Chronically administered guanosine is anticonvulsant,amnesic and anxiolytic in mice

Acute administration of intraperitoneal and oral guanosine has been shown to prevent quinolinic acid and alpha-dendrotoxin-induced seizures in rats and mice. In this study, we investigated the effects of 2 weeks ad libitum consumption of guanosine (0.5 mg/ml) added to mice water supply on seizures and lethality induced by the alpha-dendrotoxin, hole-board behavior, inhibitory avoidance task, locomotor activity, motor coordination, rectal temperature, body weight, and water and food consumption. Guanosine prevented seizures in 40% and death in 50% on mice treated with i.c.v. alpha-dendrotoxin; it also impaired inhibitory avoidance memory and increased head-dipping behavior and locomotor activity on the hole-board test. Guanosine consumption did not alter any of the other parameters evaluated. The anticonvulsant, amnesic, and anxyolytic-like effects may be associated with the ability of guanosine in modulating the glutamatergic excitatory system. Adding to previously reported data, these findings suggest a potential role for chronic guanosine in the management of diseases associated with glutamatergic excitotoxicity, including epilepsy and anxiety.     

Involvement of postsynaptic G proteins in hippocampal long-term potentiation

The possible involvement of postsynaptic guanosine 5-triphosphate (GTP)-binding proteins (G proteins) in long-term potentiation (LTP) was studied in rat hippocampal slices, using whole-cell recording techniques. The inclusion of guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) or guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) in the recording pipette significantly reduced or abolished the baclofen-induced hyperpolarization of pyramidal neurons, which indicates uncoupling of the signal transduction from G protein-coupled receptors by these compounds. Both GDP beta S and GTP gamma S significantly attenuated the magnitude of LTP in the fimbria-CA3 synapses, but not in the mossy fiber-CA3 synapses. GTP gamma S did not attenuate LTP in the Schaffer-CA1 synapses. The effects of guanine nucleotide analogs on fimbrial LTP were reversed by postsynaptic depolarization during high frequency stimulation. These results suggest that postsynaptic G proteins may be involved in the generation of LTP in the fimbrial synapses, possibly by affecting membrane depolarization during high frequency afferent activation.     

Effects of cyclic nucleotide monophosphates (cAMP,cGMP, cIMP,dibutyry-cAMP) on transtubular net fluxes in rat kidneys

Summary The direct effects of dibutyryl-cAMP, cAMP, cGMP, and cIMP on transepithelial net transfer of fluid and sodium was investigated in proximal tubules of rat kidneys using the split drop method. The cyclic phosphates were applied into the tubular lumen. All four investigated cyclic nucleotide monophosphates diminished the net transport, although high concentrations were necessary. 10^–4 M db-cAMP decreased transtubular net flux of fluid per area tubular surface significantly by 14%. In agreement with other studies, it is concluded that hormones and drugs may influence renal excretory performance via cyclic nucleotide phosphates.     

Alkylation of guanosine and 4-(p-nitrobenzyl)-pyridine by styrene oxide analogues in vitro

In vitro alkylation activity of styrene oxide (SO) and three of its analogues, 4-vinyltoluene oxide (VTO), 3,5-dimethylstyrene oxide (DMSO), and 4-nitrostyrene oxide (NSO) was assayed using 4-(p-nitrobenzyl) pyridine (NBP) and guanosine as nucleophiles. Hydrolysis rates were also determined. The half-lives of VTO, DMSO, SO, and NSO were 8, 11, 40, and 60 h, respectively in aqueous solution. The rate of NBP alkylation correlated with the rate of hydrolysis. By contrast, the rates of guanosine alkylation were quite different: SO > VTO > DMSO. NSO did not react with guanosine. Fluorescence and ultraviolet spectroscopic data on the guanosine adducts indicated that SO, VTO, and DMSO formed main alkyl products at N-7.     

Potentiation of nicotinic transmission in the rat superior cervical sympathetic ganglion: effects of cyclic GMP and nitric oxide generators

