Neurotransmitter Release Mechanisms in Sympathetic Neurons: Past,Present, and Future Perspectives

In 1969, Paton and Vizi (1) described the inhibitory actions of noradrenaline on acetylcholine release from the innervation of the guinea-pig ileum longitudinal muscle. They concluded that acetylcholine output by the nervous networks of the longitudinal strip is under the normal control of the sympathetic by a species of presynaptic inhibition mediated by receptors. This work was carried out in the Pharmacology Department at Oxford University. Clearly, a period in the Dreaming Spires of Oxford sufficiently inspired Sylvester to take up a life long career in scientific research. He has published more than 300 papers on a wide range of topics but clearly has a strong interest in neurotransmitter release mechanisms and recently, non-synaptic interactions between neurons. It seems fitting therefore to write a brief review on the continuing studies on neurotransmitter release mechanisms in sympathetic neurons in a volume honoring the now distinguished Professor Vizi.     

Osmosensitive Release of Neurotransmitter Amino Acids: Relevance and Mechanisms

Hyposmolarity activates amino acid efflux as part of the corrective volume process in a variety of cells. This review discusses the mechanism of amino acid release in brain cells preparations. Results present evidence of substantial differences between the efflux of taurine and that of GABA and glutamate, which besides a possible role as osmolytes, have a main function as synaptic transmitters. The differences found concern the efflux time course, the sensitivity to Cl^– channel blockers, the modulation by tyrosine kinases, the influence of PKC and the effect of cytoskeleton disruptive agents. While taurine efflux features fit well with the mechanisms so far described in most cell types, the efflux of GABA and glutamate does not. Alternate mechanisms for the release of these two amino acids are discussed, including a PKC-modulated, actin-dependent exocytosis.     

Regulation of Vesicle Traffic and Neurotransmitter Release in Isolated Nerve Terminals

In this overview current insights in the regulation of presynaptic transmitter release, mainly acquired in studies using isolated CNS nerve terminals are highlighted. The following aspects are described. (i) The usefulness of pinched-off nerve terminals, so-called synaptosomes, for biochemical and ultrastructural studies of presynaptic stimulus-secretion coupling. (ii) The regulation of neurotransmitter release by multiple Ca²⁺ channels, with special emphasis on the specificity of different classes of these channels with respect to the release of distinct types of neurotransmitters, that are often co-localized, such as amino acids and neuropeptides. (iii) Possible molecular mechanisms involved in targeting synaptic vesicle (SV) traffic toward the active zone. (iv) The role of presynaptic receptors in regulating transmitter release, with special emphasis on different glutamate subtype receptors. Isolated nerve terminals are of great value as model system in order to obtain a better understanding of the regulation of the release of distinct classes of neurotransmitters in tiny CNS nerve endings.     

突触小泡膜蛋白与神经递质释放的局部调节

突触小泡膜蛋白及其在神经递质释放过程中的作用已取得若干研究进展.突触素I、SY蛋白、SO蛋白、SB蛋白、SG蛋白等都是突触小泡膜的重要蛋白质,这些蛋白质在突触小泡的贴靠、膜融合及胞吐作用中起着局部自主性调节作用.     

Regulation of Neurotransmitter Release by Amyloid Precursor Protein Through Synapsin Phosphorylation

Neurochemical Research - Abnormal processing of amyloid precursor protein (APP) and aggregation of the Aβ peptide are known to play a key role in the pathogenesis of Alzheimer disease, but the...     

On the Feedback Between Theory and Experiment in Elucidating the Molecular Mechanisms Underlying Neurotransmitter Release

This review describes the development of the molecular level Ca²⁺-voltage hypothesis. Theoretical considerations and feedback between theory and experiments played a key role in its development. The theory, backed by experiments, states that at fast synapses, membrane potential by means of presynaptic inhibitory autoreceptors controls initiation and termination of neurotransmitter release. A molecular kinetic scheme which depicts initiation and termination of evoked release is discussed. This scheme is able to account for both spontaneous release and evoked release. The physiological implications of this scheme are enumerated.     

