硫酸镁用于椎管内麻醉镇痛的研究进展

硫酸镁作为天然的非竞争性N-甲基-D-天冬氨酸(NMDA)受体拮抗剂以及钙通道阻滞剂,在围手术期麻醉镇痛方面起着重要作用。本文就硫酸镁用于椎管内麻醉镇痛的研究进展作简要综述。     

突触前受体的药理学研究进展

综述了突触前受体存在的证据、分类、调节和临床意义。突触前受体按不同的分类方法可分为突触前自调受体和旁调受体;抑制性和易化性突触前受体;G-蛋白偶联型和离子通道型突触前受体。突触前受体调节递质释放的机制,可能与钙通道、钾通道及囊泡释放复合物的调节有关。通过研制合适的突触前受体的激动剂或拮抗剂,适度调节神经末梢递质的释放,可达到控制或治疗多种疾病(如高血压、精神疾患、阿尔茨海默病、心肌缺血等)的目的。     

速效抗抑郁药的作用靶点研究进展

抑郁症是一种慢性复发性精神疾病,传统抗抑郁药通常需要连续几周的治疗才能发挥显著的治疗效果。N-甲基-D-天冬氨酸受体拮抗剂氯胺酮的上市为速效抗抑郁药物的研发打开了一个全新的视角,胆碱能受体阻滞剂东莨菪碱、5-HT2A受体激动剂赛洛西宾也表现出快速抗抑郁的作用潜力。归纳了谷氨酸能速效抗抑郁药、胆碱能受体拮抗剂、5-HT2A受体激动剂（致幻剂）速效抗抑郁药的药理学靶点研究,分析了新靶点的可能策略,以期对未来抗抑郁药物研究方向有所启示。     

兴奋性氨基酸受体的非竞争性拮抗剂

根据对激动剂的反应不同,把兴奋性神经递质的谷氨酸受体分为NMDA型、QA型及KA型三种。除这些离子通道调节型受体外,还有近年发现的通过G蛋白作用的代谢调节型谷氨酸受体。以往对离子通道受体拮抗药了解较多,而对其中非竞性拮抗剂的亚单位构造和机能的研究更为重要,且与作用于脑神经的药物相关连。本文就以上拮抗剂     

左旋千金藤立定拮抗D_2受体激动剂对大鼠突触体酪氨酸羟化酶活性的负反馈调节(英文)

目的:研究左旋千金藤立定(SPD)对大鼠纹状体突触体酪氨酸羟化酶(TH)活性的影响.方法:利用高效液相-电化学法(HPLC-ECD)检测ι-DOPA的含量变化.结果:选择性D_2受体激动剂N-0437和喹吡罗均能抑制大鼠纹状体TH的活性,D_1受体激动剂SKF 38393和SPD都不能抑制TH的活性;D_2受体阻滞剂螺哌隆和SPD均能拮抗D_2受体激动剂对TH的抑制作用.结论:D_2受体介导突触前DA受体的负反馈调控,SPD对D_2受体无激动作用,而是D_2受体的阻滞剂.     

芋螺镇痛多肽研究进展

芋螺多肽由芋螺毒液管和毒囊内壁的毒腺所分泌,大多数芋螺多肽由10～40个氨基酸残基组成,且富含二硫键,能特异性作用于乙酰胆碱受体 (nAChR),及钙、钠、钾等多种离子通道亚型。目前已发现作用于N-型钙通道、nAChR的α9α10亚基、TTX-R钠通道、NMDA受体的芋螺多肽具有很强的镇痛活性,其中N-型钙通道抑制剂ω-MVIIA已于2004年上市。该类镇痛多肽具有相对分子质量小、结构稳定、活性及选择性高等特点。芋螺镇痛多肽不仅会成为镇痛机制等相关神经生物学研究的重要工具,也会为开发新一代无致瘾镇痛药起到重要作用。本文对芋螺镇痛多肽研究的最新进展予以评述,着重介绍芋螺镇痛多肽的作用靶位、构效关系及其应用进展。     

