共查询到20条相似文献，搜索用时 31 毫秒
1.
A Galindo 《Science (New York, N.Y.)》1972,178(62):753-755
Curare and pancuronium have multiple effects on previously undepressed rat diaphragm; these include depression of transmitter output and prolongation of the refractory period of prejunctional structures. The effect of curare on motor nerve terminals is greater than that of pancuronium. Both drugs depress postjunctional receptors; but curare, in addition, raises the threshold for the generation of muscle action potentials. In addition, these results raise questions about the validity of statistical methods used to calculate transmitter output. 相似文献
2.
Increases in the extracellular concentration of calcium ions above 1.8 millimoles per liter caused a reversible decrease in the sensitivity of tmuscle postiunctional membrane to carbamylcholine. A quantitative study of the inhibitory effect of calcium ions on membrane depolarization produced by carbamylcholine indicates that calcium ions compete with carbamylcholine for some common binding sites on the postjunctional membrane. Calcium ions (20 millimoles per liter) caused a neuromuscular block wherein prolonged end plate potentials were produced after nerve stimulation. Calcium ions applied ionophoretically to the postjunctional membrane decreased the amplitude and prolonged the time course of the transient depolarization produced by ionophoretically applied carbamylcholine. 相似文献
3.
Neuronal generation of the leech swimming movement 总被引：5，自引：0，他引：5
G S Stent W B Kristan W O Friesen C A Ort M Poon R L Calabrese 《Science (New York, N.Y.)》1978,200(4348):1348-1357
The swimming movement of the leech is produced by an ensemble of bilaterally symmetric, rhythmically active pairs of motor neurons present in each segmental ganglion of the ventral nerve cord. These motor neurons innervate the longitudinal muscles in dorsal or ventral sectors of the segmental body wall. Their duty cycles are phase-locked in a manner such that the dorsal and ventral body wall sectors of any given segment undergo an antiphasic contractile rhythm and that the contractile rhythms of different segments form a rostrocaudal phase progression. This activity rhythm is imposed on the motor neurons by a central swim oscillator, of which four bilaterally symmetric pairs of interneurons present in each segmental ganglion appear to constitute the major component. These interneurons are linked intra- and intersegmentally via inhibitory connections to form a segmentally iterated and inter-segmentally concatenated cyclic neuronal network. The network appears to owe its oscillatory activity pattern to the mechanism of recurrent cyclic inhibition. 相似文献
4.
IgG from patients with Lambert-Eaton syndrome blocks voltage-dependent calcium channels 总被引：14，自引：0，他引：14
Lambert-Eaton syndrome, an autoimmune disorder frequently associated with small-cell carcinoma of the lung, is characterized by impaired evoked release of acetylcholine from the motor nerve terminal. Immunoglobulin G (IgG) antibodies from patients with the syndrome, applied to bovine adrenal chromaffin cells, reduced the voltage-dependent calcium channel currents by about 40 percent. When calcium was administered directly into the cytoplasm, however, the IgG-treated cells exhibited normal exocytotic secretion, as assayed by membrane capacitance measurement. Measurement with the fluorescent calcium indicator fura-2 indicated that the IgG treatment reduced potassium-stimulated increase in free intracellular calcium concentration. The pathogenic IgG modified neither kinetics of calcium channel activation nor elementary channel activity, suggesting that a reduction in the number of functional calcium channels underlies the IgG-induced effect. Therefore, Lambert-Eaton syndrome IgG reacts with voltage-dependent calcium channels and blocks their function, a phenomenon that can account for the presynaptic impairment characteristic of this disorder. 相似文献
5.
Norepinephrine elicited a hyperpolarizing response, and acetylcholine (during nicotinic blockade) elicited a depolarizing one. Both responses showed no increase in membrane conductance. The norepinephrine response was suppressed by initial depolarization; the acetylcholine response (frog cells); by hyperpolarization. These neurotransmitters apparently can activate electrogenic mechanisms which do not involve movement of ions down their electrochemical gradients. 相似文献
6.
