Electrical Properties of Fibres from Stridulatory and Flight Muscles of a Tettigoniid

1982 ◽  
Vol 99 (1) ◽  
pp. 109-125
Author(s):  
ROBERT K. JOSEPHSON ◽  
DARRELL R. STOKES
Keyword(s):  
Electrical Properties ◽  
Transmitter Release ◽  
Longitudinal Muscle ◽  
Membrane Resistance ◽  
Neural Stimulation ◽  
Release Mechanism ◽  
Voltage Response ◽  
Voltage Dependent ◽  
Flight Muscles ◽  
Passive Electrical Properties

1. The mesothoracic dorsal longitudinal muscle (DLM) of the katydid Neoconocephalus robustus is used in stridulation and flight; the metathoracic DLM is used in flight only. The DLM's in the two segments have radically different maximum operating frequencies, 200 Hz for the mesothoracic muscle during stridulation and 20 Hz for the metathoracic muscle during flight. 2. Cable analysis was used to determine the passive electrical properties of mesothoracic and metathoracic DLM fibres. Fibres in the two segments are of similar diameter and have similar sarcoplasmic resistivity. The apparent membrane resistance is lower, the apparent membrane capacitance higher, and the time constant shorter in mesothoracic fibres than in the metathoracic homologues. 3. The depolarization evoked by neural stimulation in both mesothoracic and metathoracic fibres is principally an excitatory junctional potential (e.j.p.) with little or no contribution from voltage-dependent, inward current channels. At short interstimulus intervals the second e.j.p. of a pair is reduced in amplitude relative to the first e.j.p. The period of e.j.p. depression is shorter in mesothoracic than in metathoracic fibres. It is suggested that the faster recovery of e.j.p.'s in mesothoracic fibres is due to more rapid recovery of the transmitter release mechanism in their motorneurones. 4. In mesothoracic but not metathoracic fibres the voltage response to large depolarizing currents is usually oscillatory, and the recovery of e.j.p. amplitude as a function of time in paired shock experiments is sometimes oscillatory. The oscillation frequency is 250–300 Hz (35 °C) which is higher than the natural operating frequency of the muscle.

The effect of repetitive stimulation on the passive electrical properties of the presynaptic terminal of the squid giant synapse

1979 ◽  
Vol 206 (1164) ◽  
pp. 293-306 ◽  
Keyword(s):  
Electrical Properties ◽  
Transmitter Release ◽  
Sea Water ◽  
Presynaptic Terminal ◽  
Repetitive Stimulation ◽  
Constant Current ◽  
Current Pulses ◽  
Squid Giant Synapse ◽  
Giant Synapse ◽  
Passive Electrical Properties

The resting electrical properties of the presynaptic terminal of the squid giant synapse have been determined by using constant current pulses. After short periods of repetitive stimulation, the terminal resistance, time constant and capacitance are found to be increased. These changes are absent in terminals bathed in artificial sea water containing no calcium, and sea water containing 5 mM cobalt. It seems likely that these changes are associated with transmitter release.

scholarly journals Capacitance of the Surface and Transverse Tubular Membrane of Frog Sartorius Muscle Fibers

1969 ◽  
Vol 53 (3) ◽  
pp. 265-278 ◽  
Author(s):  
Peter W. Gage ◽  
Robert S. Eisenberg
Keyword(s):  
Electrical Properties ◽  
Time Course ◽  
Muscle Fibers ◽  
Membrane Resistance ◽  
Ringer Solution ◽  
Sartorius Muscle ◽  
Tubular Membrane ◽  
Essentially Normal ◽  
The Difference ◽  
Passive Electrical Properties