The efficacy of nicotinic transmission in the rat superior cervical ganglion in vitro (24-26 degrees C) was estimated by extracellular recording of the postganglionic compound action potential response to stimulation of the preganglionic nerve at a slow rate (one shock every 60 s). Atropine (2 microM) was included to block muscarinic transmission, and hexamethonium (200-250 microM) was used to produce a submaximal response sensitive to potentiation and inhibition of nicotinic transmission. Upon exposure to 1-100 microM 8-bromo-guanosine 3',5'-cyclic monophosphate (8-Br-cGMP), nicotinic transmission was potentiated by 6 +/- 1% (n = 4) to 89 +/- 5% (n = 5) in a dose-dependent manner. 8-Bromo-adenosine 3',5'-cyclic monophosphate (8-Br-cAMP, 10-100 microM) also potentiated nicotinic transmission (3.8 +/- 0.3% (n = 3) to 43 +/- 4% (n = 3)). However, 8-Br-cGMP was at least 2-fold more effective than 8-Br-cAMP. Sodium nitroprusside (0.1 microM to 1 mM) and sodium azide (0.1-100 microM) were used to stimulate the formation of endogenous cGMP52. Nicotinic transmission was potentiated by these substances also. The response was increased by 3.4 +/- 0.7% (n = 4) to 32 +/- 2% (n = 5) upon exposure to 0.1-100 microM sodium nitroprusside, and by 5.5 +/- 0.9% (n = 3) to 18 +/- 4% (n = 4) upon exposure to 0.1-100 microM sodium azide. Ferricyanide ion (10-100 microM) appeared to be ineffective, as would be expected if the effect of nitroprusside was due to the nitric oxide rather than the cyanide or ferric moieties.(ABSTRACT TRUNCATED AT 250 WORDS)     

炎症渗出液量与其中cAMP,cGMP浓度的关系以及电针刺激的影响

本文以鹿角菜素诱发大鼠胸膜炎动物模型,观察了炎症过程中渗出液的量、渗出液中cAMP和cGMP浓度,以及电针刺激的抗渗出作用与cAMP和cGMP浓度之间的联系。实验结果表明,在致炎后12至24小时内,随着炎症渗出液量的增加,而cAMP浓度下降,cGMP浓度却上升。电针组炎症渗出液量明显少于对照组(P<0.05),cAMP浓度明显高于对照组(P<0.01),cGMP浓度明显低于对照组(P<0.05)。     

Thioredoxin-1 promotes survival in cells exposed to S-nitrosoglutathione: Correlation with reduction of intracellular levels of nitrosothiols and up-regulation of the ERK1/2 MAP Kinases

Accumulating evidence indicates that post-translational protein modifications by nitric oxide and its derived species are critical effectors of redox signaling in cells. These protein modifications are most likely controlled by intracellular reductants. Among them, the importance of the 12 kDa dithiol protein thioredoxin-1 (TRX-1) has been increasingly recognized. However, the effects of TRX-1 in cells exposed to exogenous nitrosothiols remain little understood. We investigated the levels of intracellular nitrosothiols and survival signaling in HeLa cells over-expressing TRX-1 and exposed to S-nitrosoglutahione (GSNO). A role for TRX-1 expression on GSNO catabolism and cell viability was demonstrated by the concentration-dependent effects of GSNO on decreasing TRX-1 expression, activation of caspase-3, and increasing cell death. The over-expression of TRX-1 in HeLa cells partially attenuated caspase-3 activation and enhanced cell viability upon GSNO treatment. This was correlated with reduction of intracellular levels of nitrosothiols and increasing levels of nitrite and nitrotyrosine. The involvement of ERK, p38 and JNK pathways were investigated in parental cells treated with GSNO. Activation of ERK1/2 MAP kinases was shown to be critical for survival signaling. In cells over-expressing TRX-1, basal phosphorylation levels of ERK1/2 MAP kinases were higher and further increased after GSNO treatment. These results indicate that the enhanced cell viability promoted by TRX-1 correlates with its capacity to regulate the levels of intracellular nitrosothiols and to up-regulate the survival signaling pathway mediated by the ERK1/2 MAP kinases.     

HPLC法测定半贝丸中腺苷、鸟苷、西贝母碱和西贝母碱苷的含量

目的:建立半贝丸中腺苷、鸟苷、西贝母碱和西贝母碱苷的含量测定方法。方法:采用高效液相色谱(HPLC)法。腺苷和鸟苷的色谱柱为Hypersil C18(250 mm×4.6 mm,5μm),流速为0.9 ml/min,流动相为甲醇-1%冰醋酸(梯度洗脱),检测波长为260nm;西贝母碱和西贝母碱苷的色谱柱为Hpersil C18(250 mm×4.6 mm,5μm),流动相为乙腈-0.1%二乙胺溶液(79∶21,V/V),柱温为室温,流速为0.9 ml/min,进样量为10μl,蒸发光散射检测器漂移管温度为85℃,载气(N2)流速为2.1 L/min。结果:腺苷与鸟苷的进样量分别在0.013 4⁰.268 0μg(r=0.999 2)、0.041 20.268 0μg(r=0.999 2)、0.041 2⁰.824 0μg(r=0.999 7)范围内与峰面积积分值呈良好线性关系,平均加样回收率分别为97.66%、96.86%,RSD分别为1.72%、1.38%(n均为6);西贝母碱和西贝母碱苷进样量分别在0.031 60.824 0μg(r=0.999 7)范围内与峰面积积分值呈良好线性关系,平均加样回收率分别为97.66%、96.86%,RSD分别为1.72%、1.38%(n均为6);西贝母碱和西贝母碱苷进样量分别在0.031 6⁰.632 0(r=0.999 1)、0.065 20.632 0(r=0.999 1)、0.065 2¹.304 0μg(r=0.999 8)范围内与各自峰面积的自然对数值呈良好线性关系,平均加样回收率分别为96.51%、98.79%,RSD分别为1.37%、0.94%(n均为6)。精密度、稳定性、重复性试验的RSD均小于1%。结论:该测定方法结果准确、灵敏度高、重复性好,可为完善半贝丸的质量控制标准提供依据。     

