniculate pathway in the rat. Injections involving neurons in the intergeniculate leaflet or the medial subpart of the ventral nucleus (which presumably is part of the intergeniculate leaflet of the thalamus too) gave rise to labeled nerve fibers in the opposite lateral geniculate nucleus. The axons contained in this pathway were followed either medially via the posterior commissure, or via the optic tracts and optic chiasm, to the contralateral hemisphere. In the contralateral lateral geniculate nucleus, the intergeniculate leaflet was most densely innervated, but a substantial innervation of the ventral lateral geniculate nucleus was observed as well. Only a few labeled fibers were observed in the dorsal subnucleus. However, the dense innervation of the contralateral intergeniculate leaflet not only covered the small zone between the dorsal and ventral nuclei, but also a dorsomedial part of the ventral nucleus that merged caudally with the lateral part of the zona incerta. In the remaining part of the ventral nucleus, single Phaseolus vulgaris-leucoagglutinin-labeled fibers surrounded specific cells. The demonstration of a divergent projection between the intergeniculate leaflet and specific subparts of the contralateral geniculate nuclei indicates that the two lateral geniculate nuclei are regulating each other. The function of this pathway is suggested to be related to the regulation of circadian rhythmicity, but experimental evidence for this hypothesis is still lacking.     

Neocortical connections in fetal cats

The major extrinsic projections to and from visual and auditory areas of cerebral cortex were examined in fetal cats between 46 and 60 days of gestation (E46-E60) using axonal transport of horseradish peroxidase either alone or in combination with tritiated proline. Projections to visual cortex from the dorsal lateral geniculate nucleus and lateral-posterior/pulvinar complex exist by E46, and those from the contralateral hemisphere, claustrum, putamen, and central lateral nucleus of the thalamus are present by E54-E56. In addition, cells in the medial geniculate nucleus project to auditory cortex by E55. At E54-E56 efferent cortical projections reach the contralateral hemisphere, claustrum, putamen, lateral-posterior/pulvinar complex and reticular nucleus of the thalamus. Cells in visual cortex also project to the dorsal and ventral lateral geniculate nuclei, pretectum, superior colliculus and pontine nuclei, and cells in auditory cortex project to the medial geniculate nucleus. Except for interhemispheric projections, all pathways demonstrated are ipsilateral, and projections linking cerebral cortex with claustrum, dorsal lateral geniculate nucleus and lateral-posterior/pulvinar complex are reciprocal. The reciprocal projections formed with the dorsal lateral geniculate nucleus, lateral-posterior/pulvinar complex and the claustrum show a greater degree of topological organization compared to the projections formed with the contralateral hemisphere and superior colliculus, which show little or no topological order. Therefore, the results of the present study show that the major extrinsic projections of the cat's visual and auditory cortical areas with subcortical structures are present by the eighth week of gestation, and that the origins and terminations of many of these projections are arranged topologically.     

Comparison of the fine structure of cortical and collicular terminals in the rat medial geniculate body

Neurons throughout the rat medial geniculate body, including the dorsal and ventral divisions, display a variety of responses to auditory stimuli. To investigate possible structural determinants of this variability, measurements of axon terminal profile area and postsynaptic dendrite diameter were made on inferior colliculus and corticothalamic terminal profiles in the medial geniculate body identified by anterograde tracer labeling following injections into the inferior colliculus or cortex. Over 90% of the synapses observed were axodendritic, with few axosomatic synapses. Small (<0.5 μm²) and large (>1.0 μm²) collicular profiles were found throughout the medial geniculate, but were smaller on average in the dorsal division (0.49±0.49 μm²) than in the ventral division (0.70±0.64 μm²). Almost all corticothalamic profiles were small and ended on small-caliber dendrites (0.57±0.25 μm diameter) throughout the medial geniculate. A few very large (>2.0 μm²) corticothalamic profiles were found in the dorsal division and in the marginal zone of the medial geniculate. GABA immunostaining demonstrated the presence of GABAergic profiles arising from cells in the inferior colliculus. These profiles were compared with GABAergic profiles not labeled with anterograde tracer, which were presumed to be unlabeled inferior colliculus profiles or thalamic reticular nucleus profiles. The distributions of dendritic diameters postsynaptic to collicular, cortical and unlabeled GABAergic profiles were compared with dendritic diameters of intracellularly labeled medial geniculate neurons from rat brain slices.

