损毁弓状核区对大鼠脑内β-内啡肽、5-羟色胺、去甲肾上腺素含量及其对针刺镇痛的影响

下丘脑弓状核区是脑内合成β-内啡肽等物质的主要部位,并与脑内中缝背核、蓝斑等结构有密切的交互纤维支配。本实验用新生期大鼠注射谷氨酸—钠(MSG)损毁弓状核区的方法,观察对脑内β-内啡肽、5-羟色胺、去甲肾上腺素含量及针刺镇痛的影响。MSG 处理组大鼠下丘脑弓状核神经元减少72%左右,脑β-内啡肽含量降低67%,针刺镇痛效应明显下降,电针后脑去甲肾上腺素含量明显高于电针对照组;将 MSG 处理大鼠的垂体摘除后,针刺镇痛效应几乎消失,同时电针后脑去甲肾上腺素含量则显著高于单纯 MSG处理组。本文对可能的机理进行了讨论。     

谷氨酸单钠化大鼠弓状核对束旁核痛单位放电的影响

下丘脑弓状核(ARC)是脑内β-内啡肽(β-end)能神经元胞体主要集中的核团(Bloom et al.,1978;Finley et al., 1981)。刺激大鼠ARC能明显抑制丘脑束旁核(PF)痛单位的诱发放电,而且,这种抑制效应可被吗啡受体阻断剂纳洛酮所阻断(陈向阳等,1986)。 新生期大鼠腹腔注射谷氨酸单钠(Monosodium Glutamate,MSG)能选择性地破坏ARC区神经元胞体(Krieger et al.,1979)。本实验在新生期注射MSG的成年大鼠上观察刺激ARC对PF痛单位放电的影响,以进一步探讨ARC在痛觉调制中的作用。     

大鼠蓝斑参与下丘脑弓状核区注射谷氨酸单钠的镇痛效应

本实验以电刺激鼠尾-嘶叫法和甲醛爪内注射-行为法两种测痛方法观察到:(1)大鼠下丘脑弓状核区微量注射神经元胞体兴奋剂谷氨酸单钠(MSG)300μg/1μl 可引起明显镇痛效应。(2)双侧蓝斑内微量注射 β-内啡肽抗血清各0.1μl 可明显对抗 MSG 兴奋弓状核区神经元的镇痛效应。(3)直接在双侧蓝斑内微量注射 β-内啡肽各1ug/0.25μl 也可产生明显的镇痛效应。上述结果表明:下丘脑弓状核区注射 MSG 兴奋其中的 β-内啡肽能神经元群,可能通过下行纤维末梢释放 β-内啡肽,影响蓝斑神经元的活动,从而产生镇痛效应。     

刺激下丘脑弓状核对丘脑束旁核单位痛诱发放电的影响和初步分析

1.电刺激大鼠下丘脑弓状核(ARC)对外周伤害性刺激引起的丘脑束旁核(PF)单位的痛诱发放电有明显的抑制作用,这种抑制作用可被纳洛酮所翻转。2.切断脊髓背半部后,刺激ARC对PF单位痛诱发放电的抑制作用依然存在。3.腹腔注射对氯苯丙氨酸(色氨酸羟化酶抑制剂)后,刺激ARC 的抑制作用消失。4.从ARC到PF存在着一条有内源性阿片样物质(可能是β-内啡肽)和5-羟色胺参与的上行痛觉调制通路。     

大鼠下丘脑弓状核区在唇针镇痛中的作用

下丘脑弓状核区和脑内参与痛觉调制的结构有复杂的纤维联系,脑内β-脂肪激素-β-内啡肽-ACTH 神经元系统的胞体亦主要集中于下丘脑弓状核区。本实验用电解损毁、H 刀游离和电刺激大白鼠弓状核区的方法,研究该区在痛觉调制和唇针镇痛中的作用。(1)电解损毁或 H 刀游离弓状核区后基础痛阈未见明显改变,但唇针镇痛效应均明显降低。(2)单纯电刺激弓状核区能明显升高基础痛阈;唇针和电刺激弓状核区同时进行时的镇痛效应比单纯唇针时的镇痛效应有明显提高。根据这些结果,讨论了下丘脑弓状核区在大白鼠唇针镇痛中的作用。     

