丘脑背内侧核研究进展

综述丘脑背内侧核(MD)分区、神经元类型和轴突类型等细胞构筑特点,MD的内侧区(MDm)、中心区(MDc)、外侧区(MDl)和腹侧区(ventral,MDpl)等分区的纤维联系,MD内乙酰胆碱、L-谷氨酸、γ-氨基丁酸、多巴胺、神经降压素和生长抑素等神经递质和受体类型,以及MD在摄食行为、胃肠机能情绪、认知和学习等主要生理机能中的作用等内容。结果表明:MD作为丘脑较高级中继核,形成皮质-丘脑-皮质回路,是重要的内脏与躯体活动的整合部位,在脑的高级神经活动中有着重要地位;认为对MD的细胞构筑和纤维联系已有比较全面的认识,对MD在认知和工作记忆中的作用的认识基本统一,但应激状态下MD内活动神经元类型、神经元活动规律以及应激调控通路等问题有待研究。     

金丝雀发声和其它功能核团向原纹状体栎核的投射

用ＨＲＰ示踪方法研究金丝雀端脑原纹状体栎核的传入和传出投射，将ＨＲＰ微电泳入该核内，观察其顺、逆行记物的分布，结果表明，原纹状体栎核接受上纹状体腹侧尾核新纹状体前部巨细胞核外侧部、原纹状体带核及蓝斑核的优越性传入投射，由原纹状体栎核发出的纤维支配中脑丘间核背内侧部和大下神经气管鸣管部。     

鸣禽间脑听觉卵圆核壳区脑啡肽的免疫组织化学及神经联系

应用尼氏染色及脑啡肽免疫组织化学方法研究了鸣禽白腰文鸟(Lonchura striata)间脑听觉中继核--卵圆核(n. Ovoidalis Ov)中心核及其壳区(shell)的形态学特征,再应用神经示踪剂BDA (biotionylated dextran amine)对壳区的神经投射进行了研究.结果发现: (1) 脑啡肽免疫组织化学方法较尼氏染色更能区分中心核及壳区,仅Ov壳区存在脑啡肽纤维或细胞,而中心核几乎不存在;(2) Ov 壳发出纤维投向端脑听区L2b, L1 ,L3,下丘脑腹内侧核(ventromedial nucleus VMN)和下丘脑前内侧核(n. anterior medialis hypothalami AM); (3) Ov壳接受端脑古纹状体粗核(robust archistriatum RA)壳区、中脑背内侧核(mesencephalicus lateralis pars dorsalis MLd)与丘间核(n. intercollicularis ICo)界面区的投射.首次发现鸣禽卵圆核壳区同非鸣禽相似,也与下丘脑有神经投射联系,它为听觉发声引起内分泌活动及有关行为的改变提供了神经结构基础.     

白腰文鸟中脑丘间复合核背内侧亚核的纤维联系

本实验采用辣根过氧化物酶法(HRP)对白腰文鸟(Louchura striata Swinnoei)的中脑丘间复合核背内侧亚核(DM)进行了研究。结果发现,中脑丘间复合核背内侧亚核的传出纤维投射到臂旁核腹外侧(PBVL)、凝核(nAm)。舌下神经气管鸣管亚核(nXⅠts)和后凝核(nRAm)。由此证明:中脑丘间复合核背内侧亚核(DM)既与发声运动有关,也与呼吸调节和体感传入有关。     

大鼠前庭脊核经脑桥核接替向旁绒球的间接投射

探讨大鼠前庭脊核经脑桥核接替后向小脑旁绒球投射的间接通路,为揭示眼平稳跟踪运动的调控机制提供形态学基础.应用顺、逆行追踪结合偏离垂直轴旋转刺激激发脑内相关神经元Fos表达的方法,观察前庭脊核向脑桥核投射的顺行标记纤维与脑桥核内向小脑旁绒球投射的神经元是否有重叠.在脑桥外侧核发现前庭脊核投射来的纤维及终末与Fos/荧光金双重标记细胞有重叠.大鼠脑内存在前庭脊核经脑桥外侧核中继后投射至小脑旁绒球的间接通路.该通路有传递直线变速运动信号的作用,可能是眼平稳跟踪运动的调控途径之一.     

