Analysis of changes in duration of action potential of myocardial cells during local anaphylactic reaction and in response to histamine in guinea pigs

1978 ◽  
Vol 85 (3) ◽  
pp. 348-351
Author(s):  
V. B. Ignat'eva
Keyword(s):  
Action Potential ◽  
Anaphylactic Reaction ◽  
Guinea Pigs ◽  
Myocardial Cells ◽  
Duration Of Action

scholarly journals The effect of temperature on spontaneous action potential discharge of the isolated sinus venosus from winter and summer plaice (Pleuronectes platessa)

1995 ◽  
Vol 198 (1) ◽  
pp. 137-140 ◽  
Author(s):  
A A Harper ◽  
I P Newton ◽  
P W Watt
Keyword(s):  
Action Potential ◽  
Discharge Rate ◽  
Cardiac Pacemaker ◽  
Intrinsic Rate ◽  
Effect Of Temperature ◽  
Pacemaker Activity ◽  
Duration Of Action ◽  
Diastolic Depolarization ◽  
Significant Difference

The spontaneous cardiac pacemaker activity and conformation were recorded in vitro, using intracellular recording methods, from heart tissue of summer- and winter-caught plaice. The effects of changing temperature on the pacemaker rate, duration of action potential and diastolic depolarization were investigated by altering the temperature of the superfusing medium. The resting intrinsic rate of discharge was significantly greater in pacemaker cells from winter plaice (P=0.05), but there was no significant difference between winter and summer fish in the apparent Arrhenius activation energies for this process. However, there was a significant difference in the estimated intercept, indicating a thermal shift in the processes underlying the spontaneous pacemaker rhythm. There was no significant difference in the diastolic depolarization duration recorded from winter and summer fish over the temperature range 4­22 °C. The major effect of previous environmental temperature was on the duration of the action potential (P<0.02), indicating that the observed changes in pacemaker discharge rate were not influenced by the processes that determine the duration of the pacemaker diastolic depolarisation but were modulated by the channel events that give rise to the action potential.

Inhibition of Zn2+-induced potentiation of twitch tension by Ni2+ in frog muscle

1986 ◽  
Vol 64 (5) ◽  
pp. 625-630
Author(s):  
Toshiharu Oba ◽  
Ken Hotta
Keyword(s):  
Action Potential ◽  
Inhibitory Action ◽  
Channel Blocker ◽  
Rana Catesbeiana ◽  
Muscle Fibers ◽  
Frog Muscle ◽  
Duration Of Action ◽  
Ringer’S Solution ◽  
Mechanical Threshold ◽  
T Tubules

Effect of Ni2+ on Zn2+-induced potentiation of twitch tension was studied electrophysiologically in the toe muscle fibers of Rana catesbeiana. The major findings of this investigation are as follows. When 2 mM Ni2+ was applied to fibers in a normal Ringer's solution containing 50 μM Zn2+ (Zn2+ solution), the Zn2+-potentiated twitch tension decreased remarkably to about one-third of that before Ni2+ treatment. This concentration of Ni2+ caused a 23% decrease in the duration of action potential which had been prolonged by Zn2+ (6.61–5.09 ms). Ni2+ (2 mM) added to normal Ringer's solution led to increases of about 30 and 42% in twitch tension and in the duration of action potential, respectively. A slight increase in the mechanical threshold was induced by 2 mM Ni2+. The inhibitory action of Ni2+ on the twitch tension in Zn2+ solution was larger than that in the case of tetanus tension. Diltiazem (40 μM), aCa2+ channel blocker, did not inhibit the twitch tension potentiated in Zn2+ solution. These results suggest that the decrease in Zn2+-potentiated twitch tension by Ni2+ may possibly derive from impairment of the propagation of action potential along the T tubules.

scholarly journals Enhancement of GABAA receptor-mediated conductances induced by nerve injury in a subclass of sensory neurons

