Adrenergic potentiation on spontaneous activity of canine paranodal fibers

1984 ◽  
Vol 247 (3) ◽  
pp. H415-H421
Author(s):  
W. W. Tse
Keyword(s):  
Spontaneous Activity ◽  
Tricuspid Valve ◽  
Action Potentials ◽  
Smooth Transition ◽  
Convex Side ◽  
Av Node ◽  
Junctional Tachycardia ◽  
His Bundle ◽  
Spontaneous Rate

The present study, using in vitro preparations, was designed to determine the anatomic, histological, and automatic properties of canine paranodal fibers. This tissue, together with the atrioventricular (AV) node and His bundle, constituted the three major tissues in the AV junction. The fascicles of the paranodal fibers ran parallel and adjacent to the base of the septal cusp of the tricuspid valve. The distal end of the paranodal fibers joined the lower half of the compact AV node on its convex side. Paranodal fibers when isolated were able to initiate spontaneous activity. Action potentials of many of these fibers showed primary pacemaker characteristics, i.e., a prominent phase 4 depolarization and smooth transition from phases 4 to 0. In 14 preparations, epinephrine (2.0 micrograms injected into the tissue bath) potentiated spontaneous rates to 144 +/- 6.0 beats/min from 61 +/- 5.0, an increase of 136%. Also, under the influence of epinephrine, paranodal fibers consistently generated a spontaneous rate higher than that of the AV node or His bundle, whether they were functionally connected or separated. These findings provide a basis for explaining the junctional tachycardia that occurs under adrenergic influence and demonstrate the presence of three major automatic tissues: the paranodal fibers, AV node, and His bundle in the canine AV junction.

Effect of epinephrine on automaticity of the canine atrioventricular node

1975 ◽  
Vol 229 (1) ◽  
pp. 34-37 ◽  
Author(s):  
WW Tse
Keyword(s):  
Action Potentials ◽  
Present Experiment ◽  
Atrioventricular Node ◽  
Smooth Transition ◽  
Av Node ◽  
Single Fibers ◽  
His Bundle ◽  
Transmembrane Potentials ◽  
Spontaneous Rate ◽  
Microelectrode Techniques

Effects of epinephrine on the automaticity of canine AV nodal fibers were studied on spontaneously beating AV node-His bundle preparations. Transmembrane potentials of single fibers of the AV node or His bundle were recorded with microelectrode techniques. Action potentials of most AV nodal fibers were characterized by steep phase-4 depolarization and smooth transition from phases 4 to 0. Epinephrine (0.1-0.2 mug/ml) increased the spontaneous rate of the AV nodal fibers. The slope of phase 4 depolarization was increased and the threshold shifted to a more negative level. These changes probably accounted for the increase in the automaticity of the node. Also, in the presence of epinephrine, the pacemaker of the preparation was consistently located at the AV node had a higher degree of automaticity than the His bundle. The findings of the present experiment, therefore, further support the view that the AV node is automatic.

Stretch of mammalian nerve in vitro: Effect on compound action potentials

2000 ◽  
Vol 5 (4) ◽  
pp. 227-235 ◽  
Author(s):  
Sidney Ochs ◽  
Rahman Pourmand ◽  
Kenan Si ◽  
Richard N. Friedman
Keyword(s):  
Action Potentials ◽  
Compound Action Potentials ◽  
Vitro Effect ◽  
Mammalian Nerve ◽  
Compound Action

scholarly journals Extracellular detection of neuronal coupling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Elmer Guzman ◽  
Zhuowei Cheng ◽  
Paul K. Hansma ◽  
Kenneth R. Tovar ◽  
Linda R. Petzold ◽  
...  
Keyword(s):  
Action Potentials ◽  
Microelectrode Arrays ◽  
Short Latency ◽  
Spike Sorting ◽  
Neuronal Connectivity ◽  
Direct Stimulation ◽  
Multiple Electrodes

