scholarly journals Electrophysiological Actions of Oxytocin on the Rabbit Myometrium

1969 ◽  
Vol 53 (6) ◽  
pp. 758-780 ◽  
Author(s):  
A. L. Kleinhaus ◽  
C. Y. Kao
Keyword(s):  
Maximum Rate ◽  
Resting Potential ◽  
Spike Amplitude ◽  
Electrode Recording ◽  
Pregnant Rabbit ◽  
Sucrose Gap ◽  
The Mean ◽  
Electrical Activities ◽  
Maximum Rate Of Rise ◽  
Duration Of Pregnancy

The electrical activities of myometrial cells of the pregnant rabbit uterus have been studied by means of sucrose-gap and intracellular micro-electrode recording techniques. The resting potential of the myometrial cell was about -50 mv, and it is unaffected by the duration of pregnancy or placental attachment. Action potentials of the myometrium, although dependent on external Na+, were not always of the regenerative type; preparations from nonparturient uteri often produce mainly small spikes. The mean spike amplitude was 35 mv, rising at a mean maximum rate of 3 v/sec. Oxytocin, in concentrations less than 500 µU/ml, increased the mean spike amplitude to 48 mv and the mean maximum rate of rise to 7 v/sec, without affecting the resting potential. The relation between membrane potential and dV/dt of the spike was steepened by oxytocin, suggesting that oxytocin increased the number of normally sparse sodium gates in the myometrial membrane. By this action, oxytocin is believed to increase the probability of successful regenerative spikes and thereby initiate electrical activity in quiescent preparations, increase the frequency of burst discharges, the number of spikes in each burst, and the amplitude of spikes in individual cells.

An opiate receptor on frog sciatic nerve axons

1979 ◽  
Vol 57 (10) ◽  
pp. 1171-1174 ◽  
Author(s):  
E. G. Hunter ◽  
G. B. Frank
Keyword(s):  
Sciatic Nerve ◽  
Action Potential ◽  
Maximum Rate ◽  
Opiate Receptor ◽  
Resting Potential ◽  
Amplitude Maximum ◽  
Gap Technique ◽  
Sucrose Gap ◽  
Frog Sciatic Nerve ◽  
Maximum Rate Of Rise

The effect of meperidine (3 × 10−4 M) on the action potential of frog sciatic nerve was examined by means of the double sucrose gap technique. Meperidine decreased the amplitude, maximum rate of depolarization, and maximum rate of repolarization of the action potential but had no effect on the resting potential. This depression in amplitude and maximum rate of rise was partially blocked by naloxone (1 × 10−8 M) while the maximum rate of depolarization was further depressed. The data suggest that the effect of meperidine is due to two mechanisms, a nonspecific local anaesthetic like effect and an opiate receptor mediated effect.

Altered excitability of goldfish mauthner cell following axotomy. I. Characterization and correlations with somatic and axonal morphological reactions

1986 ◽  
Vol 55 (6) ◽  
pp. 1424-1439 ◽  
Author(s):  
M. J. Titmus ◽  
D. S. Faber ◽  
S. J. Zottoli
Keyword(s):  
Cell Body ◽  
Initial Segment ◽  
Membrane Properties ◽  
Resting Potential ◽  
M Cells ◽  
M Cell ◽  
Spike Amplitude ◽  
Axon Hillock ◽  
The Mean ◽  
Lateral Dendrite

