Allyglycine affects acetylation of putrescine and spermidine in mouse brain

Administration of allylglycine to mice (.8 mmole/kg, i.p.) results in a depletion of GABA levels, and it is accompanied by a decrease in SAM-DC activity and spermidine and spermine levels (Pajunen et al., 1979). Here we describe a biphasic effect on the acetylation of putrescine and spermidine in mouse brain homogenate. There appears to be an inverse correlation between the initial decrease in spermidine levels at 2 hours and the increase in the acetylation of spermidine. This is suggestive of a conversion of spermidine, probably through N¹-acetylspermidine to putrescine. The peak of putrescine acetylation observed by us at 4 hours may also reflect a conversion of putrescine, via acetylputrescine to GABA. The interconversion hypothesis is supported by the fact that putrescine levels remain essentially stable in spite of a significant depletion of spermidine and spermine. In addition, there is a decrease in putrescine and spermidine acetylation at 8 hours, which coincides with the increase in ODC activity and the increase towards control levels of GAD activity (Pajunen et al., 1979). Such inverse correlations suggest a mechanism for replenishment of polyamines once GAD activity returns to control levels.     

环磷酰胺处理雄小鼠对受精卵和二细胞期胚胎DNA甲基化和组蛋白H3K23乙酰化的影响

目的探讨环磷酰胺处理雄性小鼠对受精卵和早期胚胎DNA甲基化修饰和组蛋白H3第23位赖氨酸(H3K23)乙酰化修饰的影响。方法 20只性成熟的ICR雄小鼠饲喂环磷酰胺6 mg.kg-1 4周。雄鼠与雌鼠交配后收集原核期受精卵和二细胞期胚胎。间接免疫荧光染色技术结合激光共聚焦扫描显微镜技术检测胚胎细胞中DNA甲基化和组蛋白H3K23乙酰化修饰的分布和水平。结果与正常对照组相比,环磷酰胺组原核期受精卵和二细胞期胚胎的DNA甲基化修饰水平和分布没有明显差异;但与正常对照组(3%)相比,环磷酰胺组的二细胞期胚胎微核现象(20%)明显升高(P<0.01);与正常对照组相比,环磷酰胺组受精卵雄原核和二细胞期胚胎细胞核的组蛋白H3K23乙酰化水平明显降低(P<0.05),且胚胎间的变化差异明显升高,其中部分原核期受精卵(58%)和二细胞期胚胎(44%)染色水平明显偏低。结论长期低剂量环磷酰胺处理雄鼠可以导致部分受精卵和二细胞期胚胎组蛋白H3K23乙酰化异常,并且显著增加微核发生率。     

Exposure to polychlorinated naphthalenes affects GABA-metabolizing enzymes in rat brain

There is substantial evidence that polychlorinated naphthalenes (PCNs) are widespread global environmental pollutants, which accumulate in biota. The aim of our study was to characterize the effect of prolonged PCNs exposure on γ-aminobutyric acid (GABA) metabolism in rat brain regions with a high amount of GABAergic neurons (cerebellum, brain stem and basal ganglia). PCNs mixture was administered intragastrically for 7, 14 and 21 days in a dose 10 mg/kg of body weight daily, and next the activity of glutamate decarboxylase (GAD), GABA-aminotransferase (GABA-T), succinic semialdehyde dehydrogenase (SDH) and succinate dehydrogenase (SSA-DH) was assayed. PCNs administration altered all examined activities in the selected brain areas, except GAD in basal ganglia. The results suggest the correlation between PCNs action and disturbance in GABA metabolism in rat brain. Moreover, the chronic PCNs intoxication increased SDH-mediated activation of TCA cycle, and it may be a kind of protective mechanism developed in nervous tissue in response to administration of toxic compounds.     

Plasma spermidine and putrescine as markers of cancer management

The hypothesis was tested that dying tumor cells release spermidine and putrescine into the bloodstream. Therefore, a rhabdomyosarcoma was implanted in rats, irradiated and its growth and subsequent reduction compared with spermidine and putrescine plasma concentrations of the venous effluent from the tumor side and contralateral side. In the experimental set-up used the hypothesis could not be verified. It appeared that irradiation only, implantation and growth of a tumor only and an irradiated tumor, all caused elevated spermidine and putrescine concentrations in the effluent of both sides in approximately the same order of magnitude, compared to untreated controls.     

