脊髓胶状质内生长抑素免疫反应阳性结构与一级传入纤维之间的突触连接

本文用单纯免疫电镜及免疫电镜与溃变(后根切断术)相结合的方法,研究了一级传入纤维与脊髓胶状质内生长抑素(SOM)阳性结构之间的突触连结。结果在脊髓胶状质内观察到SOM阳性的胞体、轴突、树突及溃变的轴突,以上结构间形成了几种不同类型的突触连结:(1)Ⅰ型或Ⅱ型突触球的中央成份(CⅠ或CⅡ末梢)是溃变的或是SOM免疫反应阳性的,它们与周围的树突形成轴树突触、轴轴突触或树轴突触,其中有一些周围的树突还是SOM阳性的。(2)某些简单的轴突(不参与构成突触球的轴突)呈暗型溃变,并与SOM阳性的树突形成轴树突触。(3)简单的SOM阳性的致密型轴突与含SOM的树突或核周质形成轴树或轴体突触。(4)简单的SOM阳性的亮型轴突与含SOM的树突形成轴树突触。这些突触关系提示脊髓胶状质内SOM阳性树突和胞体可直接从一级传入纤维或脊髓后角固有神经元接受冲动,其中有一些一级传入纤维和脊髓后角固有神经元也是SOM阳性的。这表明在脊髓固有神经元与一级传入纤维之间及脊髓固有神经元本身都存在着自调节突触。本实验结果为SOM参与感觉信息的调节提供了超微结构证据。     

树Qu脑β—内啡肽能神经元胞体和纤维分布的研究

本文用免疫组织化学方法和免疫电镜方法对１４只树Ｑｕβ－内啡肽能神经元胞体和纤维的分布及其在细胞器的定位进行了研究。结果表明,本文首次报道在Ｂｒｏｃａ斜角带观察到β－内啡肽免疫反应阳性神经元胞体,电镜观察到β－内啡肽免疫反应物质定位于大颗粒囊泡内的小颗粒上和粗面内质网上。下丘脑弓状核及其附近区域观察到β－内啡肽免疫反应阳性神经元胞体。在室周区、室旁核、第３脑室室管膜下层及室管膜上皮细胞间、内侧基底下     

树脑β－内啡肽能神经元胞体和纤维分布的研究

本文用免疫组织化学方法和免疫电镜方法对１４只树脑β－内啡肽能神经元胞体和纤维的分布及其在细胞器的定位进行了研究。结果表明，本文首次报道在Ｂｒｏｃａ斜角带观察到β－内啡肽免疫反应阳性神经元胞体，电镜观察到β－内啡肽免疫反应物质定位于大颗粒囊泡内的小颗粒上和粗面内质网上。下丘脑弓状核及其附近区域观察到β－内啡肽免疫反应阳性神经元胞体。在室周区、室旁核、第３脑室室管膜下层及室管膜上皮细胞间、内侧基底下丘脑及其外侧区、正中隆起内带和外带部可见到β－内啡肽免疫反应阳性纤维和串珠状的膨体。对β－内啡肽的释放途径及其调节因素作了探讨。     

脊髓背角深层痛敏神经元与胶质层SP,Clu和GABA能末梢的突触联系

应用整体猫单细胞生理特性鉴定和细胞内注射辣根过氧化物酶标记法,显示了一些脊髓背角深层广动力范围型痛敏神经元有背侧树突延伸至背角浅层.并结合包埋后免疫,电镜显示这种神经元可通过分布于背角胶质层的树突接受大量P物质和谷氨酸免疫反应阳性纤维末梢的支配.由于后者主要来源于C类纤维,由此可以推测在背角浅层C类纤维介导的部分痛信息,可直接以单突触方式转送至背角深层的痛敏神经元.背角浅层的GABA免疫反应阳性轴突可与标记的远端树突形成突触,支持通过突触后抑制对脊髓痛觉传递发挥调制作用.     

