电刺激大鼠黑质网状部对脚桥核神经元自发放电的影响

目的:观察电刺激大鼠黑质网状部(substantia nigra pars reticulata,SNr)对脚桥核(pedunculopontine nucleus,PPN)神经元自发放电活动的影响,进一步探讨脑内电刺激治疗帕金森病(Parkinson's disease,PD)的机制.方法:应用细胞外记录方法观察不同...     

肝硬化大鼠黑质一氧化氮合酶阳性神经元分布的研究

目的　研究肝硬化大鼠黑质一氧化氮合酶 (NOS)阳性神经元及纤维分布的变化。方法　 2 0只Wistar大鼠随机分为肝硬化组与正常组 ,应用NADPH d组化法显示肝硬化大鼠黑质NOS阳性神经元胞体的数量及胞体灰度。结果　肝硬化大鼠黑质一氧化氮合酶阳性神经元数量明显减少但阳性胞体的灰度增加 ,正常组大鼠黑质一氧化氮合酶阳性神经元数量增加但胞体的灰度降低。结论　肝硬化大鼠体内有毒物质使脑细胞广泛受损 ,神经递质传递发生障碍 ,造成肝性脑病的一系列神经系统病症     

马桑内酯和糖皮质激素对培养脑神经元Glu和GABA免疫反应阳性的影响

为了探讨糖皮质激素与抗癌作用的关系，本研究利用培养的大鼠大脑皮质神经元，在经致痫剂马桑内酯和糖皮质激素处理后，进行Glu和GABA免疫细胞化学染色，观察它们对免疫反应阳性细胞的影响，并对实验结果进行了图象分析。结果发现：马桑内酯处理可使Glu免疫反应阳性神经元增多，使GABA免疫反应阳性神经元减少；而先加马桑内酶再加糖皮质激素，则可使Glu阳性神经元大为减少,GABA阳性神经元比只加马桑内酯组增多。上述改变均有统计学意义。此结果提示：马桑内酯诱发的癫痫可能与Glu和GABA的含量变化有关，糖皮质激素在致痫状态下，可能有降低Glu升高GABA含量的作用，从而具有抗痫效应．     

GABA与NOS在大鼠杏仁皮质核神经元内的共存

本文采用还原型尼克酰胺腺嘌呤二核苷酸脱氢酶(NADPHd)组织化学和γ氨基丁酸(GABA)免疫组化双重染色相结合的方法,观察杏仁皮质核(Co)神经元内GABA与NADPHd的共存。结果显示GABA样阳性神经元多散在分布于杏仁皮质后内侧核(PMCo)和杏仁皮质后外侧核(PLCo),以小型为主,中型较少;NADPHd阳性神经元多散在分布于PMCo、PLCo、杏仁皮质前核(ACo),以中、小型神经元为主;双标神经元(GABA/NADPHd均阳性)多散在分布于PLCo,以中、小型神经元为主。大鼠Co内有GABA与NADPHd共存的神经元,提示一氧化氮(NO)对Co内的GABA能神经元可能有调控作用。     

帕金森病大鼠纹状体神经元及黑质网状部神经递质变化的研究

本研究采用免疫细胞化学方法和形态计量学技术，观察了由6－OHDA单侧微量注射制成的帕金森病大鼠纹状体头部P物质神经元和体部GABA能神经元的变化，以及黑质网状部突触岛内P物质终末数和GABA终末数及终未总数的改变，以探讨神经递质在帕金森病发病中的作用。结果显示：6－OHDA注射侧纹状体面积、纹状体P物质神经元和GABA能神经元数量均较正常对照侧明显减少；注射侧黑质网状部突触岛单位树突膜长度内终末总数较正常侧减少54％；P物质终末数和GABA终末数亦分别减少44％和33％。本研究表明帕金森病大鼠黑质与纹状体之间团有的神经递质失衡，这可能是帕金森病发病的重要因素之一。     

几种神经递质对大鼠丘脑底核神经元自发放电活动的影响

采用微电泳法观察了谷氨酸（Glu）、乙酰胆碱（Ach）、多巴胺（DA）和γ－氨基丁酸（GABA）等药物对大鼠STN神经元自发放电活动的影响。结果表明：Ach、Glu和DA分别使67．05％（59／88），92．94％（79／85），90．02％（80．06）神经元自发放电频率加快，它们的作用依赖于电流强度。GABA抑制所有神经元的自发放电活动，其作用也依赖于电流强度。在微电泳Ach或Glu过程中，给予GABA可拮抗其兴奋作用。双钴碱（Bic）可使78．79％）（52／66）的神经元自发放电频率加快，阿托品（ATR）可使60％（15／25）神经元自发放电减少，给药前后放电频率差异显著（P＜0．05）。而MK－801对STN自发放电影响较小，但能拮抗Glu的兴奋作用。结果表明：GABA、Ach、Glu和DA等递质活动在同一STN神经元有重要会聚作用，GABA和Ach分别对STN神经元有紧张性抑制性及兴奋作用。     