亚磁场对雄性小鼠神经递质、 激素和血常规的影响

本研究主要是探讨连续亚磁场环境暴露对C57BL/6雄性小鼠（Mus musculus domesticus）神经递质、激素含量和血常规参数的影响。实验组为亚磁场暴露组（1.1 ± 0.5）μT,对照组为地磁场组（53.3 ± 0.2）μT。实验对象分别为3周龄幼年小鼠和8周龄成年小鼠。幼年小鼠随机分为实验组与对照组,每组42 只;成年小鼠也随机分为实验组与对照组,每组36只。幼年小鼠在两种磁场环境中的暴露时间为1 ~ 5周,成年小鼠的暴露时间为1、3、6、9、12周。采用液相色谱-质谱联用法（LC-MS）检测小鼠脑组织及血清中的神经递质含量,包括5-羟色胺（5-HT）、多巴胺（DA）、乙酰胆碱（Ach）、去甲肾上腺素（NA）、γ-氨基丁酸（GABA）;用 ELISA 方法检测小鼠血清中的激素含量,包括甲状腺素（T4）、生长激素（GH）、去甲肾上腺素（NA）;血常规在北京大学医学部检测。采用独立样本 t 检验对实验组与对照组的检测结果进行差异分析。与地磁场组相比,亚磁场组幼年小鼠脑组织多巴胺（DA）含量在第5周有显著降低（P < 0.05）,血清中的甲状腺素（T4）含量在第 2和5 周有显著降低（P < 0.05）,去甲肾上腺素（NA）含量在第4周出现显著性降低（P < 0.01）;与地磁场组相比,成年小鼠脑组织5-羟色胺（5-HT）、去甲肾上腺素（NA）含量在处理1周时均出现显著性降低（P < 0.05）,血清中5-羟色胺（5-HT）含量在第3周也出现显著性降低（P < 0.01）,甲状腺素（T4）含量在第 3、6、12 周出现显著性降低（P < 0.05）。血常规结果显示,成年和幼年小鼠的白细胞（WBC）在暴露早期第1周和第2周分别出现显著性增多（P < 0.01）,其他参数基本无变化。本研究发现,两个年龄段的小鼠对亚磁场响应的指标不完全一致,仅甲状腺素（T4）在两个年龄段小鼠的体内都出现显著性降低。通过本研究说明,甲状腺素（T4）、5-羟色胺（5-HT）、去甲肾上腺素（NA）、多巴胺（DA）和白细胞（WBC）可能是不同年龄段小鼠对亚磁场环境暴露较为敏感的生理指标,可在今后的亚磁场生物效应研究中重点关注。     

Actions of Tremorgenic Fungal Toxins on Neurotransmitter Release

The neurochemical effects of the tremorgenic mycotoxins Verruculogen and Penitrem A, which produce a neurotoxic syndrome characterised by sustained tremors, were studied using sheep and rat synaptosomes. The toxins were administered in vivo, either by chronic feeding (sheep) or intraperitoneal injection 45 min prior to killing (rat), and synaptosomes were subsequently prepared from cerebrocortical and spinal cord/medullary regions of rat, and corpus striatum of sheep. Penitrem A (400 mg mycelium/kg) increased the spontaneous release of endogenous glutamate, GABA (gamma-aminobutyric acid), and aspartate by 213%, 455%, and 277%, respectively, from cerebrocortical synaptosomes. Verruculogen (400 mg mycelium/kg) increased the spontaneous release of glutamate and aspartate by 1300% and 1200%, respectively, but not that of GABA from cerebrocortical synaptosomes. The spontaneous release of the transmitter amino acids or other amino acids was not increased by the tremorgens in spinal cord/medullary synaptosomes. Penitrem A pretreatment reduced the veratrine (75 microM) stimulated release of glutamate, aspartate, and GABA from cerebrocortical synaptosomes by 33%, 46%, and 11%, respectively, and the stimulated release of glycine and GABA from spinal cord/medulla synaptosomes by 67% and 32% respectively. Verruculogen pretreatment did not alter the veratrine-induced release of transmitter amino acids from cerebrocortex and spinal cord/medulla synaptosomes. Penitrem A pretreatment increased the spontaneous release of aspartate, glutamate, and GABA by 68%, 62%, and 100%, respectively, from sheep corpus striatum synaptosomes but did not alter the synthesis and release of dopamine in this tissue. Verruculogen was shown to cause a substantial increase (300-400%) in the miniature-end-plate potential (m.e.p.p.) frequency at the locust neuromuscular junction. The response was detectable within 1 min, rose to a maximum within 5-7 min, and declined to the control rate over a similar period. No change in the amplitude of the m.e.p.p.'s was observed. These effects of the tremorgens on transmitter release are interpreted in terms of their mode of action.     