以α7 nAChR为靶点的药物研究进展

α7 nAChR属于烟碱型乙酰胆碱受体,是由5个α7单体组成的配体门控离子通道。α7 nAChR的配体结合位点主要有两种,即激动剂(拮抗剂)结合位点以及变构调节位点。α7 nAChR是精神分裂症认知障碍以及阿尔茨海默病药物研究的一个重要靶点,现已有多个治疗药物处在临床试验阶段。本文主要综述了α7 nAChR激动剂以及变构调节剂药物的研究进展。     

NMDA受体的作用位点研究

N-甲基-D-天冬氨酸(NMDA)受体是离子型谷氨酸受体家族中的重要一员,是神经系统发育以及神经毒性的核心。NMDA受体通道大分子上存在着许多独立的结合位点。(1)谷氨酸(Glu)作用位点:Glu作为NMDA受体经典的激动剂,高浓度Glu的作用于NMDA受体识别部位,使细胞膜去极化,离子通道开放;低浓度的Glu则不能使NMDA门控的离子通道打开,需要甘氨酸(Gly)的参与。(2) Gly作用位点:Gly受体和NMDR有相同的分布,并对NMDA受体激活有增强作用。Gly能增加Glu与NMDA识别位点的亲和力,使通道开放频率增加4～6倍。研究表明NMDA受体被Glu激活前,需要Gly的结合,Gly起着NMDA受体协同激动剂的作用。(3)Mg2+作用位点:Mg2+是兴奋性氨基酸受体NMDA非竞争性阻断剂和Ca2+拮抗剂。NMDA受体通道的开放受配体和膜电位的双重控制。在静息态的膜蛋白条件下,Mg2+等镶嵌在通道深部,阻挡胞内外离子交换,这时即使Glu和Gly结合到NMDA受体,Mg2+也会阻断离子的流出。细胞去极化时Mg2+被电场力移开,离子得以流动,Mg2+的抑制作用逐渐减小并消失,故Mg2+是调节NMDA受体的重要位点。(4) Zn2+作用位点:Zn2+可以非竞争性地拮抗NMDA受体的反应。升高Gly的浓度不能翻转Zn2+的抑制作用,表明Zn2+有单独的结合位点。Zn2+对NMDA受体的抑制作用需要两个结合位点参与,其一是高亲和力、非电压依赖性结合位点,其二是低亲和力呈电压依赖性的结合位点。(5)多胺作用位点:多胺对NMDA的电流有多重影响。多胺的增强效应可分为:非Gly依赖性刺激作用(饱和Glu和Gly会引起全细胞电流增加);Gly依赖性刺激作用(在Gly浓度亚饱和的情况下,精胺能增加NMDA受体与Gly的亲和力,对NMDA电流有刺激效应)。多胺的抑制效应也可分为电压依赖性通道抑制作用,以及Glu受体亲和力降低作用。其中,Gly是Glu为开放受体通道所必需的,多胺对通道开放起正性调节作用,而Zn2+和Mg2+则起负性调节作用。此外,这些位点之间还存在着复杂的交互作用,NMDA受体通道是由复杂多样的因子所调节的。NMDA受体是学习记忆相关神经网络中一个相对中心的关键位点,中枢系统中广泛参与学习记忆、突触可塑性、缺血性脑损伤及神经退行性疾病等多种生理病理过程。本文以NMDA受体的作用位点为切入点,阐明NMDA受体的调节作用,以期为神经系统相关疾病的研究提供理论指导。     

以NMDAR为靶点的药物研究进展

N-甲基-D-天冬氨酸受体(NMDAR)属于离子型谷氨酸能受体,是由NR1、NR2和NR3三种亚基构成。近年来NMDAR已经逐渐成为中枢系统疾病(如抑郁症、神经痛、精神分裂症和阿尔兹海默症等)治疗的重要靶点,目前已有多个治疗药物处于临床试验阶段。本文主要综述NMDAR拮抗剂、激动剂及其调节剂的药物研究进展。     

