丁咯地尔抑制NE和GIu引起的单个脑细胞游离钙增高

目的：研究丁咯地尔对去甲肾上腺素（ＮＥ）和谷氨酸（Ｇｌｕ）引起大鼠单个脑细胞内游离钙增高的影响。方法：应用ＡＲ－ＣＭ－ＭＩＣ阳离子测定系统测量细胞内游离钙（［Ｃａ２＋］１）．结果：细胞外钙为 １．３ ｍｍｏｌ·Ｌ－１,丁咯地尔 ０．ｌ,ｌ．０,１０．０μｍｏｌ·Ｌ－１对细胞静息［Ｃａ２＋］．无明显影响,对ＮＥ诱导的［Ｃａ２＋］增高明显抑制,对Ｇｌｕ 诱导的［Ｃａ２＋］ 增高具有一定的抑制作用。结论：丁咯地尔能抑制ＮＥ和Ｇｌｕ 引起的单个脑细胞游离钙增高。     

冷冻伤性脑水肿神经细胞内钙离子浓度变化及尼莫地平的治疗作用

报告大鼠冷冻伤性脑水肿突触体内游离钙离子浓度([Ca~(2 )]_i)和脑组织水分含量变化之间的规律,并采用L-型钙离子通道阻滞剂尼莫地平进行治疗,研究其对神经细胞[Ca~(2 )]_i和脑水肿的影响.结果表明:冷冻后4h神经细胞内即已发生钙离子超载.伴随脑组织水分含量的增加.脑含水量随[Ca~(2 )]_i的升高而增加,两者呈正相关关系.应用尼莫地平治疗后神经细胞突触体内[Ca~(2 )]_i.明显下降,脑水肿亦明显减轻.     

The Oxytocin-induced Inward Current in Vagal Neurons of the Rat is Mediated by G Protein Activation but not by an Increase in the lntracellular Calcium Concentration

The neuropeptide oxytocin can depolarize parasympathetic preganglionic neurons in the dorsal motor nucleus of the vagus nerve of the rat by generating a sustained inward current, which is sodium-dependent and tetrodotoxin-insensitive. The second messenger activated by oxytocin receptor binding is, however, not yet known. In the present study, we attempted to characterize it by using the whole-cell recording technique and brainstem slices. When loaded with GTP-γ-S, a non-hydrolysable analogue of GTP, vagal neurons generated a persistent inward current in the absence of agonist and the oxytocin effect was suppressed, suggesting that the peptide-evoked current was mediated by G-protein activation. Loading vagal neurons with the calcium chelator 1 ,2–bis(2–aminophenoxy)ethane-N,N,N′,N′,-tetraacetic acid (BAPTA) suppressed a calcium-dependent, slowly decaying potassium aftercurrent but did not affect the oxytocin response, suggesting that the latter was not mediated by an agonist-induced increase in the intracellular calcium concentration. Protein kinase C (PKC) activation was probably not involved, since the peptide-evoked current was not modified by loading neurons with the PKC inhibitor H7. Thus, the oxytocin-evoked current in vagal neurons was probably not mediated by phospholipase C-β (PLC-β) activation. Loading neurons with 8–Br-CAMP or with an adenylyl cyclase activator (forskolin) reduced the oxytocin-evoked current by about half. SQ 22536, an adenylyl cyclase inhibitor, reduced this current by a similar amount. However, the peptide-evoked current was unaffected by Rp-CAMPS and Sp-CAMPS, an inhibitor and an activator, respectively, of CAMP-dependent protein kinase (PKA). We suggest that oxytocin activates two distinct signalling pathways in vagal neurons: one which is CAMP-dependent, but PKA-independent, and one, unidentified, which is PLC-β-and CAMP-independent. Each pathway accounts for about half of the peptide effect and both appear to involve G-protein activation.     

Inhibitory Effect of Dopamine on Dorsomedial Arcuate Neurons in Rat Brain Slices: Potentiation by Coadministration of Cocaine

Whether dopamine (DA) can have a direct effect on the tuberoinfundibular dopaminergic neurons has been a controversial issue. The present report used single-unit recording of neurons in dorsomedial region of the arcuate nucleus, where most tuberoinfundibular dopaminergic neurons are located, to study this question. By focusing our recording in this region, we found that DA in 25–250 nmol ranges inhibited a significant number of arcuate neurons tested (74.2% of 182 units). The inhibitory effect of DA was not only prominent in most cases, it also persisted in low Ca²⁺, high Mg²⁺ solution in several trials. Cocaine, a drug of abuse whose main effect is due to its inhibition of DA transporters and increasing the DA concentration in synaptic clefts, also inhibited a significant number of arcuate neurons by itself (51.5% of 97 units), although its effects were lesser than those of DA. Nevertheless, when coadministered with DA, cocaine significantly potentiated the inhibitory effect of DA in 82% of DA-responsive units (n = 39). These results clearly demonstrate that DA exhibits a predominantly inhibitory effect on presumed DA neurons in dorsomedial arcuate nucleus. The effects of cocaine further support this notion.     