大鼠三叉神经尾侧亚核内SPR阳性神经元与初级传入和下行投射纤维之间的突触联系

用追踪和免疫电镜技术研究三叉神经尾侧亚核（Ｖｃ）内Ｐ物质受体（ＳＰＲ）阳性神经元与初级传入和下行投射之间的突触联系。光镜观察发现,在Ｖｃ浅层,ＳＰＲ阳性神经元的分布与ＲＭｇ下行投射终末的分布有重叠。电镜观察发现,三叉初级传入终末和ＳＰＲ阳性神经元树突形成非对称性轴树突触;ＲＭｇ下行投射终末与ＳＰＲ阳性神经元树突也形成非对称性轴树突触,提示ＲＭｇ下行投射纤维可能通过直接作用于丘脑投射神经元对三叉初级传入的伤害性信息进行调控。     

大鼠脊髓胶状质内GABA能神经元突触联系的超微结构研究

本文用免疫电镜方法对脊髓胶状质内ＧＡＢＡ能神经元的突触联系进行了超微结构研究。结果表明;脊髓胶状质内有许多ＧＡＢＡ能神经元胞体和末梢分布;标记的ＧＡＢＡ能神经末梢可作为突触前成分与未标记的ＧＡＢＡ形成输一树突触。未标记的末梢可与标记的ＧＡＢＡ末梢形成输一轴突触。此外,标记的ＧＡＢＡ能神经末梢还可作为突触前成分与标记的ＧＡＢＡ能轴突、树突或胞体形成输－轴、轴－树或轴－体突触,即自调节突触。上述结果揭示：ＧＡＢＡ能末梢可对脊髓胶状质内其它神经元产生抑制或脱抑制作用。值得注意的是胶状质内含ＧＡｎＡ的神经结构可形成各种形式的自调节突触,并借此实现其对脊髓功能的复杂调节。     

大鼠口面部躯体和上消化道内脏伤害性传入汇聚于三叉神经脊束间质核含CB神经元

三叉神经脊束间质核(interstitial nucleus of the spinal trigeminal tract,INV)为位于三叉神经脊束内的一些灰质团块,经三叉神经和舌咽及迷走神经接受口面部的三叉神经躯体传入与上消化道的内脏伤害性传入。INV内含有大量含calbinding D-28k(CB)神经元,但尚不清楚支配口面部的三叉神经躯体传入与支配上消化道的内脏伤害性传入是否汇聚于INV内含CB的神经元。本文应用跨节追踪法并结合CB和Fos免疫组织化学的激光共聚焦显微镜和电镜技术,研究了下牙槽神经(interior alveolarnerve．IAN)的初级传入和上消化道伤害性信息向INV内含CB神经元的汇聚。结果如下：(1)将生物素化的葡聚糖胺(biotinylated dextran amine,BDA)和甲醛分别注入IAN和上消化道后,BDA跨节标记的浓密初级传入纤维和末梢分布于同侧INV内,在其膨大部较为集中;大量的CB和Fos免疫反应阳性神经元分布于双侧INV内,并与BDA注射侧的BDA标记末梢区相重叠：共聚焦显微镜观察显示,约半数CB免疫反应阳性的神经元同时呈Fos阳性的双标记神经元(74／153),其中部分双标神经元与IAN末梢形成紧密接触状。(2)辣根过氧化物酶(horseradish peroxidase,HRP)注射到IAN后,HRP跨节标记的纤维和末梢的分布与BDA标记的分布相似;电镜下观察到,INV内有大量CB免疫反应阳性神经元的树突和少量胞体,以及HRP标记的传入末梢,其中一些HRP标记的轴突终末分别与CB免疫反应阳性树突和胞体形成非对称型轴-树或轴-体突触。结果提示口面部躯体初级传入信息和内脏伤害性信息汇聚于INV内含CB的神经元上,可能在躯体传入信息对内脏伤害性信息的调制和内脏心血管活动中发挥重要作用。     

促生长素抑制素样免疫反应在大白鼠弓状核和正中隆起的超微结构分布

本文用免疫电镜方法证明:促生长素抑制素样免疫反应神经末梢分布于弓状棱并与未标记的树突形成轴树突触。在正中隆起的纤维层和栅状层内均可见上述免疫反应末梢,大多数紧贴门脉毛细血管基底膜周围甚至穿入基底膜内。免疫反应末梢尚可与未标记的末梢形成轴轴突触样结构。     

