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1.
Extract from the abdominal ganglia of Aplysia was fractionated by high performance liquid chromatography. Several large uv absorbing peaks were found. One of these peaks from the ganglionic extract was analyzed by displacement assay with the use of Mytilus edulis membranes. The results revealed the substance in this peak was able to displace 3H-D-Ala2, met5-enkephalinamide. In electrophysiological studies of abdominal and cerebral neurons, depolarizing and hyperpolarizing responses were obtained from some neurons, including neurons in the identified cerebral B cell cluster. A smaller population of cells exhibited biphasic responses. Some of the responses could be depressed by prior naloxone treatment. In conclusion, an endogenous opioid system, using substance related to but distinct from the enkephalins, may exist in Aplysia.  相似文献   

2.
Time intervals of 12 records of bursting discharges in Aplysia neurons were analysed by digital computer to determine the interrelations between the burst period, the interburst interval and the burst duration. The effects of membrane potential changes on the parameters of bursting discharges were examined also. A low correlation was found between burst duration and burst period in the majority of cases, and this was interpreted as an indication of probable independence between the mechanisms governing these parameters. Also, a specific temporal organization of interspike intervals seems to be present in each type of neuron. The results suggest that the mechanism governing the burst period is characterized by a slow membrane potential oscillation resembling that observed in bursting neurons when actions potentials are blocked by tetrodotoxin. The burst duration would be determined by the response of the neuron to suprathreshold depolarization.  相似文献   

3.
The combination of retrograde labelling with dextran-tetramethylrhodamine and MALDI-TOF mass spectrometry was used to analyse for the first time the peptidome of a series of morphologically identified single neurosecretory cells of an insect. Eight postero-lateral cells of the metathoracic ganglion of the American cockroach, Periplaneta americana, were used to demonstrate that: (1) the complete dissection procedure can be documented and (2) the mass spectrometric analysis of the dissected somata results in highly reproducible mass spectra. In total, 21 FMRFamide-related peptides were detected in each of the postero-lateral cells which release their neurosecretions via thoracic perisympathetic organs. Direct analysis of these neurohemal organs confirmed the co-storage of FMRFamide-related peptides. Two additional abundant peptides from thoracic perisympathetic organs which were not detectable in the postero-lateral cells were characterized using ESI-Q-TOF MS/MS. De novo sequencing yielded two related peptides (FERL/IEamides) without any similarity with known peptide families of insects.  相似文献   

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The biosynthesis and processing of low molecular weight protein (presumed neurosecretory protein) in cells R15, R14 and L11 of Aplysia californica was studied at high resolution by polyacrylamide slab gel electrophoresis in sodium dodecylsulfate. The number of low molecular weight proteins detected in each cell ranges from 3 in R14 and L11 to 5 or 6 in R15. In each of the cells studied, the low molecular weight protein consists of a primary precursor of ca. 12,000 daltons, and its proteolytic processing products. In each cell, the smallest protein, or in the case of R14, one of the two smallest proteins, accumulates to a significant extent, suggesting that it might correspond to a final processed neurohormone. In cell R15, the biosynthesis of the primary precursor and its subsequent processing to smaller peptides is largely unaffected by removal of extracellular calcium, by replacement of calcium with cobalt or by inhibition of spontaneous bursting via stimulation of the brachial nerve.  相似文献   

6.
The biosynthesis and processing of low molecular weight protein (presumed neurosecretory protein) in cells R15, R14 and L11 of Aplysia californica was studied at high resolution by polyacrylamide slab gel electrophoresis in sodium dodecylsulfate. The number of low molecular weight proteins detected in each cell ranges from 3 in R14 and L11 to 5 to 6 in R15. In each of the cells studied, the low molecular weight protein consists of a primary precursor of ca. 12,000 daltons, and its proteolytic processing products. In each cell, the smallest protein, or in the case of R14, one of the two smallest proteins, accumulates to a significant extent, suggesting that it might correspond to a final processed neurohormone. In cell R15, the biosynthesis of the primary precursor and its subsequent processing to smaller peptides is largely unaffected by removal of extracellular calcium, by replacement of calcium with cobalt or by inhibition of spontaneous bursting via stimulation of the brachial nerve.  相似文献   

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Serotonin (5-HT) produces presynaptic facilitation and FMRFamide produces presynaptic inhibition in Aplysia sensory neurons. These effects may involve the modulation of Ca2+ influx into sensory neuron terminals during action potentials. Here, we have used the Ca2+ indicator dye fura-2 to monitor directly the effects of 5-HT and FMRFamide on internal Ca2+ concentration ([Ca2+]i). 5-HT caused a 50% increase in the transient rise in [Ca2+]i in response to action potentials, whereas FMRFamide decreased the [Ca2+]i transient by 40%. Neither transmitter altered the resting [Ca2+]i, the time course of recovery of the [Ca2+]i transient, or the [Ca2+]i transients produced by intracellular injection of CaCl2 or inositol 1,4,5-trisphosphate. We conclude that the effects of the transmitters on the action potential-induced [Ca2+]i transient are due to changes in Ca2+ influx and not in intracellular Ca2+ homeostasis.  相似文献   

