Capacitance Measurements in the Mouse Rod Bipolar Cell Identify a Pool of Releasable Synaptic Vesicles

2006 ◽  
Vol 96 (5) ◽  
pp. 2539-2548 ◽  
Author(s):  
Zhen-Yu Zhou ◽  
Qun-Fang Wan ◽  
Pratima Thakur ◽  
Ruth Heidelberger
Keyword(s):  
Bipolar Cell ◽  
Synaptic Vesicles ◽  
Sine Wave ◽  
Membrane Capacitance ◽  
Membrane Properties ◽  
Intact Mouse ◽  
Time Resolved ◽  
Capacitance Measurements ◽  
Treatment Conditions ◽  
Capacitance Response

The mouse is an important model system for understanding the molecular basis of neuronal signaling and diseases of synaptic communication. However, the best-characterized retinal ribbon-style synapses are those of nonmammalian vertebrates. To remedy this situation, we asked whether it would be feasible to track synaptic vesicle dynamics in the isolated mouse rod bipolar cell using time-resolved capacitance measurements. The results demonstrate that membrane depolarization triggered an increase in membrane capacitance that was Ca2+ dependent and restricted to the synaptic compartment, consistent with exocytosis. The amplitude of the capacitance response recorded from the easily accessible soma of an intact mouse rod bipolar cell was identical to that recorded directly from the small synaptic terminal, suggesting that in the carefully selected cohort of cells presented here, axonal resistance was not a significant barrier to current flow. This supposition was supported by the analysis of passive membrane properties and a comparison of membrane capacitance measurements in cells with and without synaptic terminals and reinforced by the lack of an effect of sine-wave frequency (200–1,600 Hz) on the measured capacitance increase. The magnitude of the capacitance response increased with Ca2+ entry until a plateau was reached at a spatially averaged intraterminal calcium of about 600 nM. We interpret this plateau, nominally 30 fF, as corresponding to a releasable pool of synaptic vesicles. The robustness of this measure suggests that capacitance measurements may be used in the mouse rod bipolar cell to compare pool size across treatment conditions.

Synaptic Vesicle Endocytosis at a CNS Nerve Terminal: Faster Kinetics at Physiological Temperatures and Increased Endocytotic Capacity During Maturation

2007 ◽  
Vol 98 (6) ◽  
pp. 3349-3359 ◽  
Author(s):  
Robert Renden ◽  
Henrique von Gersdorff
Keyword(s):  
Synaptic Vesicle ◽  
Time Constant ◽  
Nerve Terminal ◽  
Membrane Capacitance ◽  
Vesicle Membrane ◽  
Calyx Of Held ◽  
Time Resolved ◽  
Capacitance Measurements ◽  
Rat Pups ◽  
Vesicle Pools

Synaptic vesicle membrane must be quickly retrieved and recycled after copious exocytosis to limit the depletion of vesicle pools. The rate of endocytosis at the calyx of Held nerve terminal has been measured directly using membrane capacitance measurements from immature postnatal day P7–P10 rat pups at room temperature (RT: 23–24°C). This rate has an average time constant of tens of seconds and becomes slower when the amount of exocytosis (measured as capacitance jump) increases. Such slow rates seem paradoxical for a synapse that can operate continuously at high-input frequencies. Here we perform time-resolved membrane capacitance measurements from the mouse calyx of Held in brain stem slices at physiological temperature (PT: 35–37°C), and also from more mature calyces after the onset of hearing (P14–P18). Our results show that the rate of endocytosis is strongly temperature dependent, whereas the endocytotic capacity of a nerve terminal is dependent on developmental stage. At PT we find that endocytosis accelerates due to the addition of a kinetically fast component (time constant: τ = 1–2 s) immediately after exocytosis. Surprisingly, we find that at RT the rate of endocytosis triggered by short (1- to 5-ms) or long (≥10-ms) depolarizing pulses in P14–P18 mice are similar (τ ≈ 15 s). Furthermore, this rate is greatly accelerated at PT (τ ≈ 2 s). Thus endocytosis becomes faster and less saturable during synaptic maturation, making the calyceal terminal more capable of sustaining prolonged high-frequency transmitter release.

