脑内5-羟色胺减少对致痫大鼠癫痫发作及学习记忆的影响

目的:于中脑正中中缝核局部微量注射5,7-二羟色胺(5,7-DHT),探讨5-羟色胺(5-HT)与癫痫的关系及匹罗卡品(PILO)致痫大鼠学习记忆改变的可能机制。方法:成年SD大鼠随机分为PILO组、PILO+5,7-DHT组、空白对照组三组,然后根据是否出现癫痫持续状态(SE)再将PILO组分成:PILO+SE组和PILO-SE组两亚组;利用视频脑电图观察大鼠癫痫发作及皮层脑电变化;运用Morris水迷宫测评大鼠空间学习记忆水平;最后运用免疫组化法观察大鼠中缝核5-HT能神经元。结果:大鼠予以5,7-DHT(PILO+5,7-DHT组)处理后造模成功率、死亡率及慢性期自发性发作频率均增高;与空白组比较PILO+SE组中缝核5-HT能神经元数目有所下降(P<0.05),而PILO+5,7-DHT组下降更明显(P<0.01);与空白组比较PILO+SE组平均逃避潜伏期延长、穿越平台次数减少、原平台象限停留时间缩短(P<0.05),而与PILO+SE组比较PILO+5,7-DHT组变化不明显。结论:脑内5-HT水平的降低容易诱发癫痫发作,尚不能认为癫痫大鼠合并认知功能障碍与脑内5-HT水平下降有关。     

大鼠脑内5-羟色胺在应激性溃疡形成中的作用

通过神经化学和神经药理学的方法,在大鼠观察了冷冻加束缚应激性溃疡的形成过程中,脑内5-羟色胺(5-HT)的作用。结果如下:1.在应激过程中,脑内5-HT 及其主要代谢产物5-羟吲哚乙酸(5-HIAA)的含量明显升高,特别是5-HIAA 的含量随着应激时间的延长持续上升,说明5-HT 的代谢加快。2.脑内5-HT 或5-HIAA 含量在应激45min 时与溃疡指数呈明显的负相关,而在应激180min 时则与溃疡指数呈明显的正相关。3.侧脑室注射5-HT或其前体5-羟色氨酸(5-HTP),对应激性溃疡的形成呈双重作用,小剂量时减轻而大剂量时加重溃疡的形成。4.腹腔注射5-HT 合成阻断剂对氯苯丙氨酸(pCPA)可降低大鼠脑内5-HT 和5-HIAA 含量,使应激60min 鼠的溃疡形成加重,而使应激180min 鼠的溃疡形成减轻。以上结果提示,在大鼠的冷冻加束缚应激性溃疡的形成过程中,脑内5-HT 起着一定的作用,它很可能在应激早期减轻而在应激晚期加重溃疡的形成。     

脉冲电流经皮刺激肝区对运动性疲劳大鼠5-HT及其代谢的影响

目的:研究脉冲电流经皮刺激肝区对运动性疲劳大鼠大脑纹状体5-羟色胺(5-HT)及其代谢的影响。方法:8周龄Wistar雄性大鼠80只随机分为安静对照组(CG组)、疲劳训练组(FG组)、运动后刺激组(SAF组)、运动前刺激组(SBF组),除CG组外各组均进行游泳训练,建立运动疲劳模型,于第1、3、5周训练的最后1d,断头处死,取外周血测游离色氨酸(F-Trp)、支链氨基酸(BCAA)、F-Trp/BCAA含量,取纹状体测F-Trp、5-HT、5-羟吲哚乙酸(5-HIAA)含量。结果:与CG组相比,各组大鼠血清BCAA含量呈下降趋势,其余各指标均呈升高趋势;与FG组相比,SAF组、SBF组第3周末纹状体5-HT明显下降(P0.01);与SBF组相比,SAF组第5周末纹状体5-HT明显下降(P0.05)。结论:经皮脉冲电流刺激具有降低疲劳大鼠5-HT及代谢产物的含量,有助于疲劳的消除,对长时间运动时中枢机能的改善具有积极作用。     

疲劳产生机理及支链氨基酸对脑内5-HT影响的实验研究

Ｎｅｗｓｈｏｌｍ曾提出脑内 5 羟色胺 (5 ＨＴ)是中枢疲劳产生的重要介质。但其不易透过血脑屏障 ,故脑中 5 ＨＴ主要依靠外周色氨酸做为前体进入人脑组织。已知色氨酸与某些中性氨基酸 ,尤其是支链氨基酸 (ＢＣＡＡ)在经载体进入血脑屏障过程中存在竞争性抑制 ,因此外源性补充支链氨基酸可能延缓运动性疲劳的产生。本文以小鼠定量或力竭运动为模型 ,研究补充支链氨基酸对疲劳小鼠脑内 5 ＨＴ水平的影响。1　材料与方法二级昆明种小鼠 ,雌雄各半 ,体重 18～ 2 2ｇ。均衡随机法分为 5组 (ｎ =12 ) :(1)正常对照组 ;(2 )定量负荷运动对照…     

