Ionic Basis of Action Potentials and Bursting Activity in the Hydromedusan Jellyfish Polyorchis Penicillatus

1979 ◽  
Vol 78 (1) ◽  
pp. 299-302
Author(s):  
PETER A. V. ANDERSON
Keyword(s):  
Action Potentials ◽  
Polyorchis Penicillatus ◽  
Ionic Basis ◽  
Bursting Activity

Effects of estrogen on action potential and membrane currents in guinea pig ventricular myocytes

1999 ◽  
Vol 277 (2) ◽  
pp. H826-H833 ◽  
Author(s):  
Seiko Tanabe ◽  
Toshio Hata ◽  
Masayasu Hiraoka
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Action Potentials ◽  
Voltage Dependence ◽  
Ventricular Myocytes ◽  
Membrane Currents ◽  
Patch Clamp Technique ◽  
17Β Estradiol ◽  
Electrophysiological Effects ◽  
Ionic Basis

To explore a possible ionic basis for the prolonged Q-T interval in women compared with that in men, we investigated the electrophysiological effects of estrogen in isolated guinea pig ventricular myocytes. Action potentials and membrane currents were recorded using the whole cell configuration of the patch-clamp technique. Application of 17β-estradiol (10–30 μM) significantly prolonged the action potential duration (APD) at 20% (APD20) and 90% repolarization (APD90) at stimulation rates of 0.1–2.0 Hz. In the presence of 30 μM 17β-estradiol, APD20 and APD90 at 0.1 Hz were prolonged by 46.2 ± 17.1 and 63.4 ± 11.7% of the control ( n = 5), respectively. In the presence of 30 μM 17β-estradiol the peak inward Ca2+ current ( I CaL) was decreased to 80.1 ± 2.5% of the control ( n = 4) without a shift in its voltage dependence. Application of 30 μM 17β-estradiol decreased the rapidly activating component of the delayed outward K+ current ( I Kr) to 63.4 ± 8% and the slowly activating component ( I Ks) to 65.8 ± 8.7% with respect to the control; the inward rectifier K+ current was barely affected. The results suggest that 17β-estradiol prolonged APD mainly by inhibiting the I Kcomponents I Krand I Ks.

The Ionic Basis of the Fast Action Potentials in the Isolated CerebroVisceral Connective of Anodonta Cygnea

1969 ◽  
Vol 51 (2) ◽  
pp. 297-318
Author(s):  
ALBERT D. CARLSON ◽  
J. E. TREHERNE
Keyword(s):  
Conduction Velocity ◽  
Action Potentials ◽  
Electrolyte Solutions ◽  
Monovalent Cations ◽  
Bathing Medium ◽  
Anodonta Cygnea ◽  
Sodium Dependent ◽  
Ionic Basis

1. The large axons in the cerebro-visceral connective have been shown to function for appreciable periods in preparations bathed in sodium-free non-electrolyte solutions. 2. The results of experiments on the effects of organic monovalent cations and anions, together with observations on the effects of tetrodotoxin, procaine and manganous ions and the changes in conduction velocity in tris chloride and dextran solutions indicate that the action potentials are, nevertheless, mediated by conventional sodium-dependent mechanisms. 3. Radioisotope experiments show that there is a small fraction, of approx. 0.5 mM/kg. tissue, which does not exchange rapidly with the 22Na in the bathing medium and which can be depleted by stimulation in sodium-free solutions. 4. On the basis of these observations it is suggested that there is sequestered extra-axonal sodium fraction which can be utilized by the large axons to maintain action potentials in preparations bathed in sodium-free solutions.

Voltage-activated potassium currents in isolated motor neurons from the jellyfish Polyorchis penicillatus

1994 ◽  
Vol 72 (2) ◽  
pp. 1010-1019 ◽  
Author(s):  
J. Przysiezniak ◽  
A. N. Spencer
Keyword(s):  
Motor Neurons ◽  
Action Potentials ◽  
Voltage Dependence ◽  
Primary Cultures ◽  
Potassium Currents ◽  
Whole Cell ◽  
Time To Peak ◽  
Polyorchis Penicillatus ◽  
Slow Onset

1. We describe two voltage-activated potassium currents in the swim motor neurons (SMNs) of the hydrozoan jellyfish, Polyorchis penicillatus. Recordings from neurons isolated in primary cultures were made using the tight-seal, whole-cell technique. 2. One current, IK-fast, turned on rapidly (time to peak = 6–15 ms), was half-activated at -10 to 0 mV, decayed with two exponential phases (tau were approximately 70 ms and approximately 1 s), and was half-inactivated by prepulses around -53 mV. It likely plays an important role in regulating the duration of SMN action potentials. IK-fast has features shared by delayed rectifiers and A-like currents in other invertebrates and vertebrates. 3. Another current, IK-slow, elicited from a holding potential of -30 mV, exhibited a slow onset (tau = 65–250 ms), was half-activated approximately +24 mV, exhibited a shallower voltage dependence than IK-fast, and did not inactivate. It was slower than most known delayed rectifiers.

Modulation of electrical activity by 5-hydroxytryptamine in crayfish neurosecretory cells.