Axonal transection 7-10 mm distal to the cell body of the goldfish Mauthner (M) cell induced alterations in its excitability; namely, the antidromic spike recorded in the soma was converted from a single-component axon-hillock response to a larger amplitude, two-component impulse. The mean spike amplitude of the axotomized cells was approximately 50% greater (59.6 +/- 15.1 mV, n = 94) than that in controls (39.4 +/- 6.3 mV, n = 73). The onset of the induced increase in spike amplitude occurs at approximately 20 days postaxotomy, and the transition to a reactive spike is complete by approximately 30-35 days. Eighty-three percent of the M-cells axotomized for more than 30 days were physiologically reactive as judged by their large spike amplitudes and/or the presence of an additional spike component. Concomitant with the enhanced spike amplitudes, there was a depression of excitability in the initial segment-axon hillock region of the axotomized cells. This depression was suggested by a decrease in the initial segment (IS) spike height (from 39.4 +/- 6.3 mV, n = 73, in controls to 27.5 +/- 5.6 mV, n = 13, in axotomized cells), a decrease in its maximum rate of rise (from 153.6 +/- 24 V/s, n = 15, to 112.5 +/- 30 V/s, n = 29), and frequent failure of antidromic invasion into the initial segment and axon hillock. These changes in excitability could not be attributed to alterations in passive membrane properties, since the mean resting potential (77.8 +/- 5.2 mV, n = 37, control; 76.9 +/- 7.8 mV, n = 87, axotomized) and input resistance (170 +/- 21.3 K omega, n = 13, control; 176 +/- 26.6 K omega, n = 21, axotomized) were not altered significantly by axotomy. Threshold voltage was also unaffected (13.4 +/- 3.2 mV, n = 11, control; 11.9 +/- 2.5 mV, n = 11, axotomized). Sequential recordings of spike amplitudes from the axon hillock, soma, and lateral dendrite suggest that the generator of the axotomy-induced component is localized to the normally passive soma and proximal dendrite. In addition, the presumed soma-dendritic In addition, the presumed soma-dendritic component contributes very little if anything to the action potentials recorded in the axon. The onset and occurrence of alterations in excitability and cell body morphology (chromatolysis and nuclear associated changes) were compared in different M-cell populations and in the same identified M-cells. The comparisons suggested that these two events tend to occur in parallel.(ABSTRACT TRUNCATED AT 400 WORDS)

Microelectrode Study of the Resting and Action Potentials of the Cockroach Giant Axon with Special Reference to the Role Played by the Nerve Sheath

1967 ◽  
Vol 47 (2) ◽  
pp. 357-373
Author(s):  
Y. PICHON ◽  
J. BOISTEL
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Maximum Rate ◽  
Diffusion Processes ◽  
Extracellular Fluid ◽  
Giant Axon ◽  
Resting Potential ◽  
Giant Axons ◽  
The Mean ◽  
Nerve Cords

1. The use of very fine-tipped and mechanically strong microelectrodes has allowed reliable recordings of resting and action potentials to be made in cockroach giant axons in sheathed and desheathed nerve cords. 2. When the microelectrode was withdrawn from a giant axon in an intact connective the first positive change in the potential from the resting level, was in most cases followed by a negative deflexion to the original zero level, the ‘sheath potential’. The values of this ‘sheath potential’ together with the resting potential, the action potential, the maximum rate of rise and maximum rate of fall of the action potential have been measured in three different salines. 3. In normal saline, resting potentials were lower in sheathed preparations (58·1 ± 55·4 mV.) than in desheathed ones (67·4 ± 6·2 mV.), whereas action potentials were higher in the former (103±5·9 mV.) than in the latter (85·9±4·6 mV.). 4. Elevation of K+ and Ca2+ concentrations in the saline to the haemolymph level resulted in a decrease of resting and action potentials in desheathed cords, to 57·3±5·3 mV. and 36·5±7·6 mV. respectively. No alterations in the membrane potentials were recorded in intact connectives bathed in this saline, the mean resting potential being 55·6±4·2 mV. and the mean action potential 107·9±6·0 mV. Local desheathing of the nerve cord led only to local disturbance of the resting and action potentials, thus indicating that diffusion processes along the extracellular spaces were very slow. 5. The use of a saline in which cation concentrations have been elevated to the extracellular level resulted in normal resting potentials (64·6±3·3 mV.) and action potentials (90·9±7·2 mV.) in desheathed cords, despite the relatively high potassium concentration (17·1 mM./l.). 6. Recordings of the maximum rates of rise and rates of fall showed that there was no significant modification in the shape of the action potential in these different experimental conditions. 7. The values of the ‘sheath potential’ were very variable from one impalement to another and it is suggested that this potential might be related to variations of the microelectrode tip potential bathed in different ionic solutions. 8. The low resting potentials and high action potentials of giant axons in intact nerve cords may result from an excess of inorganic cations in the extracellular fluid.

