Dopamine receptor antagonist blocks the release of glycine, GABA, and taurine produced by amphetamine

The effects of systemic injections of amphetamine sulfate on the extracellular levels of glycine, GABA, and taurine in the neostriatum of awake rats were studied using a push-pull perfusion system. Amphetamine produced a dose-related increase in glycine levels. Amphetamine also produced an enhancement on GABA and taurine levels, although these increases did not follow a dose-related curve. The percentage increase of amino acids produced by the highest dose of amphetamine (5 mg/kg) at the peak effect was: GLY 235.9%; GABA 218%, and TAU 177%. All these effects were blocked by the D1–D2 dopamine receptor antagonist, haloperidol. It is suggested that dopamine, released by amphetamine, induces the release of inhibitory amino acid neurotransmitters in the neostriatum. These results are consistent with the hypothesis of dopamine playing a role of an amplifier of the activity of different neurochemical circuits. The results are also in accord with the idea that dopamine could mediate the neurotoxic effects produced by amphetamines through an interplay between excitatory and inhibitory amino acids.     

Specificity of Vigabatrin for the GABAergic System in Human Epilepsy

Summary: The therapeutic action of vigabatrin (gamma vinyl GABA, GVG) has been reported to be mediated by GABAergic neurotransmission. In the present study, we evaluated different neurotransmitter systems in the cerebrospinal fluid (CSF) of patients with complex partial epilepsy, before and during GVG treatment. The markers of the GABAergic system (free GABA, total GABA, homocarnosine) showed a two- to threefold elevation. There was also an increase in glycine during the 6 months of GVG treatment. In contrast, we did not find any constant CSF changes in either excitatory amino acids or in markers of the cholinergic (acetylcholinesterase), dopaminergic (homovanillic acid), serotonergic (5-hydroxyin-doleacetic acid), or peptidergic (somatostatin, prolactin, β-endorphin) systems. This finding (except an elevation in glycine) was in agreement with previous studies which suggest a specific action of GVG on the GABAergic system. The role of glycine in antiepileptic efficacy of GVG needs further evaluation.     

Effect of antipsychotic drugs on the firing of dorsal raphe cells. II. Reversal by picrotoxin.

As reported in the preceding study, the ability of certain antipsychotic and adrenolytic agents to inhibit the spontaneous firing of serotonergic 5HT neurons in the dorsal raphe nucleus appeared to be related to adrenergic blocking efficacy. However, the interaction between adrenergic and serotonergic systems was apparently indirect. In this phase of the study we investigated the hypothesis that another transmitter system could mediate this interaction. We examined the effects of two inhibitory amino acid transmitters (GABA and glycine) for possible effects on dorsal raphe cell firing using single cell recording and microiontophoretic techniques. In addition, the ability of the GABA antagonist, picrotoxin and the glycine antagonist, strychnine to reverse the effects of the antipsychotic and alpha-blocking drugs on dorsal raphe firing was tested. Both GABA and glycine were found to inhibit raphe cell firing selectively, allowing for a possible neurotransmitter function for these amino acids within the dorsal raphe nucleus. However, picrotoxin but not strychnine was found to reverse the effects of the antipsychotic and alpha-blocking drugs on raphe firing. Based on these results, we propose that the adrenergic input may influence 5HT neurons indirectly via a GABAergic interneuron or interposed GABA neuron.     

Differential intracellular regulation of cortical GABAA and spinal glycine receptors in cultured neurons

