The relationship between estimates of Ia-EPSP amplitude and conduction velocity in human soleus motoneurons

1993 ◽  
Vol 95 (2) ◽  
Author(s):  
Friedemann Awiszus ◽  
Helmut Feistner
Keyword(s):  
Conduction Velocity ◽  
Epsp Amplitude ◽  
Ia Epsp ◽  
The Relationship

scholarly journals Investigating two kinds of cellular alternans and corresponding TWA induced by impaired calcium cycling in myocardial ischemia

2021 ◽  
Vol 18 (6) ◽  
pp. 7648-7665
Author(s):  
Jiaqi Liu ◽  
◽  
Zhenyin Fu ◽  
Yinglan Gong ◽  
Ling Xia
Keyword(s):  
Myocardial Ischemia ◽  
Conduction Velocity ◽  
Ionic Channel ◽  
Calcium Cycling ◽  
One Dimensional ◽  
T Wave ◽  
Cell Simulation ◽  
T Wave Alternans ◽  
Dimensional Simulation ◽  
The Relationship

<abstract> <sec><title>Background</title><p>The utility of T wave alternans (TWA) in identifying arrhythmia risk has been demonstrated. During myocardial ischemia (MI), TWA could be induced by cellular alternans. However, the relationship between cellular alternans patterns and TWA patterns in MI has not been investigated thoroughly.</p> </sec> <sec><title>Methods</title><p>We set MI conditions to simulate alternans. Either prolonging Ca<sup>2+</sup> release or increasing spark-induced sparks (secondary sparks) can give rise to different patterns of APD alternans and TWA. In addition, different ischemic zones and reduced conduction velocity are also considered in one dimensional simulation.</p> </sec> <sec><title>Results</title><p>Delay of Ca<sup>2+</sup> release can produce discordant Ca<sup>2+</sup>-driven alternans in single cell simulation. Increasing secondary sparks leads to concordant alternans. Correspondingly, morphology and magnitude of TWA vary in two different cellular alternans. Epi ischemia results in alternans concentrating in the first half of T wave. Endo and transmural ischemia lead to fluctuations in the second half of T wave. In addition, slowing conduction velocity has no effect on TWA magnitude.</p> </sec> <sec><title>Conclusion</title><p>Specific ionic channel dysfunction and ischemic zones affect TWA patterns.</p> </sec> </abstract>

The Relationship between Local Conduction Velocity and Amplitude in Right Atrail Flutter Reentry

2011 ◽  
Vol 27 (Supplement) ◽  
pp. PE4_036
Author(s):  
Taihei Itoh ◽  
Shingo Sasaki ◽  
Masaomi Kimura ◽  
Owada Shingen ◽  
Horiuchi Daisuke ◽  
...  
Keyword(s):  
Conduction Velocity ◽  
The Relationship

Synaptic and intrinsic control of membrane excitability of neostriatal neurons. II. An in vitro analysis

1990 ◽  
Vol 63 (4) ◽  
pp. 663-675 ◽  
Author(s):  
P. Calabresi ◽  
N. B. Mercuri ◽  
G. Bernardi
Keyword(s):  
Membrane Potential ◽  
Tetanus Toxin ◽  
Reversal Potential ◽  
Membrane Potentials ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Membrane Excitability ◽  
Epsp Amplitude ◽  
The Relationship

