scholarly journals Dependence of Transient and Residual Calcium Dynamics on Action-Potential Patterning during Neuropeptide Secretion

2000 ◽  
Vol 20 (18) ◽  
pp. 6773-6780 ◽  
Author(s):  
Martin Muschol ◽  
B. M. Salzberg
Keyword(s):  
Action Potential ◽  
Calcium Dynamics ◽  
Neuropeptide Secretion

Calcium Dynamics and Compartmentalization in Leech Neurons

2005 ◽  
Vol 94 (6) ◽  
pp. 4430-4440 ◽  
Author(s):  
Sofija Andjelic ◽  
Vincent Torre
Keyword(s):  
Information Processing ◽  
Action Potential ◽  
Action Potentials ◽  
Time Course ◽  
Ccd Camera ◽  
Calcium Dynamics ◽  
Single Action ◽  
Single Action Potential ◽  
Calcium Indicator ◽  
Mechanosensory Neurons

Calcium dynamics in leech neurons were studied using a fast CCD camera. Fluorescence changes (Δ F/ F) of the membrane impermeable calcium indicator Oregon Green were measured. The dye was pressure injected into the soma of neurons under investigation. Δ F/ F caused by a single action potential (AP) in mechanosensory neurons had approximately the same amplitude and time course in the soma and in distal processes. By contrast, in other neurons such as the Anterior Pagoda neuron, the Annulus Erector motoneuron, the L motoneuron, and other motoneurons, APs evoked by passing depolarizing current in the soma produced much larger fluorescence changes in distal processes than in the soma. When APs were evoked by stimulating one distal axon through the root, Δ F/ F was large in all distal processes but very small in the soma. Our results show a clear compartmentalization of calcium dynamics in most leech neurons in which the soma does not give propagating action potentials. In such cells, the soma, while not excitable, can affect information processing by modulating the sites of origin and conduction of AP propagation in distal excitable processes.

Activity-Related Calcium Dynamics in Motoneurons of the Nucleus Hypoglossus From Mouse

1999 ◽  
Vol 82 (6) ◽  
pp. 2936-2946 ◽  
Author(s):  
Mario B. Lips ◽  
Bernhard U. Keller
Keyword(s):  
Quantitative Analysis ◽  
Action Potential ◽  
Calcium Binding ◽  
Calcium Influx ◽  
Binding Capacity ◽  
Calcium Transients ◽  
Calcium Dynamics ◽  
The Brain

A quantitative analysis of activity-related calcium dynamics was performed in motoneurons of the nucleus hypoglossus in the brain stem slice preparation from mouse by simultaneous patch-clamp and microfluorometric calcium measurements. Motoneurons were analyzed under in vitro conditions that kept them in a functionally intact state represented by rhythmic, inspiratory-related bursts of excitatory postsynaptic currents and associated action potential discharges. Bursts of electrical activity were paralleled by somatic calcium transients resulting from calcium influx through voltage-activated calcium channels, where each action potential accounted for a calcium-mediated charge influx around 2 pC into the somatic compartment. Under in vivo conditions, rhythmic-respiratory activity in young mice occurred at frequencies up to 5 Hz, demonstrating the necessity for rapid calcium elevation and recovery in respiratory-related neurons. The quantitative analysis of hypoglossal calcium homeostasis identified an average extrusion rate, but an exceptionally low endogenous calcium binding capacity as cellular parameters accounting for rapid calcium signaling. Our results suggest that dynamics of somatic calcium transients 1) define an upper limit for the maximum frequency of respiratory-related burst discharges and 2) represent a potentially dangerous determinant of intracellular calcium profiles during pathophysiological and/or excitotoxic conditions.

scholarly journals Nonclassical Estrogen Modulation of Presynaptic GABA Terminals Modulates Calcium Dynamics in Gonadotropin-Releasing Hormone Neurons

Endocrinology ◽  
2008 ◽  
Vol 149 (11) ◽  
pp. 5335-5344 ◽  
Author(s):  
Nicola Romanò ◽  
Kiho Lee ◽  
István M. Ábrahám ◽  
Christine L. Jasoni ◽  
Allan E. Herbison
Keyword(s):  
Action Potential ◽  
Green Fluorescence Protein ◽  
Cell Voltage ◽  
Gaba Release ◽  
Calcium Dynamics ◽  
Gaba A ◽  
Transgenic Mouse Line ◽  
Gnrh Neurons ◽  
Regulatory Effects ◽  
Postsynaptic Calcium