Effect of tetraethylammonium on an evoked spike potential in feline colonic muscle

1987 ◽  
Vol 252 (6) ◽  
pp. G791-G796
Author(s):  
W. J. Snape ◽  
S. T. Tan
Keyword(s):  
Maximum Rate ◽  
Evoked Potential ◽  
Calcium Influx ◽  
K Channel ◽  
Channel Blockers ◽  
Spike Potential ◽  
Potassium Efflux ◽  
Circular Smooth Muscle ◽  
Sucrose Gap ◽  
Maximum Rate Of Rise

The purpose of these studies is to examine the contribution of calcium influx and potassium efflux to the amplitude and maximum rate of rise of an evoked spike potential in colonic circular smooth muscle. The double sucrose gap was used to record changes in the membrane potential after passing a constant depolarizing current. Tetraethylammonium (TEA) (5 mM) increased the amplitude of the evoked potential to 58 +/- 5 mV (P less than 0.001) from 32 +/- 4 mV in regular Krebs solution. The duration of the potential increased from 121 +/- 3 to 216 +/- 5 ms when a solution of 5 mM [TEA+]o bathed the tissue. The addition of [TEA+]o did not alter the dV/dtmax of the evoked spike. Other K+ channel blockers, cesium and 4-aminopyridine, did not alter the spike potential. Verapamil (10(-6) M) decreased the dV/dtmax of the evoked potential recorded from tissue bathed in 4.5 and 40 mM [K+]o. Verapamil also decreased the amplitude of the spike potential in tissue pretreated with 5 mM TEA. These studies suggest that the amplitude of an electrically evoked spike potential is dependent on Ca2+ influx in circular colonic muscle and an increase in K+ efflux, which occurs early after the current pulse, limits the amplitude of the evoked potential.

scholarly journals Calcium and Action Potentials of Bullfrog Sympathetic Ganglion Cells

1969 ◽  
Vol 53 (5) ◽  
pp. 608-623 ◽  
Author(s):  
K. Koketsu ◽  
S. Nishi
Keyword(s):  
Action Potentials ◽  
Maximum Rate ◽  
Ganglion Cells ◽  
Peak Level ◽  
Charge Carriers ◽  
Resting Potential ◽  
Ca Ions ◽  
Na Inactivation ◽  
Maximum Rate Of Rise ◽  
Potential Level

Bullfrog sympathetic ganglion cells were capable of producing action potentials (Ca spikes) in an isotonic (84 mM) CaCl2 solution. The peak level of Ca spikes showed an approximately 30 mv increase with a 10-fold increase in the Ca concentration. Na as well as Ca ions were capable of acting as charge carriers during the production of action potentials in a solution containing relatively high Ca and relatively low Na ions. A decrease in the external Ca concentration depressed the maximum rate of rise at a fixed resting potential level, and increased the maximum rate of rise of the Na spikes at a high resting potential level at which Na inactivation was completely depressed. Compared to Na spikes, Ca spikes were less sensitive to TTX and procaine. Ganglion cells were also capable of producing action potentials (Sr spikes) in an isotonic SrCl2 solution and prolonged action potentials in an isotonic BaCl2 solution, but these cells were rendered inexcitable in an isotonic MgCl2 solution. The peak level of the Sr spikes was dependent on the external Sr concentration and was insensitive to both TTX and procaine. Sr ions, like Ca ions, reduced Na inactivation during the resting state, and depressed the maximum rate of rise of the Na spikes at a high resting potential level. It was concluded that Ca (and Sr) ions exert dual actions on the membrane; namely, regulating the Na permeability and acting as charge carriers during the active state of the membrane.