非诺贝特通过上调三磷酸鸟苷环化水解酶Ⅰ促进eNOS复偶联

目的探讨非诺贝特发挥降脂外血管内皮保护作用的机制。方法体外培养人脐静脉内皮细胞（HU-VECs）,非诺贝特预处理HUVECs 2 h,再与脂多糖（LPS）共孵育24 h。采用Western blot检测三磷酸鸟苷环化水解酶Ⅰ（GTPCH-Ⅰ）的表达水平,高效液相色谱法检测四氢生物蝶呤（BH4）的表达水平,ELISA检测细胞上清一氧化氮（NO）浓度,利用Confocal方法检测细胞活性氧（ROS）产生水平。结果非诺贝特预处理后,较单纯LPS刺激组,细胞内BH4表达水平及细胞上清NO产生增多,伴有细胞内ROS产生减少（P均〈0.05）;此外,单独给予非诺贝特处理内皮细胞后,可见浓度依赖性上调细胞GTPCH-Ⅰ的表达,非诺贝特（10μmol/L）上调GTPCH-Ⅰ的表达在12 h达到高峰。结论非诺贝特通过上调内皮细胞GTPCH-Ⅰ的表达而增加BH4的水平,进而促进内皮型一氧化氮合酶的复偶联,改善血管内皮功能。     

二氮嗪预处理对糖尿病大鼠心肌保护作用减弱机制的初步研究

目的探讨二氮嗪预处理（DPC）对糖尿病大鼠心肌保护作用减弱的机制。方法取糖尿病SD大鼠及非糖尿病SD大鼠48只,建立离体心脏Langendorff灌注模型,各分为4组（每组6只）：对照组（CON组）：全心灌流120 min。缺血再灌注组（I/R组）：在心脏平衡灌流30 min后,缺血30 min再灌注KH液1 h。DPC组：在心脏平衡灌流10 min后,给予含二氮嗪（100μmol/L）的KH液灌注5 min,再复灌不含二氮嗪的KH液5 min后,再给予含二氮嗪的KH液灌注5 min,再复灌不含二氮嗪的KH液5 min,然后缺血30 min,再灌注KH液1 h。二甲基亚砜组（DMSO组）：用DMSO代替二氮嗪,过程同DPC组。比较各组冠脉流出液中肌酸激酶（CK）、心肌组织丙二醛（MDA）、超氧化物岐化酶（SOD）、心肌组织一氧化氮（NO）、环磷酸鸟苷（cGMP）、一氧化氮合酶（NOS）的变化。结果①CK活性：非糖尿病大鼠中,再灌注后DPC组CK活性与I/R组比较明显降低（P〈0.01）,DMSO组与I/R组比较差异无统计学意义（P〉0.05）;而糖尿病大鼠中,再灌注后DPC组与I/R组比较,差异均无统计学意义（P〉0.05）。②MDA、SOD含量：非糖尿病大鼠中,DPC组MDA含量明显低于I/R组（P〈0.01）、SOD含量明显高于I/R组（P〈0.01）。而在糖尿病大鼠中,DPC组与I/R组比较,MDA和SOD的含量差异无统计学意义（P〉0.05）。③心肌组织NO、cGMP及NOS含量：非糖尿病大鼠中,DPC组NO、cGMP及NOS含量与I/R组比较明显增加（P〈0.01）,DMSO组与I/R组比较差异无统计学意义（P〉0.05）;而糖尿病大鼠中,DPC组与I/R组、DMSO组比较,差异无统计学意义（P〉0.05）。结论 DPC对糖尿病大鼠心肌的保护作用减弱,其机制可能与糖尿病大鼠心肌NO-cGMP信号通路表达受抑制有关。