There is increasing recognition that estrogen exerts multifaceted regulatory effects on GnRH neurons. The acute effects of estrogen on calcium dynamics in these cells were examined using a transgenic mouse line that allows real-time measurement of intracellular calcium concentration ([Ca2+]i) in GnRH neurons in the acute brain slice preparation. 17-β-Estradiol (E2) at 100 pm–100 nm was found to activate [Ca2+]i transients in approximately 40% of GnRH neurons with an approximate 15-min latency. This effect was not replicated by E2-BSA, which limits E2 action to the membrane, 17-α-estradiol, the inactive isomer at classical estrogen receptors (ERs), or G-1 the GPR30 agonist. E2 continued to activate [Ca2+]i transients when transcription was blocked. An ER α-selective agonist was equally potent in activating [Ca2+]i transients, and E2 remained effective in ERβ knockout × GnRH-Pericam mice. E2’s activation of [Ca2+]i transients continued in the presence of tetrodotoxin, which blocks action potential-dependent transmission, but was abolished completely by the further addition of a γ-aminobutyric acid (GABA)A receptor antagonist. Exogenous GABA was found to initiate [Ca2+]i transients in GnRH neurons. Whole cell, voltage-clamp recordings of GnRH-green fluorescence protein neurons revealed that E2 generated discrete bursts of miniature inhibitory postsynaptic currents with a latency of approximately 15 min. These observations provide evidence for a new mechanism of nonclassical estrogen action within the brain. Estrogen interacts with the classical ERα at the level of the GABAergic nerve terminal to regulate action potential-independent GABA release that, in turn, controls postsynaptic calcium dynamics.

Modeling action potential generation and propagation in NRK fibroblasts

2004 ◽  
Vol 287 (4) ◽  
pp. C851-C865 ◽  
Author(s):  
J. J. Torres ◽  
L. N. Cornelisse ◽  
E. G. A. Harks ◽  
W. P. M. van Meerwijk ◽  
A. P. R. Theuvenet ◽  
...  
Keyword(s):  
Action Potential ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Cell Transformation ◽  
Rat Kidney ◽  
Potassium Conductance ◽  
Calcium Dynamics ◽  
Starting Point ◽  
Release Analysis ◽  
Intracellular Calcium Dynamics

Normal rat kidney (NRK) fibroblasts change their excitability properties through the various stages of cell proliferation. The present mathematical model has been developed to explain excitability of quiescent (serum deprived) NRK cells. It includes as cell membrane components, on the basis of patch-clamp experiments, an inwardly rectifying potassium conductance ( GKir), an L-type calcium conductance ( GCaL), a leak conductance ( Gleak), an intracellular calcium-activated chloride conductance [ GCl(Ca)], and a gap junctional conductance ( Ggj), coupling neighboring cells in a hexagonal pattern. This membrane model has been extended with simple intracellular calcium dynamics resulting from calcium entry via GCaL channels, intracellular buffering, and calcium extrusion. It reproduces excitability of single NRK cells and cell clusters and intercellular action potential (AP) propagation in NRK cell monolayers. Excitation can be evoked by electrical stimulation, external potassium-induced depolarization, or hormone-induced intracellular calcium release. Analysis shows the roles of the various ion channels in the ultralong (∼30 s) NRK cell AP and reveals the particular role of intracellular calcium dynamics in this AP. We support our earlier conclusion (De Roos A, Willems PH, van Zoelen EJ, and Theuvenet AP. Am J Physiol Cell Physiol 273: C1900–C1907, 1997) that AP generation and propagation may act as a rapid mechanism for the propagation of intracellular calcium waves, thus contributing to fast intercellular calcium signaling. The present model serves as a starting point to further analyze excitability changes during contact inhibition and cell transformation.

scholarly journals Construction and use of a zebrafish heart voltage and calcium optical mapping system, with integrated electrocardiogram and programmable electrical stimulation

2015 ◽  
Vol 308 (9) ◽  
pp. R755-R768 ◽  
Author(s):  
Eric Lin ◽  
Calvin Craig ◽  
Marcel Lamothe ◽  
Marinko V. Sarunic ◽  
Mirza Faisal Beg ◽  
...  
Keyword(s):  
Action Potential ◽  
Action Potential Duration ◽  
Large Scale ◽  
Optical Mapping ◽  
Rate Dependence ◽  
P Wave ◽  
Calcium Dynamics ◽  
Mapping System ◽  
Electrical Stimulator ◽  
Zebrafish Heart

Zebrafish are increasingly being used as a model of vertebrate cardiology due to mammalian-like cardiac properties in many respects. The size and fecundity of zebrafish make them suitable for large-scale genetic and pharmacological screening. In larger mammalian hearts, optical mapping is often used to investigate the interplay between voltage and calcium dynamics and to investigate their respective roles in arrhythmogenesis. This report outlines the construction of an optical mapping system for use with zebrafish hearts, using the voltage-sensitive dye RH 237 and the calcium indicator dye Rhod-2 using two industrial-level CCD cameras. With the use of economical cameras and a common 532-nm diode laser for excitation, the rate dependence of voltage and calcium dynamics within the atrial and ventricular compartments can be simultaneously determined. At 140 beats/min, the atrial action potential duration was 36 ms and the transient duration was 53 ms. With the use of a programmable electrical stimulator, a shallow rate dependence of 3 and 4 ms per 100 beats/min was observed, respectively. In the ventricle the action potential duration was 109 ms and the transient duration was 124 ms, with a steeper rate dependence of 12 and 16 ms per 100 beats/min. Synchronous electrocardiograms and optical mapping recordings were recorded, in which the P-wave aligns with the atrial voltage peak and R-wave aligns with the ventricular peak. A simple optical pathway and imaging chamber are detailed along with schematics for the in-house construction of the electrocardiogram amplifier and electrical stimulator. Laboratory procedures necessary for zebrafish heart isolation, cannulation, and loading are also presented.

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