GABA能中间神经元在运输应激大鼠躯体感觉皮质的分布

目的:探讨运输应激对大鼠躯体感觉皮质γ-氨基丁酸(GABA)能中间神经元分布的影响。方法:采用摇床加束缚建立大鼠运输应激模型,将24只SD雄性大鼠随机分为对照组(Control)、运输应激1 d组(TS1d)、运输应激3 d组(TS3d)、运输应激7 d组(TS7d)。应用尼氏染色、免疫组织化学染色法观察运输应激状态下大鼠躯体感觉皮质GABA能不同亚型中间神经元的表达及分布。结果:在躯体感觉皮质,运输应激之后小清蛋白(PV)阳性神经元、生长抑素(SOM)阳性神经元、钙视网膜蛋白(CR)阳性神经元数量显著减少,在TS7d时下降最明显;PV阳性神经元数量在第Ⅱ～Ⅳ层显著减少;SOM阳性神经元数量在第Ⅱ、Ⅲ、Ⅴ层显著减少;CR阳性神经元数量在第Ⅰ～Ⅵ层显著减少。结论:运输应激后,大鼠躯体感觉皮质GABA能中间神经元显著减少,其中PV和CR这两种钙结合蛋白类中间神经元数量下降最明显,提示钙结合蛋白在调节应激方面起关键作用。     

缺氧对谷氨酸能和GABA能突触传递的影响

Neurons in the mammalian central nervous sysytem (CNS) are highly sensitive to the availability of oxygen. Hypoxia alters synaptic transmission in a few minutes. Both glutamatergic and γ-aminobutyric acid (GABA)ergic synaptic transmissions respond to hypoxic exposure with prominent modification. Glutamate receptors, GABA receptors, adenosine receptor, and some endogenous neuromodulators are involved in the preservation of neuron function. Since the neuroprotection in all hypoxic tolerant species examined so far relies on significant increase in GABA and decrease in glutamate, it may be an important strategy to make a moderate balance of glutamate/GABA synaptic transmission against hypoxic insults.     

GABA样神经元和GABA能三叉一丘脑投射神经元在三叉神经感觉核簇的分布及形态学特征

用直接抗GABA免疫组化方法和与HRP逆行追踪相结合的双标记法在光镜下观察了GABA样神经元和GABA能丘脑投射神经元在大鼠三又神经惑觉核簇的分布和形态特征。结果显示:GABA样神经元广泛存在于三叉神经感觉核簇的各亚核中,但在每一亚核和尾侧亚核的各层,其分布状况和细胞形态特征各异。在尾侧亚孩,GABA样神经元的分布密度为Ⅰ、Ⅱ层>Ⅳ、Ⅴ层>Ⅲ层;在极间亚核,GABA样细胞分为背、腹二群,以腹侧群为主;在吻侧亚核,分为背内侧群、内侧带群和腹外侧群三群;在感觉主核分为背内侧群和腹外侧群;在三叉上核分为吻内侧群和尾外侧群。同样,本文首次发现,GABA能丘脑投射神经元也广泛存在于三叉神经感觉核簇各核中,而且在各亚核及各层中其分布密度及细胞形态也不相同。在尾侧亚核,双标细胞占38.6%,主要分布在Ⅰ、Ⅱ层,具有较长附突;在极间亚核,双标细胞占40%,主要分布在腹侧群;在吻侧亚核中仅在腹侧群有少量小的双标细胞;在感觉主核,双标细胞占20-30%,主要集中在背内侧群,腹外侧群仅有少量;在三叉上核,双标细胞仅出现在尾外侧群。结果提示:GABA对三叉神经感觉核簇中的各种深浅感觉功能的传导和整合可产生广泛的抑制影响,但其影响形式、程度和机制可能各不相同。     