大鼠中枢甲硫脑啡肽和亮脑啡肽含量与电针镇痛的关系

应用放射免疫法测定电针镇痛大鼠各脑区和脊髓中甲硫脑啡肽(MEK)与亮脑啡肽(LEK)样免疫活性物质含量。结果表明,电针组大鼠尾核和下丘脑内的 MEK 与 LEK 含量显著升高,丘脑、低位脑干和脊髓的含量基本不变。将每只鼠电针镇痛效果与脑内脑啡肽含量作直线相关处理,可见尾核与下丘脑的 MEK 含量与大鼠针效呈正相关(P 均<0.05),而这两个脑区的 LEK 含量与针效优劣无相关关系。本工作提示,尾核和下丘脑的 MEK 可能在电针镇痛中具有重要作用。     

中缝背核参与下丘脑弓状核对丘脑束旁核痛单位放电的抑制

电解损毁中缝背核(DR)、DR 区微量注射纳洛酮或 β-内啡肽抗血清都能明显翻转电刺激大鼠下丘脑弓状核(ARC)对丘脑束旁核(PF)单位痛诱发放电的抑制;而电解损毁中缝大核(NRM)、NRM 区微量注射纳洛酮、β-内啡肽抗血清,或 DR 区微量注射生理盐水、正常兔血清对刺激 ARC 的这种抑制效应均无明显影响。本实验结合以往实验结果提示;从 ARC 到PF 可能存在着这样一条痛觉调制通路,即通过 ARC 的β-内啡肽能纤维影响 DR 单位的活动,继而又通过 DR 的5-羟色胺能纤维影响 PF 单位的活动,从而影响痛觉的感知。     

刺激中缝背核和蓝斑对下丘脑弓状核区诱发电位的影响

实验在用水合氯醛麻醉的雄性成年大鼠上完成。目的是观察刺激中缝背核和蓝斑对刺激坐骨神经诱发下丘脑弓状核区电位的影响。结果表明:(1)电刺激中缝背核和蓝斑与腹腔注射吗啡一样,可以明显抑制外周伤害性刺激所诱发的弓状核区电位的第三个迟发成分(Sw_3);(2)脑室注射及微电泳作为中缝背核和蓝斑各自所释放的主要神经递质——5-羟色胺和去甲肾上腺素也能明显地抑制 SW_3成分。     

慢性应激性高血压大鼠中刺激弓状核引起的降压作用

用电击足底加噪音刺激的慢性应激方法,使成年雄性Sprague-Dawley大鼠获得持续性高血压。在这种慢性应激性高血压大鼠弓状核区微量注射0.3μL-谷氨酸钠(150mmol),可导致明显的血压下降。分别在中脑导水管周围灰质背内侧区和蓝斑区微量注射0.3μl和0.1μlβ—内啡肽抗血清后,上述弓状核神经元兴奋导致的降压效应明显减弱。结果表明,大鼠获得慢性应激性高血压后,弓状核神经元的兴奋具有明显降压作用,此作用可能与弓状核β—内啡肽能神经元的下行投射纤维的活动有关。     

脑和脊髓中的去甲肾上腺素在大鼠电针镇痛中起不同的作用

中枢神经系统中的去甲肾上腺素(NE)对针刺镇痛究竟起增强或对抗作用,目前的看法还不一致。本工作观察了电针镇痛时大鼠脑和脊髓 NE 及其主要代谢产物3-甲氧基4-羟基苯乙二醇硫酸盐(MHPG·SO_4的含量变化。结果表明:电针刺激使脑和脊髓 NE 含量下降而MHPG·SO_4含量显著升高,提示脑和脊髓 NE 的更新加速。给大鼠脑室或脊髓蛛网膜下腔注射 NE 的直接前体二羟基苯丝氨酸(DOPS)来加强 NE 的功能,或注射α、β受体阻断剂来削弱 NE 的功能,从而观察其对电针镇痛作用的影响,结果表明脑和脊髓中的 NE 在电针镇痛中起着截然不同的作用;脑内 NE 主要通过α受体对抗电针镇痛,此外兼有较弱的通过β受体加强电针镇痛的作用,而脊髓内 NE 则是通过α受体来加强电针镇痛的作用。     

