大鼠展神经核向动眼神经核的兴奋性和抑制性投射研究

目的:研究展神经核向动眼神经核内直肌亚核投射的神经递质通路.方法:利用荧光金(fluoro-gold,FG)逆行追踪结合免疫荧光组织化学双标技术观察大鼠展神经核内FG逆行标记细胞和谷氨酸(glutamate,Glu)、γ-氨基丁酸(γ-amino-butyric acid,GABA)、谷氨酸受体1型(glutamate...     

大鼠动眼神经核的传入结构联系

目的：观察大鼠动眼神经核传入纤维的来源和特征。方法：采用ＨＲＰ标记法对２０只大鼠动眼神经核进行了逆行追踪研究。结果：脑干到动眼神经核的投射主要来源有同侧的舌下前置核;对侧的展神经核,脑桥尾侧网状核,Ｃａｊａｌ Ｄａｒｋｓｃｈｅｗｉｔｓｃｈ核,中脑网状核。结论：展神经核、前庭神经核、舌下前置核和网状结构是眼水平运动相关的直接运动前结构,它们的损伤都会影响两眼水平协同运动,但展神经核核间神经元起着最重     

大鼠中缝背核向缰核投射的5-羟色胺能神经元对躯体伤害性刺激的fos表达

用WGA-HRP逆行追踪与抗FOS和抗5-羟色胺免疫组化的三重标记方法,观察向大鼠一侧有前跖部皮下注射8%福尔马林50μl后,中缝背核至缰核5-羟色胺能神经元的FOS表达.光镜下发现中缝背核内有七种阳性神经元.即HRP、FOS、5-HT单标细胞;FOS/HRP、FOS/5-HT、HRP/5-HT双标细胞;FOS/HRP/5-HT三标细胞.结果表明中缝背核至缰核的5-HT能投射神经元对躯体伤害性刺激起反应.     

含后叶加压素的视上核神经元及含P物质的中缝背核神经元至下丘脑室旁核投射的研究

用HRP逆行追踪与免疫细胞化学结合的方法,对某些投射至大鼠下丘脑室旁核的神经元的化学性质进行了研究.结果显示在视上核内存在三种标记细胞:HRP单标细胞、后叶加压素免疫反应阳性单标细胞和HRP后叶加压素双标细胞.双标细胞为大、中型椭圆形或圆形细胞,约占HRP标记细胞总数的22%.在中缝背核投射至室旁核的神经元中,部分为P物质免疫反应阳性,双标细胞为中小型梭形细胞,约占HRP标记细胞总数的20%.上述结果提示:视上核有后叶加压素能神经元、中缝背核有P物质能神经元投射到室旁核.     

脑桥核和脑桥被盖网状核至小脑前叶皮质GABA能投射的定性追踪—HRP和免疫细胞化学结合法研究

本实验用HRP逆行追踪和免疫细胞化学结合法研究了大鼠脑桥内GABA能神经元至小脑前叶皮质的投射。结果表明,双侧脑桥核和脑桥被盖网状核均可见到三种标记细胞,包括HRP和GABA双标记细胞。提示:脑桥核和脑桥被盖网状核至小脑皮质的投射径路部分含有GABA。这可能是脑桥影响小脑皮质功能的化学神经解剖学基础之一。本文首次证实脑桥小脑径路含有GABA。     

舌肌的GABA能神经支配-HRP逆行追踪和免疫组织化学结合法研究

用辣根过氧化物酶(HRP)逆行追踪与免疫组织化学结合的方法研究大白鼠舌下神经核至舌肌的投射.结果在舌下神经核内观察到三种标记细胞:(1)HRP单标细胞;(2)GABA单标细胞;(3)HRP和GABA双标细胞.首次证实了舌下神经核中有GABA能神经元,并可投射至舌肌.     

下丘脑室旁核经迷走神经复合体对哮喘大鼠的神经调控研究

为探讨下丘脑室旁核对哮喘大鼠的神经调控途径,取健康雄性SD大鼠制备哮喘模型并诱发哮喘发作,运用WGA-HRP逆行追踪法与免疫组织化学染色法(ABC法)相结合的双重标记方法,在光镜下观察向迷走神经复合体(DVC)发出投射的下丘脑室旁核(PVN)神经元内Fos蛋白的表达情况。结果显示:PVN内有三种阳性细胞,即HRP逆行标记神经元、Fos样免疫阳性神经元和HRP/Fos双标神经元。这些神经元主要见于PVN小细胞部的内侧亚核和外侧亚核,散在分布于背侧亚核,在前小细胞亚核内未见阳性反应;Fos样免疫阳性细胞呈双侧分布,且HRP逆标神经元,HRP/Fos双标神经元也为双侧分布,但以注射区同侧占优势。HRP/Fos双标神经元占HRP标记细胞的44.22%。本研究结果提示,哮喘大鼠发作时中枢内包括下丘脑PVN、延髓DVC的多个脑区内神经元兴奋,且两者之间通过直接投射联系参与哮喘的调控。     

