大鼠心肌细胞胞浆和核Ca2+震荡现象及其机制探讨

目的:在培养的新生大鼠心肌细胞上,观察多种刺激因素对细胞胞浆Ca²⁺([Ca²⁺]c)和核Ca²⁺([Ca²⁺]n)的影响,探讨其时间和空间关系及其机制。方法:以Fluo-4/AM荧光指示剂负载培养的心肌细胞,应用激光共聚焦扫描显微镜检测胞浆和核Ca²⁺震荡的变化。结果:正常心肌细胞内核Ca²⁺的荧光强度高于核周与细胞浆,三者均存在小幅度的钙震荡,分别加入去甲肾上腺素(10^-5mol/L)、异丙肾上腺素(10^-4mol/L)和三磷酸腺苷(ATP3×10^-3mol/L),均使心肌细胞钙震荡幅度明显升高(P＜0.01),L-型Ca²⁺通道阻滞剂维拉帕米(verapamil5×10^-4mol/L)、Ca²⁺-ATPase抑制剂thapsigargin(10^-6mol/L)和KCl(20mmol/L)使钙的周期性震荡消失。用thapsigargin10^-6mol/L预先阻断心肌细胞钙库的Ca²⁺摄取,去甲肾上腺素(10^-5mol/L)则不能引起钙震荡和荧光强度增加。结论:心肌细胞胞浆和核Ca²⁺均能产生钙震荡,而钙震荡的维持则依赖于细胞外Ca²⁺的内流、胞内钙库的Ca²⁺摄取和释放以及正常膜电位的维持。核与胞浆Ca²⁺变化不一致,提示细胞核上可能存在相对独立的Ca²⁺调节系统。     

Norepinephrine provides short-term neuroprotection against Aβ1–42 by reducing oxidative stress independent of Nrf2 activation

Pathophysiological evidence correlating locus ceruleus neuron loss with increased Alzheimer's disease pathology suggests that norepinephrine (NE) is neuroprotective. Here, we evaluated the effects of NE on amyloid-β (Aβ)1-42–induced neurotoxicity and determined how NE exerts its actions in human SK-N-SH neurons. NE protected SK-N-SH cells against Aβ1-42–induced neurotoxicity only after a 4-hour treatment. The ability of NE to reduce Aβ1-42–induced neurotoxicity was independent of the adrenoceptor signaling pathway. Notably, NE downregulated Aβ1-42–mediated increases in intracellular reactive oxygen species (ROS) production. However, NE did not affect Aβ1-42–induced activation of the nuclear factor erythroid 2–related factor 2 (Nrf2) redox signaling pathway, known to be involved in oxidative stress. Among the antioxidants tested, N-acetyl cysteine and glutathione, which are not only ROS scavengers but also thiol-reducing agents, mimicked the protective effects of NE. Consistently, Kelch-like ECH-associating protein 1 inhibitors, which activated the Nrf2 pathway, failed to decrease Aβ1-42–induced ROS generation and elicited no protection against Aβ1–42. Taken together, these findings suggest that NE could exert neuroprotective function against Aβ1–42 via redox cycling and reduction of intracellular oxidative stress regardless of downstream activation of the Nrf2 pathway.     

补经合剂对初老大鼠下丘脑内单胺类神经递质的影响

目的 :从大鼠脑内单胺类神经递质途径 ,探讨补经合剂对初老大鼠下丘脑 垂体 卵巢轴功能的影响。方法 :雌性初老大鼠为自然肾虚模型 ,采用荧光分光光度法观察该方对下丘脑内单胺类神经递质多巴胺(DA)、去甲肾上腺素 (NE)、5 羟色胺 (5 HT)含量的影响。结果 :补经合剂低剂量组 (7 8g·kg 1)、高剂量组 (3 1 g·kg 1)均可明显降低初老大鼠下丘脑内NE的影响 (P <0 .0 5 ) ;同时低剂量组还可明显降低初老大鼠脑内DA的含量 (P <0 .0 5 )。结论 :补经合剂可明显降低初老大鼠下丘脑内NE、DA含量 ,提示该方可能通过影响下丘脑内单胺类神经递质的水平而对下丘脑 垂体 卵巢轴进行调节 ,从而发挥治疗作用。     

Monoaminergic regulation of Sonic hedgehog signaling cascade expression in the adult rat hippocampus

Monoamines are implicated in the modulation of adult hippocampal neurogenesis in depression models and following chronic antidepressant treatment. Given the key role of Sonic hedgehog (Shh) in adult neurogenesis, we examined whether monoaminergic perturbations regulate the expression of Shh or its co-receptors Smoothened (Smo) and Patched (Ptc). Combined depletion of both serotonin and norepinephrine with para-chlorophenylalanine (PCPA) resulted in a significant decrease in Smo and Ptc mRNA within the dentate gyrus subfield of the hippocampus. However, selective depletion of serotonin, using the serotonergic neurotoxin 5,7-dihyrdroxytryptamine (5,7-DHT), or norepinephrine, using the noradrenergic neurotoxin DSP-4, did not alter expression of Shh and its co-receptors, Smo and Ptc. Acute treatment with the monoamine releasing agent, para-chloroamphetamine (PCA) significantly upregulated Smo mRNA within the dentate gyrus. However, acute or chronic treatment with pharmacological antidepressants that modulate monoaminergic neurotransmission did not regulate Shh cascade expression. These results indicate that robust changes in monoamine levels can regulate the expression of the Shh signaling cascade in the adult rodent brain.     