DIFFERENTIATION OF DOPAMINERGIC AND NORADRENERGIC NEURONS IN RAT SPINAL CORD

Abstract— Norepinephrine (NE), dopamine (DM) and 3-methoxy-4-hydroxyphenylacetic acid (HVA) content have been measured in different parts of rat spinal cord and cerebellum by a gas chromatographic mass spectrometric method. In cerebellum, which does not contain dopaminergic neurons, the ratio of NE to DA content was 47, whereas in parts of the spinal cord this ratio varied between 11 and 19. In the cord after desipramine (25 mg/kg, i.p.) plus 6-hydroxydopamine (6-HDA, 100/jg intracisternally), there was a significant depletion of DM but not of NE. Conversely, after benztropine (25 mg/kg, i.p.) plus 6-HDA there was a significant depletion of NE but not of DM. Chlorpromazine (10 mg/kg, i.p.) or clozapine (25 mg/kg, i.p.) caused a significant increase in spinal cord HVA concentration 1 h after treatment. Evidence is presented which suggests that the increased HVA measured in the cord did not originate in the brain. After electrolytic lesion of the locus coeruleus there was a significant reduction of NE but not of DM. Spinal cord DM and NE were depleted by reserpine in a dose-dependent manner, the threshold dose for DM depletion being less than that for NE depletion. Seven days after cord transection at T₁₀ spinal cord DM was significantly reduced in the lumbar region. These results suggest that dopaminergic neurons exist in rat spinal cord independently of noradrenergic neurons and that the DM is likely to be present in the terminals of descending axons.     

DISTRIBUTION OF SERINE HYDROXYMETHYLTRANSFERASE AND GLYCINE TRANSAMINASE IN SEVERAL AREAS OF THE CENTRAL NERVOUS SYSTEM OF THE RAT

—The regional distributions of serine hydroxymethyltransferase (SHMT) and glycine transaminase (GT) have been determined in five areas of the CNS of the rat. The SHMT activity per mg protein varied in these areas in the following order: medulia-pons and spinal cord > cerebellum > midbrain > telencephalon. The GT activity per mg protein was essentially the same in the four brain areas, whereas, in the spinal cord it was lower. The activity of GT did not correlate with the glycine content (r=?0.45. P > 0.05). However, SHMT activity per mg protein was correlated with the glycine content in four regions (the telencephalon, midbrain, medulla-pons and spinal cord; r= 0.997, P < 0.05). When the activity of SHMT was expressed per relative number of mitochondria, the enzyme levels were correlated with the glycine content in all five areas (r= 0.952, P < 0.05). The distribution of SHMT was determined in the primary subcellular fractions of the CNS. The SHMT activity in these areas of the CNS appeared to be located predominately in paniculate structures, while only 1 to 4 per cent was found in the soluble fraction. The crude nuclear (P₁) and the crude mitochondrial (P₂) fractions contained 90–97 per cent of the activity. Subfractionation of P₂ pellets obtained from the telencephalon, medulla-pons and spinal cord indicated the SHMT activity was localized in both ‘free’ and occluded mitochondria.     

REGIONAL DISTRIBUTION AND PROPERTIES OF THE GLYCINE CLEAVAGE SYSTEM WITHIN THE CENTRAL NERVOUS SYSTEM OF THE RAT: EVIDENCE FOR AN ENDOGENOUS INHIBITOR DURING IN VITRO ASSAY

—The activity of the glycine cleavage system (GCS) was determined in homogenates from five specific regions of the rat CNS (telencephalon, midbrain, cerebellum, medulla-pons, and spinal cord). An inverse trend was noted between the glycine content and the specific activity of the GCS in the regions. A 25-fold range in the enzyme activities was found between the telencephalon (highest) and the spinal cord (lowest). The properties of the GCS activity in CNS homogenates agreed with those properties previously described for this system in partially purified preparations of liver and brain mitochondria (Kikuchi , 1973; Bruin et al., 1973). Within the CNS homogenates, the liberation of CO₂ from the carboxyl carbon of glycine was quantitatively coupled to the formation of serine. The presence of an endogenous inhibitor(s) within neural tissues was suggested by the non-additivity of the activities when homogenates from the various regions were combined. Moreover, homogenates of CNS tissue inhibited the GCS activity of liver homogenates, and an inverse relationship was found between the level of GCS activity in a given region of the CNS and its ability to inhibit the GCS activity of liver homogenates. This inhibition of liver activity was greatest when liver was incubated with homogenates of spinal cord (86%) and lowest when incubated with homogenates of telencephalon (20%). Because of this endogenous inhibition, the apparent activity of the GCS measured in vitro may not reflect the contribution of this enzyme system in the metabolism of glycine in vivo. Although the significance of this inhibition is not known, a possible role is discussed for the regulation of the levels in glycine and one-carbon pools within the CNS.     

Levels of norepinephrine and 5-hydroxytryptamine in the spinal cord of the dog following ischemia and recirculation

Forty minutes of abdominal aorta ligature (partial ischemia in the lumbosacral segments of the spinal cord) did not change significantly levels of norepinephrine (NE) and 5-hydroxytryptamine (5-HT) in the spinal cord of the dog in comparison with sham-operated controls. After a 40-minute interval of recirculation NE levels dropped nonsignificantly below levels of the control group and 5-HT significantly in lumbar segments. It thus appears that even though in the stage of recirculation in the spinal cord energy metabolism is restored, the functional deficit of monoamines may persist.     