CHANGES IN THE RESTING POTENTIAL OF SKELETAL MUSCLE IN RATS WITH COLD ACCLIMATION

1966 ◽  
Vol 44 (5) ◽  
pp. 791-802 ◽  
Author(s):  
M. H. Sherebrin ◽  
A. C. Burton
Keyword(s):  
Skeletal Muscle ◽  
Electrical Properties ◽  
Cold Acclimation ◽  
White Muscle ◽  
Single Cells ◽  
Temperature Gradients ◽  
Resting Potential ◽  
The Mean ◽  
Shivering Thermogenesis ◽  
Main Factor

The resting potential of single cells in the flexor thigh muscles of rats was measured in an attempt to find a change in the electrical properties of the cell membrane with cold acclimation, in order to identify and relate metabolic changes occurring with non-shivering thermogenesis. The mean resting potential of cells in cold-acclimated rats was found to be slightly but significantly higher than in the controls. A larger temperature gradient with depth was measured in the cold-acclimated animals than in the controls. If the Q10 of resting potential with temperature is as great as 1.16, the higher potential in the cold-acclimated rats may be accounted for by this temperature difference. The resting potential was also found to vary with depth in both groups of rats. This could not be attributed to temperature gradients, and change from red to white muscle cells with depth is thought to be the main factor for the increase of potential with depth.

scholarly journals Comparison of electrocardiographic parameters of racing and non-racing horses in Sokoto Nigeria

2020 ◽  
Vol 18 (1) ◽  
pp. 33-38
Author(s):  
B. Saidu ◽  
A.J. Ishaq ◽  
H.M. Ibrahim ◽  
A. Dahiru ◽  
A.M. Abdullahi ◽  
...  
Keyword(s):  
Standing Position ◽  
P Wave ◽  
Average Weight ◽  
T Wave ◽  
Qt Intervals ◽  
Significant Difference ◽  
The Mean ◽  
Electrocardiographic Parameters ◽  
Electrical Activities ◽  
One Way Anova

The study was conducted due to the economic importance of horses and shortage of information on electrocardiographic parameters of horses in Sokoto, Nigeria. This study established the normal electrocardiographic parameters of racing and non-racing horses in Sokoto and statistically compared the values. The study used forty horses comprising of 20 racing and 20 non-racing horses with mean age of 8 ± 0.5 years and average weight of 200 ± 2.0 kg. ECG was recorded using the base apex system with the animals in standing position using single lead channel ECG recorder (EDAN VE-100 manufactured by Edan instruments China). The paper speed was set at 25mm/s while the sensitivity of the machine was adjusted to 10 mm/mV. The durations and amplitudes of P, R and T, the durations of Q and S and the durations of PR, QRS and QT intervals were all determined. These parameters were determined for the three standard limb leads (I, II and III) as well as the augmented limb leads (aVR, aVL and aVF). Descriptive statistics using SPSS version 16 was used to calculate the means and standard error of mean at 95 % confidence interval. One-way ANOVA was used to compare between the values of the racing and non-racing horses. The highest values of P amplitude, R amplitude, Q amplitude, QRS complex and P-R interval were recorded in racing horses, while highest T wave amplitude was recorded in non-racing horses. Highest duration of P wave, T wave and QRS was recorded in racing horses while highest duration of Q wave was recorded in non-racing horses. Significant difference was found in the T amplitude in racing horses in lead aVF. The mean heart rate for the racing and non-racing horses was 80.3 ± 8.4 and 63.1 ± 9.2 beats/minute respectively. Higher values recorded in racing horses indicates that exercise has influence on electrical activities in horses. Keywords: Electrocardiograph, Non-racing horses, Parameters, Racing horses, Sokoto

scholarly journals Quantitative electroencephalography as a tool for objective neurophysiological seizure diagnosis: A retrospective study