The passive electrical properties of glycerol-treated muscle fibers, which have virtually no transverse tubules, were determined. Current was passed through one intracellular microelectrode and the time course and spatial distribution of the resulting potential displacement measured with another. The results were analyzed by using conventional cable equations. The membrane resistance of fibers without tubules was 3759 ± 331 ohm-cm2 and the internal resistivity 192 ohm-cm. Both these figures are essentially the same as those found in normal muscle fibers. The capacitance of the fibers without tubules is strikingly smaller than normal, being 2.24 ± 0.14 µF/cm2. Measurements were also made of the passive electrical properties of fibers in a Ringer solution containing 400 mM glycerol (which is used in the preparation of glycerol-treated fibers). The membrane resistance and capacitance are essentially normal, but the internal resistivity is somewhat reduced. These results show that glycerol in this concentration does not directly affect the membrane capacitance. Thus, the figure for the capacitance of glycerol-treated fibers, which agrees well with previous estimates made by different techniques, represents the capacitance of the outer membrane of the fiber. Estimates of the capacitance per unit area of the tubular membrane are made and the significance of the difference between the figures for the capacitance of the surface and tubular membrane is discussed.

White noise approach for estimating the passive electrical properties of neurons

1996 ◽  
Vol 76 (5) ◽  
pp. 3442-3450 ◽  
Author(s):  
W. N. Wright ◽  
B. L. Bardakjian ◽  
T. A. Valiante ◽  
J. L. Perez-Velazquez ◽  
P. L. Carlen
Keyword(s):  
Electrical Properties ◽  
White Noise ◽  
Input Impedance ◽  
Granule Cells ◽  
Short Pulse ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Somatic Membrane ◽  
Dendritic Membrane ◽  
Passive Electrical Properties

1. The passive electrical properties of whole cell patched dentate granule cells were studied with the use of zero-mean Gaussian white noise current stimuli. Transmembrane voltage responses were used to compute the first-order Wiener kernels describing the current-voltage relationship at the soma for six cells. Frequency domain optimization techniques using a gradient method for function minimization were then employed to identify the optimal electrical parameter values. Low-power white noise stimuli are presented as a favorable alternative to the use of short-pulse current inputs for investigating neuronal passive electrical properties. 2. The optimization results demonstrated that the lumped resistive and capacitive properties of the recording electrode must be included in the analytic input impedance expression to optimally fit the measured cellular responses. The addition of the electrode resistance (Re) and capacitance (Ce) to the original parameters (somatic conductance, somatic capacitance, axial resistance, dendritic conductance, and dendritic capacitance) results in a seven-parameter model. The mean Ce value from the six cells was 5.4 +/- 0.3 (SE) pF, whereas Re following formation of the patch was found to be 20 +/- 2 M omega. 3. The six dentate granule cells were found to have an input resistance of 600 +/- 20 M omega and a dendritic to somatic conductance ratio of 6.3 +/- 1.1. The electronic length of the equivalent dendritic cylinder was found to be 0.42 +/- 0.03. The membrane time constant in the soma was found to be 13 +/- 3 ms, whereas the membrane time constant of the dendrites was 58 +/- 5 ms. Incorporation of morphological estimations led to the following distributed electrical parameters: somatic membrane resistance = 25 +/- 4 k omega cm2, somatic membrane capacitance = 0.48 +/- 0.05 microF/cm2, Ri (input resistance) = 72 +/- 5 omega cm, dendritic membrane resistance = 59 +/- 4 k omega cm2, and dendritic membrane capacitance = 0.97 +/- 0.06 microF/cm2. On the basis of capacitive measurements, the ratio of dendritic surface area to somatic surface area was found to be 34 +/- 2. 4. For comparative purposes, hyperpolarizing short pulses were also injected into each cell. The short-pulse input impedance measurements were found to underestimate the input resistance of the cell and to overestimate both the somatic conductance and the membrane time constants relative to the white noise input impedance measurements.

An Intracellular Study of the Actions of Carbon Dioxide on the Spinal Monosynaptic Pathway

1973 ◽  
Vol 51 (6) ◽  
pp. 424-436 ◽  
Author(s):  
D. W. Esplin ◽  
R. Čapek ◽  
Barbara A. Esplin
Keyword(s):  
Transmitter Release ◽  
Afferent Fiber ◽  
Membrane Resistance ◽  
Postsynaptic Membrane ◽  
Release Mechanism ◽  
Afferent Fibers ◽  
Depressant Action ◽  
Intracellular Study ◽  
Primary Afferent Fibers ◽  
Antidromic Response