Monoamine and amino acid content in brain regions of Brattleboro rats

Monoamine and amino acid content were measured in brain regions from 12 week old male, homozygous Brattleboro (DI,n=12) and Long-Evans control (LE,n=12) rats. Norepinephrine (NE) content was significantly elevated (16–25%) in the spinal cord, pons-medulla and anterior hypothalamus of DI rats when compared to LE controls. NE content of the neurointermediate lobe of pituitary in DI rats was almost twice that of LE controls. Serotonin content was also significantly elevated in the spinal cord, pons-medulla, anterior hypothalamus and forebrain of DI rats relative to the LE controls. Taurine content in DI rats was increased (31–42%) above that of LE rats in the anterior hypothalamus, striatum and forebrain. Glutamine content was also greater in DI rats than LE in the spinal cord, pons-medulla, anterior hypothalamus, striatum, hippocampus and forebrain. The changes in monoamine and amino acid content were discussed in relation to the cardiovascular and osmoregulatory deficits that are present in DI rats due to arginine vasopressin (AVP) deficiency. The possible role of AVP in modulating NE turnover was also discussed. The increase in brain TAU content in DI rats may be a physiological response to hypernatremia.     

COMPARATIVE STUDIES ON THE MYELIN PROTEINS OF BOVINE PERIPHERAL NERVE AND SPINAL CORD

Abstract— (1) Two myelin fractions of bovine peripheral nerve and spinal cord have been studied comparatively. Cholesterol as well as cerebroside content per mg of protein in the peripheral nerve myelin was less than that in the spinal cord myelin, while no significant difference in the total phospholipid content was noted.
(2) The basic proteins in myelin fractions were quantitatively estimated by disc gel electrophoresis. Around one-fourth of the total myelin protein in the bovine peripheral nerve was a basic protein with a mobility of 1.07 relative to lysozyme by Reisfeld's disc gel electrophoresis.
(3) The myelin proteins in the peripheral nerve were less completely solubilized than those of the spinal cord by treatment with deoxycholate as well as by Triton-salt solution. The protein fractions obtained from the peripheral nerve myelin by techniques similar to that for obtaining the proteolipids from the spinal cord myelin, contained different types of protein.
(4) 2',3'-Cyclic nucleotide 3'-phosphohydrolase activity in the peripheral nerve myelin was only one tenth of that in the spinal cord myelin. The Triton-salt insoluble fraction showed remarkable high activity among subfractions of the spinal cord myelin.
(5) By immunological studies, it may be concluded that an antigenic substance for experimental allergic neuritis was localized in the peripheral nerve myelin, but not in its basic protein.     

Region-specific requirement for cholesterol modification of sonic hedgehog in patterning the telencephalon and spinal cord

Sonic hedgehog (Shh) secreted from the axial signaling centers of the notochord and prechordal plate functions as a morphogen in dorsoventral patterning of the neural tube. Active Shh is uniquely cholesterol-modified and the hydrophobic nature of cholesterol suggests that it might regulate Shh spreading in the neural tube. Here, we examined the capacity of Shh lacking the cholesterol moiety (ShhN) to pattern different cell types in the telencephalon and spinal cord. In mice expressing ShhN, we detected low-level ShhN in the prechordal plate and notochord, consistent with the notion that ShhN can rapidly spread from its site of synthesis. Surprisingly, we found that low-level ShhN can elicit the generation of a full spectrum of ventral cell types in the spinal cord, whereas ventral neuronal specification and ganglionic eminence development in the Shh(N/-) telencephalon were severely impaired, suggesting that telencephalic patterning is more sensitive to alterations in local Shh concentration and spreading. In agreement, we observed induction of Shh pathway activity and expression of ventral markers at ectopic sites in the dorsal telencephalon indicative of long-range ShhN activity. Our findings indicate an essential role for the cholesterol moiety in restricting Shh dilution and deregulated spread for patterning the telencephalon. We propose that the differential effect of ShhN in patterning the spinal cord versus telencephalon may be attributed to regional differences in the maintenance of Shh expression in the ventral neuroepithelium and differences in dorsal tissue responsiveness to deregulated Shh spreading behavior.     

