scholarly journals CHANGES IN A TRAIN OF ACTION POTENTIALS IN THE RABBIT ATRIUM AFTER A REST PERIOD: EFFECTS OF VARIOUSEXTERNAL MEDIA

1971 ◽  
Vol 21 (3) ◽  
pp. 251-263 ◽  
Author(s):  
Takehiko SAITO
Keyword(s):  
Action Potentials ◽  
Rest Period ◽  
Period Effects ◽  
Rabbit Atrium

Calcium antagonist blockade of slow action potentials in cultured chick heart cells

1983 ◽  
Vol 61 (9) ◽  
pp. 957-966 ◽  
Author(s):  
Tung Li ◽  
Nick Sperelakis
Keyword(s):  
Action Potentials ◽  
Rest Period ◽  
Independent Effect ◽  
Heart Cells ◽  
Maximal Effect ◽  
Response Curves ◽  
Dependent Component ◽  
Chick Heart ◽  
Kinetics Of ◽  
Slow Action Potentials

The effects of four Ca antagonists, bepridil, diltiazem, nifedipine, and verapamil, on slow channels were studied in cultured cell reaggregates prepared from 14-day-old chick embryonic, hearts. The cell membrane was partially depolarized to about −45 mV by using 22 mM KCl to inactivate the fast Na+ channels. Slow action potentials were induced by 10−6 M isoproterenol with electrical stimulation. Cumulative dose – response curves for the effect of the four drugs on the blocking of slow action potentials (using [Formula: see text] as the indicator) were analyzed by Hill plots. The dose values for 50% of maximal effect, at a stimulation frequency of 60/min, were (in order of decreasing potencies) as follows: 5.2 × 10−9 M for nifedipine, 3.1 × 10−7 M for diltiazem, 1.2 × 10−6 M for verapamil, and 5.1 × 10−6 M for bepridil. The effect of all four Ca antagonists showed use (or frequency)-dependency, i.e., the drugs were more effective at higher stimulation rates. This may reflect a blocking action of the drugs on the nonresting states of the channels and (or) a slowing of the recovery kinetics of the channels from the inactivated state back to the resting state. In a separate type of experiment utilizing a 5-min rest period in the presence of the drugs, nifedipine blocked and bepridil exhibited some depression of the first action potential elicited, i.e., use-independent effect, indicating that these drugs may also act on resting channels. Thus, these four Ca antagonists have a prominent use-dependent component in their actions, and one or two may also have a use-independent component.

Action of sex steroids on the electrical and mechanical properties of rat atrium

1963 ◽  
Vol 205 (1) ◽  
pp. 198-200 ◽  
Author(s):  
Alvaro L. Gimeno ◽  
Martha F. Gimeno ◽  
J. Leyden Webb
Keyword(s):  
Sex Steroids ◽  
Action Potentials ◽  
Mechanical Characteristics ◽  
Mechanical Activity ◽  
Cardiac Cell ◽  
Electrical Characteristics ◽  
Atrial Cells ◽  
Period Effects ◽  
Ionic Fluxes ◽  
Definite Effect

The simultaneous effects of estradiol, testosterone, and progesterone on the electrical and mechanical characteristics of atrial cells were examined. Intracellular potentials were determined using microelectrodes; the mechanical activity was recorded from a strain gauge. Testosterone from 10–6 to 10–5 m produced a marked stimulation in normally contracting atria; while similar concentrations of progesterone and estradiol produced only contractile depression. All three sex steroids exerted a definite effect on the electrical characteristics, namely a reduction in the rates of depolarization and repolarization, without altering the magnitudes of the resting or action potentials appreciably. As a result, there is an increase in the duration and area of the action potential. They also slowed the conduction rate and increased the latent period, effects presumably associated with the slowed depolarization. The marked reduction in the rates of depolarization and repolarization is believed to be due to decreases in the ionic fluxes brought about by reducing the ionic permeability of the cardiac cell membranes. The effects are similar to those produced by antidysrhythmic drugs and may explain certain observations on the relation of cardiac excitability to steroid levels.

Effect of Heart Rate Variability on Defensive Reaction and Eating Disorder Symptomatology in Chocolate Cravers

2009 ◽  
Vol 23 (3) ◽  
pp. 95-103 ◽  
Author(s):  
Sonia Rodríguez-Ruiz ◽  
Elisabeth Ruiz-Padial ◽  
Nieves Vera ◽  
Carmen Fernández ◽  
Lourdes Anllo-Vento ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Eating Disorder ◽  
Eating Behavior ◽  
Rest Period ◽  
Food Craving ◽  
Defensive Reaction ◽  
Relevant Role ◽  
Eating Disorder Symptomatology ◽  
Uncontrolled Eating

The study examines the effect of heart rate variability (HRV) on the cardiac defence response (CDR) and eating disorder symptomatology in chocolate cravers. Female chocolate cravers (n = 36) and noncravers (n = 36) underwent a psychophysiological test to assess their HRV during a 5-min rest period, followed by three trials to explore the CDR, elicited by an intense white noise, during the viewing of chocolate, neutral, and unpleasant pictures. After the test, participants completed a questionnaire to measure eating disorder symptomatology. The HRV was inversely related to the magnitude of the CDR and to eating disorder symptomatology in chocolate cravers. In addition, the HRV was inversely related to the magnitude of the CDR when viewing unpleasant pictures but not to neutral or chocolate ones, across all participants. These findings support the idea that poor autonomic regulation, indexed by low HRV, plays a relevant role in food craving and uncontrolled eating behavior.

Characteristics of action potentials in Helianthus annuus

1991 ◽  
Vol 83 (4) ◽  
pp. 601-604 ◽  
Author(s):  
Tadeusz Zawadzki ◽  
Eric Davies ◽  
Halina Dziubinska ◽  
Kazimierz Trebacz
Keyword(s):  
Helianthus Annuus ◽  
Action Potentials
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