大鼠颈上神经节突触前释放腺苷三磷酸的多种受体调制

目的:研究大鼠颈上神经节ATP的释放及其突触前调制。方法:荧光素-荧光素酶测定技术。结果:电刺激大鼠颈上神经节引起ATP释放。腺苷,P_1(A_1)嘌呤受体激动剂环戊腺苷,M胆碱能受体激动剂氧化震颤素,5-羟色胺减少神经节ATP的释放。P_1(A_1)嘌呤受体拮抗剂8-环戊基-1,3-二丙基黄嘌呤,P_2嘌呤受体拮抗剂吡多醛-5-磷酸-6-偶氮苯基-2’,4’-二磺酸,M胆碱能受体拮抗剂阿托品,α_2肾上腺素受体拮抗剂育亨宾,D_2多巴胺受体拮抗剂舒必利和组胺增加颈上神经节ATP的释放。结论:大鼠颈上神经节释放ATP。P_1(A_1)嘌呤受体,P_2嘌呤受体,M胆碱能受体,α_2肾上腺素受体,D_2多巴胺受体,5-羟色胺受体及H_1组胺受体激动剂或拮抗剂可通过突触前机制调节ATP释放。     

Recent pharmacologic approaches to pain

The identification of compounds that can effectively and safely treat chronic pain is a major challenge of biomedical research. One approach is to optimize currently active analgesic treatments, notably by reducing their side effects. An example of this approach is the recent development of a novel class of nonsteroidal antiinflammatory drugs (NSAIDs), the cyclo-oxygenase 2 inhibitors, that lack the limiting gastrointestinal side effects of the traditional NSAIDs. Another approach, based on the recent development of molecular biology, is to develop analgesic compounds acting on new targets. These include notably ion channel blockers (TTX-resistant sodium channel blockers specific for nociceptors, N-type calcium channel blockers), nicotine receptor agonists, peptide receptor antagonists, N-methyl-D-aspartate (NMDA) receptor antagonists, vanilloids, new opioid compounds, cannabinoids, selective alpha2-adrergic agonists, purinergic modulators. Most of these compounds are currently in preclinical or early clinical investigation. However, the development of more predictable in vitro and in vivo tests and the broadening use of clinical models of experimental pain, will hopefully help increase the proportion of drugs that will become successful analgesics in clinical practice.     

The NMDA receptor complex: a long and winding road to therapeutics

Advances in our basic understanding of inhibitory and excitatory amino acid neurotransmission have provided the foundation for directed drug discovery programs to modulate inhibitory GABAergic and excitatory N-methyl-D-aspartate (NMDA) receptor-mediated synapses. Gamma-Amino butyric acid (GABA(A)) and NMDA receptors are complex ion channels formed by multiple protein subunits that act as binding sites for transmitter amino acids and as allosteric regulatory binding sites to regulate ion channel activity. In the case of the NMDA receptor complex, one such allosteric site binds the obligatory glycine and/or d-serine co-agonist. Historical data from preclinical and clinical studies of GABAergic agents have clearly demonstrated that direct receptor modulators lack sufficient therapeutic indices to warrant clinical utility. However, pharmacological modulation of allosteric sites of the GABA multimeric receptor has resulted in the clinical development of safe and efficacious agents, exemplified by the benzodiazepines. Research has also revealed a similar outcome for the NMDA receptor, with allosteric modulators demonstrating improved safety profiles in the modulation of excitatory amino acid (EAA) transmission compared with direct NMDA receptor antagonists. First-generation EAA drugs were low affinity channel blockers of the NMDA multimeric receptor complex and included the anesthetic agent ketamine and the Alzheimer's drug memantine. As predicted by preclinical studies, direct NMDA receptor antagonists (eg, selfotel (Novartis AG) and high-affinity channel blockers (eg, dizocilpine) failed in the clinic as a result of narrow therapeutic indices. More recent efforts have focused on glycine/d-serine co-agonist function. These approaches include partial glycine agonists, in their agonist dose-range, for cognitive improvement and for treating schizophrenia. Such partial glycine agonists are also being advanced for the treatment of neuropathic pain in the antagonist dose range. An alternate approach to partial glycine agonists is to inhibit the uptake carrier(s) for glycine (ie, GlyT-1 and GlyT-2), thereby potentiating the lifetime of synaptic glycine. A number of glycine uptake inhibitors have been reported and their preclinical profiles support investigation into their utility in treating schizophrenia.     