1997 ◽  
Vol 200 (23) ◽  
pp. 3079-3090 ◽  
Author(s):  
F Sáenz ◽  
U García ◽  
U Aréchiga
Keyword(s):  
Electrical Activity ◽  
Action Potentials ◽  
Procambarus Clarkii ◽  
Neurosecretory Cells ◽  
Slow Inward Current ◽  
Bathing Solution ◽  
Inward Current ◽  
Dose Dependent ◽  
Bursting Activity

The effect of 5-hydroxytryptamine (5-HT) was tested in a population of X organ neurosecretory cells in the eyestalk of the crayfish Procambarus clarkii. Tests were conducted both in situ and on isolated neurones kept in culture. The application of 5-HT induced action potentials in silent cells. In spontaneously active neurones, 5-HT increased the firing rate and either induced firing or enhanced bursting activity. The effect of 5-HT was dose-dependent within the range 1-100 micromol l-1 in cells of the intact organ. The effect persisted for 20-30 min after 5-HT had been removed from the bathing solution. Successive applications of 5-HT onto the same neurone reduced responsiveness, suggesting that desensitization had occurred. The effects of 5-HT were blocked by prior incubation with the 5-HT antagonist methysergide. In X organ cells whose axons and branches in the neuropile had been severed, 5-HT induced a depolarisation associated with a slow inward current. In X organ neurones isolated from the eyestalk and kept in culture, 5-HT was capable of evoking bursts of action potentials and elicited a slow inward current. This effect was also blocked by methysergide (10(-4 )mol l-1). These results suggest a direct modulatory effect of 5-HT on the pattern of electrical activity in the X organ cells.

scholarly journals Properties and ionic basis of the action potentials in the periaqueductal grey neurones of the guinea-pig.

1991 ◽  
Vol 440 (1) ◽  
pp. 167-187 ◽  
Author(s):  
D Sánchez ◽  
J Ribas
Keyword(s):  
Guinea Pig ◽  
Action Potentials ◽  
Periaqueductal Grey ◽  
Ionic Basis

Electrogenesis in the Euryhaline Osmoconformer Cordylophora Lacustris (Hydrozoa)

1980 ◽  
Vol 88 (1) ◽  
pp. 175-194
Author(s):  
BENJAMIN M. CHAIN
Keyword(s):  
Ionic Strength ◽  
Action Potential ◽  
Natural Environment ◽  
Action Potentials ◽  
Typical Feature ◽  
Chloride Ions ◽  
Electrical Signals ◽  
Excitable System ◽  
Ionic Concentrations ◽  
Ionic Basis

The electrical signals propagated through the ectodermal epithelium of Cordylophora lacustris (the Josephson pulses) were recorded as transepithelial action potential-like events. Experiments on the ionic basis of electrogenesis of these action potentials suggested that they result from an outward flow of chloride ions from the ectodermal cells into the enteron. Further evidence for this hypothesis came from measurements of the ionic concentrations in the tissues of Cordylophora, which showed that these cells have unusually high levels of chloride. Chloride dependent electrogenesis allows this excitable system to function in media of low and variable ionic strength, which are a typical feature of this organism's natural environment.

Simulation of the bursting activity of neuron R15 in Aplysia: role of ionic currents, calcium balance, and modulatory transmitters

1991 ◽  
Vol 66 (6) ◽  
pp. 2107-2124 ◽  
Author(s):  
C. C. Canavier ◽  
J. W. Clark ◽  
J. H. Byrne
Keyword(s):  
Fixed Point ◽  
Slow Wave ◽  
Action Potentials ◽  
Equivalent Circuit Model ◽  
Reduced Model ◽  
Slow Inward Current ◽  
Calcium Balance ◽  
Full Model ◽  
Slow Dynamics ◽  
Bursting Activity

1. An equivalent circuit model of the R15 bursting neuron in Aplysia has been combined with a fluid compartment model, resulting in a model that incorporates descriptions of most of the membrane ion channels that are known to exist in the somata of R15, as well as providing a Ca2+ balance on the cell. 2. A voltage-activated, calcium-inactivated Ca2+ current (denoted the slow inward current ISI) was sufficient to produce bursting activity without invoking any other calcium-dependent currents (such as a nonspecific cation current, INS, or a calcium-activated K+ current, IK,Ca). Furthermore, many characteristics of a typical R15 burst could be simulated, such as a parabolic variation in interspike interval, the depolarizing afterpotential (DAP), and the progressive decrease in the undershoots of spikes during a burst. 3. The dynamic activity of R15 was analyzed by separately characterizing two different temporal domains; the fast dynamics associated with action potentials and the slow dynamics associated with low-amplitude oscillations lasting tens of seconds ("slow waves"). The slow dynamics were isolated by setting the Na+ conductance (gNa) to zero and then studied by the use of a system of equations reduced to two variables: intracellular concentration of Ca2+ and membrane potential. The fixed point of the system was located at the intersection of the nullclines for these two variables. A stability analysis of the fixed point was then used to determine whether a given set of parameters would produce slow-wave activity. 4. If the reduced model predicted slow-wave oscillations for a given set of parameters with gNa set to zero, then bursting activity was observed for the same set of parameters in the full model with gNa reset to its control value. However, for certain sets of parameters with gNa at its usual value, the full model exhibited bursting activity because of a slow oscillation produced by the activation of INS by action potentials. This oscillation resulted from an interaction between the fast and slow dynamics that the reduced model alone could not predict and was not observed when gNa was subsequently set to zero. If gNS was also set to zero, this discrepancy disappeared.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals The ionic basis of action potentials in petrosal ganglion cells of the cat.

1983 ◽  
Vol 342 (1) ◽  
pp. 591-602 ◽  
Author(s):  
R Gallego
Keyword(s):  
Action Potentials ◽  
Ganglion Cells ◽  
Ionic Basis
Sign in / Sign up

Export Citation Format

Share Document