去甲肾上腺素诱导严重烧伤大鼠脑组织VEGF表达的实验研究

目的：观察去甲肾上腺素（NE）诱导严重烧 伤后24h大鼠脑组织血管内皮细胞生长因子(VEGF)的表达变化。方法:(1 )采用40%全身总体表面积（TBSA）Ⅲ°烧伤大鼠模型，用干、湿重法检测NE刺激烧伤24h大 鼠脑组织含水量；(2)用高效液相色谱法，检测烧伤大鼠脑组织去甲肾上腺素活性水平的变 化;(3) 用免疫蛋白印迹法（Western blotting）检测NE诱导脑组织VEGF蛋白表达变化。 结果：(1) 烧伤大鼠和NE刺激后的烧伤大鼠脑组织水肿明显；(2)烧伤后2 4 h大鼠脑组织NE活性增加，而NE刺激后的烧伤大鼠，脑组织NE的活性增加显著;(3) NE刺 激剂量增大时，脑组织VEGF的蛋白表达逐渐增加，烧伤后VEGF的蛋白表达增加明显，随NE刺 激剂量增大，烧伤后VEGF的蛋白表达明显增强。结论:NE可诱导严重烧 伤大鼠脑组织VEGF的蛋白表达，提示烧伤后NE水平增高是脑水肿形成的一个重要因素。     

失血性休克大鼠淋巴管低反应性的钙敏机制

目的:观察失血性休克(HS)大鼠离体淋巴管对去甲肾上腺素(NE)反应性以及钙敏感性的变化,探讨淋巴管低反应性的钙敏机制。方法:Wistar雄性大鼠随机均分为sham组(仅手术)和HS组(复制HS模型,分为休克1 h、休克2 h亚组),制备胸导管环(每组均n=48)。采用离体淋巴管张力测定技术,观察淋巴管环对NE反应性以及钙敏性[梯度Ca2+与血管紧张素Ⅱ(AngⅡ)和胰岛素(Ins)分别孵育]变化。结果:与sham组相比,HS1 h组、HS 2 h组大鼠离体淋巴管对NE反应的量效曲线以及HS 2 h组淋巴管对Ca2+的量效曲线明显右移,对NE多个浓度的反应性以及不同Ca2+浓度的收缩力、最大收缩力(Emax)、亲和力指数(pD2)均显著降低。HS大鼠离体淋巴管环与钙敏感性增强剂AngⅡ孵育后,对NE的反应性以及钙敏感性均显著升高,但仍低于sham组;与钙敏感性抑制剂Ins孵育后,对NE的反应性以及钙敏感性均显著降低。结论:HS大鼠离体淋巴管的低反应性与钙失敏有关,这是休克时淋巴管收缩性降低的机制之一。     

生物活性物质对蟾蜍心脏的双重作用

在离体蟾蜍心脏上,研究生物活性物质(NE,ACh,CaCl_2,KCl)的量—效关系。发现在不同浓度阻断剂影响下,上述药物均呈现双重作用。当阻断α和(或)β受体时,其正性变力性作用被阻抑而呈现负性作用,阻断M_1、M_2和(或)Cl~-通道时,其负性变力性作用翻转为正性作用。     

Fluoxetine, but not other selective serotonin uptake inhibitors, increases norepinephrine and dopamine extracellular levels in prefrontal cortex

RATIONALE: The selective serotonin uptake inhibitor (SSRI) fluoxetine has been shown to not only increase the extracellular concentrations of serotonin, but also dopamine and norepinephrine extracellular concentrations in rat prefrontal cortex. The effect of other SSRIs on monoamine concentrations in prefrontal cortex has not been thoroughly studied. OBJECTIVE: The aim of this study was to compare the ability of five systemically administered selective serotonin uptake inhibitors to increase acutely the extracellular concentrations of serotonin, norepinephrine and dopamine in rat prefrontal cortex. METHODS: The extracellular concentrations of monoamines were determined in the prefrontal cortex of conscious rats using the microdialysis technique. RESULTS: Fluoxetine, citalopram, fluvoxamine, paroxetine and sertraline similarly increased the extracellular concentrations of serotonin from 2- to 4-fold above baseline. However, only fluoxetine produced robust and sustained increases in extracellular concentrations of norepinephrine and dopamine after acute systemic administration. Fluoxetine at the same dose blocked ex vivo binding to the serotonin transporter, but not the norepinephrine transporter, suggesting that the increase of catecholamines was not due to non-selective blockade of norepinephrine uptake. Prefrontal cortex extracellular concentrations of fluoxetine at the dose that increased extracellular monoamines were 242 nM, a concentration sufficient to block 5-HT(2C) receptors which is a potential mechanism for the fluoxetine-induced increase in catecholamines. CONCLUSION: Amongst the SSRIs examined, only fluoxetine acutely increases extracellular concentrations of norepinephrine and dopamine as well as serotonin in prefrontal cortex, suggesting that fluoxetine is an atypical SSRI.     