AbstractWe developed a method to non-invasively detect synaptic relationships among neurons from in vitro networks. Our method uses microelectrode arrays on which neurons are cultured and from which propagation of extracellular action potentials (eAPs) in single axons are recorded at multiple electrodes. Detecting eAP propagation bypasses ambiguity introduced by spike sorting. Our methods identify short latency spiking relationships between neurons with properties expected of synaptically coupled neurons, namely they were recapitulated by direct stimulation and were sensitive to changing the number of active synaptic sites. Our methods enabled us to assemble a functional subset of neuronal connectivity in our cultures.

scholarly journals A predictive in vitro risk assessment platform for pro-arrhythmic toxicity using human 3D cardiac microtissues

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Celinda M. Kofron ◽  
Tae Yun Kim ◽  
Fabiola Munarin ◽  
Arvin H. Soepriatna ◽  
Rajeev J. Kant ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Action Potentials ◽  
Induced Pluripotent Stem Cell ◽  
Human Action ◽  
Environmental Toxicants ◽  
Pharmaceutical Drugs ◽  
Industrial Chemicals ◽  
Endocrine Disrupting Chemical

AbstractCardiotoxicity of pharmaceutical drugs, industrial chemicals, and environmental toxicants can be severe, even life threatening, which necessitates a thorough evaluation of the human response to chemical compounds. Predicting risks for arrhythmia and sudden cardiac death accurately is critical for defining safety profiles. Currently available approaches have limitations including a focus on single select ion channels, the use of non-human species in vitro and in vivo, and limited direct physiological translation. We have advanced the robustness and reproducibility of in vitro platforms for assessing pro-arrhythmic cardiotoxicity using human induced pluripotent stem cell-derived cardiomyocytes and human cardiac fibroblasts in 3-dimensional microtissues. Using automated algorithms and statistical analyses of eight comprehensive evaluation metrics of cardiac action potentials, we demonstrate that tissue-engineered human cardiac microtissues respond appropriately to physiological stimuli and effectively differentiate between high-risk and low-risk compounds exhibiting blockade of the hERG channel (E4031 and ranolazine, respectively). Further, we show that the environmental endocrine disrupting chemical bisphenol-A (BPA) causes acute and sensitive disruption of human action potentials in the nanomolar range. Thus, this novel human 3D in vitro pro-arrhythmic risk assessment platform addresses critical needs in cardiotoxicity testing for both environmental and pharmaceutical compounds and can be leveraged to establish safe human exposure levels.

Optical mapping of atrioventricular node reveals a conduction barrier between atrial and nodal cells

1998 ◽  
Vol 274 (3) ◽  
pp. H829-H845 ◽  
Author(s):  
Bum-Rak Choi ◽  
Guy Salama
Keyword(s):  
Action Potentials ◽  
Imaging Techniques ◽  
Atrioventricular Node ◽  
Small Cells ◽  
Av Node ◽  
Propagation Pattern ◽  
Voltage Sensitive Dyes ◽  
Decremental Conduction ◽  
Microelectrode Techniques ◽  
Av Delay

The mechanisms responsible for atrioventricular (AV) delay remain unclear, in part due to the inability to map electrical activity by conventional microelectrode techniques. In this study, voltage-sensitive dyes and imaging techniques were refined to detect action potentials (APs) from the small cells comprising the AV node and to map activation from the “compact” node. Optical APs (124) were recorded from 5 × 5 mm (∼0.5-mm depth) AV zones of perfused rabbit hearts stained with a voltage-sensitive dye. Signals from the node exhibited a set of three spikes; the first and third ( peaks I and III) were coincident with atrial (A) and ventricular (V) electrograms, respectively. The second spike ( peak II) represented the firing of midnodal (N) and/or lower nodal (NH) cell APs as indicated by their small amplitude, propagation pattern, location determined from superimposition of activation maps and histological sections of the node region, dependence on depth of focus, and insensitivity to tetrodotoxin (TTX). AV delays consisted of τ1 (49.5 ± 6.59 ms, 300-ms cycle length), the interval between peaks I and II (perhaps AN to N cells), and τ2 (57.57 ± 5.15 ms), the interval between peaks II and III (N to V cells). The conductance time across the node was 10.33 ± 3.21 ms, indicating an apparent conduction velocity (ΘN) of 0.162 ± 0.02 m/s ( n = 9) that was insensitive to TTX. In contrast, τ1 correlated with changes in AV node delays (measured with surface electrodes) caused by changes in heart rate or perfusion with acetylcholine. The data provide the first maps of activation across the AV node and demonstrate that ΘN is faster than previously presumed. These findings are inconsistent with theories of decremental conduction and prove the existence of a conduction barrier between the atrium and the AV node that is an important determinant of AV node delay.

scholarly journals Synaptically triggered action potentials begin as a depolarizing ramp in rat hippocampal neurones in vitro.