The actions of CO2 were studied on 48 lumbosacral motoneurones impaled with microelectrodes in spinal cats. CO2 produced a reversible depolarization in some cells tested and a reversible hyper-polarization in other cells tested. Both increases and decreases in membrane resistance were produced by CO2, and these were significantly correlated with hyperpolarizations and depolarizations of the membrane, respectively. The after-hyperpolarization following an antidromic response was always reduced by CO2, irrespective of the CO2-induced change in membrane potential. The firing threshold of the motoneurone in response to injected depolarizing currents was increased by CO2. Statistical analysis of excitatory postsynaptic potentials produced by activity in a single afferent fiber revealed that the principal depressant action of CO2 on this pathway is to block intraspinal branches of the primary afferent fibers. Neither the transmitter release mechanism nor the sensitivity of the postsynaptic membrane to the released transmitter was significantly affected.

On the physiological role of internodal potassium channels and the security of conduction in myelinated nerve fibres

1984 ◽  
Vol 220 (1221) ◽  
pp. 415-422 ◽  
Keyword(s):  
Electrical Properties ◽  
Potassium Channels ◽  
Theoretical Analysis ◽  
Physiological Role ◽  
Resting Potential ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Voltage Dependent ◽  
Passive Electrical Properties

A theoretical analysis of the passive electrical properties of normal myelinated nerve suggests that the function of the voltage-dependent potassium channels in the internodal axolemma under the myelin sheath is to permit the generation of an internodal resting potential. Calculation shows that if this internodal potential were not present, the nodal potential would be reduced (by electrotonic short-circuiting) thus impairing the security of conduction. This impairment is particularly pronounced with smaller diameter fibres.

scholarly journals A synthetic strand of cardiac muscle: its passive electrical properties.

1975 ◽  
Vol 65 (4) ◽  
pp. 527-550 ◽  
Author(s):  
M Lieberman ◽  
T Sawanobori ◽  
J M Kootsey ◽  
E A Johnson
Keyword(s):  
Electrical Properties ◽  
Cardiac Muscle ◽  
Numerical Solutions ◽  
Unit Length ◽  
Current Source ◽  
Membrane Resistance ◽  
Membrane Capacitance ◽  
Cable Equation ◽  
Cross Sectional ◽  
Passive Electrical Properties

The passive electrical properties of synthetic strands of cardiac muscle, grown in tissue culture, were studied using two intracellular microelectrodes: one to inject a rectangular pulse of current and the other to record the resultant displacement of membrane potential at various distances from the current source. In all preparations, the potential displacement, instead of approaching a steady value as would be expected for a cell with constant electrical properties, increased slowly with time throughout the current step. In such circumstances, the specific electrical constants for the membrane and cytoplasm must not be obtained by applying the usual methods, which are based on the analytical solution of the partial differential equation describing a one-dimensional cell with constant electrical properties. A satisfactory fit of the potential waveforms was, however, obtained with numerical solutions of a modified form of this equation in which the membrane resistance increased linearly with time. Best fits of the waveforms from 12 preparations gave the following values for the membrane resistance times unit length, membrane capacitance per unit length, and for the myoplasmic resistance: 1.22 plus or minus 0.13 x 10-5 omegacm, 0.224 plus or minus 0.023 uF with cm-minus 1, and 1.37 plus or minus 0.13 x 10-7 omegacm-minus 1, respectively. The value of membrane capacitance per unit length was close to that obtained from the time constant of the foot of the action potential and was in keeping with the generally satisfactory fit of the recorded waveforms with solutions of the cable equation in which the membrane impedance is that of a single capacitor and resistor in parallel. The area of membrane per unit length and the cross-sectional area of myoplasm at any given length of the preparation were determined from light and composite electron micrographs, and these were used to calculate the following values for the specific electrical membrane resistance, membrane capacitance, and the resistivity of the cytoplasm: 20.5 plus or minus 3.0 x 10-3 omegacm-2, l.54 plus or minus 0.24 uFWITHcm-minus 2, and 180 plus or minus 34 omegacm, respectively.