饲料中胆固醇含量对雄性红螯光壳螯虾生长及生殖的影响

为了确定饲料中胆固醇含量对雄性红螯光壳螯虾(Cherax quadricarinatus)生长和生殖的影响,本研究通过对初始体长为10 cm左右的雄虾投喂胆固醇添加量分别为对照组(0%)、实验1组(0.25%)、实验2组(0.50%)、实验3组(0.75%)、实验4组(1.00%)的人工配合饲料10周后,测定各组实验虾...     

神经递质释放过程中的可溶性NSF附着蛋白受体(SNARE)和相关蛋白

近年来,对突触小泡释放神经递质分子机制的研究迅速发展,发现了大量位于神经末梢的蛋白质.它们之间的相互作用与突触小泡释放神经递质相关,特别是位于突触小泡膜上的突触小泡蛋白/突触小泡相关膜蛋白(synaptobrevin/VAMP),位于突触前膜上的syntaxin和突触小体相关蛋白(synaptosome-associated protein of 25 ku),三者聚合形成的可溶性NSF附着蛋白受体(SNARE)核心复合体在突触小泡的胞裂外排、释放递质过程中有重要作用.而一些已知及未知的与SNARE蛋白有相互作用的蛋白质,可通过调节SNARE核心复合体的形成与解离来影响突触小泡的胞裂外排,从而可以调节突触信号传递的效率及强度,在突触可塑性的形成中起重要作用.     

Environmental and Endocrine Influences on Reproduction of Fundulus heteroclitus

Reproduction in Fundulus heteroclitus is adapted to the temperateclimate and the tidal environment of the coastal marshes whichare its primary habitat. Egg deposition and spawning are closelylinked to the tidal cycle. Concentration of spawning on springtides gives the fish access to sites in the high intertidalzone. Eggs are deposited near the high water mark, usually insand in New England populations and in Spartina alternifloraor empty Geukensia demissa shells in Middle Atlantic and southernpopulations. Aerial incubation of eggs appears to be essentialfor their survival in the salt marsh. Loss of eggs due to lackof fertilization, mortality during development and predationwas always less than 30 percent in our observations. Hatchingoccurs only when the eggs are inundated, usually on spring tides.An endogenous semilunar gonadal cycle appears to be involvedin control of spawning, but an effective environmental synchronizerhas not been found. Cyclic changes in estradiol-17ßaccompany the gonadal cycle, while spawning behavior is stimulatedby neurohypophyseal hormones. Both temperature and photoperiodhave been implicated in the control of seasonal reproductionin F. heteroclitus. Early workers focused on males and concludedthat increasing temperature was the stimulus that initiatedgonadal recrudescence in spring. These experiments were notrigorous tests of the effects of photoperiod. We have shownthat in females both warm temperatures and long photoperiodsare involved. In female F. heteroclitus, as in most mammalsand birds, it is the timing rather than the duration of thelight exposure which determines its effectiveness in stimulatinggonadal maturation. Maintenance of gonadal maturity in femaleF. heteroclitus depends on long photoperiods, but the ovarymay become refractory and regress even when stimulatory photoperiodsare sustained in the laboratory. Ovarian maturity can be stimulatedwith gonadotropin injection in refractory animals, indicatingthat the brain-pituitary axis is the site of refractoriness.The pathway by which light influences ovarian maturity may involvean encephalic photoreceptor, since neither the eyes nor thepineal gland is necessary.     

钙调蛋白及其结合蛋白对神经递质释放的调控作用

钙离子（Ca2+）是调节突触前神经递质的胞吐释放的关键离子信号.作为胞内最普遍存在的钙离子感受器的钙调蛋白（CaM）被发现能通过与多种蛋白的相互作用,调控着突触小泡的生发、运输及再填充,从而传递胞内Ca2+浓度变化的信号,对神经递质的释放及突触电生理活动起到至关重要的调控作用.本文综述了CaM及其结合蛋白是如何参与对突触小泡的胞吐释放和胞吞恢复的调控,并探讨了其中可能的分子机制.     