咪达氟对兔脑5-羟色胺释放和多巴胺含量的影响

1.用~3H-5-羟色胺脑室灌流清醒动物的方法,测定了脑内5-羟色胺的释放。实验结果表明,给兔静注咪达氟(4mg/kg)后,因动物挣扎引起5-羟色胺释放加强,可能咪达氟不直接加强兔脑5-羟色胺的释放。因此,必须指出,在用清醒动物脑室灌流的方法研究药物对神经递质释放是否有影响时,必须考虑到清醒动物的活动状态。2.用荧光方法测定了多巴胺含量。实验结果表明,给兔静注眯达氟(4或8mg/kg)以后10分钟,颈部和前肢产生明显肌松时海马中多巴胺含量虽有增加的趋势,但无统计学意义,尾核中多巴胺含量基本不变。因此,可以认为咪达氟所引起的肌肉松弛可能与脑内多巴胺含量关系不大。     

大鼠脑内5-HT能神经元对咽肌的支配及调控

用ＰＲＶ和５－ＨＴ免疫组织化学双标记方法研究脑内５－ＨＴ能神经元对咽肌的神经支配及调控。观察到中缝核群的中缝苍白核、中缝隐核、中缝大核、中缝桥核、中缝正中核、中缝背核、和中缝尾侧线形核等部位有ＰＲＶ和５－ＨＴ双标记细胞,直接证明中缝核群的５－ＨＴ能神经元投射到支配咽肌的疑核运动神经元和孤束核中的前运动神经元,调控咽肌的运动。并推测脑干中缝核群中的５－ＨＴ能神经元对咽肌运动的调控可能经由５ＨＴ３和５ＨＴ１Ａ两种受体介导。     

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。     

电刺激家兔脊髓对若干脑区5-羟色胺及其代谢产物含量的影响

电刺激家兔脊髓背部能产生明显的镇痛和肌松效应。此时,延脑中缝核区、中脑中缝核区、丘脑内侧核群和下丘脑5-HT含量均明显升高,升高百分率依次为29％、27％、36％和33％,都有统计意义;这些脑区5-HIAA含量亦明显升高,升高百分率依次为75％、36％、64％和35％,除下丘脑外均有统计意义。这就说明,上述脑区5-HT的合成代谢和分解代谢均加速,5-HT能神经元活动明显加强。结合以前在同样实验条件下,尾核和黑质单胺类递质及其代谢产物的测定结果,我们讨论了脑干中缝核易化上述效应是通过它的上行和下行5-HT通路而实现的可能性.     

大鼠脑内代谢型谷氨酸受体5亚型(mGluR5)定位分布的免疫细胞化学研究

本研究用免疫细胞化学技术观察了大鼠脑内参与兴奋性突触传递的代谢型谷氨酸受体5亚型(mGluR5)的精确定位分布.mGluR5阳性浓染的神经元胞体和纤维密集地分布于大脑皮质浅层、嗅球、伏核、尾壳核、前脑基底部、隔区、苍白球、腹侧苍白球、海马CA1和CA2区、下丘中央核、被盖背侧核和三叉神经脊束核尾侧亚核浅层;淡染而稀疏的mGluR5阳性神经元胞体和纤维见于屏状核、终纹床核、杏仁中央核、丘脑部分核团、上丘浅灰质层、外侧丘系背侧核和延髓中央灰质.     

脑内5—羟色胺和儿茶酚胺在针刺镇痛中的作用

许多资料证明,针刺感觉由外周神经传入中枢,经过脊髓、脑干和丘脑各级水平的整合,达到抗痛的目的。针刺具有复杂的调整作用,它既能激发某些神经元的功能,又要抑制另一些神经元的功能,而神经递质正是实现这两方面作用的重要物质基础。因此,研究神经递质在针刺过程中的变化规律颇受大家的重视。本文部分工作者曾用5、6-双羟色胺选择性损毁猫脑内5-羟色胺(5-HT)神经元功能后,观察到针刺镇痛因此     

EFFECTS OF ETHANOL ON SEROTONIN METABOLISM IN BRAIN

The effect of ethanol on serotonin metabolism in brains of mice was determined both after a single injection and ‘chronic’ administration of ethanol. Behavioral effects were also monitored.‘Chronic’ administration of ethanol by inhalation to mice resulted in an increased susceptibility to Metrazole induced seizures. This susceptibility was evident for 48 h after ‘withdrawal’ of mice from ethanol chambers. No differences in brain 5-HT levels between control and ethanol treated mice were evident during withdrawal. However, a significant elevation in brain 5-HIAA levels was noted during this period. Short lived increases in brain 5-HIAA levels were also noted after a single injection of ethanol. Ethanol treatment produced no significant changes in the activity of brain MAO, aldehyde dehydrogenase, or aldehyde reductase. Other mechanisms for ethanol induced increases in brain 5-HIAA are discussed.     