Characteristics of muscimol accumulation in mouse brain after systemic administration.

Studies on the chemical characteristics of tritiated substances accumulated in mouse brain and heart after intravenous administration of ³H-muscimol indicate that the bulk of this agent is chemically modified in the periphery with only a small amount (0.02%) of unchanged substance reaching the brain. In vivo competition experiments using unlabeled muscimol and bicuculline suggest that the ³H-muscimol present in the brain may not be specifically localized to synaptic GABA receptor sites. Comparison of ³H-muscimol, ³H-GABA and ³H-phenobarbital accumulation reveals that muscimol and GABA penetrate the brain to a similar extent which is at least an order of magnitude less than phénobarbital. Chloroform/water partition coefficients of these three compounds indicate that GABA and muscimol have similar relative lipid solubilities, being 300 times less lipophilic than phenobarbital. These results suggest that the behavioral and biochemical effects observed after the systemic administration of muscimol may not be solely due to the presence of muscimol in brain, but rather may be related to the combined action of muscimol and some derivative or to the derivative alone.     

Modulation of mouse brain dopamine,serotonin and metabolites by methionine: Implications for schizophrenia and genetics

The effect of methionine, an essential amino acid, on brain regional distribution of dopamine, serotinin and major acidic metabolites was studied in two genetically different strains of mice. These were the inbred albino BALB/C and the black C₅₇BL/6 mouse strains. The later strain was more sensitive than the former mouse strain to the methionine treatment. This has been demonstrated by methionine-produced change in dopamine metabolites in cerebellum, cortex and medulla regions, which suggests a decrease in dopamine turnover in the C₅₇BL/6 mice. Conversely, methionine-mediated changes in BALB/C mouse medullary region was suggestive of an increase in dopamine turnover. Little changes occurred in cerebral serotonin or 5-hydroxyindoleacetic acid levels, except for an increased serotonin in C₅₇BL/6 mouse midbrain region. The results suggest that methionine possesses CNS pharmacological property pertaining to dopamine, other than its well-known action as a methyl donor in transmethylation processes, which is genotypic-dependent. Alternatively, modulation of the monoamines by methionine may explain its antidepressant property and possible contribution to the pharmacological hypotheses relevant to the biology of schizophrenia.     

柱前衍生化高效液相色谱法测定人唾液中腐胺和精胺的含量

目的建立柱前衍生化高效液相色谱法同时测定人唾液中腐胺和精胺含量的方法。方法唾液经纯化、丹酰氯衍生化后用苯提取,以Hypersil BDS CN为正相色谱柱,丙酮-氯仿(2∶98)为流动相,流速1 mL/min进行测定,检测波长为425 nm。结果腐胺和精胺均在50~1 000 nmo1/mL范围内线性关系良好,r分别为0.999 1和0.999 2,此法回收率分别为94.65%和90.48%,RSD分别为1.6%和2.1%。结论此法灵敏、稳定,重现性好,可检测人唾液中多胺含量。     

腐胺对异丙肾上腺素致大鼠心肌损伤的保护作用

在大鼠ｓｃ异丙肾上腺素（０．８３μｍｏｌ·ｋｇ－１·ｄ－１）造成的心肌损伤模型上观察腐胺的作甲。结果表明，腐胺（１．８５×１０－１，６．１７×１０－１ｍｏｌ·ｋｇ－１·ｄ－１．ｉｖ）可明显减轻由异丙肾上腺素引起的心肌损伤，缓解心功能衰竭，抑制乳酸脱氢酶的漏出，减少异丙肾上腺素引起的心肌丙二醛和心肌组织钙的聚集。提示腐胺对于缺血性心脏疾病可能具有一定的防治作用。     

Depletion and time-course of recovery of brain serotonin after repeated subcutaneous dexfenfluramine in the mouse. A comparison with the rat