1995 ◽  
Vol 74 (2) ◽  
pp. 673-683 ◽  
Author(s):  
A. A. Oyelese ◽  
D. L. Eng ◽  
G. B. Richerson ◽  
J. D. Kocsis
Keyword(s):  
Action Potential ◽  
Nerve Injury ◽  
Action Potential Duration ◽  
Action Potentials ◽  
Resting Potential ◽  
Drg Neurons ◽  
Duration Of Action ◽  
Whole Cell ◽  
The Mean ◽  
Large Neurons

1. The effects of axotomy on the electrophysiologic properties of adult rat dorsal root ganglion (DRG) neurons were studied to understand the changes in excitability induced by traumatic nerve injury. Nerve injury was induced in vivo by sciatic nerve ligation with distal nerve transection. Two to four weeks after nerve ligation, a time when a neuroma forms, lumbar (L4 and L5) DRG neurons were removed and placed in short-term tissue culture. Whole cell patch-clamp recordings were made 5–24 h after plating. 2. DRG neurons were grouped into large (43–65 microns)-, medium (34–42 microns)-, and small (20–32 microns)- sized classes. Large neurons had short duration action potentials with approximately 60% having inflections on the falling phase of their action potentials. In contrast, action potentials of medium and small neurons were longer in duration and approximately 68% had inflections. 3. Pressure microejection of gamma-aminobutyric acid (GABA, 100 microM) or muscimol (100 microM) onto voltage-clamped DRG neurons elicited a rapidly desensitizing inward current that was blocked by 200 microM bicuculline. To measure the peak conductance induced by GABA or muscimol, neurons were voltage-clamped at a holding potential of -60 mV, and pulses to -80 mV and -100 mV were applied at a rate of 2.5 or 5 Hz during drug application. Slope conductances were calculated from plots of whole cell current measured at each of these potentials. 4. GABA-induced currents and conductances of control DRG neurons increased progressively with cell diameter. The mean GABA conductance was 36 +/- 10 nS (mean +/- SE) in small neurons, 124 +/- 21 nS in medium neurons, and 527 +/- 65 nS in large neurons. 5. After axotomy, medium neurons had significantly larger GABA-induced conductances compared with medium control neurons (390 +/- 50 vs. 124 +/- 21; P < 0.001). The increase in GABA conductance of medium neurons was associated with a decrease in duration of action potentials. In contrast, small neurons had no change in GABA conductance or action potential duration after ligation. The GABA conductance of large control neurons was highly variable, and ligation resulted in an increase that was significant only for neurons > 50 microns. The mean action potential duration in large neurons was not significantly changed, but neurons with inflections on the falling phase of the action potential were less common after ligation. There was no difference in resting potential or input resistance between control and ligated groups, except that the resting potential was less negative in small cells after axotomy.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Different Densities of Na-Ca Exchange Current in T-Tubular and Surface Membranes and Their Impact on Cellular Activity in a Model of Rat Ventricular Cardiomyocyte

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
M. Pásek ◽  
J. Šimurda ◽  
G. Christé
Keyword(s):  
Action Potential ◽  
Transport Systems ◽  
Duration Of Action ◽  
Rat Cardiomyocytes ◽  
Adult Rat ◽  
Before And After ◽  
Action Potential Waveform ◽  
Intracellular Ca ◽  
Tubular Membranes ◽  
Potential Waveform

The ratio of densities of Na-Ca exchanger current (INaCa) in the t-tubular and surface membranes (INaCa-ratio) computed from the values ofINaCaand membrane capacitances (Cm) measured in adult rat ventricular cardiomyocytes before and after detubulation ranges between 1.7 and 25 (potentially even 40). Variations of action potential waveform and of calcium turnover within this span of theINaCa-ratio were simulated employing previously developed model of rat ventricular cell incorporating separate description of ion transport systems in the t-tubular and surface membranes. The increase ofINaCa-ratio from 1.7 to 25 caused a prolongation of APD (duration of action potential at 90% repolarisation) by 12, 9, and 6% and an increase of peak intracellular Ca2+transient by 45, 19, and 6% at 0.1, 1, and 5 Hz, respectively. The prolonged APD resulted from the increase ofINaCadue to the exposure of a larger fraction of Na-Ca exchangers to higher Ca2+transients under the t-tubular membrane. The accompanying rise of Ca2+transient was a consequence of a higher Ca2+load in sarcoplasmic reticulum induced by the increased Ca2+cycling between the surface and t-tubular membranes. However, the reason for large differences in theINaCa-ratio assessed from measurements in adult rat cardiomyocytes remains to be explained.

