Continuous measurement of calcium influx in mammalian nonmyelinated nerve fibers: Effects of Na o , Ca o , and electrical activity

1986 ◽  
Vol 91 (2) ◽  
pp. 157-164 ◽  
Author(s):  
P. Jirounek ◽  
W. F. Pralong ◽  
J. Vitus ◽  
R. W. Straub
Keyword(s):  
Electrical Activity ◽  
Continuous Measurement ◽  
Calcium Influx ◽  
Nerve Fibers

scholarly journals Deletion of α 2 δ-1 Calcium Channel Subunit Reduces Calcium Influx and Alters the Electrical Activity of Mouse Chromaffin Cells

2017 ◽  
Vol 112 (3) ◽  
pp. 244a
Author(s):  
Matteo M. Ottaviani ◽  
Vincenzo Mastrolia ◽  
Laura Guarina ◽  
Emilio Carbone ◽  
Petronel Tuluc
Keyword(s):  
Electrical Activity ◽  
Calcium Channel ◽  
Chromaffin Cells ◽  
Calcium Influx

Electrical pacemakers of canine proximal colon are functionally innervated by inhibitory motor neurons

1989 ◽  
Vol 256 (3) ◽  
pp. C466-C477 ◽  
Author(s):  
T. K. Smith ◽  
J. B. Reed ◽  
K. M. Sanders
Keyword(s):  
Electrical Activity ◽  
Motor Neurons ◽  
Circular Muscle ◽  
Proximal Colon ◽  
Nerve Fibers ◽  
Pacemaker Activity ◽  
Intracellular Recordings ◽  
Potential Oscillations ◽  
Circular Layer ◽  
Different Populations

Pacemaker activity in the canine proximal colon occurs at the submucosal and myenteric borders of the circular layer [Am. J. Physiol. 252 (Cell Physiol. 21): C215-C224 and C290-C299, 1987]. The present study investigated the neural regulation of rhythmic electrical activity. Spontaneous inhibitory junction potentials (IJPs) were observed in intracellular recordings from circular muscle cells near the myenteric border. The amplitudes of these events decayed with distance through the circular layer. Stimulation at the myenteric plexus surface evoked IJPs that mimicked the spontaneous events. Stimulation at the submucosal surface evoked IJPs in adjacent cells that were of shorter duration and of different waveform than myenteric IJPs. Amplitudes of IJPs evoked by stimulation near either surface decayed with distance from the site of stimulation. The decay functions for IJPs were essentially identical to the decay of spontaneous slow waves or myenteric potential oscillations. Spontaneous and evoked IJPs affected the amplitudes, durations, and patterns of ongoing rhythmic electrical activity. The data suggest that myenteric and submucosal pacemaker populations may be innervated by different populations of inhibitory nerve fibers. Innervation appears to be heterogeneous with dense populations of inhibitory nerve fibers predominantly located in the pacemaker regions. Neural regulations of pacemaker activity influences rhythmic electrical activity throughout the muscularis.

Factors determining the frequency content of the electromyogram

1983 ◽  
Vol 55 (2) ◽  
pp. 392-399 ◽  
Author(s):  
H. Kranz ◽  
A. M. Williams ◽  
J. Cassell ◽  
D. J. Caddy ◽  
R. B. Silberstein
Keyword(s):  
Electrical Activity ◽  
Action Potentials ◽  
Nerve Fibers ◽  
Frequency Content ◽  
Muscle Properties ◽  
Spectral Content ◽  
Unit Discharge ◽  
Compound Action Potentials ◽  
Motor Unit Discharge ◽  
Compound Action

The contribution of central and peripheral factors to the frequency content of the electromyogram was examined in 10 subjects performing maximal 45-s contractions of thenar muscles. The median frequencies (Fm) of surface-recorded electromyograms and compound action potentials were similar early (P greater than 0.6) and late (P greater than 0.5) in the contractions. There was a mean decrease in the Fm during contraction of 39% for electromyograms and 35% for compound potentials (P greater than 0.1). The Fm of electromyograms increased 11% (P less than 0.02) in only the 1st s of contraction as force was raised from 25 to 100% of maximum. Only one of five subjects showed evidence of increasing synchronization of motor unit discharge during contraction. There was no evidence that delay or dispersion of action potential propagation in terminal nerve fibers or at the neuromuscular junction had a significant effect on frequency content. The findings indicated that the spectral content of muscle electrical activity, and its shift during contraction, primarily reflects intrinsic muscle properties.