Dizocilpine-like discriminative stimulus effects of competitive NMDA receptor antagonists in mice

 Several non-competitive NMDA receptor ion channel blockers, competitive NMDA antagonists and compounds acting at other sites on the NMDA receptor complex were examined for their ability to substitute for the discriminative stimulus effects of dizocilpine. Swiss-Webster mice were trained with food to discriminate the non-competitive NMDA receptor antagonist, dizocilpine (0.17 mg/kg), from saline in a T-maze. Mice rapidly acquired the discrimination with minimal amounts of drugs required for training and testing. Several non-competitive antagonists dose-dependently substituted for dizocilpine with a rank order of potency of dizocilpine>TCP>(–)-MK-801>SKF 10,047>dextrorphan>PCP. There was a positive correlation between the potencies of the compounds that substituted for dizocilpine and their previously reported affinities for the [³H]dizocilpine binding site of the NMDA receptor ion channel. Compounds acting at other sites on the NMDA receptor complex, including NMDA, the partial agonist at the strychnine-insensitive glycine site, ACPC, and the polyamine antagonist, ifenprodil, failed to substitute fully. In addition, the AMPA antagonist, NBQX, the monoamine uptake inhibitor, cocaine, and the GABA_A receptor agonists, diazepam and phenobarbital, failed to substitute fully for dizocilpine. However, like the ion channel blockers, the competitive NMDA antagonists, CGS 19755, NPC 17742, (±)CPP and LY 233536 dose-dependently substituted for dizocilpine. The competitive antagonist, LY 274614, and its active enantiomer, LY 235959, failed to substitute for dizocilpine, each producing severe disruptions in locomotor activity. That most of the competitive antagonists substituted for dizocilpine is in accordance with other behavioral data (e.g., ataxia, locomotor activity) documenting similarities in the effects of non-competitive and competitive antagonists. These findings are also consistent with results of clinical investigations suggesting overlap in the behavioral and subjective profiles of competitive and non-competitive NMDA blockers. Received: 29 October 1996 / Final version: 9 April 1997     

Spermine and related polyamines produce a voltage-dependent reduction of N-methyl-D-aspartate receptor single-channel conductance.

Several polyamines have been shown to interact with a site on the N-methyl-D-aspartate (NMDA) receptor that regulates the binding of open channel blockers. Spermine (SP) and spermidine (SD), polyamine agonists, enhanced binding of open channel blockers, whereas arcaine (ARC), diethylenetriamine (DET), and putrescine (PUT), polyamine antagonists, reduced the polyamine enhancement of open channel blocker binding. We previously showed that SP had multiple actions on NMDA receptor single-channel currents that underlie its effect on whole-cell NMDA receptor current. At high concentrations, SP produced a voltage-dependent decrease in NMDA receptor single-channel conductance and average open time. In the present study, another polyamine agonist (SD) produced a similar reduction of NMDA receptor single-channel conductance at higher concentrations. The polyamine antagonists (ARC, DET, and PUT), however, produced a voltage-dependent reduction in NMDA receptor whole-cell currents and reductions in single-channel conductance and average open time, even in the absence of polyamine agonists. The rank order of potency for reduction of NMDA receptor single-channel conductance by polyamines was ARC greater than SP greater than SD greater than PUT = DET, a rank order similar to that for the inhibitory actions of polyamines in receptor binding assays and for the effects of the antagonists on NMDA receptor whole-cell currents. The polyamine antagonist DET did not block the reduction of single-channel conductance by the polyamine agonist SP. In fact, the effects of SP and DET on single-channel conductance were additive. DET also showed a variable enhancement of NMDA receptor whole-cell currents in some neurons, suggesting polyamine agonist-like properties. These results are not consistent with the standard pharmacological profile for agonists and antagonists acting at the same site. Potential mechanisms for the effects of the polyamines on single-channel conductance are discussed.     