Using patch-clamp techniques we studied several aspects of intracellular GABA_A and glycine Cl⁻ current regulation in cortical and spinal cord neurons, respectively. Activation of PKA with a permeable analog of cyclic AMP (cAMP) produced a potentiation of the Cl⁻ current activated with glycine, but not of the current induced with GABA. The inactive analog was without effect. Activation of PKC with 1 μM PMA reduced the amplitude of the GABA_A and glycine currents. Internal application of 1 mM cGMP, on the other hand, had no effect on the amplitude of either current. The amplitude of these inhibitory currents changed slightly during 20 min of patch-clamp recording. Internal perfusion of the neurons with 1 μM okadaic acid, a phospatase inhibitor, induced potentiation in both currents. The amplitude of GABA_A and glycine currents recorded with 1 mM internal CaCl₂ and 10 mM EGTA (10 nM free Ca²⁺) decayed by less than 30% of control. Increasing the CaCl₂ concentration to 10 mM (34 μM free Ca²⁺) induced a transient potentiation of the GABA_A current. A strong depression of current amplitude was found with longer times of dialysis. The glycine current, on the contrary, was unchanged by increasing the intracellular Ca²⁺ concentration. Activation of G proteins with internal FAl⁻₄ induced an inhibition of the GABA_A current, but potentiated the amplitude of the strychnine-sensitive Cl⁻ current. These results indicate that GABA_A and glycine receptors are differentially regulated by activation of protein kinases, G proteins and Ca²⁺. This conclusion supports the existence of selectivity in the intracellular regulation of these two receptor types.     

肺结核患者血清甘胆酸放免检测的临床意义

对１００例肺结核患者采用放射免疫分析（ＲＩＡ）和全自动生化分析仪分别检测了血清甘胆酸（ＣＧ），丙氨酸转氨酶（ＡＬＴ），天门冬氨酸转氨酶（ＡＳＴ）和γ－谷氨酰转肽酶（γ－ＧＴ）在服药前后的含量变化。结果表明，服药后ＣＧ，ＡＬＴ，ＡＳＴ和γ－ＧＴ均较正常对照组或服药前显著升同。其中ＣＧ的升同尤为显著，经比较分析，认为血清ＣＧ是早期肝功能损害的灵敏指标。     

Both agonists and antagonists of the strychnine-insensitive glycine site of N-methyl-D-aspartate receptors modulate polysynaptic excitations in slices of mouse olfactory cortex

Summary In this study, it is reported that bath application of D-serine and, to a lesser extent glycine, potentiated polysynaptic but not monosynaptic excitations evoked in slices of mouse olfactory cortex perfused with solution containing Mg²⁺ (1 mmol/l), picrotoxin and strychnine (both 25 μmol/l). Effects were largely confined to the longer latency components of the field potentials and occurred at amino acid concentrations of between 0.01 and 1 mmol/l. The effects of D-serine and glycine were antagonized by 7-chlorokynurenate and indole-2-carboxylate, antagonists of the glycine regulatory site of the N-methyl-D-aspartate (NMDA) receptor complex. D-Serine (glycine not tested) also potentiated, and 7-chlorokynurenate partially inhibited the longer latency components of the polysynaptic field potentials evoked in slices perfused in the absence of picrotoxin and strychnine. However, neither D-serine nor glycine potentiated responses evoked by the bath application of NMDA. It is concluded that under the present experimental conditions, the glycine regulatory sites of those NMDA receptor involved in the mediation of polysynaptic excitations in the mouse olfactory cortex are not saturated with endogenous glycine.     

黄豆叶蛋白营养价值的实验评价

目的：对黄豆叶蛋白质营养价值予以实验评价。方法：从黄豆的鲜叶中提取黄豆叶蛋白，测定粗蛋白、必需和半必需氨基酸，采用Ｗｉｓｔａｒ大鼠，喂饲黄豆叶蛋白配合饲料，以酪蛋白作为参考蛋白，以分离大豆蛋白作为对比物，参照ＡＯＡＣ方法，分析比较真消化率、生物价、蛋白质净利用率等指标。结果：黄豆叶粗蛋白含量为６１％，氨基酸评分（ＡＡＳ）为９８。黄豆叶蛋白的营养评价指标与分离大豆蛋白无差异，提示两者营养价值相似。结论：利用黄豆叶资源提取黄豆叶蛋白，是蛋白质食物来源的重要途径之一。     