The indole-depleting effects of repeated subcutaneous doses of dexfenfluramine ( -F) (2.5, 5, 10, 20 and 40 mg/kg/day, for four days) in mice were examined with regard to the initial response and time-course of recovery and related to the pharmacokinetics of -F and its active metabolite dexnorfenfluramine ( -NF). Steady-state plasma and brain concentrations of -F rose dose-dependently with a metabolite-to-drug ratio averaging 0.4 in brain. This confirmed that in mice -NF contributes less than in other species to the effects of -F. Regional serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) contents were decreased dose-dependently 4 hr after the last injection of -F. However, two weeks after -F (2.5–10 mg/kg/day) brain indoles had almost totally recovered, and the long-term effects of the 20 mg/kg/day dose were completely reversed by six weeks, when significant effects are still observable in rats. Although substantial recovery was evident even at 40 mg/kg/day, 5-HT but not 5-HIAA was still slightly reduced nine weeks later. Comparative studies in rats given 2.5–20 mg/kg/day -F indicated much more severe initial indole depletions than in mice. Brain levels of -F and -NF were much higher in rats than in mice. The total active drug brain concentration ( -F + -NF) was significantly correlated with 5-HT content in both species, with approx 20 nmol/g of total drug causing 50% reduction. These findings point to species differences in -F kinetics as a main reason for differences in the neurochemical response, supporting the view that the recovery of indoles over time is related to the extent of initial depletion, which in turn depends on critical drug brain concentrations. In view of the qualitative and quantitative species differences in the pharmacodynamics and pharmacokinetics of -F neither of these rodent species is a suitable model for predicting potential drug toxicity in humans.     

Effect of metabolites of valproic acid on the metabolism of GABA in brain and brain nerve endings

Seven metabolites of valproic acid (VPA), i.e. 2-en-VPA, 3-en-VPA, 4-en-VPA, 3-hydroxy-VPA, 4-hydroxy-VPA, 5-hydroxy-VPA and 3-keto-VPA and valproic acid itself were examined for their effects on the metabolism of γ-aminobutyric acid (GABA) in the brain and brain nerve endings (synaptosomes) in mice. Administered in anticonvulsant doses, valproic acid and its metabolites caused elevations of the synaptosomal GABA content which were correlated with their anticonvulsant potency. No relationship was observed between the relative anticonvulsant activity of the respective compounds and the increase of GABA in the whole brain. The synaptosomal activity of glutamate decarboxylase (GAD) was increased parallel to the elevation of GABA and the activity of GABA aminotransferase (GABA-T) was partly inhibited. The present results emphasise the usefulness of determining the in vivo effects of drugs on GABA metabolism in brain nerve terminals which is thought to be the critical factor controlling the functioning of the amino acid as a neurotransmitter.     

胍丁胺代谢产物腐胺对吗啡镇痛、耐受和依赖的影响

目的观察腐胺对吗啡镇痛、耐受及依赖的影响,探讨腐胺治疗阿片耐受性和依赖性的潜力。方法小鼠醋酸扭体模型和55℃热板法测痛阈;吗啡恒定剂量给药制备耐受模型,55℃热板法测痛阈;吗啡递增剂量给药制备依赖模型,纳洛酮催促观察戒断症状,以胍丁胺(40 mg.kg-1,ig)为阳性对照药,腐胺灌胃给药剂量分别为10,20,40,80 mg.kg-1。结果在小鼠醋酸扭体模型中腐胺具有镇痛作用;而在小鼠55℃热板实验中,腐胺本身无镇痛作用,能较弱地增强吗啡镇痛;腐胺能够减弱吗啡耐受的形成,对已形成的吗啡耐受也有治疗作用;腐胺能够减弱吗啡躯体依赖的形成和表达。结论腐胺和胍丁胺具有相似的生物学活性,具有治疗阿片耐受和依赖的潜力。     

Effect of aminooxyacetic acid (AOAA) on GABA levels in some parts of the rat brain

Summary The accumulation of GABA in the cerebellum and medulla oblongata-pons of rats has been studied after inhibition of GABA-T (EC 2.6.1.19) by different doses of AOAA. It was found that intraperitoneal (i.p.) injections of AOAA were, at least during the first hour after injection, much less effective than intravenous (i.v.) injections probably due to poor absorption i.p. After i.v. injection, AOAA caused a maximal accumulation of GABA in the cerebellum at a dose of 50 mg/kg. This maximal effect was virtually unchanged up to a dose of 150 mg/kg (the highest dose tested i.v.). If GAD (EC 4.1.1.15) was inhibited by 3-mercaptopropionic acid 30 min after AOAA (90 mg/kg i.v.) the GABA level was stable for at least another 30 min. The rate of GABA accumulation in the cerebellum during the first 15 min after AOAA (50–150 mg/kg i.v.) was 0.086 mol/g/min and thereafter 0.034 mol/g/min. It is concluded that AOAA in vivo in a wide dose range inhibits GABA-T almost 100% without affecting GAD to any great extent, and that the onset of action is rapid after i.v. but not after i.p. injection.     