Current and future prospects for drugs to suppress cough

Cough is an important defensive reflex of the airway and a common symptom of respiratory disease. After an upper respiratory tract virus infection, cough is transient, but is more persistent with conditions such as asthma, rhinosinusitis, gastroesophageal reflux, chronic obstructive pulmonary disease (COPD) and lung cancer. Treatment directed at these conditions may improve cough, but there remains a need to control cough directly. The most effective antitussives are opioids, such as morphine, codeine or pholcodeine, but they produce side effects including drowsiness, nausea, constipation and physical dependence. Opioids such as k- and d-opioid receptor agonists, non-opioids such as nociceptin, neurokinin and bradykinin receptor antagonists, vanilloid receptor VR(1) antagonists, blockers of sodium-dependent channels, and maxi-K calcium-dependent channel activators of afferent nerves may all represent novel antitussives and this needs to be confirmed in clinical trials.     

Influence of external magnesium ions on the NMDA receptor channel block by different types of organic cations

The NMDA type of ionotropic glutamate receptors plays a unique role in synaptic functions because of high permeability for calcium and because of a voltage-dependent block by endogenous Mg(2+). Activity and voltage dependence of the NMDA receptor channel block by organic cations are strongly affected by competition with magnesium ions for the binding site in the channel pore. It complicates prediction of action of NMDA receptor channel blockers in vivo. In the present work we studied the NMDA receptor channel block in the presence of Mg(2+) by several organic blockers with different characteristics of voltage dependence and mechanism of action. The action of NMDA receptor channel antagonists was studied in native NMDA receptors of hippocampus CA1 pyramidal neurons isolated from rat brain slices. It was demonstrated that the IC(50) values of NMDA receptor channel blockers at -30 mV are increased 1.5-5 times compared with magnesium-free conditions. The voltage dependence of the channel block is decreased, abolished or even inversed in the presence of magnesium. Although simple competition between magnesium ion and organic channel blockers provides a general explanation of the observed effects, certain disagreements were revealed. Diversity in Mg(2+) effects on the NMDAR channel block by different organic cations reported herein likely reflects interaction of NMDAR channel blockers with additional binding site(s) and suggests that individual analysis in the presence of Mg(2+) is required for newly developed NMDAR channel blocking drugs.     

Pharmacological regulation of the phencyclidine-binding site associated with the N-methyl-D-Aspartate receptor-operated ion channel

The ion channel operated by N-methyl-D-aspartate (NMDA) receptor agonists is modified by several positive and negative effectors. A variety of chemical structures are known to antagonize the effects of NMDA agonists by preferentially binding with high affinity to the open state of the ion channel. Binding of two of these noncompetitive antagonists has been study extensively in recent months as a probe of NMDA receptor function. It has been found that NMDA agonists and antagonists increase and decrease, respectively, the binding of ³H-TCP or ³H-MK-801 by altering the affinity of the putative phencyclidine (PCP) receptor localized within the ion channel. This affinity change is presumed to be correlated with the conformational change associated with channel opening. This model is also discussed in relationship to one in which binding is increased under nonequilibrium conditions because of a simple increased accessibility to the channel binding site. The modulatory effects of glycine, other amino acids, certain polyamines, and divalent cations on ³H-TCP and/or ³H-MK-801 binding are discussed in relation to their effects on NMDA function in more intact, physiological preparations. It is concluded that the complexity of NMDA receptor regulation provides many possibilities for pharmacological intervention, and that the use of noncompetitive antagonists to probe NMDA receptor function could play a key role in drug development.     