EFFECTS OF LEUCINE ON BRAIN SEROTONIN

Abstract— The effect of excess leucine in the diet on serotonin metabolism in the brain was investigated in experimental animals. It was found that:
(1) Animals receiving diets containing 3 % and 8 % leucine and those receiving jowar diets had significantly lower levels of serotonin in the brain.
(2) Intraperitoneal administration of the precursor amino acid 5-HTP increased the serotonin concentration in brain in both control and leucine-fed animals. However, the serotonin concentration in leucine-fed animals was significantly lower than that of pairfed controls. Larger amounts of the synthesized serotonin were found to be catabolized in 3 hr in leucine-fed animals than in control animals.
(3) The in vitro uptake of [¹⁴C]5-HTP by brain slices of animals fed leucine was found to be similar to that of control animals.
(4) The basal concentration of 5-HIAA in brain was higher in leucine-fed animals, suggesting a higher rate of catabolism of serotonin.
(5) Administration of nicotinic acid resulted in a further fall of serotonin concentration in the brains of leucine-fed animals but not in control animals.     

EFFECTS OF DI-ISOPROPYLFLUOROPHOSPHATE ON THE METABOLISM OF CHOLINE AND PHOSPHATIDYLCHOLINE IN RAT BRAIN

—The subcutaneous administration of 2·0 mg DFP per kg to rats causes a diminution in the lysophosphatidylcholine content in the brain, which is followed by a decrease of glycerylphosphorylcholine concentration and by a reduced post mortem choline increase. This supports the hypothesis that a post mortem increase in choline is due to phosphatidylcholine breakdown. Since the amount of phosphatidylcholine in brains of di-isopropylfluorophosphate-treated rats increases, it is concluded that phospholipase A is inhibited by di-isopropylfluorophosphate, which corresponds to findings of other authors in vitro. The activity of glycerylphosphorylcholine diesterase (EC 3.1.4.2) is not altered.     

EFFECTS OF SODIUM FLUOROACETATE ON THE METABOLISM OF N-ACETYLASPARTATE AND ASPARTATE IN MOUSE BRAIN

A subconvulsant dose of sodium fluoroacetate inhibited the metabolic utilization of intracerebrally-administered N-acetyl-l -[U-¹⁴C]asparticacid and the labelling of glutamine from this precursor in mouse brain, but not the labelling of glutamate or aspartate. A convulsant dose also inhibited the utilization of l -[U-¹⁴C]aspartic acid. When intraperitoneal injection of a convulsant dose of sodium fluoroacetate was followed by intracerebral injection of N-acetyl-l -[U-¹⁴C]asparticacid, the levels of N-acetylaspartate, aspartate and glutamate in brain were lowered, while the glutamine content was increased. The specific radioactivity of glutamine relative to that of glutamate was much lower when these compounds were labelled from l -[U-¹⁴C]aspartic acid than when N-acetyl-l -[U-¹⁴C]aspartic acid was used as the precursor. Intracerebral injection of tracer amounts of l -[U-¹⁴C]aspartic acid reduced the content of N-acetylaspartate in brain and raised the glutamine content. Sodium fluoroacetate had no additional effect on the relative specific radioactivity of glutamine or the content of N-acetylaspartate, aspartate, glutamate or glutamine when l -[U-¹⁴C]aspartic acid was the precursor. We consider the results to be consistent with a selective inhibition both by sodium fluoroacetate and by exogenous aspartic acid of the tricarboxylic acid cycle in brain associated with the biosynthesis of glutamine. We suggest that the activity of this pathway may regulate the metabolism of N-acetylaspartate and aspartate.     

EFFECTS OF HYPOPHYSECTOMY ON RNA METABOLISM IN RAT BRAIN STEM

Abstract— Ribosomal aggregates were isolated from rat brain stem and characterized as polysomes by sedimentation analysis and by their sensitivity to RNase and EDTA treatment.
Three weeks following hypophysectomy there was a significant decrease in the content of large polysomes in the rat brain stem. The incorporation of radioactive uridine into RNA was studied using a double-labelling technique with [³H]- and [¹⁴C]uridine and labelling periods of 70 and 180 min. It was found that after hypophysectomy the incorporation of radioactive uridine into total, nuclear and cytoplasmic RNA and in polysomes was decreased after 70 and 180 min. Information on the nature of the rapidly-labelled RNA in the various subcellular fractions was obtained by sucrose gradient sedimentation analysis.
After 70 min of labelling the nucleus contained heterogeneous RNA with a considerable fraction of RNA sedimenting faster than 28 S. In the cytoplasmic fraction heterogeneous 4 to 30 S RNA was found, presumably associated with RNP particles, whereas after 180 min the polyribosomal aggregates were also labelled.
The present results indicate a profound effect of hypophysectomy on the metabolism of all species of brain RNA investigated.     