9.
Tiedge H 《Neuron》2005,48(1):13-16
A workshop entitled "RNA Control of Neuronal Function" was recently held in Kfar Blum, Israel. The main topics discussed at the meeting included neuronal RNA targeting mechanisms and the contributing codes and components, translational control mechanisms in dendrites and axons, and the relevance of these mechanisms for neuronal development, plasticity, and dysfunction.  相似文献   

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Two long-lasting discharges of action potentials were recorded from a buccal cell of the pond snail, respectively, before and after superfusing the preparation with low-calcium solution. The corresponding sequences of interspike intervals were then analysed by the nonlinear prediction methods. The results yield evidence of a small but clear nonlinearity only in the second of analysed tachograms. This finding is evaluated and discussed.  相似文献   

12.
We report a simple and rapid method to label individual neurons in live zebrafish embryos and to examine their gene expression profiles. Injection of plasmid DNA encoding an alpha-tubulin promotor driving GFP expression results in mosaic embryos containing a limited number of GFP-positive neurons. Labeled neurons express GFP in their soma and axon, providing the opportunity to analyze pathfinding behaviors of identified neurons in vivo. Moreover, the presence of only a small subset of GFP tagged neurons permits the rapid anatomical identification of these neurons based on soma position and axonal trajectory. Analysis of injected embryos reveals that most, if not all, spinal cord cell types and many other neuronal cell types elsewhere in the nervous system can be GFP tagged. Finally, by combining GFP labeling of individual neurons with fluorescent in situ hybridization, we demonstrate the potential of this method to elucidate gene expression patterns at single cell resolution.  相似文献   

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To determine the influence that an appropriate target cell has on the axonal structure of a presynaptic neuron in vivo, we examined the morphologies of individual Aplysia sensory neurons in dissociated cell culture in the presence or absence of identified target motor neurons. We find that an appropriate target, the motor cell L7, regulates the morphological differentiation of the presynaptic sensory neurons in two ways: the target induces the axons of the sensory neurons to develop a more elaborate structure and to form active zones, and the target guides the outgrowth of the sensory neurons. The influence of the appropriate target, L7, on the morphological differentiation of sensory neurons appears to be related to the formation of chemical synaptic connections between the sensory neurons and L7, since sensory neurons co-cultured with an inappropriate target motor neuron do not exhibit a comparable elaboration of their axonal processes.  相似文献   

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Intracellular trafficking of RNA in neurons   总被引:5,自引:0,他引:5  
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17.
The linear-nonlinear cascade model (LN model) has proven very useful in representing a neural system’s encoding properties, but has proven less successful in reproducing the firing patterns of individual neurons whose behavior is strongly dependent on prior firing history. While the cell’s behavior can still usefully be considered as feature detection acting on a fluctuating input, some of the coding capacity of the cell is taken up by the increased firing rate due to a constant “driving” direct current (DC) stimulus. Furthermore, both the DC input and the post-spike refractory period generate regular firing, reducing the spike-timing entropy available for encoding time-varying fluctuations. In this paper, we address these issues, focusing on the example of motoneurons in which an afterhyperpolarization (AHP) current plays a dominant role regularizing firing behavior. We explore the accuracy and generalizability of several alternative models for single neurons under changes in DC and variance of the stimulus input. We use a motoneuron simulation to compare coding models in neurons with and without the AHP current. Finally, we quantify the tradeoff between instantaneously encoding information about fluctuations and about the DC.  相似文献   

18.
Adenosine deaminases that act on RNA (ADARs) convert adenosines to inosine in both coding and noncoding double-stranded RNA. Deficiency in either ADAR1 or ADAR2 in mice is incompatible with normal life and development. While the ADAR2 knockout phenotype can be attributed to the lack of editing of the GluR-B receptor, the embryonic lethal phenotype caused by ADAR1 deficiency still awaits clarification. Recently, massive editing was observed in noncoding regions of mRNAs in mice and humans. Moreover, editing was observed in protein-coding regions of four mRNAs encoding FlnA, CyFip2, Blcap, and IGFBP7. Here, we investigate which of the two active mammalian ADAR enzymes is responsible for editing of these RNAs and whether any of them could possibly contribute to the phenotype observed in ADAR knockout mice. Editing of Blcap, FlnA, and some sites within B1 and B2 SINEs clearly depends on ADAR1, while other sites depend on ADAR2. Based on our data, substrate specificities can be further defined for ADAR1 and ADAR2. Future studies on the biological implications associated with a changed editing status of the studied ADAR targets will tell whether one of them turns out to be directly or indirectly responsible for the severe phenotype caused by ADAR1 deficiency.  相似文献   

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Differential action of tetrodotoxin on identified leech neurons   总被引:2,自引:0,他引:2  
1. In leech segmental ganglia, the maximum rate of depolarization of action potentials was found to depend largely on Na in the Retzius (R) cell, the mechanosensory P, N and T cells and an identifiable neuron of unknown function, the X cell. 2. Tetrodotoxin (TTX) 15 100 mumol/l had little or no effect on R and X cells. In contrast, membrane excitation in N, P and T cells was depressed in dose- and use-dependent fashion. 3. The data imply the existence of two kinds of Na channels in normal, fully differentiated leech neurons. Correlation of such differences should lead to a better understanding of how particular neurons perform different functions.  相似文献   

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