阿魏酸钠对培养的皮质神经细胞内游离Ca2+的影响

目的 :研究阿魏酸钠对谷氨酸诱导培养的皮质神经细胞损伤的作用。方法 :采用新生大鼠皮质神经细胞原代培养建立谷氨酸神经细胞损伤模型 ,用Ca2 +指示剂Fura 2 /AM检测神经细胞内游离钙浓度 ( [Ca2 +] i)的变化 ,并观察反映神经细胞受损程度的培养液中乳酸脱氢酶 (LDH)的释放量的变化。结果 :阿魏酸钠 40～ 10 0 μmol·L-1能剂量依赖性抑制谷氨酸钠所引起的 [Ca2 +] i 升高及LDH释放。结论 :阿魏酸钠通过抑制谷氨酸钠所引起的 [Ca2 +] i 升高可能是其抗氧化性神经损伤作用的重要机制     

凝血酶对原代培养海马神经元游离钙浓度的影响

目的研究原代培养的海马神经元内游离Ca2 水平及凝血酶的影响.方法大鼠海马神经元进行体外原代培养,用钙离子指示剂Fura-2双波长法测定海马神经元内游离[Ca2 ]i及不同浓度的凝血酶作用后细胞内[Ca2 ]i.结果原代培养的海马神经元生长旺盛,密度高,符合实验要求.在胞外Ca2 浓度为0.0 mmol/L时,静息状态下海马神经元游离[Ca2 ]i为(79.83±18.78)nmol/L.当胞外Ca2 浓度为1.3 mmol/L时,海马神经元游离[Ca2 ]i为(106.41±22.53)nmo1/L.(1～40)U/ml凝血酶可使海马神经元内游离Ca2 水平显著升高,与对照组相比均有显著性差异(P＜0.01).随凝血酶浓度的增加,胞内游离[Ca2 ]i之呈剂量依赖性增加.结论凝血酶可使原代培养的海马神经元内游离Ca2 浓度明显升高.     

急性脑梗死镁钙变化的实验研究

目的:观察急性脑梗死镁钙含量的变化,探讨其潜在机制。方法:用栓线法制成大脑中动脉阻塞梗死模型(MCAO),在MCAO后6h、12h分别测定梗死侧、对侧脑皮质匀浆及血清镁、钙含量。结果:MCAO 6h后缺血区脑皮质匀浆镁含量明显低于、钙含量明显高于健侧脑皮质区及对照组,血清镁钙含量与对照组比较无显著差异;MCAO 12h后,缺血区脑皮质匀浆镁含量进一步下降、钙含量进一步升高与对照组及MCAO 6h组比较有显著差异(P＜0.001),同时血清镁下降、钙升高(与对照组及MCAO 6h组比,P＜0.001)。结论:急性脑梗死时缺血区脑组织及血清镁含量下降、钙含量升高;镁参与了缺血性脑坏死的病理生理过程。     

地塞米松对嘧啶亚硝脲诱导人脑胶质瘤细胞凋亡的影响

目的观察地塞米松（DEX）对嘧啶亚硝脲（ACNU）诱导的人脑胶质瘤细胞凋亡的影响。方法分别以ACNU、DEX、ACNU联合DEX,作用于体外培养的人脑胶质瘤细胞系SHG—4460h,通过细胞形态学及流式细胞仪分析检测细胞凋亡。结果①形态学观察：ACNU组、ACNU联合DEX组,大部分瘤细胞呈现细胞凋亡的形态学改变。而DEX组及正常对照组仅个别细胞出现上述形态改变。②荧光显微镜观察及流式细胞仪分析：ACNU组、ACNU联合DEX组有典型的凋亡峰,且其瘤细胞的凋亡率明显高于DEX组及正常对照组瘤细胞的凋亡率（P〈0．01）,但ACNU组的SHG～44细胞的凋亡率与ACNU联合DEX组相差不显著（P〉0．05）。结论DEX对ACNU诱导人脑胶质瘤细胞凋亡没有明显影响。     

Effect of Thiol Reagents on Phosphoinositide Hydrolysis in Rat Brain Synaptoneurosomes

Some divalent ions, such as Cd²⁺ and Zn²⁺, are able to stimulate phosphoinositide (PI) breakdown and to inhibit receptor-mediated PI metabolism. These ions are also known to react with the free – SH groups of proteins. This prompted us to investigate the effects of more potent sulphhydryl reagents, Hg²⁺ and p -chloromercuric benzosulphonic acid (PCMBS), on the inositol phosphate (IP) accumulation triggered by the neuroactive substances: glutamate, carbachol and K⁺, using synaptoneurosomes from 8-day-old rat forebrains. Hg²⁺ and PCMBS, depending on their concentration, had two distinct effects on IP accumulation: at low doses, Hg²⁺ (from 1 to 10 μM) and PCMBS (0.1 mM) by themselves stimulated PI breakdown, inhibited glutamate-elicited IP accumulation and had additive effects with respect to carbachol-induced IP stimulation. At higher doses, Hg²⁺ (from 0.01 to 1 mM) inhibited both basal and neuroactive substance-stimulated IP accumulation. PCMBS (1 mM), provoked only an inhibition of the agonist-stimulated IP formation. Monitoring membrane potential and intracellular Ca²⁺ with the fluorescent dyes diSC2(5) and fura2, respectively, indicated that these mercurials could strongly depolarize the synaptoneurosomal membrane and produce a Ca²⁺ influx dependent on extracellular Ca²⁺. The stimulatory effects of low concentrations of mercurials on PI turnover could be linked to the depolarization they provoke and the subsequent Ca²⁺ rise, which in turn is known to stimulate some phospholipase C enzymes. The inhibitory effects observed at high concentrations might be due to a loss of activity of proteins involved in PI breakdown, as all receptor-mediated IP accumulations were inhibited.