Effect of New O-Superfamily Conotoxin on Voltage-Activated Currents of Hippocampal Neurons

The effects of a new O-superfamily conotoxin, SO3, on sodium current (INa), transient A-type potassium currents (IA), and delayed rectified potassium currents (IK), were examined in cultured rat hippocampal neurons using the whole-cell patch clamp technique. Addition of SO3 caused a concentration-dependent, rapidly developing, and reversible inhibition of voltage-activated currents. The IC50 values for the blockage of INa, IA, and IK were calculated as 0.49, 33.9, and 7.6 μmol/L, respectively. The determined Hill coefficients were 1.7, 0.6, and 1.2, respectively. These results indicate that SO3 can selectively inhibit neuronal sodium and potassium currents.     

热应激对果蝇早老素突变体钙电流的影响

为研究与淀粉样前体蛋白(am y lo id precursorprote in,APP)无关的早老素引发阿尔茨海默氏病(A lzhe im er’s d isease,AD)的致病机理,用双电极电压钳方法记录果蝇体壁肌肉细胞的钙通道。结果显示:在几种早老素突变体果蝇中,无论是正常条件下培养还是将幼虫暴露在持续稳定的高温下,电压激活的C a2 电流都没有受到影响。而撤去高温条件后,C a2 尾电流失活速度明显变慢,但其他过程不受影响。说明在正常或应激条件下并不需要早老素来维持C a2 通道的功能,但是在撤去应激条件后的一段时期内,早老素对于C a2 通道的正常功能是必要的。提示早老素对于细胞在波动环境中维持正常功能起重要作用。     

Spontaneous Neurotransmitter Release Depends on Intracellular Rather than ER Calcium Stores in Cultured Xenopus NMJ

Introduction During development, many cell types exhibit sponta-neous neurotransmitter release, with synaptic transmis-sions crucial for normal nervous system activity. Syn-aptic transmissions are initiated when an action poten-tial triggers the neurotran…     

Effect of Calcium on Spontaneous Quantal Transmitter Secretion from ACh-Loaded Myocytes

Introduction Transmitter secretion requires specialized secretory or- ganelles, the synaptic vesicles, for the packaging, stor- age, and exocytotic release of the transmitters[1,2]. The neurotransmitter acetylcholine (ACh) is released at the neuromuscular…     

Melittin Makes “Ion Channel” on the Membrane of Cells

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Effects of Muscle Electrical Activity on the Transmission of Developing Neuromuscular Junction

Miniature endplate potentials (MEPPS) caused by the spontaneous release of ACh from the growth cone of cholinergic neurons, are recorded by the whole-cell patch-clamp technique on a large number of 1-day cultured myoballs which have contact neurites of co-cultured neurons. Both muscle cell and neuron are dissociated from the 1-day-old (about stage 20) Xenopus embryo. Frequency and/or amplitude of MEPPs can obviously increase after the repetitive high-level depolarization caused by the stimuli on muscle cells. No detectable changes of single ACh receptor channel property are observed by using the single-channel recording technique. These results suggest that the mechanism of the increase of MEPPs after electrical activity of postsynaptic muscle cells probably involve some alteration of presynaptic membrane.     

WHOLE-CELL CLAMP STUDY OF XENOPUS EMBRYONIC CHOLINERGIC NEURONS

Whole-cell clamped myoballs are placed into direct visible contact with the growth cones of isolated neurons in embryonic Xenopus culture to serve as probe of acetylchollne (AcCHo) release in order to determine whether these neurons are cholinergic or not. Using a GQ-seal, whole-cell recording method, the electrophysiological properties of these identified cholinergic neurons are studied. It is found that these embryonic neurons, like adult frog motor neurons, exhibit repetitive firings in a certain embryonic developing stage. A development of repetitive firings is observed simultaneously. Tracing the development of one neuron, we find that the development of repetitive firing is completed at the 48th h after fertilization. Tetrodotoxin (TTX) which blocks Na~+ channels can abolish all firings; and tetraethyl ammonium chloride (TEA), the blocker of K~+ channels, reverses this development, i. e. it makes the repetitive firings disappear again. These data show that the nature of the development of repetiti     

The Effects of Glutamate and GABA (Gamma-Amino-Butyric-Acid) on Spontaneous Acetylcholine Release at the Neuromuscular Junction in Xenopus Laevis Embryo Cell Cultures

The miniature endplate currents (MEPC's) were recorded at the neuromuscular junction of Xenopus laevis embryo neuron-muscle co-cultured cells. These MEPC's were due to the spontaneous release of acetylcholine from the nerve terminal. After perfusion with glutamate (10 μmol/L), both frequency and amplitude of the MEPC's increased. After washing away of glutamate, this effect persisted. We named this phenomena "Long-Term Facilitation".GABA (20 μmol/L) on the other hand had an inhibitory effect on both frequency and amplitude of the MEPC's. After washing away of GABA, the MEPC frequency and amplitude increased. We named this effect "Post-Potentiation". Local perfusion experiments furthermore indicated that the effect of glutamate was restricted to the neuromuscular junction, the effect of GABA was restricted to the soma.     

谷氨酸和γ-氨基丁酸对爪蟾胚胎神经肌肉接点乙酰胆碱自发释放的作用

在培养的爪蟾胚胎神经肌肉细胞的接点上,探测到由于神经末梢自发释放乙酰胆碱(Ach)而在肌细胞上造成的微终板电流(MEPC)活动,灌流10μmol/L谷氨酸后,这种活动的频率和幅度都有明显的增加,去除谷氨酸后,这种效应仍能保持相当长时间,我们将这一现象称为长时程易化作用,与谷氨酸相反,20μmol/L的γ-氨基丁酸(GABA)对这一电活动的频率和幅度均有明显的抑制作用,去除GABA后,这一电活动反而比加药前更活跃,呈现出一种后增强作用(post potentiation),局部施加药物证明谷氨酸的作用部位在接头,而GABA的作用部位在神经元胞体。     

Electroporation Transfection as an Effective Tool to Trace Transplanted NSCs in Adult Central Nervous System

Neural stem cells, which are clonogenic cells with self-renewal and multilineage differentiation properties, are currently considered as powerful candidates for cell replacement therapy in neurodegenerative disorders such as Parkinson‘s disease. A key issue is whether stem cells can survive, migrate and differentiate following transplantation into the adult central nervous system. This research shows that enhanced green fluorescent protein (EGFP) plasmid electreporation transfected neural stem cells can functionally differentiate in vitro and that most of the EGFP-positive cells can survive and migrate towards the damaged areas when transplanted into the brain of a Parkinson‘s disease model rat. The results suggest an effective and maneuverable tracing tool to detect whether transplanted neural stem and progenitor cells function in the adult brain in vivo.