The passive anaphylactic reaction in guinea pigs elicited by whole and cathepsin D-degraded antigen

1974 ◽  
Vol 19 (1) ◽  
pp. 71-78
Author(s):  
J. Štefanovič ◽  
D. Kotulová ◽  
L’. Bergendi ◽  
I. Huzuláková
Keyword(s):  
Anaphylactic Reaction ◽  
Guinea Pigs ◽  
Cathepsin D

scholarly journals ALLERGIC IRRITABILITY

1928 ◽  
Vol 47 (3) ◽  
pp. 437-448 ◽  
Author(s):  
Paul A. Lewis ◽  
Dorothy Loomis
Keyword(s):  
Anaphylactic Reaction ◽  
Antibody Production ◽  
Guinea Pigs ◽  
Natural Resistance ◽  
Experimental Result ◽  
Second Phase ◽  
Reaction Complex

The allergic irritability of closely inbred guinea pigs as represented by their capacity to produce hemolytic antibodies for beef and sheep corpuscles, and agglutinins for Bacillus typhosus and Bacillus abortus (Bang) differs by families and therefore is at least partly dependent on inherited characteristics. These differences show an imperfect but suggestive correlation with the differences in resistance of the same families to inoculation tuberculosis as previously determined by Wright and Lewis. The differences in antibody production also show an imperfect correlation with the differences in response in the anaphylactic reaction complex as previously determined by Lewis and Loomis. These studies suggest very strongly that the allergic irritability is one of the several inheritable characters which form a partial basis for the natural resistance to tuberculosis. The antibody-producing capacity is only satisfactorily defined when minimal or moderate amounts of antigen are used and this in single treatments. The irregularities in experimental result when repeated treatments or very large single treatments are used suggest that antibody production in the second or "acquired capacity" phase may rest on a somewhat different fundamental basis than the latent or potential natural capacity. There is some very slight evidence that production in the second phase may also be influenced by inherited qualities.

Effects of Nimodipine on Quinine Ototoxicity

2003 ◽  
Vol 112 (2) ◽  
pp. 163-168 ◽  
Author(s):  
Kentaro Ochi ◽  
Hirotsugu Kinoshita ◽  
Hirohito Nishino ◽  
Mutsumi Kenmochi ◽  
Toru Ohashi
Keyword(s):  
Action Potential ◽  
Guinea Pigs ◽  
Round Window ◽  
Compound Action Potential ◽  
Simultaneous Administration ◽  
Quinine Hydrochloride ◽  
Click Train ◽  
Compound Action

The compound action potential (CAP) in response to a click train stimulus was recorded at the round window of guinea pigs. Administration of quinine hydrochloride (200 mg/kg) significantly elevated the CAP thresholds by 5 to 25 dB (p < .05), and the CAP waveform elicited by the click train stimulus was abnormal. The amplitude of the CAP elicited by the second click was bigger than that elicited by the first click. These changes may be caused by an abnormally broadened N1 response to the first click in the click train. In contrast, CAP waveforms elicited by the second and subsequent clicks appeared normal. After administration of nimodipine (2 mg/kg), the CAP thresholds and waveforms elicited by the click train stimulus were unchanged. Simultaneous administration of both quinine (200 mg/kg) and nimodipine (2 mg/kg) resulted in the same electrophysiological changes as those induced by quinine alone. These results suggest that nimodipine prevents neither the deterioration in the CAP nor the abnormal properties in the response to a click train stimulus.

Sign in / Sign up

Export Citation Format

Share Document