锌及锌转运蛋白ZnT3在小鼠海马苔藓纤维的一致性分布

目的 研究游离锌离子和锌转运蛋白ZnT3在小鼠海马的定位以及二的分布是否具有一致性。方法 应用锌TSQ荧光技术、锌金属自显影技术检测含锌神经元内的游离锌离子;应用免疫电镜技术检测ZnT3在含锌神经元轴突终末的分布。结果 游离锌离子和ZnT3免疫反应产物的分布在海马苔藓纤维内的分布具有一致性。在齿状回和CA3区的苔藓纤维内,锌和ZnT3蛋白定位于轴突终末的突触小泡。富含锌离子的含锌神经元轴突终末与CA3区锥体细胞的胞体和树突形成突触。尚可见锌离子存在于突触间隙内。结论 ZnT3向突触小泡内转运锌离子使锌离子聚积在含锌神经元轴突终末的突触小泡内,发挥锌离子的神经生物学功能。     

中国树鼠句伏隔核促肾上腺皮质激素释放激素能神经元免疫组织化学研究

应用免疫组织化学碱性磷酸酶标Ａ蛋白（ＰＡＡＰ）技术在光镜水平研究中国树鼠句伏隔核内促肾上腺皮质激素释放激素（ＣＲＦ）能神经元的形态和分布特点。结果显示,该核内ＣＲＦ免疫反应阳性神经元胞体多数呈多边形、圆形或卵圆形,梭形极少;直径多数为１３－１９ｕｍ,少数＜１３ｕｍ;胞质免疫反应强度不等。对左右侧伏隔核内ＣＲＦ免疫反应阳性神经元数目、胞体大小、形态和免疫反应强度进行分析,除免疫反应强阳性神经元计数项（Ｐ＜００１）外,其他项都无显著意义。ＣＲＦ免疫反应阳性神经元在伏隔核内分布不均,主要位于该核的前半段背侧区,核芯区较少     

Electron microscopic analysis of tyrosine hydroxylase, dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase immunoreactive innervation of the hypothalamic paraventricular nucleus in the rat

The catecholaminergic innervation of the hypothalamic paraventricular nucleus (PVN) of the rat was studied by preembedding immunocytochemical methods utilizing specific antibodies which were generated against catecholamine synthesizing enzymes. Phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive terminals contained 80-120 nm dense core granules and 30-50 nm clear synaptic vesicles. The labeled boutons terminated on cell bodies and dendrites of both parvo- and magnocellular neurons of PVN via asymmetric synapses. The parvocellular subnuclei received a more intense adrenergic innervation than did the magnocellular regions of the nucleus. Dopamine-beta-hydroxylase (DBH)-immunopositive axons were most numerous in the periventricular zone and the medial parvocellular subnucleus of PVN. Labeled terminal boutons contained 70-100 nm dense granules and clusters of spherical, electron lucent vesicles. Dendrites, perikarya and spinous structures of paraventricular neurons were observed to be the postsynaptic targets of DBH axon terminals. These asymmetric synapses frequently exhibited subsynaptic dense bodies. Paraventricular neurons did not demonstrate either PNMT or DBH immunoreactivity. The fibers present within the nucleus which contained these enzymes are considered to represent extrinsic afferent connections to neurons of the PVN. Tyrosine hydroxylase (TH)-immunoreactivity was found both in neurons and neuronal processes within the PVN. In TH-cells, the immunolabel was associated with rough endoplasmic reticulum, free ribosomes and 70-120 nm dense granules. Occasionally, nematosome-like bodies and cilia were observed in the TH-perikarya. Unlabeled axons established en passant and bouton terminaux type synapses with these TH-immunopositive cells. TH-immunoreactive axons terminated on cell bodies as well as somatic and dendritic spines of paraventricular parvocellular neurons. TH-containing axons were observed to deeply invaginate into both dendrites and perikarya of magnocellular neurons. These observations provide ultrastructural evidence for the participation of central catecholaminergic neuronal systems in the regulation of the different neuronal and neuroendocrine functions which have been related to hypothalamic paraventricular neurons.     

Electron microscopic analysis of tyrosine hydroxylase,dopamine-β-hydroxylase and phenylethanolamine-N-methyltransferase immunoreactive innervation of the hypothalamic paraventricular nucleus in the rat

