Passive and active membrane properties of canine gastric antral circular muscles

1986 ◽  
Vol 251 (2) ◽  
pp. C268-C273 ◽  
Author(s):  
A. J. Bauer ◽  
K. M. Sanders
Keyword(s):  
Electrical Activity ◽  
Time Constant ◽  
Myenteric Plexus ◽  
Circular Muscle ◽  
Membrane Properties ◽  
Time Constants ◽  
Active Membrane ◽  
Cable Properties ◽  
Length Constant ◽  
Chamber Technique

Experiments were performed to determine the mechanisms responsible for the gradient of electrical activity within circular muscle of the canine gastric antrum. Cable properties of canine gastric antral circular muscles were determined using the partitioned chamber technique of Abe and Tomita (J. Physiol. Lond. 196: 87-100, 1968). The length constant of the circular muscle near the myenteric plexus was 2.4 mm. This was significantly greater than the length constant of the circular muscle near the submucosa (1.7 mm). Membrane time constants were determined by two techniques. Although the time constant of the circular muscle near the myenteric plexus tended to be greater than that of the circular muscle near the submucosa, this difference was not statistically significant. The two regions of circular muscle also differed in their relative levels of excitability. Submucosal circular muscles demonstrated considerably more outward rectification on depolarization and were difficult to bring to threshold for slow waves. This study demonstrates that significant differences exist in the passive and active membrane properties of myenteric and submucosal circular muscle cells. The data help explain the gradient of electrical activity through the thickness of antral circular muscle.

Correlation between electrical and morphological properties of canine pyloric circular muscle

1991 ◽  
Vol 260 (3) ◽  
pp. G390-G398 ◽  
Author(s):  
F. Vogalis ◽  
S. M. Ward ◽  
K. M. Sanders
Keyword(s):  
Single Cells ◽  
Electrical Coupling ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Morphological Properties ◽  
Morphological Examination ◽  
Isolated Cells ◽  
Time Constants ◽  
Morphological Studies ◽  
Cable Properties

Electrical slow waves decay in amplitude as they conduct from the myenteric to the submucosal regions of the circular muscle layer in the canine pyloric sphincter. We used the partitioned chamber method to study the passive and active properties of pyloric muscles, and we found that length constants of circular muscles of myenteric region were significantly longer than muscles near the submucosal surface. These data suggested differences in either membrane resistance, junctional resistance, or cytoplasmic resistance. The first parameter was evaluated by measuring time constants in intact tissues and single cells isolated from the submucosal and myenteric regions. Membrane time constants were not different in the two regions, nor were differences found in the input resistances of isolated cells. Morphological studies failed to demonstrate differences in cell diameters in the two regions suggesting that cytoplasmic resistances are similar. These findings suggest that the different cable properties in the two regions may be due to differences in electrical coupling. Morphological examination revealed similar numbers of gap junctions between cells in the two regions, but large differences were noted in the size of muscular bundles. Muscles of the myenteric region were arranged into large, tightly packed bundles, whereas muscles of the submucosal region consisted of small bundles with an extensive extracellular space filled with connective tissue. We suggest that the difference in cable properties may be due to differences in electrical coupling between bundles. These data suggest that submucosal muscles function more like a multiunit smooth muscle, whereas myenteric muscles behave as a single unit.

Passive current flow and morphology in the terminal arborizations of the posterior pituitary

1993 ◽  
Vol 69 (3) ◽  
pp. 692-702 ◽  
Author(s):  
M. B. Jackson
Keyword(s):  
Action Potentials ◽  
Current Flow ◽  
Membrane Properties ◽  
Nerve Terminals ◽  
Posterior Pituitary ◽  
Cable Theory ◽  
Cable Properties ◽  
Length Constant ◽  
Passive Current ◽  
Current Transients

