NMDA受体介导了加兰他敏对阿尔茨海默病大鼠认知功能的改善

目的研究加兰他敏对阿尔茨海默病(AD)大鼠认知功能的影响及NMDA受体在其中的作用。方法雄性SD大鼠65只,随机分为假手术、链脲菌素(STZ)组,加兰他敏、MK-801和犬尿烯酸3个治疗组。侧脑室注射STZ制备大鼠AD模型,水迷宫试验测定大鼠的学习记忆能力。3个治疗组分别给予加兰他敏、MK-801 加兰他敏、犬尿烯酸 加兰他敏,共6周。结果术后第10天各组潜伏期明显延长,过平台次数明显减少,差异均无统计学意义。治疗6周后加兰他敏组潜伏期缩短,过平台次数增加,与STZ组比较,有显著差异,而MK-801和犬尿烯酸组潜伏期和过平台次数与STZ组比较,无明显差异。结论加兰他敏对AD大鼠的认知功能具有明显的改善作用,而应用NMDA受体阻断剂后其治疗作用消失。说明NMDA受体介导了加兰他敏对AD大鼠认知功能的改善。     

Effect of age and caloric restriction on insulin receptor binding and glucose transporter levels in aging rats

We report on the effect of age and chronic caloric restriction (CR) on insulin binding and glucose transporter content in both diaphragm and heart muscle membrane of young (11 months), mid-age (17 months), and old (29 month) ad libitum fed and CR Brown-Norway rats. The control animals received rat chow ad lib and CR animals were allowed 60% of ad libitum food. The CR regimen was initiated at four months of age and the animals were maintained on their respective diets until necropsy. There was no effect of age on insulin binding for either ad libitum or CR animals at each age evaluated. Caloric restriction significantly lowered insulin levels at each age studied when compared to the ad libitum-fed rats. However, CR animals were noted to have increased insulin binding (p < 0.001) compared to ad libitum-fed animals at each age for diaphragm muscle. For the heart, there appeared to be a decreased binding, particularly at higher insulin concentrations, in CR-fed animals. There was no net change in Glut-1 or Glut-4 levels for heart muscle membrane, or Glut-4 levels for diaphragm muscle membrane between ad libitum or CR animals. This data indicates that caloric restriction may have tissue-specific effects for insulin receptor binding, and that the improved insulin sensitivity in CR states is not a result of altered glucose transporter protein content.     

Effects of 6R-L-erythro-5,6,7,8-tetrahydrobiopterin on the dopaminergic and cholinergic receptors as evaluated by positron emission tomography in the Rhesus monkey

Summary The effects of 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (R-THBP) on the central cholinergic and dopaminergic systems in the Rhesus monkey brain were investigated by positron emission tomography (PET) with the muscarinic cholinergic receptor ligands (N-[¹¹C]methyl-benztropine) and dopaminergic receptor ligands selective for D₁ D₂, and D₃ subtypes ([¹¹C]SCH23390, N-[¹¹C]methyl-spiperone, and (+)[¹¹C]UH232, respectively). None of the doses (3, 10, and 30 mg/kg i.v.) of R-THBP used significantly affected the regional cerebral blood flow (rCBF as determined by Raichle's H₂ ¹⁵O method), and 10 mg/kg of R-THBP had little effect on the regional cerebral metabolic rate of glucose (rCMRglc) in the Rhesus monkey brain, as assessed by the graphical [¹⁸F]fluoro-deoxyglucose method. The effect of R-THBP on the muscarinic cholinergic system was dose dependent; while 3 mg/kg of R-THBP did not significantly alter the uptake ratio of N-[¹¹C]methyl-benztropine in several brain regions to that in the cerebellum, 10 and 30 mg/kg of R-THBP significantly reduced the uptake ratio in the thalamus, as well as in the frontal and temporal cortices. None of the doses (3, 10, and 30 mg/kg i.v.) of R-THBP tested affected [¹¹C]SCH23390 (dopamine D₁ receptor) binding. However, the k3 value for N-[¹¹C]methyl-spiperone (dopamine D₂ receptor) binding, which represents the association rate × B_max value, was significantly decreased in the striatum. The uptake ratio of (+)[¹¹C]UH232 (dopamine D₃ receptor) in the striatum to that in the cerebellum was also decreased by administration of R-THBP (3 and 30 mg/kg i.v.). These findings suggest that R-THBP acts on dopamine D₂ and D₃ receptors selectively without markedly affecting dopamine D₁ receptor binding. Furthermore, the changes in cholinergic and dopamine D₂ and D₃ receptors in vivo can not be attributed to a change in rCBF but may depend on the action of R-THBP.Abbreviations R-THBP 6R-L-erythro-5,6,7,8-tetrahydrobiopterin - PET positron emission tomography - rCBF regional cerebral blood flow - rCMRglc regional cerebral metabolic rate of glucose     

Effect of amyloid peptides on the increase in TrkA receptor expression induced by nicotine in vitro and in vivo