Summary The catecholaminergic innervation of the hypothalamic paraventricular nucleus (PVN) of the rat was studred by preembedding immunocytochemical methods utilizing specific antibodies which were generated against catecholamine synthesizing enzymes. Phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive terminals contained 80–120 nm dense core granules and 30–50 nm clear synaptic vesicles. The labeled boutons terminated on cell bodies and dendrites of both parvo- and magnocellular neurons of PVN via asymmetric synapses. The parvocellular subnuclei received a more intense adrenergic innervation than did the magnocellular regions of the nucleus. Dopamine--hydroxylase (DBH)-immunopositive axons were most numerous in the periventricular zone and the medial paryocellular subnucleus of PVN. Labeled terminal boutens contained 70–100 nm dense granules and clusters of spherical, electron lucent vesicles. Dendrites, perikarya and spinous structures of paraventricular neurons were observed to be the postsynaptic targets of DBH axon terminals. These asymmetric synapses frequently exhibited subsynaptic dense bodies. Paraventricular neurons did not demonstrate either PNMT or DBH immunoreactivity. The fibers present within the nucleus which contained these enzymes are considered to represent extrinsic afferent connections to neurons of the PVN.Tyrosine hydroxylase (TH)-immunoreactivity was found both in neurons and neuronal processes within the PVN In TH-cells, the immunolabel was associated with rough endoplasmic reticulum, free ribosomes and 70–120 nm dense granules. Occasionally, nematosome-like bodies and cilia were observed in the TH-perikarya. Unlabeled axons established en passant and bouton terminaux type synapses with these TH-immunopositive cells. TH-immunoreactive axons terminated on cell bodies as well as somatic and dendritic spines of paraventricular parvocellular neurons. TH-containing axons were observed to deeply invaginate into both dendrites and perikarya of magnocellular neurons.These observations provide ultrastructural evidence for the participation of central catecholaminergic neuronal systems in the regulation of the different neuronal and neuroendocrine functions which have been related to hypothalamic paraventricular neurons.Supported by NIH Grant NS 19266 to W.K. Paull     

The synaptic relationships between the primary afferent terminals and the cuneo-thalamic relay neurons in the rat cuneate nucleus

In order to establish the synaptic relationship between the primary afferent terminals and the cuneothalamic relay neurons in the cuneate nucleus, the combined retrograde transport of horseradish peroxidase (HRP) and experimental degeneration have been applied in the young adult albino rats. 10 to 30% HRP was injected contralaterally (0.5 microliter) in the ventrobasal thalamic nucleus and multiple dorsal rhizotomies (C5 to T1) in the cervicothoracic dorsal roots were performed on the side ipsilateral to the cuneate nucleus. The results showed that: The cuneo-thalamic relay (CTN) neurons were the major neuronal type of the nucleus. More than 55% of neurons have been labelled. These neurons were 18-30 micron X 15-25 micron in sizes. They distributed in the whole rostrocaudal extent of the nucleus, particularly dense in the middle portion. The cells varied from round, oval, spindle to multipolar in shapes. They were rich in cytoplasmic organelles and had well-developed roughed endoplasmic reticulum. Their nucleus was either centrally or eccentrically located and was rather regular. The HRP-positive granules were randomly distribute in the perikaryon, dendrites and initial segment of the axons; At least three types of the experimental degeneration of the primary afferent terminals (PAT) were observed in the cuneate nucleus two to three days after dorsal rhizotomy, namely, electron-dense, granular and neurofilamentous. These PAT were mostly large and contained round vesicles. They were commonly found within synaptic complex, in which they were presynaptic to dendrites of various sizes, and were themselves postsynaptic to smaller axon terminals containing flattened vesicles. Degenerating PAT forming isolated synapses were less commonly seen; The PAT in the synaptic complex were directly presynaptic to the dendrites originating from the CTN neurons. The dendrites forming PAT-CTN synases were of large and medium-sized. The PAT did not form direct axo-somatic synapses with the somata of CTN or of any other cell types in the cuneate nucleus.     

Neural Organization of the Median Ocellus of the Dragonfly : II. Synaptic structure

Two types of presumed synaptic contacts have been recognized by electron microscopy in the synaptic plexus of the median ocellus of the dragonfly. The first type is characterized by an electron-opaque, button-like organelle in the presynaptic cytoplasm, surrounded by a cluster of synaptic vesicles. Two postsynaptic elements are associated with these junctions, which we have termed button synapses. The second synaptic type is characterized by a dense cluster of synaptic vesicles adjacent to the presumed presynaptic membrane. One postsynaptic element is observed at these junctions. The overwhelming majority of synapses seen in the plexus are button synapses. They are found most commonly in the receptor cell axons where they synaptically contact ocellar nerve dendrites and adjacent receptor cell axons. Button synapses are also seen in the ocellar nerve dendrites where they appear to make synapses back onto receptor axon terminals as well as onto adjacent ocellar nerve dendrites. Reciprocal and serial synaptic arrangements between receptor cell axon terminals, and between receptor cell axon terminals and ocellar nerve dendrites are occasionally seen. It is suggested that the lateral and feedback synapses in the median ocellus of the dragonfly play a role in enhancing transients in the postsynaptic responses.     