Bohr DF 《Science (New York, N.Y.)》1963,139(3555):597-599
The first part of the contractile response of rabbit aorta to epinephrine is depressed by elevation of calcium concentration; the second is potentiated. These observations suggest that the rate-limiting factor for the former is membrane excitability (depressed by increased calcium), while that for the latter is the role that calcium plays in coupling membrane excitation with the development of tension by the contractile protein (a function that is augmented by increased calcium). 相似文献
7.
Acetylcholine responses in L cells 总被引：3，自引：0，他引：3
L cells, a family of continuous cell lines of mouse fibroblastic origin, generate a prolonged active membrane hyperpolarization (the hyperpolarizing activation response) when stimulated mechanically or electrically. lontophoretically applied acetylcholine elicits a similar response; atropine blocks the acetylcholine but not the electrically or mechanically elicited responses. The hyperpolarizing activation response can also be elicited by electrical, mechanical, or acetylcholine stimulation of cells adjacent to the recorded cell. Propagation of the response from one cell to another is not dependent on direct electrical coupling between cells and is not blocked by application of a bath containing atropine or curare. These results show that L cells are capable of generating an active electrical response. that they are sensitive to at least one neurotransmitter (acetylcholine), and that humorally mediated interaction (probably noncholinergic) between L cells occurs. 相似文献
8.
Gap junctional conductance and permeability are linearly related 总被引：3，自引：0，他引：3
The permeability of gap junctions to tetraethylammonium ions was measured in isolated pairs of blastomeres from Rana pipiens L. and compared to the junctional conductance. In this system, the junctional conductance is voltage-dependent and decreases with moderate transjunctional voltage of either sign. The permeability to tetraethylammonium ions was determined by injecting one cell of a pair with tetraethylammonium and monitoring its changing concentration in the prejunctional and postjunctional cells with ion-selective electrodes. Junctional conductance was determined by current-clamp and voltage-clamp techniques. For different cell pairs in which the transjunctional voltage was small and the junctional conductance at its maximum value, the permeability to tetraethylammonium ions was proportional to the junctional conductance. In individual cell pairs, a reduction in the junctional conductance induced by voltage was accompanied by a proportional reduction in the permeability of the gap junction over a wide range. The diameter of the tetraethylammonium ion (8.0 to 8.5 A, unhydrated) is larger than that of the potassium ion (4.6 A, hydrated), the predominant current-carrying species. The proportionality between the permeability to tetraethylammonium ions and the junctional conductance, measured here with exceptionally fine time resolution, indicates that a common gap junctional pathway mediates both electrical and chemical fluxes between cells, and that closure of single gap junction channels by voltage is all or none. 相似文献
9.
小菜蛾nAChR靶标敏感性与沙蚕毒素类药物的抗性关系 总被引：1，自引：0，他引：1
【目的】研究抗杀虫双、杀螟丹和溴氰菊酯品系的神经乙酰胆碱受体及与它们对沙蚕毒素类药物的抗性间的关系。【方法】测定不同品系小菜蛾的神经乙酰胆碱受体与125I标记的α-银环蛇毒素的结合率。【结果】抗杀虫双、杀螟丹品系小菜蛾的神经乙酰胆碱受体对沙蚕毒素药物有显著的靶标不敏感性,它们与配体的结合率大约分别是敏感品系的66%和60%,在溴氰菊酯抗性品系中没有明显变化。【结论】神经乙酰胆碱受体对杀虫剂敏感性下降可能是小菜蛾对沙蚕毒素药物产生抗性的一种作用机理。 相似文献
10.
