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1.
在切除大鼠刚髭部皮肤的刺激下,从常规醛-锇酸固定的三叉神经脊束核尾侧亚核的超薄切片中观察到:1.大颗粒小泡轴突终末非突触部位的胞吐影像;2.含致密物质的大有衣小泡,由终末质膜内陷而成,提示大颗粒小泡在终末通过有衣小泡进行膜再循环;3.大颗粒小泡也可由含致密物质的平滑内质网样的管状结构形成。本研究支持大颗粒小泡在非突触部位,通过胞吐释放递质或神经调节物的假说。  相似文献   

2.
切断眶下神经的各组大鼠存活2~30天后分别杀死,于其三叉神经尾侧脊束核胶状质亚核内观察了一级传入纤维轴突终末的溃变过程.非突触部位胞吐及突触联系.结果发现:(1)眶下神经的跨节溃变、以突触小泡聚集、融合、空泡形成为主要特征,无微丝增生现象:(2)部分溃变终末内的线粒体明显肿胀变暗.呈球形改变:(3)大致密核心小泡的溃变时间远滞后于突触小泡.两者并不同步进行;(4)轴突终未在溃变过程中,其内的大致密核心小泡仍然进行非突触部位胞吐;(5)溃变纤维终末于胶状质内分别形成轴一树、轴一体、轴一轴三种类型的突触、并参与了突触复合体的形成.  相似文献   

3.
本文在以前的工作基础上,进一步用电镜及免疫细胞化学方法,研究了大颗粒小泡非突触部位胞吐作用。实验结果表明,切除大鼠刚髭部皮肤1—24小时之后,术侧延髓后角浅层大颗粒小泡胞吐比对照侧明显增多(P<0.01),术后3—9天复又下降(近似对照动物),术后14—15天又急剧上升(P<0.01)。这些胞吐大部分出现于延髓后角浅层四种轴突终末的非突触部位,少最也发生于树突及轴突中。从术后第6天开始,术侧P物质明显减弱,而甲硫-脑腓肽略有增强。研究结果提示;1)后角浅层胞吐增多,P物质下降及脑腓肽增高,反映了中枢内不同神经元对去传入神经的功能调整作用;2)大颗粒小泡在非突触部位释放神经肽,弥散地作用于远距离的受体,可能起着神经调制物的作用。  相似文献   

4.
大鼠延髓后角神经降压肽(NT)的亚细胞定位和胞吐释放   总被引:4,自引:0,他引:4  
神经降压肽(NT)广泛分布于哺乳动物的中枢神经系统,具有明显的镇痛作用,为了探索其镇痛机理的形态学基础,本文应用电镜免疫组化技术,对大鼠延髓后角NT的超微结构和胞吐释放进行了研究。超微结构显示延髓后角浅层NT轴突终末形态多样,大小不一,含有圆形或多形性清亮小泡及数量不等的大颗粒小泡,它们主要与未标记的树突形成轴-树突触,其突触后成分有的还含有少量清亮小泡。NT免疫反应阳性树突可分为两类:一类主要含微管;另一类主要含大颗粒小泡,有的尚可见少量清亮小泡。这两类NT树突可成为未标记的含圆形小泡终末、多形性小泡终末以及突触小球中央轴突终末的突触后成分,提示后角浅层NT神经元可接受不同种类轴突终末(包括一级伤害性传入纤维)的传入(?)动,然后可能再通过一个抑制性中间神经元,抑制痛觉的传递。本文还观察到有少量NT终末内的大颗粒小泡靠近突触活性区处,而更多见它们沿非突触部位轴膜分布,并与其融合,形成胞吐。本文认为NT既可在突触活性区处又可能在非突触部位释放。  相似文献   

5.
<正>突触结合蛋白-1(synaptotagmin-1,Syt-1)是脑内小突触囊泡和大致密核心囊泡特有的膜内在蛋白质,是在膜融合机制中起重要作用的一个蛋白,可以作为Ca2+感受器调节刺激偶联的快速化学突触传递,对胞吐及递质释放过程皆有影响。本文旨在讨论Syt-1通过调节神经递质释放进而影响到  相似文献   

6.
切断眶下神经的各组大鼠存活2-30天后分别杀列,纡其三叉神经尾侧脊束核胶状质亚核内观察了一级传入纤维轴突终末的溃变过程,非突触部位胞吐及突触联系。  相似文献   