大鼠孤束核内脑啡肽样免疫反应阳性结构及其轴突终末的突触联系

本文应用免疫细胞化学方法在光镜与电镜下观察了大鼠孤束核内脑啡肽样免疫反应（ＥＮＫ－ＬＩ）阳性结构的分布特征和ＥＮＫ－ＬＩ轴突终末的突触联系以及非突触性关系。结果表明：（１）经秋水仙素处理的大鼠,其孤束核内有许多ＥＮＫ－ＬＩ胞体的分布;而未经秋水仙素处理的大鼠,其孤束核内可见密集的ＥＮＫ－ＬＩ纤维与终末;ＥＮＫ－ＬＩ胞体、纤维和终末主要分布于锥体交叉平面至闩平面的孤束核内侧亚核与胶状质亚核。（２）ＥＮＫ－ＬＩ阳性产物主要定位于小圆形清亮囊泡外表面、大颗粒囊泡内和线粒体外表面等处。（３）ＥＮＫ－ＬＩ轴突终末主要与阴性树突形成轴－树突触。（４）阴性轴突终末终止于ＥＮＫ－ＬＩ轴突终末上,形成轴－轴突触。（５）ＥＮＫ－ＬＩ轴突终末与阴性轴突终末形成非突触性的轴－轴并靠。以上结果提示孤束核内的ＥＮＫ－ＬＩ神经成分主要通过突触后机制、也不排除突触前作用,参与孤束核中内脏信息的整合过程,而且这一作用又受到非ＥＮＫ－ＬＩ神经成分的调控。     

Ultrastructural changes in the superficial layers of the superior colliculus in Galago crassicaudatus (primates) after eye enucleation

Summary Several types of terminals were found in the three superficial collicular layers of Galago. At least two axon terminals with round vesicles (R1 and R2) could be distinguished on the basis of vesicle packing and electron density of the cytoplasmic and mitochondrial matrices. R1 axon terminals were characterized by aggregations of vesicles in an electron lucent cytoplasm and mitochondria with a relatively dark matrix, while in R2 axon terminals the vesicles were more evenly distributed in an electron dense cytoplasm and the mitochondrial matrix was pale. R2 endings occurred in clusters in the stratum griseum superficiale; they were absent in the stratum zonale. R1 endings were found in all three superficial collicular layers. Both types of R terminals made asymmetrical contacts with small dendrites, dendritic spines and F profiles. Profiles containing flattened vesicles and establishing symmetrical contacts were numerous, and many could be identified as dendrites by accepting as criteria for dendrites evenly spaced microtubules, clusters of ribosomes and the fact that these F profiles were postsynaptic to other terminals. F terminals were presynaptic to other F profiles, dendrites and somata; they were postsynaptic to R terminals and took part in serial synapses. Dendrodendritic contacts were frequent, somatodendritic contacts rare. After eye enucleation most R2 axon terminals underwent the electron dense degenerative reaction. The degeneration process was a lengthy one; many degenerating boutons were found 30 days after axotomy and some persisted up to 180 days postoperatively. There was strong indication that the superior colliculus received more crossed than uncrossed retinofugal fibers. The crossed and uncrossed retinocollicular axons terminated in two different substrata of the stratum griseum superficiale.This study was supported by N.I.H. Grant RR-00165 to Yerkes Regional Primate Research Center and N.I.H Grant EY 00638-03 to J. Tigges. — The opportunity to use the electron microscopic facilities of the Fernbank Science Center for the initial stage of this work is gratefully acknowledged.     