1992 ◽  
Vol 453 (1) ◽  
pp. 663-687 ◽  
Author(s):  
G Y Hu ◽  
O Hvalby ◽  
J C Lacaille ◽  
B Piercey ◽  
T Ostberg ◽  
...  
Keyword(s):  
Action Potentials

Membrane resistance increases when automaticity develops in explanted rat heart cells

1990 ◽  
Vol 258 (1) ◽  
pp. H145-H152 ◽  
Author(s):  
O. F. Schanne ◽  
M. Lefloch ◽  
B. Fermini ◽  
E. Ruiz-Petrich
Keyword(s):  
Spontaneous Activity ◽  
Action Potentials ◽  
Ventricular Myocytes ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Resting Potential ◽  
Heart Cells ◽  
Membrane Capacity ◽  
Rat Heart Cells ◽  
Specific Membrane

We compared the passive electrical properties of isolated ventricular myocytes (resting potential -65 mV, fast action potentials, and no spontaneous activity) with those of 2- to 7-day-old cultured ventricle cells from neonatal rats (resting potential -50 mV, slow action potentials, and presence of spontaneous activity). In myocytes the specific membrane capacity was 0.99 microF/cm2, and the specific membrane resistance increased from 2.46 k omega.cm2 at -65 mV to 7.30 k omega.cm2 at -30 mV. In clusters, the current-voltage relationships measured under current-clamp conditions showed anomalous rectification and the input resistance decreased from 1.05 to 0.48 M omega when external K+ concentration was increased from 6 to 100 mM. Using the model of a finite disk we determined the specific membrane resistance (12.9 k omega.cm2), the effective membrane capacity (17.8 microF/cm2), and the lumped resistivity of the disk interior (1,964 omega.cm). We conclude that 1) the voltage dependence of the specific membrane resistance cannot completely explain the membrane resistance increase that accompanies the appearance of spontaneous activity; 2) a decrease of the inwardly rectifying conductance (gk1) is mainly responsible for the increase in the specific membrane resistance and depolarization; and 3) approximately 41% of the inward-rectifying channels are electrically silent when spontaneous activity develops in explanted ventricle cells.

Single-unit recordings of arterial chemoreceptors from mouse petrosal ganglia in vitro

2000 ◽  
Vol 88 (4) ◽  
pp. 1489-1495 ◽  
Author(s):  
David F. Donnelly ◽  
Ricardo Rigual
Keyword(s):  
Mouse Model ◽  
Carotid Body ◽  
Unit Activity ◽  
Action Potentials ◽  
Single Unit ◽  
Gene Deletions ◽  
Suction Electrode ◽  
Single Unit Recordings ◽  
Unit Action

A preparation was developed that allows for the recording of single-unit chemoreceptor activity from mouse carotid body in vitro. An anesthetized mouse was decapitated, and each carotid body was harvested, along with the sinus nerve, glossopharyngeal nerve, and petrosal ganglia. After exposure to collagenase/trypsin, the cleaned complex was transferred to a recording chamber where it was superfused with oxygenated saline. The ganglia was searched for evoked or spontaneous unit activity by using a glass suction electrode. Single-unit action potentials were 57 ± 10 (SE) ( n = 16) standard deviations above the recording noise, and spontaneous spikes were generated as a random process. Decreasing superfusate[Formula: see text] to near 20 Torr caused an increase in spiking activity from 1.3 ± 0.4 to 14.1 ± 1.9 Hz ( n = 16). The use of mice for chemoreceptor studies may be advantageous because targeted gene deletions are well developed in the mouse model and may be useful in addressing unresolved questions regarding the mechanism of chemotransduction.

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