1. Patch-clamp techniques were used to study the morphology and electrotonic properties of the terminal arborizations of the posterior pituitary. 2. Neurobiotin-labeling experiments revealed axons and swellings connected to the structure that was patch clamped. The large swellings were en passant and situated along axons in a topological arrangement identical to that of the small varicosities. Axons had many varicosities and few branches, reflecting a predominant architectural motif of beads on a string rather than berries on a bush. 3. Cable theory was used to analyze passive current transients produced by voltage steps under whole-cell clamp. Most charging transients were not consistent with an equivalent cylinder representation as posited by the Rall model for a motoneuron. A few charging transients were consistent with the Rall model and provided estimates for basic membrane and cable properties. 4. Some of the charging transients that violated predictions of the Rall model were consistent with an alternative model, in which the patch-clamped swelling was assumed to be coupled to another swelling by a segment of axon. This model was called the Dumbbell model, and it, together with the neurobiotin-labeling experiments, indicated that a significant number of large swellings were less than one length constant away from another large swelling. 5. Large swellings can have diameters approximately 30 times larger than the diameters of the connecting axons. These swellings lie along the axon such that action potentials must propagate through them to spread excitation through the entire terminal arborization. These large swellings could be sites where action-potential propagation is more likely to fail. 6. The information presented here about neurohypophysial nerve terminals should be useful in further investigations of how terminal arborization geometry and membrane properties influence neurosecretion and synaptic transmission.

scholarly journals Quantitative Analysis of Electrotonic Structure and Membrane Properties of NMDA-Activated Lamprey Spinal Neurons

1995 ◽  
Vol 7 (3) ◽  
pp. 486-506 ◽  
Author(s):  
C. R. Murphey ◽  
L. E. Moore ◽  
J. T. Buchanan
Keyword(s):  
Steady State ◽  
Voltage Clamp ◽  
Membrane Properties ◽  
Neuronal System ◽  
Cable Model ◽  
Spinal Neurons ◽  
Time Constants ◽  
Cable Properties ◽  
Wide Range ◽  
Voltage Dependent

Parameter optimization methods were used to quantitatively analyze frequency-domain-voltage-clamp data of NMDA-activated lamprey spinal neurons simultaneously over a wide range of membrane potentials. A neuronal cable model was used to explicitly take into account receptors located on the dendritic trees. The driving point membrane admittance was measured from the cell soma in response to a Fourier synthesized point voltage clamp stimulus. The data were fitted to an equivalent cable model consisting of a single lumped soma compartment coupled resistively to a series of equal dendritic compartments. The model contains voltage-dependent NMDA sensitive (INMDA), slow potassium (IK), and leakage (IL) currents. Both the passive cable properties and the voltage dependence of ion channel kinetics were estimated, including the electrotonic structure of the cell, the steady-state gating characteristics, and the time constants for particular voltage- and time-dependent ionic conductances. An alternate kinetic formulation was developed that consisted of steady-state values for the gating parameters and their time constants at half-activation values as well as slopes of these parameters at half-activation. This procedure allowed independent restrictions on the magnitude and slope of both the steady-state gating variable and its associated time constant. Quantitative estimates of the voltage-dependent membrane ion conductances and their kinetic parameters were used to solve the nonlinear equations describing dynamic responses. The model accurately predicts current clamp responses and is consistent with experimentally measured TTX-resistant NMDA-induced patterned activity. In summary, an analysis method is developed that provides a pragmatic approach to quantitatively describe a nonlinear neuronal system.

Passive and Active Membrane Properties of Isolated Rat Intracardiac Neurons: Regulation by H- and M-Currents

1997 ◽  
Vol 78 (4) ◽  
pp. 1890-1902 ◽  
Author(s):  
J. Cuevas ◽  
A. A. Harper ◽  
C. Trequattrini ◽  
D. J. Adams
Keyword(s):  
Temperature Dependence ◽  
Time Constant ◽  
Action Potentials ◽  
Neonatal Rat ◽  
Membrane Properties ◽  
Active Membrane ◽  
Discharge Activity ◽  
The Mean ◽  
Isolated Rat ◽  
Intracardiac Neurons