Postnatal Changes in Membrane Properties of Mice Trigeminal Ganglion Neurons

2002 ◽  
Vol 87 (5) ◽  
pp. 2398-2407 ◽  
Author(s):  
Carmen Cabanes ◽  
Mikel López de Armentia ◽  
Félix Viana ◽  
Carlos Belmonte
Keyword(s):  
Postnatal Development ◽  
Trigeminal Ganglion ◽  
Input Resistance ◽  
Membrane Capacitance ◽  
Membrane Properties ◽  
Inward Rectification ◽  
Resting Membrane Potential ◽  
Depolarization Rate ◽  
Ganglion Neurons

Intracellular recordings from neurons in the mouse trigeminal ganglion (TG) in vitro were used to characterize changes in membrane properties that take place from early postnatal stages (P0–P7) to adulthood (>P21). All neonatal TG neurons had uniformly slow conduction velocities, whereas adult neurons could be separated according to their conduction velocity into Aδ and C neurons. Based on the presence or absence of a marked inflection or hump in the repolarization phase of the action potential (AP), neonatal neurons were divided into S- (slow) and F-type (fast) neurons. Their passive and subthreshold properties (resting membrane potential, input resistance, membrane capacitance, and inward rectification) were nearly identical, but they showed marked differences in AP amplitude, AP overshoot, AP duration, rate of AP depolarization, rate of AP repolarization, and afterhyperpolarization (AHP) duration. Adult TG neurons also segregated into S- and F-type groups. Differences in their mean AP amplitude, AP overshoot, AP duration, rate of AP depolarization, rate of AP repolarization, and AHP duration were also prominent. In addition, axons of 90% of F-type neurons and 60% of S-type neurons became faster conducting in their central and peripheral branch, suggestive of axonal myelination. The proportion of S- and F-type neurons did not vary during postnatal development, suggesting that these phenotypes were established early in development. Membrane properties of both types of TG neurons evolved differently during postnatal development. The nature of many of these changes was linked to the process of myelination. Thus myelination was accompanied by a decrease in AP duration, input resistance ( R in), and increase in membrane capacitance (C). These properties remained constant in unmyelinated neurons (both F- and S-type). In adult TG, all F-type neurons with inward rectification were also fast-conducting Aδ, suggesting that those F-type neurons showing inward rectification at birth will evolve to F-type Aδ neurons with age. The percentage of F-type neurons showing inward rectification also increased with age. Both F- and S-type neurons displayed changes in the sensitivity of the AP to reductions in extracellular Ca2+ or substitution with Co2+ during the process of maturation.

Temperature-Driven Oxidation Behavior of Pure Iron Surface Investigated by Time-Resolved EXAFS Measurements

1998 ◽  
Vol 524 ◽  
Author(s):  
S. J. Doh ◽  
J. M. Lee ◽  
D. Y. Noh ◽  
J. H. Je
Keyword(s):  
Heat Treatment ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Rapid Heating ◽  
Oxidation Mechanism ◽  
Front Surface ◽  
Time Resolved ◽  
Treatment Conditions ◽  
Surface Front ◽  
Prolonged Heat