大鼠展神经核的细胞构筑及其向动眼神经核的投射

为了探讨核间性眼肌麻痹的发生机制 ,本实验应用荧光金逆行标记法研究了大鼠展神经核的细胞构筑及其与动眼神经核之间的联系。结果表明 :(1)展神经核至少含有两类神经元 ,即除展神经核运动神经元之外还含有一定数量的位于展神经核和动眼神经核之间的核间神经元 ;(2 )运动神经元多为大、中型多极神经元和梨状神经元 ,核间神经元多为小梭形神经元 ;(3 )展神经核由腹内侧亚群和背外侧亚群两个部分组成 ;背外侧亚群以核间神经元为主 ,腹内侧亚群在吻侧 1/ 3部核间神经元和展神经核运动神经元各独立成群而在尾侧 2 / 3部它们则混杂在一起     

大鼠红核酪氨酸羟化酶、生长抑素和亮啡吠能神经元至延髓外侧网状核的研究

用HRP逆行追踪和免疫细胞化学ABC法相结合研究了红核内酪氨酸羟化酶、生长抑素和亮啡呔免疫活性神经元至延髓外侧网状核的投射.结果表明,红核内HRP标记细胞为对侧性,主要分布于其尾侧2/3,同时,还可见酪氨酸羟化酶、生长抑素、亮啡呔单标细胞及HRP/酪氨酸羟化酶、HRP/生长抑素、HRP/亮啡呔双标细胞,其中HRP/酪氨酸羟化酶双标细胞约占HRP单标细胞25.2%,HRP/生长抑素双标细胞约占21.3%,HRP/亮啡呔双标细胞约占15.4%.红核参与镇痛和心血管活动的调节可能与上述神经递质有关.     

杏仁核参与大鼠哮喘发作及其机制探讨

为探讨杏仁核是否参与大鼠哮喘发作及其机制,采用卵蛋白致敏哮喘大鼠模型,运用WGA-HRP逆行追踪与免疫组织化学染色相结合的双重标记方法,在光镜下观察向下丘脑室旁核(PVN)发出投射的杏仁核神经元内Fos蛋白的表达情况。结果显示:杏仁核内可观察到三种阳性细胞,即HRP逆标神经元、Fos阳性神经元和HRP/Fos双标神经元。Fos阳性细胞呈双侧分布,主要分布在杏仁核的内侧亚核(MeA)和中央亚核(CeA);HRP逆标神经元和HRP/Fos双标神经元分布在注射区同侧的内侧杏仁核,内侧杏仁核内HRP/Fos双标神经元占HRP单标神经元的33.55%。本研究结果提示,哮喘大鼠发作时,杏仁核、下丘脑室旁核的神经元兴奋,且杏仁核到下丘脑室旁核的直接投射可能参与了哮喘发作的调控。     

大鼠中缝背核接触脑脊液神经元化学性质的研究

用CB-HRP追踪与免疫细胞化学结合的方法,对大鼠中缝背核接触脑脊液神经元(简称触液神经元)的化学性质进行了研究.将CB-HRP注入第三脑室后,中缝背核内观察到CB-HRP标记细胞,标记细胞分布于中缝背核的背侧部和腹侧部.在CB-HRP与P物质或5-羟色胺免疫细胞化学结合的切片上,中缝背核内出现三种标记细胞:HRP单标细胞,P物质或5-羟色胺免疫反应阳性单标细胞,HRP/SP或HRP/5-HT双标细胞,双标细胞为中、小型梭形或圆形细胞.上述结果提示:中缝背核存在SP能和5-HT能触液神经元.     