The ability of nicotine to induce a cytoprotective or neuroprotective action occurs through several down-stream mechanisms. One possibility is that the drug increases the expression of tyrosine kinase A (TrkA) nerve growth factor (NGF) receptors. Certain β-amyloid peptides (e.g., Aβ1–42) have been shown to bind with high affinity to α7 nicotinic receptors and thus interfere with a potentially neurotrophic influence. Treatment of differentiated PC-12 cells with nicotine produced a concentration-dependent increase in cell-surface TrkA receptors that occurred concomitantly with cytoprotection. The effect of nicotine was blocked by either of the α7 receptor antagonists α-bungarotoxin (α-BTX) or methyllycaconatine. The cytoprotective action of nicotine also was inhibited by pretreatment with 10–100 nM Aβ1–42. Nicotine also was administered (four injections of 30 μg, spaced evenly over 24 h) to rats by direct injection into a lateral cerebral ventricle. Brain TrkA expression was increased significantly in hippocampus and entorhinal cortex (up to 32% above control), with no changes found in cerebral cortex or hypothalamus. The nicotine-induced increases in TrKA expression in hippocampus and entorhinal cortex were significantly inhibited by 10 μg α-BTX or by 10 nmol Aβ1–42. Therefore, physiologically relevant concentrations of Aβ1–42 can prevent nicotine-induced TrkA receptor expression in brain regions containing cholinergic neurons susceptible to the neurotoxicity associated with Alzheimer’s disease.     

Effect of estradiol and progesterone on muscle weight and acetylcholine receptors in “myasthenic” rats

Summary Clinical evidence suggests that endocrinal factors are involved in fluctuations of the symptoms of women with myasthenia gravis. We studied the effect of estradiol and progesterone in an animal model for myasthenia gravis in rats. Although it was found that the mass of muscles was dependent on sex, and in female rats affected by estradiol, the number of acetylcholine receptors in these muscles was independent of sex and hormone administration. Sex hormones failed to influence the severity of muscle weakness in myasthenic rats.     

Antagonism of novel inotropic agents at A1 adenosine receptors and m-cholinoceptors in human myocardium

Summary The effects of the new inotropic agents saterinone, sulmazole, UD-CG 212.C1 and milrinone at A₁ adenosine receptors and m-cholinoceptors were evaluated in human myocardium from patients with heart failure. At A₁ adenosine receptors, all compounds inhibited ³H-DPCPX-binding to ventricular membrane preparations at micromolar concentrations. As judged from the K_i-values, the rank order of potency was saterinone > sulmazole > UD-CG 212.C1 > milrinone. The new inotropic agents also displaced the binding of ³H-QNB at m-cholinoceptors. Except for saterinone, the concentration ranges of mean K_i-values were considerably higher at m-cholinoceptors than at A₁ adenosine receptors. The rank order of potency was saterinone > sulmazole > UD-CG 212.Cl > milrinone. Competition of the A₁ adenosine receptor agonist R-PIA to ³H-DPCPX-binding showed a biphasic curve with a shallow slope (Hill coefficient n_H = 0.63) and revealed two affinity states of the A₁ adenosine receptor. In the presence of guanine nucleotides [Gpp(NH)p], the competition curve showed one low affinity class of binding sites and was shifted to the right. In contrast, the competition curves of the new inotropic agents were characterized by a monophasic, steeper slope (mean Hill coefficient n_H = 0.98). Guanine nucleotides had no effect. Similar results were obtained with saterinone and carbachol at m-cholinoceptors. Competition with carbachol revealed three affinity states of the m-cholinoceptor, the superhigh affinity binding was reversed by Gpp(NH)p. Competition with saterinone revealed one class of binding sites which was not influenced by Gpp(NH)p. Accordingly, in isolated, electrically driven human atrial trabeculae, the negative inotropic effect of adenosine was antagonized concentration-dependently by saterinone, sulmazole and UD-CG 212.Cl. Similarly the negative inotropic effect of carbachol was antagonized concentration-dependently by saterinone. It is concluded that the new inotropic agents bind to A₁ adenosine receptors and that their interaction is of antagonist nature. This mechanism might contribute to their capacity to enhance force of contraction by stimulation of cAMP-formation in addition to phosphodiesterase inhibition. The effects of saterinone may be partially due to antagonism at m-cholinoceptors. This is presumably not the case with the other inotropic agents studied given their low affinity for this receptor.Send offprint requests to M. Böhm at the above addressSupported by the Deutsche Forschungsgemeinschaft     

Mast cell activation involves plasma membrane potential- and thapsigargin-sensitive intracellular calcium pools