THE EFFECTS OF HYPERKETONEMIA ON GLUTAMATE AND GLUTAMINE METABOLISM IN DEVELOPING RAT BRAIN

Abstract— The effect of increased exposure to ketone bodies in the developing rat brain suggest that intrauterine and postnatal hyperketonemia lead to an altered metabolism of glutamine and glutamate. It is postulated that this effect is related to the delayed development of glutaminase ( l -glutamine amido-hydrolase EC 3.5.1.2) and glutamate dehydrogenase ( l -glutamate: NAD oxidoreductase EC 1.4.1.2).
The specific activities of glutamate dehydrogenase (GDH), glutaminase and glutamine synthetase ( l -glutamate: ammonia ligase EC 6.3.1.2) in the brains of newborn rats increased during early development. A positive correlation was observed between the specific activity of glutaminase and the concentration of glutamate in the brain as well as between the concentrations of blood and brain glutamine and glutamate in both control and hyperketonemic pups. This indicates a different degree of permeability and metabolism for glutamine and glutamate in the brain during the neonatal period, as compared to adulthood.
In hyperketonemic pups, glutamine and glutamate metabolism were found to differ from that in control animals. The concentrations of glutamate were higher, and glutamine lower, in both the blood and brain as compared to that in controls. The concentrations of α-ketoglutarate were also lower in their brain. In the brains of hyperketonemic and control pups, the concentration of malate was the same. During the first 3 weeks of life the increase of spec. act. of GDH and glutaminase was found to be suppressed in the brains of hyperketonemic pups. However, the spec. act. of glutamine synthetase was similar to that of the control pups.     

THE EFFECTS OF CHRONIC REGIMENS OF CLORGYLINE AND PARGYLINE ON MONOAMINE METABOLISM IN THE RAT BRAIN

The effects of chronic administration of clorgyline and pargyline on rat brain monoamine metabolism have been examined. The inhibitory selectivity of these drugs towards serotonin deamina-tion (MAO type A) and phenylethylamine deamination (MAO type B) can be maintained over a 21-day period by proper selection of low doses of these drugs (0.5-1.0 mg/kg/24h). The results are consistent with MAO type A catalyzing the deamination of serotonin and norepinephrine and with MAO type B having little effect on these monoamines. Dopamine appears to be dcaminated in vivo principally by MAO type A. Clorgyline administration during a 3-week period was accompanied by persistent elevations in brain norepinephrine concentrations; serotonin levels were also increased during the first 2 weeks, but returned towards control levels by the third week of treatment. Low doses of pargyline did not increase brain monoamine concentrations, but treatment with higher doses for 3 weeks led to elevations in brain norepinephrine and 5-hydroxytryptamine; at this time significant MAO-A inhibition had developed. The changes in monoamine metabolism seen at the end of the chronic clorgyline regimen are not due to alterations in tryptophan hydroxylase activity. At this time tyrosine hydroxylase activity was also unaffected.     

THE EFFECTS OF BOTULINUM TOXIN ON ACETYLCHOLINE METABOLISM IN MOUSE BRAIN SLICES AND SYNAPTOSOMES

The effects of Type A botulinum toxin on acetylcholine metabolism were studied using mouse brain slice and synaptosome preparations. Brain slices that had been incubated with the toxin for 2h exhibited a decreased release of acetylcholine into high K⁺ media. Botulinum toxin did not affect acetylcholine efflux from slices in normal K⁺ media. When labeled choline was present during the release incubation, a‘newly-synthesized’pool of acetylcholine was formed in the tissue. In toxin-treated slices exposed to high K⁺, both the production and the release of this‘newly-synthesized’acetylcholine were depressed. A possible explanation for these actions of botulinum toxin would be via an inhibition of the high affinity uptake of choline. This hypothesis was tested by measuring the high affinity uptake of [³H]choline into synaptosomes prepared from brain slices. Previous exposure of slices to botulinum toxin caused a significant reduction in the accumulation of label by the synaptosomes. These data are discussed in terms of our current understanding of the mechanism of action of botulinum toxin and the toxin's interaction with the mechanisms regulating acetylcholine turnover.