scholarly journals CALCIUM INFLUX IN SKELETAL MUSCLE AT REST, DURING ACTIVITY, AND DURING POTASSIUM CONTRACTURE

1959 ◽  
Vol 42 (4) ◽  
pp. 803-815 ◽  
Author(s):  
C. Paul Bianchi ◽  
A. M. Shanes
Keyword(s):  
Skeletal Muscle ◽  
Rana Pipiens ◽  
Calcium Influx ◽  
Nerve Fibers ◽  
Sartorius Muscle ◽  
Potassium Contracture ◽  
Anion Substitution ◽  
Cent Increase ◽  
Fast Twitch ◽  
Passive Influx

Calcium influx in the sartorius muscle of the frog (Rana pipiens) has been estimated from the rate of entry of Ca45. In the unstimulated preparation it is about equal to what has been reported for squid giant axons, but that per impulse is at least 30 times greater than in nerve fibers. The enhanced twitch when NO-2 replaces Cl- in Ringer's is associated with at least a 60 per cent increase in influx during activity, whereas this anion substitution does not affect the passive influx significantly. Calcium entry during potassium contracture is even more markedly augmented than during electrical stimulation, but only at the beginning of the contracture; thus, when a brief Ca45 exposure precedes excess K+ application, C45 uptake is increased three- to fivefold over the controls not subjected to K+, whereas when C45 and K+ are added together, no measurable increase in Ca45 uptake occurs. These findings are in keeping with the brevity of potassium contracture in "fast (twitch)" fibers such as in sartorius muscle.

scholarly journals Synaptic Ribbon Enables Temporal Precision of Hair Cell Afferent Synapse by Increasing the Number of Readily Releasable Vesicles: A Modeling Study

2008 ◽  
Vol 100 (4) ◽  
pp. 1724-1739 ◽  
Author(s):  
John H. Wittig ◽  
Thomas D. Parsons
Keyword(s):  
Auditory Nerve ◽  
Calcium Influx ◽  
Vesicle Fusion ◽  
Nerve Fibers ◽  
Biophysical Model ◽  
Synaptic Ribbon ◽  
Temporal Precision ◽  
Calcium Buffer ◽  
Synaptic Vesicle Exocytosis ◽  
Vesicle Exocytosis

Synaptic ribbons are classically associated with mediating indefatigable neurotransmitter release by sensory neurons that encode persistent stimuli. Yet when hair cells lack anchored ribbons, the temporal precision of vesicle fusion and auditory nerve discharges are degraded. A rarified statistical model predicted increasing precision of first-exocytosis latency with the number of readily releasable vesicles. We developed an experimentally constrained biophysical model to test the hypothesis that ribbons enable temporally precise exocytosis by increasing the readily releasable pool size. Simulations of calcium influx, buffered calcium diffusion, and synaptic vesicle exocytosis were stochastic (Monte Carlo) and yielded spatiotemporal distributions of vesicle fusion consistent with experimental measurements of exocytosis magnitude and first-spike latency of nerve fibers. No single vesicle could drive the auditory nerve with requisite precision, indicating a requirement for multiple readily releasable vesicles. However, plasmalemma-docked vesicles alone did not account for the nerve's precision—the synaptic ribbon was required to retain a pool of readily releasable vesicles sufficiently large to statistically ensure first-exocytosis latency was both short and reproducible. The model predicted that at least 16 readily releasable vesicles were necessary to match the nerve's precision and provided insight into interspecies differences in synaptic anatomy and physiology. We confirmed that ribbon-associated vesicles were required in disparate calcium buffer conditions, irrespective of the number of vesicles required to trigger an action potential. We conclude that one of the simplest functions ascribable to the ribbon—the ability to hold docked vesicles at an active zone—accounts for the synapse's temporal precision.