γ-氨基丁酸与一氧化氮在大鼠大脑皮质内的共存

目的观察大鼠大脑皮质内是否存在γ-氨基丁酸(GABA)与一氧化氮(NO)共存的神经元。方法以大鼠为研究对象,采用还原型尼克酰胺腺嘌呤二核苷酸脱氢酶(NADPH-d)组织化学和免疫组化双重染色相结合的方法。结果显示GABA阳性神经元的胞体和突起染成棕黄色多散在分布于皮质以小型为主,中型较少,NADPH-d阳性神经元的胞体和突起染成蓝色多散在分布于皮质以中、小型神经元为主。双标神经元(GABA/NADPH-d均阳性)的胞体和突起染成棕褐色,多散在分布于嗅周皮质(PRh),以中、小型神经元为主。双标神经元与单标神经元的比例分别7.5%(GABA),12.7%(NADPH-d)。结论大鼠皮质内有GABA与NO共存的神经元,在嗅周皮质数量最多。     

Age-dependent changes in dopaminergic projections from the substantia nigra pars compacta to the neostriatum

Age-dependent changes in dopaminergic (DA) innervation of the neostriatum (Str) were studied in male F344/N rats. Projections from the substantia nigra pars compacta (SNc) to the neostriatum were quantified using electrophysiological methods at age points from 6 to 24 months. The percentage of DA neurons activated antidromically by electrical stimulation (P-index) of Str increased between 18 and 24 months. Additionally, the percentage of DA neurons showing multiple antidromic latencies from striatal stimulation (M-index), which suggests axonal branching of individual DA neurons, increased significantly between 6 and 12 months and 6 and 24 months. These results suggest that DA neurons exhibit increased axonal branching in the aged brain.     

Behavioral and electrophysiological changes following microinjections of colchicine into the substantia nigra.

Male Sprague-Dawley rats received bilateral microinjections of colchicine (2 or 4 μg in 1 μl) into the substantia nigra. During the first 2 days the animals were hyperactive, intense gnawing and chewing were observed, and food intake was significantly increased. During the next 3 or 4 days, activity, food and water intakes and body weight gain were markedly reduced; the behavior was similar to that previously observed following damage to the substantia nigra and nigrostriatal pathway from 6-hydroxydopamine or electrolytic lesions. This period of hypophagia and hypodipsia was followed by a rebound increase in food and water intake for several days until body weight returned to normal levels. Field potentials recorded from the caudate nucleus in response to electrical stimulation of the substantia nigra were reduced in amplitude during the first 4 days following microinjections of colchicine into the substantia nigra and recovered by Day 7.These reversible behavioral effects of microinjections of colchicine into the substantia nigra confirm the importance of the nigrostriatal pathway in motor and ingestive behaviors.     

The role of the substantia nigra in a striatally-evoked motor response in the rat: effects of intranigral drugs and lesions

Turning of the head towards the contralateral side was induced in the conscious unrestrained rat by electrical stimulation of the neostriatum through permanent indwelling electrodes. The importance of the substantia nigra in mediating this response was investigated using electrolytic and kainic acid lesions. Contralateral head-turning was attenuated by small electrolytic lesions of the substantia nigra on the stimulated side and abolished by large electrolytic lesions that destroyed the entire nucleus. The injection of kainic acid into the substantia nigra caused persistent circling behaviour but did not modify the head-turn response to striatal stimulation; these injections destroyed some of the neurons in the pars compacta but the majority of neurons in the pars reticulata were undamaged. Drugs that alter the function of nigral neurotransmitters were injected through an indwelling cannula in the zona reticulata. Interference with the function of γ-aminobutyrate in the nigra produced small changes in the latency of the motor response. However the following drugs did not modify the response: substance P, nicotine, atropine, apomorphine, glutamic acid diethylester, glycine, strychnine, met-enkephalin and 5-methoxy-N,N-dimethyltryptamine.It is concluded that descending projections from the basal ganglia which pass through or very close to the nigra, probably without forming synapses in the pars reticulata, may be important for the mediation of the striatally-evoked response.     

Evidence for functional interactions of morphine in substantia nigra and striatum in relation to muscular rigidity in rats

Systemic administration of morphine (15 mg/kg i.p.) induced muscular rigidity in rats, which was recorded from the gastrocnemius-soleus muscle as tonic activity in the electromyogram. Administration of morphine (5 or 10 μg) into the pars compacta of the substantia nigra antagonized the rigidity in a dose-dependent manner, whereas administration of morphine at a dose of 5 μg into the pars reticulata of the substantia nigra enhanced the tonic EMG activity. When morphine and naloxone were co-administered intranigrally, the tonic EMG activity was not affected.     