2020 ◽  
Vol 0 ◽  
pp. 1-6
Author(s):  
Rajesh Kumar ◽  
Tribhuwan Kumar ◽  
Kamlesh Jha ◽  
Yogesh Kumar
Keyword(s):  
Energy Level ◽  
Matched Control ◽  
Age Groups ◽  
Quantitative Electroencephalography ◽  
Beta Band ◽  
Significant Difference ◽  
Males And Females ◽  
The Mean ◽  
The Difference ◽  
Electrical Activities

Objectives: Seizure is the fourth most common neurological disorder in the world; it affects all age groups with equal possibility of occurrence in both males and females. Many antiepileptic drugs are available today, but its diagnosis is challenging. The present study attempted to see if seizure activities could be predicted by analyzing the pre-seizure electrical activities. The prediction may help in taking preventive measures appropriately beforehand in the individuals with seizure proneness. Material and Methods: We selected 11 generalized seizure patients and 19 control patients out of total 115 patients referred for electro-diagnostics for various reasons. EEG of the subjects recorded, segmented as per protocol, and analyzed using MATLAB and EEGLAB tools. Results: The mean energy level in alpha and beta band of the study subject was significantly lower (P = 0.04 and 0.004, respectively) as compared to the age matched control subjects. Theta and delta bands did not show any significant difference between the groups. The difference between the pre- and post-electrical seizure energy and entropy was statistically insignificant. Conclusion: The study shows that the energy level remains low in the seizure patients in the alpha and beta bands. This further goes down when electrophysiological seizure activities starts. The randomness or entropy does not alter significantly among the seizure subjects in comparison to non-seizure subjects.

Effects of Octopamine on Calcium Action Potentials in Insect Oocytes

1989 ◽  
Vol 142 (1) ◽  
pp. 115-124
Author(s):  
M. J. O'DONNELL ◽  
B. SINGH
Keyword(s):  
Action Potentials ◽  
Rank Order ◽  
Potassium Conductance ◽  
Membrane Resistance ◽  
Threshold Concentration ◽  
Resting Potential ◽  
Calcium Dependent ◽  
Octopamine Receptors ◽  
Voltage Dependent ◽  
Maximum Rate Of Rise

Our experiments show that octopamine receptors are present on the developing follicles of an insect, Rhodnius prolixus. Application of D,L-octopamine decreased the duration and overshoot of calcium-dependent action potentials (APs), and increased the intrafollicular concentration of cyclic AMP. The threshold concentration of D,L-octopamine for the reduction in electrical excitability was between 1 and 5×10−7moll−1, and maximal effects of a 40–50% reduction in AP overshoot and duration were apparent at 10−4moll−1. At concentrations above 10−5moll−1, a small (<10%) hyperpolarization of the resting potential was also apparent. Effects of D,L-octopamine on oocyte excitability were independent of these small shifts in resting potential. Current injection experiments, in which calcium entry was blocked by cobalt, demonstrated that D,L-octopamine reduced membrane resistance at both hyperpolarizing and depolarizing potentials. Octopamine did not affect the maximum rate of rise of the AP, dV/dtmax, which is an indicator of inward calcium current. It is suggested that octopamine may mediate its effects on excitability through an increase in a voltage-dependent potassium conductance. Application of other phenolamines indicated a rank order of potency of D, Loctopamine > D,L-synephrine > tyramine. The α-adrenergic agonists clonidine, naphazoline and tolazoline were without significant effect at 10−5-10−3moll−1. Reduction of excitability by D,L-octopamine was effectively blocked by phentolamine and metoclopramide. Yohimbine and gramine were less effective as antagonists. Possible functions of octopamine receptors in insect follicles are discussed.

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)

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