7.
针刺大鼠“人中”、“四白”穴使之产生明显镇痛效果后,再将针刺时间分别延长至1、2、4、6、8、10、12h,到预定时间立即将动物灌流杀死取材,采用定量电镜方法观察计数了三叉神经尾侧脊束核胶状质亚核内各种有衣小泡的数量、形态以及在不同针刺时间内数量的变化。结果发现:大单壁有衣小泡的形成与针刺时间无明显正比例关系;而双壁有衣小泡则显然与之不同,它不仅形态多样,数目也随针刺时间而改变。本文将观察到的双壁有衣小泡归纳为以下五种类型:1、尚未与相邻两终末质膜脱离的孤立存在者。2、游离于终末内孤立存在者。3、与终末质膜相连且融合而成簇存在者;4、游离于终末内融合成簇者;5、树突棘凸入另一轴突或树突内并与之共同形成的不典型的双壁有衣小泡簇。本研究还发现,在针刺过程中双壁有衣小泡在1~8h内的形成与时间成正比,即1h时开始增多,4h显著增多,8h达高峰;以后开始下降,10h已恢复到4h的水平,到12h恢复到针刺前的状态。对照组仅见少数孤立的双壁有衣小泡,其形成基本上不随时间而变化。本文认为双壁有衣小泡的形成,是较大单壁有衣小泡的形成更为有效地继大致密核心小泡非突触部位胞吐之后膜再循环的一条新途径。  相似文献   

8.
神经肌肉连接形成是肌细胞与运动神经元前膜相互识别、相互作用 ,从而逐步形成特异突触结构的复杂过程。突触前分化是通过插入含有活性成分细胞骨架复合体的前体小泡 ,导致功能活性区的快速形成等过程实现的。突触后分化是通过递质受体和突触后致密物的信号传导分子来收集突触后致密物的脚手架分子和稳定突触的结构等来完成的。综述神经肌肉连接形成过程中突触前后膜的特化以及相关分子研究进展。  相似文献   

9.
<正> 突触传递是神经系统细胞间联系的主要基础,此过程是在电刺激条件下突触前神经终末内储存神经递质的突触囊泡向突触前膜移动,与其融合,通过胞吐作用释放神经递质入突触间隙再与突触后膜相互作用而完成的。这些功能的行使必需一系列特异蛋白质参加,现已发现哺乳类神经系统突触囊泡膜蛋白至少有15种之多,  相似文献   

10.
应用单宁酸增加致密核心小泡电子密度的研究   总被引:4,自引:2,他引:2  
对如何应用单宁酸提高密核心小泡电子密度进行了研究,结果发现实验组动物应用单宁酸后,其延髓背角胶状质的超微结构出现了如下特征性变化;(1)膜结构清晰度增加,反差鲜明;(2)大、小致密核心小泡均被媒染,其电子密度显著提高、大致密核心小泡于突触部位胞吐入细胞间隙内的介质,被即时媒染、固定。  相似文献   

11.
The cerebral peptidergic caudodorsal cells of the freshwater snail Lymnaea stagnalis control egg laying and egg-laying behaviour by releasing peptides into (1) the haemolymph, from neurohaemal axon terminals in the periphery of the cerebral commissure and (2) the intercellular space of the central nervous system, from collaterals in the inner compartment of this commissure. Recently, it was shown that collateral release occurs from nonsynaptic release sites, which lack the morphological specializations that are characteristic of classical synapses. Probably, these sites enable the caudodorsal cells to communicate with central neurons in a nonsynaptic ("paracrine", "diffuse", "hormone-like") fashion. The structural and ionic bases of nonsynaptic release were studied using the tannic acid-Ringer incubation-method for the detection of exocytotic release of secretory granule contents in vitro. Elevation of the extracellular potassium concentration strongly stimulates exocytotic activity in the collaterals. No stimulation was found in the absence of extracellular calcium ions. Similar results have been obtained for the neurohaemal axon terminals. Electron-dense material occurs apposed at the cytoplasmic side of the axolemma of collaterals (ethanolic phosphotungstic acid method). This material appears homologous with the presynaptic dense projections forming the "vesicular grid" in classical synapses. Such projections are also present in the neurohaemal axon terminals. It is concluded that secretion from nonsynaptic release sites in caudodorsal cell collaterals shares fundamental characteristics with secretion from conventional neuronal release sites (neurohaemal axon terminals and classical synapses); release occurs by exocytosis of secretory granules, is associated with a vesicular grid, is stimulated by membrane depolarization, and depends on the presence of extracellular calcium ions.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
阿片肽在后角镇痛的作用机理,被认为是通过突触前抑制一级传入纤维P物质释放的结果,然而始终未获得形态学的证实。鉴于一级传入纤维存在大量阿片受体的事实,曾提出阿片肽突触前抑制可能是通过非突触的轴-轴作用。为了验证这一设想,本文用免疫组化方法,详细观察了大鼠延髓后角浅层亮氨酸脑啡肽(L-ENK)轴突终末的突触结构和胞吐释放。电镜观察显示,延髓后角ENK终末可分为两类,第一类终末除了含圆形小清亮囊泡外,还有较多的大颗粒小泡(一般7个以上),主要分布于Ⅰ层,很少看到此类终末形成突触;第二类终末,一般含较多圆形清亮小泡和少量大颗粒小泡(一般不超过3个),它们分布于Ⅰ层和Ⅱ层,此类终末主要形成轴-树突触和少量的轴-体突触。只见到一例轴-轴突触,其突触后成分为未标记的R型终末,此外还见到ENK阳性树突成为中央终末的突触后成分。在去传入神经条件下,上述各类终末皆可见到ENK阳性大颗粒小泡的胞吐形成,它们皆位于非突触区,而在突触部位可见到清亮小泡胞吐像,上述结果提示后角ENK非突触部位释放可能是哭触后抑制一级传入纤维P物质释放的形态学基础。  相似文献   