黄喉鹀延髓舌下神经核发声控制中枢的神经联系

用辣根过氧化物酶(HRP)顺、逆行追踪技术,研究鸣禽类黄喉(巫鸟)延髓舌下神经核气管鸣管部(nXIIts)的中枢联系。向该核内微电泳入HRP后,发现在中脑背内侧核(DM)及端脑古纹状体粗核(RA)等处有密布的逆行标记细胞;在舌下神经气管鸣管支有标记纤维。结果表明,延髓舌下神经核气管鸣管部接受中脑背内侧核和端脑古纹状体粗核的传入投射;由它发出的轴突组成舌下神经气管鸣管支。因此,黄喉(巫鸟)的舌下神经核气管鸣管部是延髓内发声控制的基本运动神经核团。     

黑质注射鱼藤酮对大鼠行为和丘脑VL核自发放电的影响

研究中脑黑质注射鱼藤酮对大鼠行为和丘脑VL核神经元电活动的影响.运用网格、斜板和开阔试验检测大鼠行为改变;微电极记录丘脑VL核神经元自发电活动.鱼藤酮脑内注射28 d后,大鼠在网格上的移动潜伏期明显增长,沿斜板下滑次数显著增多,自主活动减少,而静止性蹲坐时间显著增多;丘脑VL核神经元自发放电频数显著降低,电频谱峰向低频区聚集,Ⅰ型簇状放电型式减少,更多的表现为规律型放电或Ⅱ型簇状放电.结果表明黑质注射鱼藤酮能诱发大鼠出现肌僵直、行动迟缓、震颤等类帕金森病征状,丘脑VL核神经元自发放电活动相应减弱,放电型式有所改变.     

条件性视觉——运动学习的研究

大脑皮层的广泛区域参与条件性视觉－运动学习，视皮层对物体的视觉信号进行处理；运动皮层发出指令完成运动动作；联合皮层接受不同区域的信号输入后进行整合形成视知觉并通知运动皮层完成条件性运动。运用前区背外侧部（ＰＭｄ）、基底神经节和前额叶皮层腹侧部（ＰＦｖ）在条件性视觉－运动学习中起重要的作用，海马参与条件性视觉－运动学习。     

黄喉鹀（Emberiza elegans）发声控制中枢─—中脑背内侧核的纤维

用ＨＲＰ顺、逆行追踪方法，研究黄喉中脑背内侧核的中枢联系。将ＨＲＰ微电泳入中脑背内侧核，在同侧古纹状体粗核内见到密布的逆行标记细胞，在同侧延髓舌下神经核气管鸣管部出现了密集的标记终未，上述结果表明，中脑背内侧核接受古纹状体粗核的传入投射，由它发出的纤维投射至延髓舌下神经核气管鸣管部．因此中脑背内侧核是发声控制通络中的重要中继站。     

内源性过氧化物酶在鸣禽鸟脑内的分布

成年鸣禽脑经常规颈动脉灌流固定，冰冻切片，ＴＭＢ处理，光镜下观察。结果显示，鸣禽鸟脑内存在内源性过氧化物酶，主要分布在带核，中脑背外侧核，视顶盖，外膝体，上纹状体附属部，视峡核，中央和周转等处，脑桥与延髓亦有分布。     

大脑前额叶扣带回皮层调制丘脑触觉信息的途径研究

大脑前额叶扣带回皮层是一个与感觉功能密切相关的脑区,它能够对丘脑触觉反应进行调制.实验在10只戊巴比妥钠（1%）麻醉的SD雄性大鼠上进行,采用辣根过氧化物酶（horseradish peroxidase,HRP）逆行标记的方法,对扣带皮层前部调制丘脑腹侧基底核（ventrobasal,VB）感觉信息的途径进行了研究.实验结果显示,VB核可以接受扣带皮层后部的投射,而且扣带皮层前部有纤维投射到扣带皮层后部.由此提示了前扣带皮层对丘脑腹侧基底核神经元触觉信息调制的可能神经环路是：扣带皮层前部-扣带皮层后部-丘脑腹侧基底核.     

Lack of regional specificity for connections formed between thalamus and cortex in coculture

The mammalian cerebral cortex consists of many structurally and functionally specialized areas, with characteristic input from particular nuclei of the thalamus. Some localized external influence, such as the arrival of fibres from the appropriate thalamic nucleus before or around the time of birth, could trigger the emergence of committed cortical fields from an undifferentiated 'protocortex. The guidance of axons from each thalamic nucleus to its appropriate target area in the cortex could, then, be crucial in the regulation of cortical differentiation. Recently, Yamamoto et al. and Bolz et al. have demonstrated that cocultured explants of rat lateral geniculate nucleus and visual cortex can form layer-specific interconnections. We have now tested the possibility that each cortical area exerts a selective trophic influence on axons from its appropriate thalamic nucleus, and vice versa, by coculturing explants of different regions of the thalamus and cortex taken at various stages of development. Although thalamo-cortical and cortico-thalamic connections formed in vitro can be remarkably normal in many respects, they lack regional specificity.     