Role of glutamate receptors and voltage-dependent calcium channels in glutamate toxicity in energy-compromised cortical neurons.

We have examined the effect of glutamate receptor antagonists and voltage-dependent calcium channel blockers on the neuronal injury induced by the combination of a low concentration of N-methyl-D-aspartate (NMDA) or kainate and energy compromise resulting from the use of glucose-free incubation buffer. Toxicity induced by NMDA or kainate was enhanced in the glucose-free buffer. NMDA-or non-NMDA-receptor antagonists added to the glucose-free buffer at the same time inhibited the neuronal cell death induced by each agonist. An NMDA-receptor antagonist, MK-801, but not non-NMDA-receptor antagonists, inhibited the toxicity when added to the culture medium after exposure of the cells to the agonists. P/Q-type calcium channel blockers, omega-agatoxin IVA and omega-agatoxin TK, and an N-type calcium channel blocker, omega-conotoxin GVIA, significantly attenuated the neuronal injury, although an L-type calcium channel blocker, nifedipine, showed little neuroprotective effect. A combination of calcium channel blockers of the three subtypes showed the most prominent neuroprotective effect. These observations suggest that the overactivation of NMDA and non-NMDA receptors and consequent activation of the voltage-dependent calcium channels lead to neuronal cell death in energy-compromised cortical neurons.     

Excitatory amino acid antagonists: Behavioral and biochemical approaches for the development of new central nervous system therapeutic agents

A general summary of behavioral and biochemical procedures that have been used for the evaluation of excitatory amino acid (EAA) antagonists, primarily those of the N-methyl-D-aspartate (NMDA) subtype, is presented. The effects of both competitive NMDA receptor antagonists and noncompetitive ion channel blockers are compared. In some tests, a specificity by 2-amino-5-phosphonovaleric acid (AP5), phencyclidine, and MK-801 for antagonism of NMDA receptors vs. other subtypes of EAA receptors has been demonstrated. Antagonists of the quisqualate or kainate subtypes of EAA receptor have been less well characterized.     

Pharmacologic treatment of chronic pediatric hypertension

Improved recognition of the relationship between childhood and adult blood pressures and identification of end-organ damage in children, adolescents, and young adults with hypertension has led to increased focus by pediatricians and general practitioners on the detection, evaluation, and treatment of hypertension. Notably, detection, evaluation, and treatment of pediatric hypertension has increased significantly since the first Task Force Report on High Blood Pressure in Children and Adolescents in 1977 with advances in both nonpharmacologic and pharmacologic treatments.Angiotensin-converting enzyme inhibitors (e.g. captopril, enalapril, lisinopril, ramipril) and calcium channel antagonists (e.g. nifedipine, amlodipine, felodipine, isradipine) are the most commonly prescribed antihypertensive medications in children due to their low adverse-effect profiles. Diuretics (e.g. thiazide diuretics, loop diuretics, and potassium-sparing diuretics) are usually reserved as adjunct therapy. Newer agents, such as angiotensin receptor antagonists (e.g. irbesartan), are currently being studied in children and adolescents. These agents may be an option in children with chronic cough secondary to angiotensin-converting enzyme inhibitors. beta-Adrenoreceptor antagonists (e.g. propranolol, atenolol, metoprolol, and labetalol), alpha-adrenoreceptor antagonists, alpha-adrenoreceptor agonists, direct vasodilators, peripheral adrenoreceptor neuron agonists, and combination products are less commonly used in pediatric patients because of adverse events but may be an option in children unresponsive to calcium channel blockers, angiotensin converting-enzyme inhibitors, or angiotensin receptor blockers.