大鼠丘脑前核内海马下托复合体谷氨酸能传入终末与皮质投射神经元的突触联系

目的 探讨大鼠丘脑前核-海马下托复合体神经元环路的突触结构及谷氨酸分布特征.方法 应用HRP束路追踪结合包埋后胶体金免疫电镜技术.结果 在丘脑前核内,可见HRP顺行标记的海马下托复合体传入轴突终末,终末多为卵圆形,内含圆形透亮突触小泡和数个线粒体.其做为突触前成分与HRP标记的树突或非HRP标记的树突形成非对称性突触.在谷氨酸胶体金免疫反应切片上,胶体金颗粒标记胞体、树突、轴突终末等.HRP标记的轴突终末和一些非HRP标记的与突触后成分形成非对称性突触的轴突终末(Gray Ⅰ型)内,胶体金颗粒密度明显大于背景(胞体、树突、Gray Ⅱ型轴突终末等)的胶体金颗粒密度.其平均胶体金颗粒密度为突触后树突的3倍多,为对称性轴突终末(Gray Ⅱ型)的6倍多.在两张邻近的连续切片,γ-氨基丁酸(GABA)胶体金免疫反应切片上,GABA胶体金颗粒浓重标记Gray Ⅱ型轴突终末,背景标记极少;而非对称性轴突终末(Gray Ⅰ型)胶体金颗粒标记极弱.谷氨酸胶体金免疫反应切片上,Gray Ⅱ型轴突终末胶体金颗粒标记极弱.GABA阳性轴突终末与HRP标记的树突形成对称性突触,在同一树突上可见GABA能轴突终末形成的对称性突触和其他轴突终末形成的非对称性突触.结论 丘脑前核内来自海马下托复合体投射神经元的轴突终末是谷氨酸能的;来自海马下托复合体皮质投射神经元轴突终末,在丘脑前核与投射至海马下托皮质的神经元树突形成非对称性轴-树突触.     

Floccular modulation of vestibuloocular pathways and cerebellum-related plasticity: An in vitro whole brain study

The isolated whole brain (IWB) preparation of the guinea pig was used to investigate the floccular modulation of vestibular-evoked responses in abducens and oculomotor nerves and abducens nucleus; for identification of flocculus target neurons (FTNs) in the vestibular nuclei and intracellular study of some of their physiological properties; to search for possible flocculus-dependent plasticity at the FTN level by pairing of vestibular nerve and floccular stimulations; and to study the possibility of induction of long-term depression (LTD) in Purkinje cells by paired stimulation of the inferior olive and vestibular nerve. Stimulation of the flocculus had only effects on responses evoked from the ipsilateral (with respect to the stimulated flocculus) vestibular nerve. Floccular stimulation significantly inhibited the vestibular-evoked discharges in oculomotor nerves on both sides and the inhibitory field potential in the ipsilateral abducens nucleus while the excitatory responses in the contralateral abducens nerve and nucleus were free from such inhibition. Eleven second-order vestibular neurons were found to receive a short-latency monosynaptic inhibitory input from the flocculus and were thus characterized as FTNs. Monosynaptic inhibitory postsynaptic potentials from the flocculus were bicuculline sensitive, suggesting a GABA(A)-ergic transmission from Purkinje cells to FTNs. Two of recorded FTNs could be identified as vestibulospinal neurons by their antidromic activation from the cervical segments of the spinal cord. Several pairing paradigms were investigated in which stimulation of the flocculus could precede, coincide with, or follow the vestibular nerve stimulation. None of them led to long-term modification of responses in the abducens nucleus or oculomotor nerve evoked by activation of vestibular afferents. On the other hand, pairing of the inferior olive and vestibular nerve stimulation resulted in approximately a 30% reduction of excitatory postsynaptic potentials evoked in Purkinje cells by the vestibular nerve stimulation. This reduction was pairing-specific and lasted throughout the entire recording time of the neurons. Thus in the IWB preparation, we were able to induce a LTD in Purkinje cells, but we failed to detect traces of flocculus-dependent plasticity at the level of FTNs in vestibular nuclei. Although these data cannot rule out the possibility of synaptic modifications in FTNs and/or at other brain stem sites under different experimental conditions, they are in favor of the hypothesis that the LTD in the flocculus could be the essential mechanism of cellular plasticity in the vestibuloocular pathways.     

Role of GABA in the extraocular motor nuclei of the cat: a postembedding immunocytochemical study.

