scholarly journals Presynaptic calcium channels in rat cortical synaptosomes: fast- kinetics of phasic calcium influx, channel inactivation, and relationship to nitrendipine receptors

1986 ◽  
Vol 6 (5) ◽  
pp. 1349-1357 ◽  
Author(s):  
JB Suszkiw ◽  
ME O'Leary ◽  
MM Murawsky ◽  
T Wang
Keyword(s):  
Calcium Channels ◽  
Calcium Influx ◽  
Fast Kinetics ◽  
Channel Inactivation ◽  
Presynaptic Calcium ◽  
Kinetics Of

Calcium Channels Involved in Synaptic Transmission From Reticulospinal Axons in Lamprey

1999 ◽  
Vol 81 (4) ◽  
pp. 1699-1705 ◽  
Author(s):  
P. Krieger ◽  
A. Büschges ◽  
A. el Manira
Keyword(s):  
Calcium Channels ◽  
Synaptic Transmission ◽  
Calcium Channel ◽  
Calcium Channel Blocker ◽  
Presynaptic Inhibition ◽  
Channel Blocker ◽  
Metabotropic Glutamate Receptor ◽  
Calcium Influx ◽  
Combined Application ◽  
Presynaptic Calcium

Calcium channels involved in synaptic transmission from reticulospinal axons in lamprey. The pharmacology of calcium channels involved in glutamatergic synaptic transmission from reticulospinal axons in the lamprey spinal cord was analyzed with specific agonists and antagonists of different high-voltage activated calcium channels. The N-type calcium channel blocker ω-conotoxin GVIA (ω-CgTx) induced a large decrease of the amplitude of reticulospinal-evoked excitatory postsynaptic potentials (EPSPs). The P/Q-type calcium channel blocker ω-agatoxin IVA (ω-Aga) also reduced the amplitude of the reticulospinal EPSPs, but to a lesser extent than ω-CgTx. The dihydropyridine agonist Bay K and antagonist nimodipine had no effect on the amplitude of the reticulospinal EPSP. Combined application of ω-CgTx and ω-Aga strongly decreased the amplitude the EPSPs but was never able to completely block them, indicating that calcium channels insensitive to these toxins (R-type) are also involved in synaptic transmission from reticulospinal axons. We have previously shown that the group III metabotropic glutamate receptor agonistl(+)-2-amino-4-phosphonobutyric acid (l-AP4) mediates presynaptic inhibition at the reticulospinal synapse. To test if this presynaptic effect is mediated through inhibition of calcium influx, the effect of l-AP4 on reticulospinal transmission was tested before and after blockade of N-type channels, which contribute predominantly to transmitter release at this synapse. Blocking the N-type channels with ω-CgTx did not prevent inhibition of reticulospinal synaptic transmission by l-AP4. In addition, l-AP4 had no affect on the calcium current recorded in the somata of reticulospinal neurons or on the calcium component of action potentials in reticulospinal axons. These results show that synaptic transmission from reticulospinal axons in the lamprey is mediated by calcium influx through N-, P/Q- and R-type channels, with N-type channels playing the major role. Furthermore, presynaptic inhibition of reticulospinal transmission byl-AP4 appears not to be mediated through inhibition of presynaptic calcium channels.

Single atom catalysts supported on N-doped graphene toward fast kinetic Li−S batteries: a theoretical study

2021 ◽  
Author(s):  
Xu Han ◽  
Zeyun Zhang ◽  
Xuefei Xu
Keyword(s):  
Theoretical Study ◽  
Single Atom ◽  
Discharge Process ◽  
Fast Kinetics ◽  
Shuttle Effect ◽  
Sufficient Stability ◽  
Doped Graphene ◽  
Fast Kinetic ◽  
Kinetics Of ◽  
Charge Discharge

To suppress the shuttle effect of lithium polysulfides and promote fast kinetics of charge−discharge process in Li−S batteries, it is essential to search promising catalysts with sufficient stability and high...

scholarly journals The poly(ADP-ribose)-dependent chromatin remodeler Alc1 induces local chromatin relaxation upon DNA damage

2016 ◽  
Vol 27 (24) ◽  
pp. 3791-3799 ◽  
Author(s):  
Hafida Sellou ◽  
Théo Lebeaupin ◽  
Catherine Chapuis ◽  
Rebecca Smith ◽  
Anna Hegele ◽  
...  
Keyword(s):  
Dna Damage ◽  
Structural Changes ◽  
Cellular Responses ◽  
Dna Lesions ◽  
Fast Kinetics ◽  
Important Player ◽  
Chromatin Relaxation ◽  
Kinetics Of ◽  
Laser Microirradiation

Chromatin relaxation is one of the earliest cellular responses to DNA damage. However, what determines these structural changes, including their ATP requirement, is not well understood. Using live-cell imaging and laser microirradiation to induce DNA lesions, we show that the local chromatin relaxation at DNA damage sites is regulated by PARP1 enzymatic activity. We also report that H1 is mobilized at DNA damage sites, but, since this mobilization is largely independent of poly(ADP-ribosyl)ation, it cannot solely explain the chromatin relaxation. Finally, we demonstrate the involvement of Alc1, a poly(ADP-ribose)- and ATP-dependent remodeler, in the chromatin-relaxation process. Deletion of Alc1 impairs chromatin relaxation after DNA damage, while its overexpression strongly enhances relaxation. Altogether our results identify Alc1 as an important player in the fast kinetics of the NAD+- and ATP-dependent chromatin relaxation upon DNA damage in vivo.