Relationship of Dihydropyridine Binding Sites with Calcium-Dependent Neurotransmitter Release in Synaptosomes

In the present work, we have studied the effect of ruthenium red (RuR), La3+ and 4-aminopyridine (4-AP) on the specific binding of (+)-[3H]PN200-110 to synaptosomes, as well as the effect of nitrendipine, nifedipine, and BAY K 8644 on gamma-[3H]aminobutyric acid [( 3H]GABA) release induced by potassium depolarization and by 4-AP in synaptosomes. Scatchard plots indicated that neither RuR nor 4-AP modifies the KD and Bmax of [3H]PN200-110 specific binding, whereas La3+ decreased the Bmax by about 25%; when the effect of the drugs on the total binding of PN200-110 was studied, a similar inhibition by La3+ was found. The calcium antagonists, nitrendipine and nifedipine, did not affect at all the potassium-stimulated release of [3H]GABA nor its release induced by 4-AP. The calcium agonist BAY K 8644 failed to affect both the spontaneous and the potassium-stimulated GABA release. Our results suggest that the binding sites of dihydropyridines in presynaptic membranes are not related to the calcium channels involved in neurotransmitter release with which RuR, La3+, and 4-AP interact.     

Effect of Taurine on Neurotransmitter Release from Insect Synaptosomes

The effect of taurine on the release of [3H]acetylcholine ([3H]ACH) and [3H]gamma-aminobutyric acid ([3H]GABA) from preloaded locust synaptosomes has been studied. Veratridine (100 microM) and K+ (100 mM) both evoked [3H]ACh release and this was reduced in a concentration-dependent manner by taurine (5, 10, and 20 mM). In contrast to this, veratridine induced no observable release of [3H]GABA, and the response to K+ was slight. In the presence of taurine, however, a concentration-dependent enhancement of [3H]GABA release was observed. Since nipecotic acid (1 mM), an inhibitor of neuronal GABA uptake, also revealed [3H]GABA release induced by veratridine, it is suggested that both this effect and that of taurine are due to prevention of GABA reuptake. These results suggest that taurine may act as a neuromodulator in insects.     

胃溃疡患者血清多肽类激素及胃粘膜中单胺类神经递质的水平及其临床意义

目的:分析胃溃疡患者血清多肽类激素及单胺类神经递质的水平变化及其临床意义。方法:选取2014年8月-2015年8月在我院经胃镜检查确诊为胃溃疡的患者103例作为研究组,另选取54例健康志愿者作为对照组。检测两组血清中胃动素(MTL)、肾上腺髓质素(AM)、胃肠激素胃泌素(Gas)、生长抑素(SS)及降钙素基因相关肽水平(CGRP),以及胃黏膜中血管活性肠肽(VIP)、5-羟色胺(5-HT)、去甲肾上腺素(NE)、P物质(SP)水平。结果:胃溃疡患者血清Gas,AM及MTL明显高于对照组,而SS及CGRP明显低于对照组,差异具有统计学意义(P0.05)。胃溃疡活动期患者血清Gas,AM及MTL明显高于愈合期及瘢痕期患者,而SS及CGRP低于愈合期及瘢痕期患者,差异具有统计学意义(P0.05);胃溃疡愈合期患者血清Gas,AM及MTL高于瘢痕期患者,而SS及CGRP低于瘢痕期患者,差异具有统计学意义(P0.05)。胃溃疡患者胃粘膜内5-HT,SP及NE明显低于对照组,而VIP明显高于对照组,差异具有统计学意义(P0.05)。胃溃疡活动期患者胃粘膜5-HT,SP及NE明显低于愈合期及瘢痕期患者,而VIP明显高于愈合期及瘢痕期患者,差异具有统计学意义(P0.05);胃溃疡愈合期患者胃粘膜5-HT,SP及NE明显低于瘢痕期患者,而VIP明显高于瘢痕期患者,差异具有统计学意义(P0.05)。结论:胃溃疡患者血清多肽类激素及胃黏膜中单胺类神经递质的水平变化与疾病进展密切相关,对胃溃疡的诊断及疗效评价具有指导意义。     

Seasonal Rhythm of Red Pigment Concentrating Hormone in the Crayfish

The content of red pigment concentrating hormone (RPCH) in the eye-stalk of the crayfish Procambarus clarkii varies seasonally, with maximum values during the summer months and the lowest values in winter. The responsiveness of tegumentary chromatophores to synthetic RPCH varies concurrently. (Chronobiology International, 14(6), 639–645, 1997)     

Endocrine Disruption and Developmental Abnormalities of Female Reproduction

The developing organism is particularly sensitive to exposureto estrogenic chemicals during a critical period in the inductionof longterm changes in female reproductive organs, and persistentmolecular alterations induced by the perinatal estrogenic agents.The perinatal mouse model can be utilized as an indicator ofpossible longterm consequences of exposure to exogenous estrogeniccompounds including environmental endocrine disruptors. Attentionshould be paid to abnormalities in female genital organs exposedto estrogenic endocrine disruptors during fetal and early postnataldevelopment in mammals including humans.     

