共查询到20条相似文献，搜索用时 31 毫秒
1.
K J Futamachi 《Science (New York, N.Y.)》1972,175(28):1373-1375
The tonic flexor muscles of the crayfish abdomen respond with a large depolarizing potential to acetylcholine iontophoresed onto a neuromuscular Junction, but not to glutamate. Excitatory junctional potentials are abolished by d-tubocurarine and enhanced by a cholinesterase inhibitor. The membrane is depolarized and the junctional potentials are desensitized by excess acetylcholine. Thus acetylcholine is thought to be the neuromuscular transmitter. 相似文献
2.
3.
DDT: interaction with nerve membrane conductance changes 总被引：5，自引：0，他引：5
The falling phase of action potentials of lobster giant axons is prolonged by DDT; finally a plateau phase is produced like cardiac action potentials. In axons poisoned with DDT, peak transient (sodium) currents associated with step depolarizations are turned off very slowly, and steady-state (potassium) currents are markedly suppressed. These two changes would cause the prolongation of action potentials and are considered the major ionic mechanisms of DDT action. 相似文献
4.
目的:调查早期胚胎细胞分化的诱因。方法:使用Patch clamp7型膜电位测定仪,测定ICR小鼠4、8、16、32细胞期胚胎的细胞膜电位。结果:①细胞位置无差异时,胚胎细胞的膜电位差异不显著;②早期胚胎的细胞膜电位存在个体差异;③早期胚胎的细胞在不同发育阶段具有不同的膜电位,且其膜电位值显著下降;④同—胚胎的周边细胞与内部细胞之间,细胞膜电位存在显著性差异。结论:早期胚胎分化的诱因是不同位置的细胞受到"胚胎场"的影响不同,"胚胎场"是指构成胚胎的细胞,因其具有的膜电位因素在相互之间形成的影响力。 相似文献
5.
Metacontrast: its relation to evoked potentials 总被引：2，自引：0，他引：2
Electrophysiological correlates of metacontrast were studied by means of averaged evoked potentials recorded from the scalp in man. Under conditions in which the brightness of the first of two successive stimuli appears diminished there is no accompanying attenuation of the evoked potentials to that stimulus. The results suggest that the amplitude and latency of evoked potentials correlate with stimulus intensity but not with brightness. 相似文献
6.
The effects of pentobarbital (Nembutal) on synaptic transmission and postsynaptic potentials were studied by the use of several invertebrate preparations. Pentobarbital selectively and reversibly depressed both excitatory postsynaptic potentials and sodium-dependent postsynaptic responses to putative excitatory transmitters without affecting either inhibitory postsynaptic potentials or chloride- and potassium-dependent postsynaptic responses to putative transmitters. A selective depression of postsynaptic excitatory events was also observed with other central nervous system depressants (ethanol, chloroform, chloralose, diphenylhydantoin, and urethane). The results suggest that central and peripheral depression observed during general anesthesia is due to a selective depression of excitatory synaptic events. 相似文献
7.
Self-stimulation alters human sensory brain responses 总被引：3，自引：0，他引：3
Human electrocortical potentials evoked by self-administered auditory and visual stimuli manifest much smaller amplitude and faster poststimulus timing than do average brain responses evoked by identical machine-delivered stimuli. Auditory evoked potentials show this "self-stimulation effect" to a greater degree than do visual responses. For visual evoked potentials, the effect appears greater at the vertex association area than over the occipital cortex. Individual differences in the magnitude of the "self-stimutlation effect" relate to level of intelligence. 相似文献
8.
Digital computer techniques have been employed to extract cortical evoked potentials to paired visual stimuli. Changes in the evoked potentials have been related to perceptual phenomena varying as a function of the interval between flashes. Evoked potentials to paired stimuli, which gave rise to perceptual interactions, could be approximated by algebraic summation of the responses to the stimuli when presented separately. 相似文献
9.
根据广义氧化还原理论,发现生物体内存在电位缓冲体系。并给出电位的计算公式,分析了影响缓冲体系电位的主要因素。 相似文献
10.
The united efforts of assemblies of neurons in the brain's primary visual cortex translate incoming visual signals into action potentials. These action potentials encode, for example, the contrast and orientation of different parts of the image. Some neurons are sensitive to one particular orientation, other are sensitive to other orientations, but all neurons respond equally well to the image contrast. In a Perspective, Volgushev and Eysel explain the finding (Anderson et al.) that neurons are able to maintain this sensitivity to the orientation of a stimulus regardless of the contrast by adding noise to the membrane potential, such that action potentials can also be generated in response to weak signals at low contrast. 相似文献
11.
The earliest known response of eggs to sperm in many species is a change in egg membrane potential. However, for no species is it known what components of the sperm cause the opening of the egg plasma membrane channels. Protein isolated from sperm acrosomal granules of the marine worm Urechis caused electrical responses in oocytes with the same form, amplitude, and ion dependence as the fertilization potentials induced by living sperm. Sperm initiated fertilization potentials in oocytes when sperm-oocyte fusion, but not binding, was inhibited by clamping oocyte membrane potentials to positive values. Acrosomal protein also initiated electrical responses in clamped oocytes. These results support the hypothesis that it is the sperm acrosomal protein that opens ion channels in the oocyte membrane. 相似文献
12.