Estimation of local kinetic parameters of exchange of lithium in various substructures of the mouse brain, using the 6Li(n, alpha)3H-nuclear reaction

The time-constant of lithium (Li)-clearance from the plasma was of the order of 2 hr, while the mean time-constant of lithium-clearance from the bulk of the body cells into the plasma was about 10 times this value. The mean time-constant of lithium ion (Li+)-clearance from various brain substructures (corpus callosum, striatum, hippocampus, neocortex) was comparable to the latter (15-25 hr). Comparison of samples where either a slight diffusion or no diffusion at all had occurred, suggest that between the nerve bodies and the trunks, lithium ions are not uniformly distributed.     

γ-Aminobutyric acid in brain areas of isolated aggressive or non-aggressive inbred strains of mice

In order to investigate the effects of social isolation on aggressive behavior and GABA levels in different brain areas, inbred mice of the C57 B1/6 and the DBA/2 strains were housed inidividually over a period of 8 weeks. Social isolation induced a clear increase of aggressive responses only in the DBA/2 strain and a decrease of GABA levels in septum, striatum, olfactory bulb and posterior colliculus in both the C57B1/6 and in the DBA/2 strains. An increase of neurotransmitter concentration was observed in amygdala of DBA mice. DBA mice when compared when compared to C57 mice showed significantly lower levels of GABA in olfactory bulb and striatum. These results are discussed in light of several previous studies which have pointed out a correlation between a deficiency of GABA mediated inhibition in some brain areas and different kinds of aggressive behavior as well as the possibility of blockade of aggressive behavior by potentiation of GABAergic mediated inhibition. A possible suggestion emerging from our results is that the aggressive responses exhibited by isolated DBA mice but not by isolated C57 mice may be related to lower levels of the inhibitory neurotransmitter in the olfactory bulb and striatum.     

远志提取物对小鼠脑内多巴胺含量的影响

目的:探讨远志提取物对小鼠脑内多巴胺含量的影响.方法:40只小鼠,随机分为空白对照组,阳性对照组,低剂量组,高剂量组,采用远志提取物进行灌胃,采用荧光分析法测定小鼠脑内多巴胺的含量.结果:远志提取物能够降低小鼠脑内多巴胺的含量,给药组与空白对照组相比有显著差异(P＜0.05),与阳性对照组相比无明显差异(P＞0.05)...     

The action of structural analogues of γ-aminobutyric acid on binding sites in mouse brain

Nineteen structural analogues of γ-aminobutyric acid (GABA) and the anxiolytics buspirone and diazepam were tested for their ability to modify GABA function in vitro. Each compound was added to the GABA receptor binding assay, the flunitrazepam receptor binding assay, the sodium-dependent GABA binding assay, and the assay for GABA aminotransferase. It was anticipated that some of these analogues would substantially affect several of these assays. The most interesting compound to emerge was phenylthiohydantoic acid. This not only inhibited GABA receptor binding (K_i = 121 μM) but also stimulated flunitrazepam binding and inhibited the activity of GABA aminotransferase. In light of the evidence that a reduced GABA function can be a factor in anxiety, phenylthiohydantoic acid has the potential to be a GABA-mimetic and thus be useful in the treatment of anxiety.     

Allylglycine, and inhibitor of the uptake of L-leucine and L-proline in rat brain slices

The convulsant allylglycine inhibited the uptake of l-leucine and l-proline in rat brain slices and was without influence on the uptake of acetylcholine, dopamine, l-glutamic acid, glycine and l-lysine under the conditions studied. l-Leucine uptake could also be inhibited by the “large neutral” amino acids l-methionine, l-phenylalanine and l-valine. No kinetic studies of l-leucine uptake were possible due to the inability to measure initial rates of uptake. The time course of l-leucine uptake was not linear under a variety of conditions and appeared to be complicated by a rapid efflux of radioactive label in the form of acidic metabolite(s). l-Proline uptake was mediated by a “high affinity” saturable system (K_m 50 μM), and was non-competitively inhibited by allylglycine (K_i{ca.} 50 μM). l-Leucine competitively inhibited (K_i, 75 μM) l-proline uptake, although l-leucine uptake was unaffected by l-proline. l-Norleucine, DL-pipecolic acid and l-azetidine-2-carboxylic acid inhibited l-proline uptake.     

