Effects of 5-Hydroxytryptamine on Action Potentials and on Contractile Force in the Ventricle of Dolabella Auricularia

1974 ◽  
Vol 61 (2) ◽  
pp. 529-539
Author(s):  
ROBERT B. HILL
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Entire Range ◽  
Contractile Force ◽  
Cardiac Action Potential ◽  
Force Of Contraction ◽  
Plateau Phase ◽  
Cardiac Action ◽  
Dolabella Auricularia

1. Concentrations of 5-hydroxytryptamine from 10-8 to 10-5M had the effect of starting quiescent ventricles, with a slow slight depolarization followed by the onset of beating, with hyperpolarization between beats. 2. Concentrations of 5-hydroxytryptamine from 10-7 to 10-3M had the effect of prolonging the cardiac action potential and increasing force. Over the entire range, an increase in concentration led to an increase in the duration and amplitude of the plateau phase of the action potential, and an increase in force of contraction.

Effects of Acetylcholine on Resting and Action Potentials, and on Contractile Force in the Ventricle Of Dolabella Auricularia

1974 ◽  
Vol 61 (3) ◽  
pp. 629-637
Author(s):  
ROBERT B. HILL
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Contractile Force ◽  
Inotropic Effect ◽  
Cardiac Action Potential ◽  
Cardiac Action ◽  
Dolabella Auricularia ◽  
Isolated Ventricle

Acetylcholine (2x10-8 to 2x10-3 M depolarized the isolated ventricle of Dolabella auricularia. The depolarization was accompanied by a negatively inotropic effect from 2x10-8 M to 2x10-4 M, and by a positively tonotropic effect from 2x10-4 M to 2x10-3 M. The interaction of acetylcholine and 5-hydroxytryptamine was studied by artificially prolonging the plateau of the cardiac action potential by treatment with 5-HT. Acetylcholine had the effect of shortening the plateau established by 5-hydroxytryptamine. Force was reduced correspondingly.

AN ANALYSIS OF CONTROL OF THE VENTRICLE OF THE MOLLUSC MERCENARIA MERCENARIA

1993 ◽  
Vol 179 (1) ◽  
pp. 47-61
Author(s):  
C. L. Devlin
Keyword(s):  
Action Potential ◽  
Mercenaria Mercenaria ◽  
Lanthanum Chloride ◽  
Cardiac Action Potential ◽  
Extracellular Potassium ◽  
Plateau Phase ◽  
Progressive Reduction ◽  
Barium Ions ◽  
Cardiac Action ◽  
Ionophore Monensin

During spontaneous beating (autorhythmicity) in the bivalve ventricle, the cardiac action potential (AP) was generated by calcium (Ca2+) and sodium (Na+) influx. The initial fast rising phase (the ‘spike’) of the cardiac AP was dependent on extracellular Ca2+ concentration, whereas the slow plateau phase was Na+-dependent. The initial fast rising phase of the cardiac AP was abolished by treatment with a Ca2+-free saline or inorganic Ca2+ entry blockers, such as lanthanum chloride or cobalt. Conversely, this fast rising phase of the AP was potentiated by treatment with barium ions, the dihydropyridine-sensitive Ca2+ channel agonist Bay K 8644 or, unexpectedly, by the organic Ca2+ entry blocker diltiazem. The force of systolic beating was directly proportional to the amplitude of the fast rising phase of the cardiac AP. The Ca2+-dependent, fast rising phase of the AP was modulated by the level of extracellular Na+. Both the amplitude of the fast rising phase of the AP and coupled systolic force were increased by progressive reduction of extracellular Na+ concentration. The slow plateau phase was abolished by treatment with a Na+-free saline and potentiated by the Na+ ionophore monensin. The size of the Na+-dependent plateau was modulated by the level of extracellular Ca2+. When extracellular Ca2+ was removed from the bathing saline, both the amplitude and duration of the plateau phase were increased. Conversely, restoring extracellular Ca2+ to physiological levels decreased the size of the Na+-dependent plateau. Autorhythmicity was dependent on the level of extracellular potassium. In the absence of K+, neither a Ca2+-dependent fast rising phase nor a Na+-dependent plateau phase was recorded.

Components of the cardiac action potential

1962 ◽  
Vol 203 (2) ◽  
pp. 258-260 ◽  
Author(s):  
T. Hoshiko ◽  
Nick Sperelakis
Keyword(s):  
Action Potential ◽  
Slow Wave ◽  
Action Potentials ◽  
The Other ◽  
Cardiac Action Potential ◽  
Intercalated Disc ◽  
Ringer’S Solution ◽  
Current Pulses ◽  
Cardiac Action ◽  
Intracellular Action

Two components have been observed in the intracellular action potentials of frog ventricular strips under conditions of impaired transmission. The strips were bathed in Ca-free, Mg Ringer's solution and were subjected to passage of current pulses through their length. Under these conditions a "notch" gradually developed at the beginning of the plateau and separated the action potential into a spike and a slow wave. In any given cell, the notch was often more prominent when the conditioned strip was stimulated from one end than from the other. Occasionally a spike in isolation spontaneously alternated with a spike plus slow wave response. The slow waves were generally graded in duration and magnitude with stimulus intensity or duration. The results are discussed in terms of a possible junctional response at the intercalated disc.

SIMPLE EXPERIMENTS TO UNDERSTAND THE IONIC ORIGINS AND CHARACTERISTICS OF THE VENTRICULAR CARDIAC ACTION POTENTIAL

2002 ◽  
Vol 26 (3) ◽  
pp. 185-194 ◽  
Author(s):  
Jean-Yves Le Guennec ◽  
Christophe Vandier ◽  
Gilles Bedfer
Keyword(s):  
Action Potential ◽  
Electrical Activity ◽  
Voltage Clamp ◽  
Undergraduate Students ◽  
Papillary Muscle ◽  
Action Potentials ◽  
Heart Function ◽  
Cardiac Action Potential ◽  
Extracellular Potassium ◽  
Cardiac Action

Electrophysiological experiments are helpful for students to understand the role of electrical activity in heart function. Papillary muscle, which belongs to the ventricle, offers the advantage of being easily studied using glass microelectrodes. In addition, there is commercially available software that simulates ventricular electrical activity and can help overcome some difficulties, such as voltage clamp experiments, which need expensive apparatus when used for studies on living preparations. Here, we present a class practical session that is taken by undergraduate students at our University. In the first part of this class, students record action potentials from papillary muscles with the use of glass microelectrodes, and they change extracellular conditions to study the ionic basis of the action potential. In the second part of the class, students simulate action potentials using the Oxsoft Heart model (v. 4.0) and model their previous experiments on papillary muscle to quantify the effects. In particular, the model is very helpful in promoting understanding of the effect that extracellular potassium has on cardiac action potential by simulating voltage clamp experiments. This twin approach of papillary muscle experiments and computer modeling leads to a good understanding of the functioning of the action potential and can help introduce discussion of some abnormal cardiac functioning.

scholarly journals Stochastic pacing reveals the propensity to cardiac action potential alternans and uncovers its underlying dynamics

2016 ◽  
Vol 594 (9) ◽  
pp. 2537-2553 ◽  
Author(s):  
Yann Prudat ◽  
Roshni V. Madhvani ◽  
Marina Angelini ◽  
Nils P. Borgstom ◽  
Alan Garfinkel ◽  
...  
Keyword(s):  
Action Potential ◽  
Cardiac Action Potential ◽  
Cardiac Action
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