Noradrenergic mediation of traumatic spinal cord autodestruction

Acute spinal injury initiates hemorrhagic necrosis (HN), a novel tissue destructive process, within traumatized cord tissues. HN assures permanent paralysis within 24 hours by locally destroying the injured cord. It results from microvascular failure and subsequent lethal tissue hypoxia. Norepinephrine (NE) a normal spinal cord transmitter material rapidly increases (four to tenfold) at the injury site. This vasoactive substance has been implicated in post wounding vascular stasis and permanent spinal paralysis because: 1. Direct spinal NE injections reproduce histological HN. 2. Phenoxybenzamine (alpha receptor blockade) pretreatment significantly diminishes traumatic lesion size. 3. NE synthesis inhibition by alpha methyl tyrosine (acts upon tyrosine hydroxylase), alpha methyl dopa (acts upon L dopa decarboxylase) and FLA-63 (acts upon dopamine beta hydroxylase) all variously protect the wounded cord against HN traumatic lesions. 4. Reserpine (NE depletion) provides significant tissue protection. This drug restores some useful spinal function after severe experimental injuries which consistently paralyze untreated animals.NE bulbospinal fibers are modulated, as determined by tissue lesion size, by two other neural systems. 1. Facilitation occurs from afferent dorsal rootposterior spinal column fibers (non-catecholamine) because prior surgical interruptions significantly diminish traumatic lesions. 2. Inhibition by dopaminergic (DA) fibers was detected by: a. Cord protection with apomorphine DA receptor stimulation. b. Aggravation of traumatic lesions by Pimozide DA receptor blockade. Although these studies are early and incomplete, there is convincing evidence for NE post wounding involvement. As this system is better understood we believe treatments will be developed for spinal injured man.     

MKP-1和磷酸化ERK蛋白在急性脊髓损伤大鼠模型中表达的实验研究

探讨丝裂原活化蛋白激酶(Mitogen activated protein kinase,MAPK)相关蛋白丝裂原活化蛋白激酶磷酸酶(Mitogen activated protein kinase phoshatase-1,MKP-1)和磷酸化细胞外信号调节激酶(Extracellular sigIlal-regulated kinases,ERK)在大鼠脊髓损伤后表达的变化及其意义.20只SD大鼠随,机分为实验组及假手术对照组.实验组采用改良Allen'S打击法制作脊髓损伤动文为实验组及假手术对照组同法暴露脊髓,但不损伤脊髓.2组大鼠术后12h取手术段脊髓,用苏木精--伊红染色观察损伤脊髓组织病理变化和检测脊髓标本损伤段的MKP-1和磷酸化ERK蛋白表达的差异.实验组脊髓HE染色显示存在大量出血坏死后形成的囊腔,组织和神经细胞水肿以及神经纤维溶解消失.免疫组化和Western Blot结果发现.术后第12h实验组MKP-1蛋白的表达减少,同时磷酸化ERK-1蛋白的表达量却明显增加,差别有显著性意义(P<0.01).脊髓组织受重物打击后可下调MKP-1蛋白的表达,同时显著增加磷酸化ERK蛋白,而这可能是脊髓损伤的机制之一.     

Sonic hedgehog-dependent emergence of oligodendrocytes in the telencephalon: evidence for a source of oligodendrocytes in the olfactory bulb that is independent of PDGFRalpha signaling.

Most studies on the origin of oligodendrocyte lineage have been performed in the spinal cord. By contrast, molecular mechanisms that regulate the appearance of the oligodendroglial lineage in the brain have not yet attracted much attention. We provide evidence for three distinct sources of oligodendrocytes in the mouse telencephalon. In addition to two subpallial ventricular foci, the anterior entopeduncular area and the medial ganglionic eminence, the rostral telencephalon also gives rise to oligodendrocytes. We show that oligodendrocytes in the olfactory bulb are generated within the rostral pallium from ventricular progenitors characterized by the expression of PLP: We provide evidence that these Plp oligodendrocyte progenitors do not depend on signal transduction mediated by platelet-derived growth factor receptors (PDGFRs), and therefore propose that they belong to a different lineage than the PDGFRalpha-expressing progenitors. Moreover, induction of oligodendrocytes in the telencephalon is dependent on sonic hedgehog signaling, as in the spinal cord. In all these telencephalic ventricular territories, oligodendrocyte progenitors were detected at about the same developmental stage as in the spinal cord. However, both in vivo and in vitro, the differentiation into O4-positive pre-oligodendrocytes was postponed by 4-5 days in the telencephalon in comparison with the spinal cord. This delay between determination and differentiation appears to be intrinsic to telencephalic oligodendrocytes, as it was not shortened by diffusible or cell-cell contact factors present in the spinal cord.