Xenopus oocytes injected with rat uterine RNA express very slowly activating potassium currents 总被引：3，自引：0，他引：3
M B Boyle E M Azhderian N J MacLusky F Naftolin L K Kaczmarek 《Science (New York, N.Y.)》1987,235(4793):1221-1224
Under the influence of estrogen, uterine smooth muscle becomes highly excitable, generating spontaneous and prolonged bursts of action potentials. In a study of the mechanisms by which this transition in excitability occurs, polyadenylated RNA from the uteri of estrogen-treated rats was injected into Xenopus oocytes. The injected oocytes expressed a novel voltage-dependent potassium current. This current was not observed in oocytes injected with RNA from several other excitable tissues, including rat brain and uterine smooth muscle from ovariectomized rats not treated with estrogen. The activation of this current on depolarization was exceptionally slow, particularly for depolarizations from relatively negative membrane potentials. Such a slowly activating channel may play an important role in the slow, repetitive bursts of action potentials in the myometrium. 相似文献
13.
Two identified interneurons in each buccal ganglion of Aplysia can mediate conjoined excitation and inhibition to a single follower cell. A single presynaptic action potential in one of these interneurons produces a diphasic, depolarizing-hyperpolarizing synaptic potential apparently as a result of a single transmitter acting on two types of postsynaptic receptors in the follower cell. These receptors produce synaptic potentials with differing reversal potentials, ionic conductances, time courses, rates of decrement with repetition, pharmacological properties, and functional consequences. The excitatory receptor controls a sodium conductance, the inhibitory receptor controls a chloride conductance. Both components of the synaptic potentials can be produced by iontophoretic application of acetylcholine on the cell body of the follower cell, and each component is differentially sensitive to different cholinergic blocking agents. 相似文献
14.
15.
In mammalian excitatory neurons, dendritic spines are separated from dendrites by thin necks. Diffusion across the neck limits the chemical and electrical isolation of each spine. We found that spine/dendrite diffusional coupling is heterogeneous and uncovered a class of diffusionally isolated spines. The barrier to diffusion posed by the neck and the number of diffusionally isolated spines is bidirectionally regulated by neuronal activity. Furthermore, coincident synaptic activation and postsynaptic action potentials rapidly restrict diffusion across the neck. The regulation of diffusional coupling provides a possible mechanism for determining the amplitude of postsynaptic potentials and the accumulation of plasticity-inducing molecules within the spine head. 相似文献
16.
Voltage-dependent calcium channels in glial cells 总被引：16，自引：0，他引：16
B A MacVicar 《Science (New York, N.Y.)》1984,226(4680):1345-1347
The electrophysiological properties of glial cells were examined in primary culture in the presence of tetraethylammonium and Ba2+, a treatment that reduces K+ permeability of the membrane and enhances currents through voltage-dependent Ca2+ channels. Under these conditions, glial cells showed both spontaneous action potentials and action potentials evoked by the injections of current. These responses appear to represent entry of Ba2+ through Ca2+ channels because they were resistant to tetrodotoxin but were blocked by Mn2+ or Cd2+. 相似文献
17.
In the mammalian cortex, it is generally assumed that the output information of neurons is encoded in the number and the timing of action potentials. Here, we show, by using direct patchclamp recordings from presynaptic hippocampal mossy fiber boutons, that axons transmit analog signals in addition to action potentials. Excitatory presynaptic potentials result from subthreshold dendritic synaptic inputs, which propagate several hundreds of micrometers along the axon and modulate action potential-evoked transmitter release at the mossy fiber-CA3 synapse. This combined analog and action potential coding represents an additional mechanism for information transmission in a major hippocampal pathway. 相似文献
18.
There are two types of inhibitory postsynaptic potentials in the cerebral cortex. Fast inhibition is mediated by ionotropic gamma-aminobutyric acid type A (GABA(A)) receptors, and slow inhibition is due to metabotropic GABA(B) receptors. Several neuron classes elicit inhibitory postsynaptic potentials through GABA(A) receptors, but possible distinct sources of slow inhibition remain unknown. We identified a class of GABAergic interneurons, the neurogliaform cells, that, in contrast to other GABA-releasing cells, elicited combined GABA(A) and GABA(B) receptor-mediated responses with single action potentials and that predominantly targeted the dendritic spines of pyramidal neurons. Slow inhibition evoked by a distinct interneuron in spatially restricted postsynaptic compartments could locally and selectively modulate cortical excitability. 相似文献
19.
Mediation of responses to calcium in taste cells by modulation of a potassium conductance 总被引：4，自引：0，他引：4
Calcium salts are strong taste stimuli in vertebrate animals. However, the chemosensory transduction mechanisms for calcium are not known. In taste buds of Necturus maculosus (mud puppy), calcium evokes depolarizing receptor potentials by acting extracellularly on the apical ends of taste cells to block a resting potassium conductance. Therefore, divalent cations elicit receptor potentials in taste cells by modulating a potassium conductance rather than by permeating the cell membrane, the mechanism utilized by monovalent cations such as sodium and potassium ions. 相似文献
20.
We have recorded from the granular layer of the turtle cerebellum extracellular unitary potentials that appear to reflect pre- and postsynaptic events at the synapse between a single swelling of a mossy fiber and the dendritic tips of several granule cells. The presynaptic component is an all-or-none potential. It can be directly activated by spinal stimulation and is unaltered by repetitive activity or by high concentrations of magnesium. The postsynaptic component is a graded potential. It follows the presynaptic component by approximately 1 millisecond and is depressed by repetitive activity and by high concentrations of magnesium. The recording of large potentials produced by the flow of postsynaptic current within a single glomerulus suggests powerful transmission. Electron micrographs demonstrate large cerebellar glomeruli in the turtle and a substantial accumulation of mitochondria in the dendritic tips of granule cells. 相似文献