The combinative rate measurement of (3-[Ⅰ125] iodotyrosyl) α-bungarotoxin was applied in the analysis of the relation between nerve acetylcholine receptor and three types of insecticide resistance in diamondback moth, Plutella xylostella (L.). In the dimehypo-resistant strain and in the cartap-resistant strain, the nerve acetylcholine receptor showed the remarkable insensitivity to dimehypo and cartap, of which the binding rate to ligand was approximately 66 and 60%, respectively, of the susceptible strain. The sensitivity to deltamethrin in the deltamethrin-resistant strain did not show visible change. These results indicated that the decline in the sensitivity of nerve acetylcholine receptor to insecticide might be a potential mechanism to nereistoxin insecticides resistance in the diamondback moth. 相似文献
11.
Perineurium: evidence for contractile elements 总被引：1，自引：0，他引：1
Electron-microscopic study of mouse sciatic nerve reveals that perineurial cells contain filaments and associated opaque regions similar to those observed in smooth muscle. This finding is consistent with obsevations Which suggest that nerve might have a contractile property. In addition to their function in maintaining the connective tissue stroma of perineurium, as well as being a selective diffusion barrier, perineurial cells may serve the nerve in a contractile capacity. 相似文献
12.
The combinative rate measurement of （3-[I125] iodotyrosyl） α-bungarotoxin was applied in the analysis of the relation between nerve acetylcholine receptor and three types of insecticide resistance in diamondback moth, Plutella xylostella （L.）. In the dimehypo-resistant strain and in the cartap-resistant strain, the nerve acetylcholine receptor showed the remarkable insensitivity to dimehypo and cartap, of which the binding rate to ligand was approximately 66 and 60%, respectively, of the susceptible strain. The sensitivity to deltamethrin in the deltamethrin-resistant strain did not show visible change. These results indicated that the decline in the sensitivity of nerve acetylcholine receptor to insecticide might be a potential mechanism to nereistoxin insecticides resistance in the diamondback moth. 相似文献
13.
Rosas-Ballina M Olofsson PS Ochani M Valdés-Ferrer SI Levine YA Reardon C Tusche MW Pavlov VA Andersson U Chavan S Mak TW Tracey KJ 《Science (New York, N.Y.)》2011,334(6052):98-101
Neural circuits regulate cytokine production to prevent potentially damaging inflammation. A prototypical vagus nerve circuit, the inflammatory reflex, inhibits tumor necrosis factor-α production in spleen by a mechanism requiring acetylcholine signaling through the α7 nicotinic acetylcholine receptor expressed on cytokine-producing macrophages. Nerve fibers in spleen lack the enzymatic machinery necessary for acetylcholine production; therefore, how does this neural circuit terminate in cholinergic signaling? We identified an acetylcholine-producing, memory phenotype T cell population in mice that is integral to the inflammatory reflex. These acetylcholine-producing T cells are required for inhibition of cytokine production by vagus nerve stimulation. Thus, action potentials originating in the vagus nerve regulate T cells, which in turn produce the neurotransmitter, acetylcholine, required to control innate immune responses. 相似文献
14.
A substance P antagonist, [D-Pro2, D-Trp7,9]SP, inhibits inflammatory responses in the rabbit eye 总被引：6，自引：0，他引：6
G Holmdahl R H?kanson S Leander S Rosell K Folkers F Sundler 《Science (New York, N.Y.)》1981,214(4524):1029-1031
Neurogenic factors released by antidromic nerve stimulation are thought to be in part responsible for the vasodilation and breakdown of the blood-aqueous barrier that follows trauma to the eye. Substance P is one candidate for the mediation of the inflammatory response since it is thought to be a neurotransmitter in sensory afferents and since exogenous substance P is capable of eliciting a response characteristic of inflammation. In rabbits, intravitreal or topical application onto the eye of a specific substance P antagonist, [d-Pro2, D-Trp7,9]SP, inhibited not only the irritant effects of exogenous substance P but also the inflammatory response to a standardized trauma (infrared irradiation of the iris). These observations suggest that substance P, or a related peptide, is a neurogenic mediator of the inflammatory response in the eye. 相似文献
15.