Neuroendocrine Regulation of Growth Hormone Secretion in Teleost Fishes with Emphasis on the Involvement of Gonadal Sex Steroids

In teleost fishes, growth hormone (GH) appears to play an important regulatory role in several, apparently disparate, physiological events, including reproduction, osmotic or ionic regulation, metabolism, growth and development. GH secretion is regulated by hypothalamic neuroendocrine factors that either act directly on the somatotrophic cells in the pituitary gland, or modulate the secretion or activity of other neuroendocrine factors. In addition, the degree of the neuroendocrine influence on GH release is influenced by the nutritional and reproductive state of the fish; moreover, there appear to be marked species differences in some aspects of this neuroendocrine-physiological condition relationship among fish species. Thus, the neuroendocrine control of GH secretion in fishes is complex, and still poorly understood. The neuropeptides, gonadotrophin-releasing hormone, growth hormone-releasing hormone, thyrotrophin-releasing hormone, neuropeptide Y, serotonin and pituitary adenylate cyclase-activating polypeptide have all been demonstrated to stimulate GH in fish, as has the glutamate agonist, N-methyl-d,l-aspartate. Conversely, somatostatin has a potent inhibitory action on GH release in goldfish and carp, but is less effective in salmon and trout species.This review examines the interactive nature of the neuroendocrine control of GH secretion in fishes, and the manner in which gonadal steroids, directly or indirectly, modulate GH secretion and/or the release, or the activity, of the neuroendocrine factors.     

Inhibitory Coupling of Hormone and Neurotransmitter Receptors to Adenylate Cyclase

Abstract

The last few years have provided evidence that beside the familiar and partially well characterized stimulation of the adenylate cyclase the enzyme is also subject to a hormone and neurotransmitter-induced inhibition serving as a general information-transfer system. Similar to hormonal stimulation, the coupling of the inhibitory hormone receptors to adenylate cyclase is mediated by a GTP-dependent process. In some membrane systems, the inhibitory coupling is additionally amplified by sodium ions. Inhibitory hormones stimulate a high affinity GTPase in plasma membranes. The observed correlation suggests that there is a close connection between the hormone-induced adenylate cyclase inhibition and GTPase stimulation. Several lines of evidence are presented suggesting that the guanine nucleotide-dependent component apparently involved in adenylate cyclase inhibition and apparently exhibiting GTPase activity is at least partially different from that involved in adenylate cyclase stimulation by hormones.     

Interactions Among Lithium, Calcium, Diacylglycerides, and Phorbol Esters in the Regulation of Adrenocorticotropin Hormone Release from AtT-20 Cells

Interactions among lithium, calcium, and phorbol esters in the regulation of adrenocorticotropin hormone (ACTH) release were examined in a tumor cell line (AtT-20) of the anterior pituitary. Lithium, which blocks the phosphatase that converts inositol phosphates (IPs) to inositol, increases the levels of IPs in these cells and stimulates ACTH release. This ion potentiates the ability of calcium, an activator of phospholipase C, to raise levels of IPs in these cells and to stimulate ACTH secretion. Pretreatment of AtT-20 cells with calcium specifically abolishes the ACTH release response to lithium or calcium, a result suggesting that these secretagogues may act through a common mechanism to induce hormone secretion. Prior exposure of AtT-20 cells to either lithium or calcium also attenuates the ACTH release induced by phorbol ester, an activator of protein kinase C. To examine the link among lithium, calcium, phosphatidylinositol (PI) turnover, and phorbol ester-evoked ACTH secretion, AtT-20 cells were treated with 1-oleoyl-2-acetoyl-sn-3-glycerol (OAG), an analogue of the diacylgylcerols that are formed by phospholipase C during PI metabolism and that also activate protein kinase C. OAG itself does not alter ACTH release or the levels of IPs in AtT-20 cells. Pretreatment of AtT-20 cells with OAG, however, selectively blocks the ACTH release response to lithium, calcium, or phorbol ester. Furthermore, such pretreatment reduced the ability of lithium to increase levels of IPs. The results suggest that one mechanism of action of lithium is to potentiate selectively an action of calcium, possibly the stimulation of phospholipase C activity.(ABSTRACT TRUNCATED AT 250 WORDS)