Accessibility to residues in transmembrane segment four of the glycine receptor

Glycine receptors (GlyRs) are members of the ligand-gated ion channel superfamily. Each subunit has four transmembrane segments (TM1-TM4). Several studies suggest that amino acids in all four TMs face into a water-filled, alcohol and anesthetic binding cavity in the extracellular portion of the transmembrane domain. TM4 should contribute a "wall" to this cavity, but the residues involved are unknown. Here, we determined the ability of an alcohol analog, propyl methanethiosulfonate (propyl MTS), to covalently react with twelve GlyR TM4 positions (I401-I412) after mutating the original amino acids to cysteines. Reactivity of a cysteine with propyl MTS implies that the cysteine is exposed to water. W407C, I409C, Y410C, and K411C showed altered receptor function following reaction with propyl MTS in the presence or absence of glycine. The cysteine mutations alone eliminated the effects of ethanol for I409C, Y410C, and K411C, and reduced the effects of octanol for I409C and isoflurane for K411C. The ability of propyl MTS to reduce isoflurane and chloroform potentiation was examined in the reactive mutants. Potentiation by isoflurane was significantly reduced for I409C after reaction. These data demonstrate water-accessibility of specific TM4 positions in the GlyR and suggest involvement of these residues with alcohol and anesthetic action.     

Potentiation of inhibitory amino acid receptors-mediated responses by lanthanum in rat sacral dorsal commissural neurons

Lanthanum is one of rare earth cations with extremely active chemical property and has been reported to influence neuronal transmitter systems. To date, little attention has been directed towards the sacral dorsal commissural nucleus (SDCN), which serves as a relay of sensory information from the pelvic viscera in the spinal cord. Therefore, the effect of lanthanum on the inhibitory neurotransmitter γ-aminobutyric acid (GABA) and glycine (Gly) responses in neurons acutely dissociated from the rat SDCN was investigated using the nystatin-perforated patch-recording configuration under voltage-clamp conditions. At a holding potential of − 40 mV, La³⁺ reversibly potentiated GABA (3 μM)-activated currents (I_GABA) in a concentration-dependent manner over the concentration range of 10 μM to 30 mM, with the EC₅₀ value of 67.3 ± 16.4 μM. Similarly, La³⁺ reversibly potentiated glycine (10 μM)-activated currents (I_Gly) in a concentration-dependent manner over the concentration range of 1 μM to 1 mM, with the EC₅₀ value of 52.3 ± 10.9 μM. The effects of La³⁺ on I_GABA and I_Gly were voltage-independent. Moreover, both of the potentiations were not use-dependent and were overcome by increasing the concentration of agonist. Our results indicate that La³⁺ potentiates the inhibitory amino acid receptors-mediated responses in SDCN, which may reduce the transmission of the pelvic visceral information. The information provided by this work may help to elucidate the mechanisms and effects of lanthanum on brain functions.     

联合应用甘氨酸和甲强龙对失血性休克大鼠肝脏枯否细胞的影响

目的探讨失血性休克大鼠肝脏枯否细胞的功能变化以及联合应用甘氨酸和甲强龙对枯否细胞的影响。方法50只大鼠随机分成假休克组（仅进行手术操作但不放血诱导休克）、休克组、甘氨酸组、甲强龙组和联合治疗组（甘氨酸＋甲强龙）,每组10只。大鼠经动脉放血,造成失血性休克,随后用自体血和生理盐水回输进行复苏。复苏后2h,行肝脏枯否细胞的分离和培养,细胞培养24h后分别用1、10、100和1000ng/ml的脂多糖（LPS）刺激,测定细胞内Ca^2＋和肿瘤坏死因子α（TNF-α）水平。结果枯否细胞内Ca^2＋在20min左右开始大幅度增高,大约27min达到高峰,同时细胞内Ca^2＋浓度增加呈现LPS剂量依赖性。联合治疗组细胞内Ca^2＋浓度和TNF-a含量明显低于休克组以及低于甘氨酸、甲强龙治疗组,差异具有统计学意义（P〈0．005）。结论联合应用甘氨酸和甲强龙比单一制剂更有效抑制失血性休克后枯否细胞内Ca^2＋升高、抑制枯否细胞的激活,抑制TNF-α的过度产生和机体炎症反应。