Ionic mechanisms of cholinergic excitation in molluscan neurons 总被引：2，自引：0，他引：2
Acetylcholine appears to be an excitatory transmitter at synapses on two different types of molluscan nerve cells: the so-called D- and CILDA neurons. The action of this substance is different in the two cases. In D-neurons, this compound increases the permeability of the subsynaptic or somatic membrane to chloride ions, and through a net efflux of this anion, depolarizes the cell. In CILDA neurons, on the other hand, acetylcholine depolarzies the cell by increasing its permeability to sodium ions. 相似文献
16.
Perineural epithelium: a new concept of its role in the integrity of the peripheral nervous system 总被引：3，自引：0，他引：3
A multilayered, squamous-celled epithelial cell membrane covering the individual nerve fasciculi of the entire peripheral nervous system ( both voluntary and autonomic) including the sensory and motor end organs has been demonstrated in various species of animals, including man. This membrane is the direct continuation of the pia-arachnoid mater from the central nervous system.Functional significance of this membrane, especially as a diffusion barrier and as a protector of the peripheral nervous system, is briefly discussed. 相似文献
17.
蛇毒突触前磷脂酶A2神经毒素(Snake presynaptic phospholipase A2 neurotoxins,SPANs)是蛇毒中毒性最大的成分之一,主要作用于脊椎动物神经-肌肉接头(Neuromuscular junction,NMJ)处,阻断神经递质乙酰胆碱的释放致使动物肌肉麻痹、呼吸衰竭直至死亡。SPANs与突触前膜特异性结合,水解膜磷脂生成溶血磷脂(Lysophospholipids,LysoPC)和脂肪酸(Fatty acids,FA),改变膜构象、膜通透性提高导致Ca2+大量内流至神经末梢、突触囊泡(Synaptic vesicles,SV)枯竭、线粒体功能障碍等。对蛇毒突触前磷脂酶A2神经毒素的受体分子及其引发的一系列胞内分子事件进行综述。 相似文献
18.
Chen CC Lamping KG Nuno DW Barresi R Prouty SJ Lavoie JL Cribbs LL England SK Sigmund CD Weiss RM Williamson RA Hill JA Campbell KP 《Science (New York, N.Y.)》2003,302(5649):1416-1418
Calcium ion (Ca2+) influx through voltage-gated Ca2+ channels is important for the regulation of vascular tone. Activation of L-type Ca2+ channels initiates muscle contraction; however, the role of T-type Ca2+ channels (T-channels) is not clear. We show that mice deficient in the alpha1H T-type Ca2+ channel (alpha(1)3.2-null) have constitutively constricted coronary arterioles and focal myocardial fibrosis. Coronary arteries isolated from alpha(1)3.2-null arteries showed normal contractile responses, but reduced relaxation in response to acetylcholine and nitroprusside. Furthermore, acute blockade of T-channels with Ni2+ prevented relaxation of wild-type coronary arteries. Thus, Ca2+ influx through alpha1H T-type Ca2+ channels is essential for normal relaxation of coronary arteries. 相似文献
19.
Trophic regulation of acetylcholine sensitivity of muscle: effect of electrical stimulation 总被引：17，自引：0，他引：17
Denervation of skeletal muscle results in a spread of acetylcholine sensitivity over the entire surface membrane. Electrical stimulation, programmed to mimic the normal activity pattern, was applied continuously to the denervated rat diaphragm in vivo. After 4 days, the acetylcholine sensitivity was far less in the stimulated diaphragms than in denervated controls. Muscle activity may account for "neurotrophic" regulation of the acetylcholine sensitivity. 相似文献
20.
文章以番茄为材料研究喷施外源ABA、SA、CaCl2处理对低温胁迫番茄幼苗膜脂过氧化作用的影响。结果表明,喷施10mg.L-1ABA、1400mg.L-1CaCl2、300mg.L-1SA能够明显地降低相对电导率,抑制膜脂过氧化作用,提高过氧化物酶(POD)活性,从而减轻了低温胁迫对番茄幼苗的伤害,降低幼苗的膜脂过氧化作用。 相似文献