ABSTRACTThe surface-front oxidation mechanism of iron was investigated by time-resolved, glancingangle Fe K-edge fluorescence EXAFS measurements at various oxidation temperatures of 200-700 C. The glancing angle was chosen according to the depth of the oxide layer, roughly 1500-2000A. The oxidation behavior under rapid heating(up to 600°C within 10 minutes) was compared with the slowly heated oxidation process using the Quick-EXAFS measurements. In the slowly heated process, Fe3O4 was the dominating phase at a relatively low temperature (300-400 C) initially. However, at a relatively high temperature (above 600°C), the Fe2O3 and FeO crystalline phases are gradually enriched as the successive oxidation process involving intrusive oxygen proceeded. Remarkably under a prolonged heat treatment above 600°C, the stable FeO phase that exists in a deep-lying interface structure and Fe2O3 phase eventually dominates the thick front-surface structure. In a quickly heated process, however, Fe3O4 phase is less dominating, which is contradictory to the commonly accepted oxidation models. The EXAFS results are discussed in conjunction with the x-ray diffraction features under the same heat treatment conditions.

How Neurons Communicate: Gap Junctions and Neurosecretion

The Neuron ◽  
2015 ◽  
pp. 153-186
Author(s):  
Irwin B. Levitan ◽  
Leonard K. Kaczmarek
Keyword(s):  
Synaptic Vesicles ◽  
Fluorescent Dyes ◽  
Imaging Techniques ◽  
Electrical Coupling ◽  
Snare Complex ◽  
Biologically Active ◽  
Nerve Terminals ◽  
Capacitance Measurements ◽  
Complex Process ◽  
Cytoplasmic Vesicles

Two ways that neurons communicate with one another are by direct electrical coupling and by the secretion of neurotransmitters. Electrical coupling arises from the existence of proteins, known as connexins, that form pores linking the cytoplasm of adjacent cells. Ions and small molecules can carry signals from one cell to another through these pores. Neurosecretion is a more complex process whereby different categories of molecules are sorted into cytoplasmic vesicles. Chemical processes within these vesicles ensure that they contain biologically active transmitters or hormones. SNARE complex proteins cooperate with other proteins to allow synaptic vesicles containing neurotransmitter to release their components into the external medium following calcium entry into nerve terminals. Such exocytosis of synaptic vesicles can be monitored with imaging techniques using fluorescent dyes or proteins, or by capacitance measurements. A second set of molecules retrieves the membrane of synaptic vesicles back from the plasma membrane through endocytosis.

scholarly journals Regulation of transferrin-induced endocytosis by wild-type and C282Y-mutant HFE in transfected HeLa cells

2002 ◽  
Vol 282 (5) ◽  
pp. C973-C979 ◽  
Author(s):  
Lukas Schwake ◽  
Andreas W. Henkel ◽  
Hans D. Riedel ◽  
Thorsten Schlenker ◽  
Matthias Both ◽  
...  
Keyword(s):  
Hela Cells ◽  
Single Cells ◽  
Hereditary Hemochromatosis ◽  
Inhibitory Effect ◽  
Membrane Capacitance ◽  
Wild Type ◽  
Time Resolved ◽  
Cell Membrane Capacitance ◽  
Endocytic Vesicles ◽  
In Cells

The hereditary hemochromatosis protein HFE is known to complex with the transferrin receptor; however, its function regarding endocytosis of transferrin is unclear. We performed patch-clamp capacitance measurements in transfected HeLa cells carrying wild-type or C282Y-mutant HFE cDNA under the control of a tetracycline-sensitive promoter. Whole cell experiments in cells with suppressed expression of wild-type HFE revealed a decrease in membrane capacitance, reflecting predominance of endocytosis in the presence of transferrin. Cells overexpressing C282Y-mutant HFE displayed less intense capacitance decreases, whereas no significant decrease was observed in cells overexpressing wild-type HFE. The formation of single endocytic vesicles in cells with suppressed expression of wild-type HFE was greatly increased in the presence of transferrin as revealed by cell-attached recordings. According to their calculated diameters, many of these vesicles corresponded to clathrin-coated vesicles. These results suggest that wild-type HFE negatively modulates the endocytic uptake of transferrin. This inhibitory effect is attenuated in cells expressing C282Y-mutant HFE. Time-resolved measurements of cell membrane capacitance provide a powerful tool to study transferrin-induced endocytosis in single cells.

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