Differential regulation of nicotinic receptor-mediated neurotransmitter release following chronic (-)-nicotine administration

The objective of this study was to compare nAChR-mediated neurotransmitter release from slices of rat striatum, frontal cortex and hippocampus following chronic (-)-nicotine (Nic) administration (tartrate salt, 2 mg/kg twice daily for 10 days). Binding studies were also conducted to measure changes in receptor density. Relative to saline-treated animals, the number of nAChRs measured by [(3)H]-cytisine (CYT) binding was significantly increased in all brain regions examined by 15% to 25% following chronic Nic administration. Using a relatively high throughput method to measure neurotransmitter release, we found that Nic, CYT, and (+/-)-epibatidine (EB) evoked similar concentration-dependent striatal [(3)H]-dopamine (DA) and hippocampal [(3)H]-norepinephrine (NE) release from both saline (rank order of potency for [(3)H]-DA: EB>CYT>Nic; pEC(50) values, EB (9 +/- 0.1), CYT (8 +/- 0.13), Nic (7.3 +/- 0.19); rank order potency for [(3)H]-NE: EB>Nic=CYT; pEC(50) values, EB (8 +/- 0.18), Nic (5.5 +/- 0.09), CYT (5.12 +/- 0.1)) -and Nic-treated animals (pEC(50) values [(3)H]-DA, EB (9.5 +/- 0.15), Nic (8 +/- 0.16, CYT (6.6 +/- 0.52); [(3)H]-NE, EB (8.4 +/- 0.23), Nic (5.19 +/- 0.1), CYT (5.18 +/- 0.29)). Although no change in potency was detected between the two treatment groups, the agonist efficacies in both tissues were significantly reduced by approximately 17-54% following chronic Nic administration. In contrast to striatum, treatment with Nic did not affect the maximal [(3)H]-DA response (efficacy) in the frontal cortex. However, as observed in the striatum, no change in agonist potency was observed in the frontal cortex following chronic Nic administration (pEC(50) values, saline; EB (9.2 +/- 0.2), >CYT (6.95 +/- 0.75) = Nic (6.9 +/- 0.16); Nic-treated, EB (9 +/- 0.42)>CYT (6.88 +/- 0.27) = Nic (7.1 +/- 0.17)). Chronic Nic treatment did not significantly affect KCl-evoked [(3)H]-NE release from hippocampus or [(3)H]-DA release from frontal cortex or striatum. Since previous work has demonstrated that different nAChR subtypes display various sensitivities to chronic Nic exposure, we suggest that the subtypes of nAChRs involved in regulating [(3)H]-DA release may be different in the striatum and frontal cortex. These results support findings from earlier studies comparing the pharmacology of nAChR-evoked striatal versus cortical [(3)H]-DA release.     

Cyclooxygenase inhibitors attenuate endothelin ET(B) receptor-mediated contraction in human temporal artery

Phendimetrazine is an effective and widely prescribed appetite suppressant. Preclinical findings show that phendimetrazine displays stimulant properties similar to amphetamine, but few studies have examined the neurochemical mechanism of the drug. In the present work, we characterize the activity of phendimetrazine and its putative metabolites [phenmetrazine, pseudophenmetrazine, and associated stereoisomers] at biogenic amine transporters. All drugs were tested in vitro using assays to measure uptake and release of [3H]dopamine, [3H]norepinephrine, and [3H]serotonin ([3H]5-HT) in rat brain synaptosomes. Selected drugs were tested in vivo using microdialysis to measure extracellular dopamine and serotonin (5-HT) in rat nucleus accumbens. Phendimetrazine itself had no effect on uptake or release of any transmitter. In contrast, the trans-configured N-demethylated metabolite, phenmetrazine, was a potent releaser of [3H]norepinephrine (EC(50)=50 nM) and [3H]dopamine (EC(50)=131 nM). The cis N-demethylated metabolite, pseudophenmetrazine, displayed modest potency at releasing [3H]norepinephrine (EC(50)=514 nM) and blocking [3H]dopamine re-uptake (IC(50)=2630 nM). All drugs tested were inactive or weak in the [3H]5-HT assays. When injected intravenously, phendimetrazine had minimal effects on extracellular transmitter levels, whereas phenmetrazine produced dose-related elevations in extracellular dopamine. The collective findings suggest that phendimetrazine is a "prodrug" that is converted to the active metabolite phenmetrazine, a potent substrate for norepinephrine and dopamine transporters.