Electron microscopy examination of galanin-like peptide (GALP)-containing neurons in the rat hypothalamus

Galanin-like peptide (GALP) is a novel peptide which is isolated from the porcine hypothalamus. GALP-containing neurons are present in the arcuate nucleus (ARC), being particularly densely concentrated in medial posterior regions. To observe the ultrastructure and synaptic relationships of GALP-containing neurons in the ARC, light and immunoelectron microscopy techniques were used. At the light microscope level, GALP-containing neurons were observed distributed rostrocaudally throughout the ARC, with the majority present in the posterior, periventricular zones. At the electron microscope level, many immunopositive dense-cored vesicles were evident in the perikarya, dendrites and axon terminals of the GALP-containing neurons. Furthermore, these neurons received synapses from immunonegative axon terminals that were symmetric in the case of synapses made on perikarya, and both asymmetric and symmetric for synapses made on dendrites. Axon terminals of GALP-containing neurons often made synapses on immunonegative dendrites. Such synapses were all symmetric. Synapses were also found between axon terminals and perikarya as well as dendrites of GALP-containing neurons. These findings suggest that the physiological role of the GALP-containing neurons in the ARC is based on complex synaptic relationships between GALP-containing neurons and either GALP-immunopositive or -immunonegative neurons.     

Whisker-related circuitry in the trigeminal nucleus principalis: Ultrastructure

Trigeminal (V) nucleus principalis (PrV) is the requisite brainstem nucleus in the whisker-to-barrel cortex model system that is widely used to reveal mechanisms of map formation and information processing. Yet, little is known of the actual PrV circuitry. In the ventral “barrelette” portion of the adult mouse PrV, relationships between V primary afferent terminals, thalamic-projecting PrV neurons, and gamma-aminobutyric acid (GABA)-ergic terminals were analyzed in the electron microscope. Primary afferents, thalamic-projecting cells, and GABAergic terminals were labeled, respectively, by Neurobiotin injections in the V ganglion, horseradish peroxidase injections in the thalamus, and postembedding immunogold histochemistry. Primary afferent terminals (Neurobiotin- and glutamate-immunoreactive) display asymmetric and multiple synapses predominantly upon the distal dendrites and spines of PrV cells that project to the thalamus. Primary afferents also synapse upon GABAergic terminals. GABAergic terminals display symmetric synapses onto primary afferent terminals, the somata and dendrites (distal, mostly) of thalamic-projecting neurons, and GABAergic dendrites. Thus, primary afferent inputs through the PrV are subject to pre- and postsynaptic GABAergic influences. As such, circuitry exists in PrV “barrelettes” for primary afferents to directly activate thalamic-projecting and inhibitory local circuit cells. The latter are synaptically associated with themselves, the primary afferents, and with the thalamic-projecting neurons. Thus, whisker-related primary afferent inputs through PrV projection neurons are pre- and postsynaptically modulated by local circuits.     

Electron Microscopic Observations on the Taste Buds of the Rabbit

An examination of the fine structure of the taste buds in the rabbit was undertaken. Gustatory epithelium was fixed in OsO₄ or 1 per cent KMnO₄ solution, containing polyvinylpyrrolidone (PVP). Thick sections were examined in the phase microscope and contiguous sections prepared for the electron microscope. The bud contains two types of cells, gustatory receptors and sustentacular cells. The receptors are characterized by a dark nucleus and densely granular cytoplasm. The apical processes bear numerous microvilli which extend into the taste pore. Imbedded between the microvilli there is a dense substance, which is also present in the apical cytoplasm of the receptors. The sustentacular cells contain a large pale nucleus and less dense cytoplasm. Their basal surfaces rest upon a basement membrane. The subepithelial nerve plexuses comprise the fibers which innervate the gustatory receptors. The nerve fibers vary in diameter from 500 A to 0.3 µ, and are ensheathed by Schwann cells. The intragemmal fibers enter the taste bud between adjacent cells, and are ensheathed by the plasma membranes of the supporting cell until they synapse upon the gustatory cell. The synaptic terminals contain synaptic vesicles, which at this junction reside in the postsynaptic element. This observation is discussed with reference to synapses described elsewhere in the nervous system.     

Synaptic relations of neurotensinergic neurons in the dorsal raphe nucleus

The ultrastructure and synaptic relations of neurotensinergic neurons in the rat dorsal raphe nucleus (DRN) were examined. The neurotensin-like immunoreactive (NT-LI) neurons in the DRN were fusiform or spherical. The NT-LI perikarya could only be detected in colchicine-treated animals whereas the immunoreactive axon terminals could only be found in the anirnals not treated with colchicine. Although many NT-LI dendrites received synapses from nonimmunoreactive axon terminals, the NT-LI perikarya received few synapses. NT-LI axon terminals also made synapses on nonimmunoreactive dendrites. Occasionally, synapses were found between the NT-LI axon terminals and NT-LI dendrites in the cases in which the animals were not treated with colchicine.