Functional expression of a large-conductance Ca-activated K channel in mouse substantia nigra pars compacta dopaminergic neurons

The existence of large-conductance Ca²⁺-activated K⁺ (BK) channels in substantia nigra pars compacta (SNc) has been a matter of debate. Using the patch-clamp technique in the inside-out configuration, we have recorded BK channel currents in SNc dopaminergic neurons. The channel has a conductance of 301 pS with a slight inward rectification and is both voltage- and calcium-dependent. Paxilline, a specific BK channel blocker, can completely block the channel, while tetraethylammonium (TEA), a nonspecific blocker of voltage-gated potassium channels, reduces its conductance and a high concentration of TEA (30 mM) inhibits its activity. ATP and GTP reduce the channel activity, while ADP is less potent, and AMP has no effect. The channel is also sensitive to changes in intracellular pH. Our results indicate that functional BK channels are expressed in SNc and suggest the possibility that the BK channel may be involved in the response of SNc dopaminergic neurons to metabolic stress.     

Possible intermixing of neurons from the subthalamic nucleus and substantia nigra pars compacta in the guinea-pig

A population of cells in the anterior substantia nigra pars compacta (SNPc) of the guinea-pig have been reported previously that differ from classical dopaminergic neurons in terms of their active and passive membrane properties. To investigate this population further, anterior nigral neurons (n=17) were compared with neurons in the adjacent subthalamic nucleus (STN; n=26). The anterior nigral neurons were found to be indistinguishable from STN neurons in their action potential characteristics, firing rate, resting membrane potential and input resistance. A low-threshold calcium conductance and anomalous rectification could be demonstated in cells from both groups. Furthermore, the gross morphological characteristics of anterior nigral neurons and STN neurons were very similar, as assessed following the intracellular injection of biocytin. A further similarity was seen in the response of the two cell groups to cyanide (200 M) and apomorphine (500 M). Cyanide hyperpolarised the membrane potential of all STN neurons and the majority (77.8%) of anterior nigral neurons, in both cases producing a concomitant reduction in firing rate. These changes were accompanied by an increase in membrane conductance for potassium ions. Apomorphine depolarised the membrane potential of all STN neurons and anterior nigral neurons, in most cases increasing the input resistance (83.3% of STN neurons and 100% of anterior nigral neurons). In both groups of cells, when firing rate was affected, an increase was usually seen. Given the physiological, morphological and pharmacological similarities of STN and anterior nigral neurons, the most parsimonious interpretation is that the anterior nigral neurons belong to the STN. However, the anterior nigral neurons were found in slices that, when resectioned, contained tyrosine hydroxylase (TH)-immunoreactive cell bodies in every section, in a location corresponding to the SNPc. The implication is that in the guinea pig the SNPc and STN (usually considered to be anatomically distinct nuclei) intermix at this level for several hundred microns. This close association of the STN and the compacta was further demonstrated by the presence of TH-positive varicose and non-varicose neuronal processes within the STN.     

Influence of aging on the calbindin-D-28k immunoreactive positive dopaminergic neurons in the substantia nigra pars compacta of rats

We studied the relationship between aging and the vulnerability of substantia nigra pars compacta (SNc) calbindin-D-28k immunoreactive positive (CB⁺) dopaminergic (DA) neurons. Immunohistochemistry and cell counting were used to determine the number of CB⁺ DA neuron in aged rats (24 mon) compared to adult rats (5 mon). Furthermore, the expression of CB mRNA and protein levels in SN was studied by semi-quantitative RT-PCR and Western blotting. An 11% loss of CB⁺ DA neurons was detected in both the rostral (8.9%) and caudal (1.7%) segments but not in the intermedial segment of SNc in aged rats compared to adult rats (P < 0.05). No difference was detected in CB mRNA and protein levels between aged and adult rats (P > 0.05). These data suggest that expression levels of CB mRNA and protein may increase in the existing SNc DA neurons, which may compensate for the partial age dependent loss of CB⁺ DA neurons in the SNc.     

The activity of pars compacta neurons of the monkey substantia nigra is depressed by apomorphine

In the substantia nigra of anesthetized and awake monkeys, presumptive dopamine cells of the pars compacta were electrophysiologically discriminated against non-dopaminergic cells of the pars reticulata by their lower discharge rate (0.5–8 vs 20–130 imp./s), their longer impulse duration (means 2.05 vs 0.92 ms), and their exclusive depression following systemic injection of the dopamine agonist apomorphine (24 out of 30 compacta neurons at 0.05–0.1 mg/kg s.c.).