1. The effects of intrinsic membrane properties on the spontaneous and synaptically evoked activity of neostriatal neurons were studied in an in vitro slice preparation with the use of intracellular recordings. The recorded neurons did not show spontaneous action potentials at rest; depolarizing current pulses triggered a tonic firing pattern. 2. Subthreshold spontaneous depolarizing potentials (SDPs) were observed in 52% of the recorded neurons. The amplitude of these potentials at rest ranged between 2 and 15 mV, and their duration between 4 and 100 ms. The frequency and the amplitude of the SDPs were functions of the membrane potential: membrane depolarization by constant positive current increased the frequency of the SDPs and reduced their amplitude; hyperpolarization of the membrane decreased their frequency and increased their amplitude. Often, at membrane potentials more negative than -90 mV, SDPs were completely suppressed. 3. SDPs were blocked by low calcium-cobalt containing solutions. In the presence of tetrodotoxin (TTX, 1-3 microM), SDPs were completely abolished in 50% of the tested neurons; in the remaining neurons, small (1-4 mV) TTX-resistant SDPs were observed. In most of the neurons, bicuculline (BIC, 10-100 microM) and low concentrations of tetanus toxin (5-10 micrograms/ml) did not clearly affect the SDPs. Higher concentrations of tetanus toxin (100 micrograms/ml) blocked the SDPs as well as the synaptic potentials evoked by intrastriatal stimulation. 4. At resting membrane potential, intrastriatal stimulation produced a fast depolarizing postsynaptic potential (EPSP) that was reduced by BIC (10-100 microM). The relationship between EPSP amplitude and membrane potential was studied either by utilizing K(+)-chloride electrodes or by the use of cesium-chloride electrodes. In both these cases, the reversal potential for the EPSPs was between 0 and -14 mV. In cesium-loaded neurons, the decrease of the EPSP, usually observed at negative membrane potentials (below -85 mV), was clearly reduced. Internal cesium prolonged the duration of the SDPs and the EPSPs evoked by intrastriatal stimulation. 5. The relationship between spontaneous and evoked synaptic activity and membrane potential was studied in the presence of different external potassium blockers. 4-Aminopyridine (4AP, 0.1-1 mM) increased the EPSP amplitude and the frequency of the SDPs, but did not decrease membrane rectification and the shunt of the EPSPs present at negative membrane potentials. On the contrary, rectification of the membrane and the shunt of the EPSPs below -85 mV were clearly reduced by tetraethylammonium (TEA, 10-20 mM).(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Interstitial volume modulates the conduction velocity-gap junction relationship

2012 ◽  
Vol 302 (1) ◽  
pp. H278-H286 ◽  
Author(s):  
Rengasayee Veeraraghavan ◽  
Mohamed E. Salama ◽  
Steven Poelzing
Keyword(s):  
Guinea Pig ◽  
Gap Junction ◽  
Conduction Velocity ◽  
Important Determinant ◽  
Cardiac Conduction ◽  
Cell Width ◽  
Interstitial Volume ◽  
Ventricular Tachycardias ◽  
The Relationship ◽  
Isolated Cell

Cardiac conduction through gap junctions is an important determinant of arrhythmia susceptibility. Yet, the relationship between degrees of Gj uncoupling and conduction velocity (θ) remains controversial. Conflicting results in similar experiments are normally attributed to experimental differences. We hypothesized that interstitial volume modulates conduction velocity and its dependence on Gj. Interstitial volume (VIS) was quantified histologically from guinea pig right ventricle. Optical mapping was used to quantify conduction velocity and anisotropy (ARθ). Albumin (4 g/l) decreased histologically assessed VIS, increased transverse θ by 71 ± 10%, and lowered ARθ. Furthermore, albumin did not change isolated cell size. Conversely, mannitol increased VIS, decreased transverse θ by 24 ± 4%, and increased ARθ. Mannitol also decreased cell width by 12%. Furthermore, mannitol was associated with spontaneous ventricular tachycardias in three of eight animals relative to zero of 15 during control. The θ-Gj relationship was assessed using the Gj uncoupler carbenoxolone (CBX). Whereas 13 μM CBX did not significantly affect θ during control, it slowed transverse θ by 38 ± 9% during mannitol (edema). These data suggest changes in VIS modulate θ, ARθ, and the θ-Gj relationship and thereby alter arrhythmia susceptibility. Therefore, VIS may underlie arrhythmia susceptibility, particularly in diseases associated with gap junction remodeling.

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