scholarly journals Tonic Activation of Extrasynaptic NMDA Receptors Decreases Intrinsic Excitability and Promotes Bistability in a Model of Neuronal Activity

2019 ◽  
Vol 21 (1) ◽  
pp. 206
Author(s):  
David Gall ◽  
Geneviève Dupont
Keyword(s):  
Potassium Channels ◽  
Electrical Activity ◽  
Nmda Receptors ◽  
Neuronal Activity ◽  
Neuronal Excitability ◽  
Calcium Influx ◽  
Tonic Activity ◽  
Stimulus Interval ◽  
Simple Description ◽  
Calcium Activated Potassium Channels

NMDA receptors (NMDA-R) typically contribute to excitatory synaptic transmission in the central nervous system. While calcium influx through NMDA-R plays a critical role in synaptic plasticity, experimental evidence indicates that NMDAR-mediated calcium influx also modifies neuronal excitability through the activation of calcium-activated potassium channels. This mechanism has not yet been studied theoretically. Our theoretical model provides a simple description of neuronal electrical activity that takes into account the tonic activity of extrasynaptic NMDA receptors and a cytosolic calcium compartment. We show that calcium influx mediated by the tonic activity of NMDA-R can be coupled directly to the activation of calcium-activated potassium channels, resulting in an overall inhibitory effect on neuronal excitability. Furthermore, the presence of tonic NMDA-R activity promotes bistability in electrical activity by dramatically increasing the stimulus interval where both a stable steady state and repetitive firing can coexist. These results could provide an intrinsic mechanism for the constitution of memory traces in neuronal circuits. They also shed light on the way by which β -amyloids can alter neuronal activity when interfering with NMDA-R in Alzheimer’s disease and cerebral ischemia.

Effects of isoquinolonesulfonamides on action potential secretion coupling in pituitary cells

2010 ◽  
Vol 1 (1) ◽  
Author(s):  
Marko A. Popovic ◽  
Stanko S. Stojilkovic ◽  
Arturo E. Gonzalez-Iglesias
Keyword(s):  
Protein Kinase ◽  
Electrical Activity ◽  
Protein Kinases ◽  
Cyclic Nucleotide ◽  
Calcium Influx ◽  
Pituitary Cells ◽  
Prolactin Release ◽  
Dependent Protein Kinase ◽  
Voltage Gated ◽  
Dependent Protein

Abstract: Pituitary lactotrophs fire action potentials spontaneously and the associated voltage-gated calcium influx is sufficient to maintain high and steady prolactin release. Several intracellular proteins can mediate the action of calcium influx on prolactin secretion, including calmodulin-dependent protein kinases. Here, we studied effects of isoquinolonesulfonamides KN-62 and KN-93, calmodulin-dependent protein kinase inhibitors, and KN-92, an inactive analog, on spontaneous electrical activity, voltage-gated calcium influx, cyclic nucleotide production, and basal prolactin release.: The effects of these compounds on electrical activity and calcium signaling was measured in single lactotrophs and cyclic nucleotide production and prolactin release were determined in static culture and perifusion experiments of anterior pituitary cells from postpubertal female rats.: KN-62 and KN-93 blocked basal prolactin release in a dose- and time-dependent manner, suggesting that calmodulin-dependent protein kinase could mediate the coupling of electrical activity and secretion. However, a similar effect on basal prolactin release was observed on application of KN-92, which does not inhibit this kinase. KN-93 also inhibited cAMP and cGMP production, but inhibition of prolactin release was independent of the status of cyclic nucleotide production. Single cell measurements revealed abolition of spontaneous and depolarization-induced electrical activity and calcium transients in KN-92/93-treated cells, with a time course comparable to that observed in secretory studies.: The results suggest that caution should be used when interpreting data from studies using isoquinolonesulfonamides to evaluate the role of calmodulin-dependent protein kinases in excitable endocrine cells, because inactive compounds exhibit comparable effects on action potential secretion coupling to those of active compounds.

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