Atorvastatin affects the tissue concentration of hydrogen sulfide in mouse kidneys and other organs

Hydrogen sulfide (H2S) is a crucial co-modulator of cardiovascular, nervous, digestive and excretory systems function. The pleiotropic action of atorvastatin exceeds simple 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibition and involves multiple biological mechanisms. This study assesses the influence of atorvastatin on the H2S tissue concentration in mouse brain, liver, heart and kidney. Twenty-four female CBA strain mice received an intraperitoneal injection. The mice were given one of the following solutions: 0.1 mg atorvastatin (5 mg/kg of body weight (b.w.)/day--group D1, n=8), 0.4 mg atorvastatin (20 mg/kg b.w./day--group D2, n=8) or a saline physiological control (0.2 ml--group C, n=8). A modified Siegel spectrophotometric method was used for the H2S tissue concentration measurements. There was a remarkable rise in the H2S concentration [μg/g] in the kidney (C: 5.26±0.09, D1: 5.77±0.11, p=0.0003; D2: 7.48±0.09, p<0.0001). There were also slight H2S tissue level changes in the brain (C: 1.61±0.01, D1: 1.75±0.03, p=0.0001; D2: 1.78±0.03, p<0.0001), the heart (C: 4.54±0.08, D1: 4.86±0.10, p=0.0027; D2: 4.56±0.07, p=0.6997) and the liver (C: 3.45±0.03, D1: 3.27±0.02, p=0.0001; D2: 3.31±0.02, p=0.0003). Our study supports the influence of atorvastatin on H2S tissue concentration in kidneys and other mouse organs.     

Chronic benzodiazepine treatment increases [3H]muscimol binding in mouse brain

High affinity [3H]muscimol receptors were analyzed in the forebrain and cerebellum of mice that had been treated on a chronic regimen with chlordiazepoxide and clonazepam. In the forebrain, only clonazepam induced an increase in the number of muscimol binding sites 2 hr after drug treatment. In the cerebellum, both the chlordiazepoxide and clonazepam-treated animals showed an increased number of muscimol binding sites 2 hr after drug treatment. At 26 hr after drug treatment, only the clonazepam-treated animals still revealed an increased number of cerebellar muscimol binding sites. Chronic benzodiazepine administration, therefore, induced an increase in the apparent number of high affinity muscimol binding sites in both the forebrain and cerebellum.     

Pharmacological doses of gamma-hydroxybutyrate (GHB) potentiate histone acetylation in the rat brain by histone deacetylase inhibition

Several small chain fatty acids, including butyrate, valproate, phenylbutyrate and its derivatives, inhibit several HDAC activities in the brain at a several hundred micromolar concentration. Gamma-hydroxy-butyrate (GHB), a natural compound found in the brain originating from the metabolism of GABA, is structurally related to these fatty acids. The average physiological tissue concentration of GHB in the brain is below 50 μM, but when GHB is administered or absorbed for therapeutic or recreative purposes, its concentration reaches several hundred micromolars. In the present scenario, we demonstrate that pharmacological concentrations of GHB significantly induce brain histone H3 acetylation with a heterogeneous distribution in the brain and reduce in vitro HDAC activity. The degree of HDAC inhibition was also different according to the region of the brain considered. Taking into account the multiple physiological and functional roles attributed to the modification of histone acetylation and its consequences at the level of gene expression, we propose that part of the therapeutic or toxic effects of high concentrations of GHB in the brain after therapeutic administration of the drug could be partly due to GHB-induced epigenetic factors. In addition, we hypothesize that GHB, being naturally synthesized in the cytosolic compartment of certain neurons, could penetrate into the nuclei and may reach sufficient levels that could significantly modulate histone acetylation and may participate in the epigenetic modification of gene expression.