Thermal dependence of passive electrical properties of lizard muscle fibres

1987 ◽  
Vol 133 (1) ◽  
pp. 169-182 ◽  
Author(s):  
B. A. Adams
Keyword(s):  
Electrical Properties ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Effect Of Temperature ◽  
Muscle Fibres ◽  
Thermal Dependence ◽  
Thermophilic Species ◽  
Length Constant ◽  
Increasing Temperature ◽  
Passive Electrical Properties

1. The thermal dependence of passive electrical properties was determined for twitch fibres from the white region of the iliofibularis (IF) muscle of Anolis cristatellus (15–35 degrees C) and Sceloporus occidentalis (15–40 degrees C), and for twitch fibres from the white (15–45 degrees C) and red (15–40 degrees C) regions of the IF of Dipsosaurus dorsalis. These species differ in thermal ecology, with Anolis being the least thermophilic and Dipsosaurus the most thermophilic. 2. Iliofibularis fibres from the three species reacted similarly to changing temperature. As temperature was increased, input resistance (Rin) decreased (average R10 = 0.7), length constant (L) decreased (average R10 = 0.9), time constant (tau) decreased (average R10 = 0.8), sarcoplasmic resistivity (Rs) decreased (average R10 = 0.8) and apparent membrane resistance (Rm) decreased (average R10 = 0.7). In contrast, apparent membrane capacitance (Cm) increased with increasing temperature (average R10 = 1.3). 3. Rin, L, tau and apparent Rm were lowest in fibres from Anolis (the least thermophilic species) and highest in fibres from Dipsosaurus (the most thermophilic species). Anolis had the largest and Dipsosaurus the smallest diameter fibres (126 and 57 micron, respectively). Apparent Cm was highest in fibres from Sceloporus, which had fibres of intermediate diameter (101 micron). Rs did not differ significantly among species. 4. The effect of temperature on the passive electrical properties of these lizard fibres was similar to that reported for muscle fibres from other ectothermic animals (crustaceans, insects, fish and amphibians) but qualitatively different from that reported for some mammalian (cat tenuissimus, goat intercostal) fibres. The changes that occur in the passive electrical properties render the fibres less excitable as temperature increases.

Dopamine Modulation of Calcium Currents in Pyloric Neurons of the Lobster Stomatogastric Ganglion

2003 ◽  
Vol 90 (2) ◽  
pp. 631-643 ◽  
Author(s):  
Bruce R. Johnson ◽  
Peter Kloppenburg ◽  
Ronald M. Harris-Warrick
Keyword(s):  
Calcium Channel ◽  
Transmitter Release ◽  
Stomatogastric Ganglion ◽  
Calcium Currents ◽  
Voltage Gated ◽  
Pyloric Network ◽  
Pyloric Dilator ◽  
Voltage Dependent ◽  
Inward Currents ◽  
Dopamine Modulation

We examined the dopamine (DA) modulation of calcium currents (ICa) that could contribute to the plasticity of the pyloric network in the lobster stomatogastric ganglion. Pyloric somata were voltage-clamped under conditions designed to block voltage-gated Na+, K+, and H currents. Depolarizing steps from –60 mV generated voltage-dependent, inward currents that appeared to originate in electrotonically distal, imperfectly clamped regions of the cell. These currents were blocked by Cd2+ and enhanced by Ba2+ but unaffected by Ni2+. Dopamine enhanced the peak ICa in the pyloric constrictor (PY), lateral pyloric (LP), and inferior cardiac (IC) neurons and reduced peak ICa in the ventricular dilator (VD), pyloric dilator (PD), and anterior burster (AB) neurons. All of these effects, except for the AB, are consistent with DA's excitation or inhibition of firing in the pyloric neurons. Enhancement of ICa in PY and LP neurons and reduction of ICa in VD and PD neurons are also consistent with DA-induced synaptic strength changes via modulation of presynaptic ICa. However, the reduction of ICa in AB suggests that DA's enhancement of AB transmitter release is not directly mediated through presynaptic ICa. ICa in PY and PD neurons was more sensitive to nifedipine block than in AB neurons. In addition, nifedipine blocked DA's effects on ICa in the PY and PD neurons but not in the AB neuron. Thus the contribution of specific calcium channel subtypes carrying the total ICa may vary between pyloric neuron classes, and DA may act on different calcium channel subtypes in the different pyloric neurons.

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