Requirement for subplate neurons in the formation of thalamocortical connections

The neurons of layer 4 in the adult cerebral cortex receive their major ascending inputs from the thalamus. In development, however, thalamic axons arrive at the appropriate cortical area long before their target layer 4 neurons have migrated into the cortical plate. The axons accumulate and wait in the zone below the cortical plate, the subplate, for several weeks before invading the cortical plate. The subplate is a transient zone that contains the first postmitotic neurons of the telencephalon. These neurons mature well before other cortical neurons, and disappear by cell death after the thalamic axons have grown into the overlying cortical plate. The close proximity of growing thalamocortical axons and subplate neurons suggests that they might be involved in interactions important for normal thalamocortical development. Here we show that early in development the deletion of subplate neurons located beneath visual cortex prevents axons from the lateral geniculate nucleus of the thalamus from recognizing and innervating visual cortex, their normal target. In the absence of subplate neurons, lateral geniculate nucleus axons continue to grow in the white matter past visual cortex despite the presence of their target layer 4 neurons. Thus the transient subplate neurons are necessary for appropriate cortical target selection by thalamocortical axons.     

Arousal by stimulation of deep-brain nuclei

Schiff et al. show that deep-brain stimulation of the unspecific thalamocortical system through certain midline thalamic nuclei produces an alerting effect in a patient in a minimally conscious state. Such nuclei include the central lateral nucleus, paralaminar regions of the median dorsalis, and the posterior-medial aspect of the centromedian/parafascicularis nucleus complex.     

Acetylcholine induces burst firing in thalamic reticular neurones by activating a potassium conductance

Recent studies have emphasized the role of acetylcholine (ACh) as an excitatory modulator of neuronal activity in mammalian cortex and hippocampus. Much less is known about the mechanism of direct cholinergic inhibition in the central nervous system or its role in regulating neuronal activities. Here we report that application of ACh to thalamic nucleus reticularis (nRt) neurones, which are known to receive a cholinergic input from the ascending reticular system of the brain stem, causes a hyperpolarization due to a relatively small (1-4 nS) increase in membrane conductance to K+. This cholinergic action appears to be mediated by the M2 subclass of muscarinic receptors and acts in conjunction with the intrinsic membrane properties of nucleus reticularis neurones to inhibit single spike activity while promoting the occurrence of burst discharges. Thus, cholinergic inhibitory mechanisms may be important in controlling the firing pattern of this important group of thalamic neurones.     

鸟类视觉系统的离顶盖通路

离顶盖通路是鸟类视觉系统的一条主要途径,由视网膜-顶盖-圆核-外纹体等组成．视网膜接受外界视觉后主要沿这条通路直接传送到端脑,也有些视觉信息通过一些侧支回路间接地投射到端脑．顶盖-峡核回路构成离顶盖通路的一个侧支,峡核大细胞部-顶盖的兴奋性通路和峡核小细胞部-顶盖的抑制性通路构成了峡核-顶盖之间的正负反馈回路．离顶盖通路中的神经元参与识别物体的运动、颜色、亮度和形状分辨等特征．     

Escape of DNA from mitochondria to the nucleus in Saccharomyces cerevisiae

The migration of genetic information from ancestral prokaryotic endosymbionts into eukaryotic nuclei is thought to have had an important role in the evolution of mitochondria and chloroplasts. Here we describe an assay for the detection of movement of DNA between mitochondria and the nucleus in yeast. Because recombinant plasmid DNA replicates after transformation into mitochondria of yeast strains lacking endogenous mitochondrial DNA we were able to propagate the nuclear genetic marker URA3 in mitochondria. As expected, the wild-type URA3 gene in mitochondria failed to complement the uracil auxotrophy (Ura-) caused by a nuclear ura3 mutation. But selection of Ura+ prototrophs from a Ura- strain carrying URA3 on a plasmid in its mitochondria enabled us to detect plasmid movement to the nucleus. Conversely, as the plasmid used also contained the mitochondrial gene COX2 required for respiratory growth, we were able to set up corresponding selections to detect migration of DNA from the nucleus to the mitochondria. Our results show that, in yeast, DNA escapes from mitochondria and appears in the nucleus at a surprisingly high frequency (approximately 2 x 10(-5) per cell per generation). But the rate at which DNA makes the journey in the opposite direction--nucleus to mitochondria--is apparently at least 100,000 times less.     

鸣禽间脑听觉卵圆核壳区脑啡肽的免疫组织化学？…

应用尼氏染色及脑啡肽免疫组织化学方法研究了鸣禽白腰文鸟（Ｌｏｎｃｈｕｒａ ｓｔｒｉａｔａ）间脑听觉中－卵圆核（ｎ．Ｏｖｏｉｄａｌｉｓ Ｏｖ）中心核及其壳区（ｓｈｅｌｌ）的形态学特征,再应用神经示踪剂ＢＤＡ（ｂｉｏｔｉｏｎｙｌａｔｅｄ ｄｅｘｔｒａｎ ａｍｉｎｅ）对壳区的神经投射了研究,结果发现（１）脑啡肽免疫组织方法尼氏染色更能区分中心核及壳区,仅Ｏｖ壳区存在脑啡肽纤维或细胞,而忠订户站不存在;