Expression of myogenic constrictor tone in the aorta of hypertensive rats

2001 ◽  
Vol 280 (4) ◽  
pp. R968-R975 ◽  
Author(s):  
Michelle Rapacon-Baker ◽  
Fan Zhang ◽  
Michael L. Pucci ◽  
Hui Guan ◽  
Alberto Nasjletti
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Calcium Channels ◽  
Thoracic Aorta ◽  
Calcium Influx ◽  
Intraluminal Pressure ◽  
Hypertensive Rats ◽  
Calcium Dependent ◽  
Kinase C ◽  
Basal Tone

We investigated the effect of intraluminal pressure or stretch on the development of tone in the descending thoracic aorta from rats with aortic coarctation-induced hypertension of 7–14 days duration. Increments of pressure >100 mmHg decreased the diameter of thoracic aortas from hypertensive but not from normotensive rats. The pressure-induced constriction was not demonstrable in vessels superfused with calcium-free buffer. Stretched rings of aorta from hypertensive rats exhibited a calcium-dependent constrictor tone accompanied by elevated calcium influx that varied in relation to the degree of stretch. Blockers of l-type calcium channels and inhibitors of protein kinase C reduced both basal tone and calcium influx in aortic rings of hypertensive rats. Hence, the thoracic aorta of hypertensive rats expresses a pressure- and stretch-activated constrictor mechanism that relies on increased calcium influx throughl-type calcium channels via a protein kinase C-regulated pathway. The expression of such a constrictor mechanism is suggestive of acquired myogenic behavior.

scholarly journals Gating of Single N-type Calcium Channels Recorded from Bullfrog Sympathetic Neurons

1999 ◽  
Vol 113 (1) ◽  
pp. 111-124 ◽  
Author(s):  
Hye Kyung Lee ◽  
Keith S. Elmslie
Keyword(s):  
Calcium Channels ◽  
Calcium Influx ◽  
Sympathetic Neurons ◽  
Channel Gating ◽  
Open Probability ◽  
Maximum Value ◽  
Open Time ◽  
Time Component ◽  
Patch Technique ◽  
Single Exponential

For many neurons, N-type calcium channels provide the primary pathway for calcium influx during an action potential. We investigated the gating properties of single N-type calcium channels using the cell-attached patch technique. With 100 mM Ba2+ in the pipet, mean N-channel open probability (Po, measured over 100 ms) increased with depolarization, but the range at a single voltage was large (e.g., Po at +40 mV ranged from 0.1 to 0.8). The open dwell time histograms were generally well fit by a single exponential with mean open time (τo) increasing from 0.7 ms at +10 mV to 3.1 ms at +40 mV. Shut time histograms were well fit by two exponentials. The brief shut time component (τsh1 = 0.3 ms) did not vary with the test potential, while the longer shut time component (τsh2) decreased with voltage from 18.9 ms at +10 mV to 2.3 ms at +40 mV. Although N-channel Po during individual sweeps at +40 mV was often high (∼0.8), mean Po was reduced by null sweeps, low Po gating, inactivation, and slow activation. The variability in mean Po across patches resulted from differences in the frequency these different gating processes were expressed by the channels. Runs analysis showed that null sweeps tended to be clustered in most patches, but that inactivating and slowly activating sweeps were generally distributed randomly. Low Po gating (Po = 0.2, τo = 1 ms at +40 mV) could be sustained for ∼1 min in some patches. The clustering of null sweeps and sweeps with low Po gating is consistent with the idea that they result from different modes of N-channel gating. While Po of the main N-channel gating state is high, the net Po is reduced to a maximum value of close to 0.5 by other gating processes.

Cell proliferation, calcium influx and calcium channels

Biochimie ◽  
2011 ◽  
Vol 93 (12) ◽  
pp. 2075-2079 ◽  
Author(s):  
Thierry Capiod
Keyword(s):  
Cell Proliferation ◽  
Calcium Channels ◽  
Calcium Influx

scholarly journals PresyNaptic Calcium Channels: Why Is P Selected before N?

2015 ◽  
Vol 108 (3) ◽  
pp. 451-452 ◽  
Author(s):  
Elise F. Stanley
Keyword(s):  
Calcium Channels ◽  
Presynaptic Calcium
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