Summary— The regulation and role of the intracellular Ca²⁺ pools were studied in rat peritoneal mast cells. Cytosolic free calcium concentration ([Ca²⁺]i) was monitored in fura-2 loaded mast cells. In the presence of Ca²⁺ and K+, compound 48/80 induced a biphasic increase in [Ca²⁺]i composed of a fast transient phase and an apparent sustained phase. The sustained phase was partially inhibited by the addition of Mn²⁺. DTPA, a cell-impermeant chelator of Mn²⁺, reversed this inhibition, suggesting that a quenching of fura-2 fluorescence occurs in the extracellular medium. In the absence of extracellular Ca²⁺, the transient phase, but not the sustained one, could be preserved, provided that mast cells were depolarized. The transient phase was completely abolished by thapsigargin, a microsomal Ca²⁺-ATPase inhibitor. Maximum histamine release induced by either compound 48/80 or antigen was obtained in the absence of added Ca²⁺ only when mast cells were depolarized. These histamine releases were inhibited by low doses (< 30 nM) of thapsigargin. Thapsigargin at higher doses induced histamine release which was unaffected by changing the plasma membrane potential, but was completely dependent on extracellular Ca²⁺, showing that a Ca²⁺ influx is required for thapsigargin-induced exocytosis. Together, these results suggest that the mobilization of Ca²⁺ from thapsigargin sensitive-intracellular pools induced by compound 48/80 or antigen is sufficient to trigger histamine release. The modulation of these pools by the plasma membrane potential suggest their localization is close to the plasma membrane.     

烟碱对脑M胆碱能受体信息跨膜转导的调节

采用体外实验研究烟碱对大鼠脑Ｍ受体信息跨膜转导的调节作用．脑突触体以烟碱１．０μｍｏｌ·Ｌ－１预处理后，［３Ｈ］ｌ－二苯羟乙酸奎宁酯与Ｍ受体结合及解离动力学过程减慢．在溶脱的大脑皮层Ｍ受体与Ｇ蛋白复合体上，烟碱１．０μｍｏｌ·Ｌ－１可减慢［３５Ｓ］－腺苷５＇－［γ－硫］三磷酸与Ｇ蛋白的结合，并增强Ｍ受体与Ｇ蛋白之间的偶联关系．烟碱０．１～１０００μｍｏｌ·Ｌ－１既不影响纹状体腺苷酸环化酶的基础活性，也不影响氟化钠激活腺苷酸环化酶的作用．烟碱０．１～３０μｍｏｌ·Ｌ－１浓度依赖性地提高脑细胞内Ｃａ２＋浓度．据此提出烟碱对脑Ｍ受体信息跨膜转导系统有多点调节作用．     

Serotonin 5- HT (2C) receptor knockout mice: autoradiographic analysis of multiple serotonin receptors.

Quantitative receptor autoradiography was used to study possible alterations of the densities of multiple serotonin (5-HT) receptor subtypes and of serotonin transporter in the brain of 5-HT(2C) receptor knockout mice. The radioligands employed were [(3)H]citalopram, [(3)H]WAY100,635, [(3)H]8-OH-DPAT, [(3)H]GR125743, [(3)H]sumatriptan, [(3)H]MDL100,907, [(125)I](+/-)DOI, [(3)H]mesulergine, [(3)H]5-HT, [(3)H]GR113808, and [(3)H]5-CT. As expected, radioligands that label 5-HT(2C) receptors showed a complete absence of labeling in mutant mice choroid plexus and significantly reduced densities in other brain regions expressing 5-HT(2C) receptors. With the rest of the radioligands, no significant alterations in the densities of labeled sites were found in any brain region. In situ hybridization showed no changes in 5-HT(2A) receptor and serotonin transporter mRNA levels, whereas 5-HT(2C) receptor mRNA levels were reduced in certain brain regions. The present results indicate that the mouse serotonergic system does not exhibit compensatory up- or down-regulation of the majority of its components (serotonin transporter and most 5-HT receptor subtypes) in response to the absence of 5-HT(2C) receptors.     

急性淋巴细胞白血病细胞分化与花生凝集素受体表达

用系列单抗与标记的花生凝集素（ＰＮＡ）对３８例急性淋巴细胞白血病（ＡＬＬ）细胞行免疫分型与确定分化阶段，检测ＡＬＬ细胞ＰＮＡ受体表达情况，与正常成熟淋巴细胞（ＮＭＬ）对照。发现Ｔ－ＡＬＬ，Ｎｏｎ－Ｔ－ＡＬＬ细胞大多表达ＰＮＡ受体，而ＮＭＬ细胞极少表达ＰＮＡ受体，两者有显著差别（Ｐ＜０．０１）。经神经氨酸酶（ＮＡ）预处理后，Ｎｏｎ－Ｔ－ＡＬＬ与ＮＭＬ细胞ＰＮＡ受体表达明显增加（Ｐ＜０．０５），以ＮＭＬ为甚，而Ｔ－ＡＬＬ细胞ＮＡ处理前后ＰＮＡ受体表达未见明显区别；ＡＬＬ细胞ＰＮＡ受体表达与细胞分化程度存在显著的等级相关（ｒ８＝－０．３５７，Ｐ＜０．０５）。结果表明ＡＬＬ细胞上大多存在Ｄ－半乳糖－β（１－３）－Ｎ－乙酰氨基半乳糖基（Ｄ－Ｇａｌ－β（１－３）－Ｎ－ＧａｌＮＡＣ）；ＡＬＬ细胞分化程度越高。细胞上Ｄ－Ｇａｌ－β（１－３）－Ｎ－ＧａｌＮＡＣ连接唾液酸末端越多。