13.
The fine structure of the axons of the cerebral, egg-laying stimulating caudodorsal cells of the snail Lymnaea stagnalis has been studied with various light and electron microscope techniques. Special attention was paid to exocytotic release of secretory material (demonstrated with the tanic acid method) from nonsynaptic release sites in the cerebral commissure. This phenomenon has been compared with neurohaemal release. The commissure consists of two morphological compartments, separated by a sheath of glial cells. The outer compartment is formed by the neurohaemal area of the caudodorsal cells, the inner consists of thousands of, mainly unidentified, axons. Furthermore, ventral caudodorsal cells send axons through the inner compartment. These give rise to collaterals, which divide into smaller collaterals, forming an extensive network ("collateral system") throughout the inner compartment. Eventually, collaterals end blindly within the inner compartment. They contain the same three morphological types of secretory granule as the neurohaemal axon terminals. The collaterals never form synaptic contacts; exocytotic release of the contents of secretory granules takes place at nonsynaptic release sites. These sites occur rather dispersed and do not face one particular type of neighbouring neural element. As in the neurohaemal area, both single and multiple exocytoses occur. Widened intercellular spaces, filled with flocculent, electron-dense material, occur near highly active nonsynaptic release sites. The spaces are often bordered by glial cells and may facilitate diffusion of released secretory material through the inner compartment. Apparently, a ventral caudodorsal cell releases secretory material in two fashions: from neurohaemal axon terminals into the haemolymph, and nonsynaptically, from the collaterals into the intercellular space of the central nervous system. Possible functions of the glial sheath between the neurohaemal area and the inner compartment are proposed. Most likely, the collateral system enables the caudodorsal cells to communicate with targets within the central nervous system in a nonsynaptic fashion. A possible target is the cerebral Ring Neuron, which sends an axon branch through the inner compartment and, as was previously shown neurophysiologically, is controlled by the caudodorsal cells in a nonsynaptic fashion.  相似文献   

14.
It has been hypothesized that chemical interactions between neurons in the central nervous system can occur in the absence of well defined synaptic complexes, but morphological correlates have been difficult to find. The present study demonstrates exocytotic release from large (70-130 nm) dense cored vesicles at structurally nonspecialized areas along the plasmalemma of structurally different categories of terminals and occasionally from dendrites and axons within the neuropil of the trigeminal subnucleus caudalis. In rats, the marginal (lamina I) and substantia gelatinosa (lamina II) layers contain the central terminals of primary afferent fibers from the infraorbital nerve that supply the skin and whiskers (vibrissae). Different types of interneurons are also present and may modify the input being relayed to higher centers. While exocytotic profiles were present in control animals, they increased significantly (P less than 0.01) on the ipsilateral side 1-24 h after a unilateral skin lesion in the vibrissae area. A second increase (P less than 0.001) occurred 14-15 days after the lesion. Virtually all examples of large vesicle exocytosis were observed at structurally nonspecialized sites while those at the active synaptic zones involved small clear vesicles. Substance P-like immunofluorescence, present in controls and on the ipsilateral side during the first 6 days, subsequently declined until 4 weeks after surgery when some recovery was noted. The increase in large vesicle exocytosis and the decrease in substance P are interpreted to reflect functional adjustments of different neurons in response to the lesion. The exocytosis involving large dense cored vesicles may serve to deliver transmitters and/or neuropeptide modulators to appropriate receptors in a wider area than release into a specialized synaptic cleft would allow.  相似文献   

15.
Following conventional glutaraldehyde-osmium tetroxide fixation, a rich myenteric plexus was detected in the gastrointestinal tract of the snail Helix pomatia. Although hundreds of nerve processes were observed in the extensive myoneural neuropil, true synaptic specializations were not recognized in them. In the absence of synaptic specializations, tannic acid-Ringer incubation was applied to visualize the non-synaptic release sites in the enteric nerve plexus. After incubation for 1 h, a great number of exocytosis profiles were recorded at nerve-muscle contacts, at axoglial connections and in the myoneural neuropil. The frequency of occurrence of exocytosis profiles was the same for adrenergic and peptidergic fibres. In some gut wall areas, a dense staining of both basal lamina and collagen fibres was observed. Invagination of dense basal lamina into the omega-shaped profiles of the axolemma led to "false exocytosis" profiles. A detailed morphological analysis is needed to distinguish false exocytosis profiles from the true transmitter-releasing loci.  相似文献   

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