Our results demonstrate a corticothalamic projection to medial geniculate body that is similar to other sensory corticothalamic projections. However, the heterogeneous distributions of excitatory inferior collicular terminal sizes and postsynaptic dendritic diameters, along with the presence of a GABAergic inferior collicular projection to dendrites in the medial geniculate body, suggest a colliculogeniculate projection that is more complex than the ascending projections to other sensory thalamic nuclei. These findings may be useful in understanding some of the differences in the response characteristics of medial geniculate neurons in vivo.     

Time of origin of neurons of the rat superior colliculus in relation to other components of the visual and visuomotor pathways

Summary Groups of pregnant rats were injected with two successive daily doses of ³H-thymidine from gestational day 12 and 13 (E12+E13) until the day before parturition (E21+22) in order to label all the multiplying precursors of neurons. At 60 days of age the proportion of neurons generated (or no longer labelled) on specific days was determined in the separate layers of the superior colliculus. Neurogenesis begins with the production of a few large multipolar neurons in layers V and IV on day E12; the bulk (87%) of these cells are generated on day E13. This early-produced band of large neurons, the intermediate magnocellular zone, divides the superior colliculus into two cytogenetically distinct regions. In both the deep and the superficial superior colliculus neuron production is relatively protracted. In the deep superior colliculus neuron production peaks on day E15 in layer VII, on day E15 and E16 in layer VI, and on day E16 (the large neurons excluded) in layer V, indicating an inside-out sequence. In the superficial superior colliculus peak production time of layer III cells is on day E15 and of layer IV cells on day E16; peak production time of both layer I and II is on day E16 but in the latter region neuron production is more prolonged and ends on day El8. One interpretation of these results is that the two pairs of superficial layers are produced in an outside-in sequence. These three cytogenetic subdivisions of the superior colliculus may be correlated with its structural-functional parcellation into an efferent spinotectal, a deep somatomotor and a superficial visual component.A comparison of neurogenesis in different components of the visuomotor and visual pathways of the rat indicates that the motor neurons of the extraocular muscles, the abducens, trochlear and oculomotor nuclei, and neurons of the nucleus of Darkschewitsch are produced first. Next in line are source neurons of efferents to the bulb and the spinal cord: those of the Edinger-Westphal nucleus and the intermediate magnocellular zone of the superior colliculus. These are followed by the relay neurons of the dorsal nucleus of the lateral geniculate body. The neurons of the superficial superior colliculus and of the visual cortex implicated in visual sensori-motor integrations are produced last.Abbreviations A aqueduct - ap stratum album profundum (layer VII) - bi brachium of the inferior colliculus - c caudal - CGd central gray, pars dorsalis - CGl central gray, pars lateralis - CGv central gray, pars ventralis - dm deep magnocellular zone - EW Edinger-Westphal nucleus - gi stratum griseum intermediale (layer IV) - gp stratum griseum profundum (layer VI) - gs stratum griseum superficiale (layer II) - IC inferior colliculus - im intermediate magnocellular zone - LGd lateral geniculate nucleus, pars dorsalis - ll lateral lemniscus - lm stratum lemnisci (layer V) - MG medial geniculate nucleus - ND nucleus of Darkschewitsch - NO nucleus of the optic tract - op stratum opticum (layer III) - ot optic tract - r rostral - SC superior colliculus - vIII third ventricle - ZO stratum zonale (layer I) - III oculomotor nucleus - IV trochlear nucleus - Vm mesencephalic nucleus of the trigeminal - VI abducens nucleus