The GABAergic innervation of the extraocular motor nuclei in the cat was evaluated using postembedding immunocytochemical techniques. The characterization of GABA-immunoreactive terminals in the oculomotor nucleus was carried out at the light and electron microscopic levels. GABA-immunopositive puncta suggestive of boutons were abundant in semithin sections throughout the oculomotor nucleus, and were found in close apposition to somata and dendrites. Ultrathin sections revealed an extensive and dense distribution of GABA-immunoreactive synaptic endings that established contacts with the perikarya and proximal dendrites of motoneurons and were also abundant in the surrounding neuropil. GABAergic boutons were characterized by the presence of numerous mitochondria, pleiomorphic vesicles and multiple small symmetrical synaptic contacts. The trochlear nucleus exhibited the highest density of GABAergic terminations. In contrast, scarce GABA immunostaining was associated with the motoneurons and internuclear neurons of the abducens nucleus. In order to further elucidate the role of this neurotransmitter in the oculomotor system, retrograde tracing of horseradish peroxidase was used in combination with the GABA immunostaining. First, medial rectus motoneurons were identified following horseradish peroxidase injection into the corresponding muscle. This was carried out because of the peculiar afferent organization of medial rectus motoneurons that contrasts with the remaining extraocular motoneurons, especially their lack of direct vestibular inhibition. Semithin sections of the oculomotor nucleus containing retrogradely labeled medial rectus motoneurons and immunostained for GABA revealed numerous immunoreactive puncta in close apposition to horseradish peroxidase-labeled somata and in the surrounding neuropil. At the ultrastructural level, GABAergic terminals established synaptic contacts with the somata and proximal dendrites of medial rectus motoneurons. Their features and density were similar to those found in the remaining motoneuronal subgroups of the oculomotor nucleus. Second, oculomotor internuclear neurons were identified following the injection of horseradish peroxidase into the abducens nucleus to determine whether they could give rise to GABAergic terminations in the abducens nucleus. About 20% of the oculomotor internuclear neurons were doubly labeled by retrograde horseradish peroxidase and GABA immunostaining. A high percentage (80%) of the oculomotor internuclear neurons projecting to the abducens nucleus showed immunonegative perikarya. It was concluded that the oculomotor internuclear pathway to the abducens nucleus comprises both GABAergic and non-GABAergic neurons and, at least in part, the GABA input to the abducens nucleus originates from this source. It is suggested that this pathway might carry excitatory and inhibitory influences on abducens neurons arising bilaterally.     

Morphology of posterior canal related secondary vestibular neurons in rabbit and cat

The morphology of secondary vertical vestibular neurons was investigated by injection of horseradish peroxidase (HRP) into cells connected to the posterior canal system in rabbits (lateral-eyed animals) and cats (frontal-eyed animals). Vestibular neurons were identified by stimulation with bipolar electrodes implanted into the ampullae of the anterior and posterior (PC) semicircular canals of pigmented rabbits; in the cat, these cells were identified by natural and electrical stimulation. Axons monosynaptically activated by PC stimulation were injected with HRP in the medial longitudinal fasciculus (MLF). These were later reconstructed by light microscopy after the brains had been processed with a DAB-CoCl2 method. In the rabbit the majority of the axons bifurcated after crossing the midline with one branch ascending and the other descending in the MLF. The ascending branches gave rise to collaterals that terminated in both the trochlear nucleus and the inferior rectus subdivision of the oculomotor nucleus. In addition some axons also sent collaterals into the paramedian pontine reticular formation, the periaqueductal grey and the interstitial nucleus of Cajal. The descending branches were followed to the caudal part of the medulla in the MLF and gave rise to collaterals terminating in the vestibular nuclei, the medullary reticular formation, the perihypoglossal nuclei, the abducens nucleus, and the facial nucleus. In another cell type axons crossed the midline without giving off any collaterals and proceeded caudally in the caudal MLF. The synaptic effects of the two types of cells were concluded to be excitatory and inhibitory, respectively. Cell bodies of contralaterally projecting neurons were located in either the medial or ventro-lateral vestibular nuclei. In the cat we observed two neuron classes, with contralaterally projecting axons, whose synaptic effects are presumably excitatory. Their cell somata were located in the medial vestibular nucleus. Termination patterns were similar to both the trochlear and oculomotor nuclei, but neither projected to the abducens nucleus. One class of neurons was almost identical to that found in the rabbit with the main axon bifurcating in the MLF. The second type lacked a descending branch in the MLF. Axon collaterals of the latter type crossed the midline within the oculomotor nucleus after terminating in the inferior rectus subdivision to reach a similar portion of the ipsilateral oculomotor nucleus. Collaterals of these axons also terminated bilaterally in the supraoculomotor region between trochlear and oculomotor nucleus, the interstitial nucleus of Cajal and prerubral loci (including the fields of Forel). In similarity to the rabbit, presumed inhibitory vestibular neurons were found with axons directed caudally in the MLF without brain stem collaterals.(ABSTRACT TRUNCATED AT 400 WORDS)     

Eye movement related activity and morphology of second order vestibular neurons terminating in the cat abducens nucleus

Summary Intracellular records were obtained from axons of second order vestibular neurons in, and around, the left abducens nucleus in alert cats implanted with stimulating electrodes on both vestibular nerves and the left VIth nerve. Twelve secondary vestibular neurons were identified by their increase in firing rate with horizontal head rotation to the left and/or increasing eye position to the right. Following HRP injection, somatic location, axonal trajectory and termination sites were determined. Each of the above cells collateralized extensively in the abducens nucleus in a fashion consistent with their being either inhibitory (n = 7; left) or excitatory (n = 6; right) vestibular neurons in the disynaptic horizontal vestibulo-ocular reflex pathway. These vestibular neurons also arborized extensively in other posterior brainstem eye-movement related areas as well as sending an axon to the spinal cord.This work was supported by CNRS, NS-13742, and EY-02007