Cuevas, J., A. A. Harper, C. Trequattrini, and D. J. Adams. Passive and active membrane properties of isolated rat intracardiac neurons: regulation by H- and M-currents. J. Neurophysiol. 78: 1890–1902, 1997. The electrical characteristics of isolated neonatal rat intracardiac neurons were examined at 22 and 37°C using the perforated-patch whole cell recording technique. The mean resting membrane potential was −52.0 mV at 37°C and exhibited no temperature dependence. Lowering the temperature from 37 to 22°C decreased the mean input resistance from 854 to 345 MΩ, respectively, and reduced the membrane time constant approximately threefold yielding a Q 10 of 2.1. Hyperpolarizing current pulses induced time-dependent rectification of the voltage response in all neurons at both temperatures. This behavior was previously not observed in dialyzed neurons and was reversibly blocked by external Cs+ (2 mM) but not Ba2+ (1 mM). Voltage-clamp studies of isolated neurons revealed a hyperpolarization-activated inward current. This inwardly rectifying conductance was isolated from other membrane currents using external Cs+. The time and voltage dependence of this current is consistent with I h and contributes to the passive electrical properties of rat intracardiac neurons. In >90% of the neurons studied, depolarizing currents evoked firing of multiple, adapting, action potentials at 22°C. The number of action potentials increased with current strength producing a mean discharge of 5.1 (+100 pA, 1 s pulse), which was attenuated at 37°C to a mean of 1.4. The amplitude and kinetics of the slow, muscarine-sensitive inward and outward currents ( I M) were highly temperature dependent. Lowering the temperature from 37 to 22°C reduced the steady-state current amplitude by approximately one-third and the rate of deactivation of I M by six- to ninefold at all voltages examined. The average Q 10 for the time constant of deactivation of I M was 3.7 ± 0.3 (mean ± SE). Acetylcholine (ACh) induced tonic discharges in response to depolarizing currents (+100 pA, 1 s pulse) at both temperatures. This effect of ACh was inhibited by the muscarinic receptor antagonists, pirenzepine (100 nM), and mL-toxin (60 nM). At 37°C, a mean discharge of 1.5 was increased to 23.5 in the presence of ACh. A similar switch from phasic to tonic discharge was also produced by the potassium channel inhibitors, Ba2+ (1 mM) and uridine-5′-triphosphate (UTP; 100 μM), whereas cadmium, 4-aminopyridine, apamin, charybdotoxin, and dendrotoxin did not alter discharge activity. The pharmacological sensitivity profile and temperature dependence of the active membrane properties are consistent with the muscarine-sensitive potassium current ( I M) regulating the discharge activity in rat intracardiac neurons.

scholarly journals Individual motion perception parameters and motion sickness frequency sensitivity in fore-aft motion

2021 ◽  
Author(s):  
Tugrul Irmak ◽  
Ksander N. de Winkel ◽  
Daan M. Pool ◽  
Heinrich H. Bülthoff ◽  
Riender Happee
Keyword(s):  
Motion Sickness ◽  
Motion Perception ◽  
Time Constant ◽  
Storage Time ◽  
Velocity Storage ◽  
Strong Positive Correlation ◽  
Subjective Vertical ◽  
Time Constants ◽  
Frequency Sensitivity ◽  
Observer Model

AbstractPrevious literature suggests a relationship between individual characteristics of motion perception and the peak frequency of motion sickness sensitivity. Here, we used well-established paradigms to relate motion perception and motion sickness on an individual level. We recruited 23 participants to complete a two-part experiment. In the first part, we determined individual velocity storage time constants from perceived rotation in response to Earth Vertical Axis Rotation (EVAR) and subjective vertical time constants from perceived tilt in response to centrifugation. The cross-over frequency for resolution of the gravito-inertial ambiguity was derived from our data using the Multi Sensory Observer Model (MSOM). In the second part of the experiment, we determined individual motion sickness frequency responses. Participants were exposed to 30-minute sinusoidal fore-aft motions at frequencies of 0.15, 0.2, 0.3, 0.4 and 0.5 Hz, with a peak amplitude of 2 m/s2 in five separate sessions, approximately 1 week apart. Sickness responses were recorded using both the MIsery SCale (MISC) with 30 s intervals, and the Motion Sickness Assessment Questionnaire (MSAQ) at the end of the motion exposure. The average velocity storage and subjective vertical time constants were 17.2 s (STD = 6.8 s) and 9.2 s (STD = 7.17 s). The average cross-over frequency was 0.21 Hz (STD = 0.10 Hz). At the group level, there was no significant effect of frequency on motion sickness. However, considerable individual variability was observed in frequency sensitivities, with some participants being particularly sensitive to the lowest frequencies, whereas others were most sensitive to intermediate or higher frequencies. The frequency of peak sensitivity did not correlate with the velocity storage time constant (r = 0.32, p = 0.26) or the subjective vertical time constant (r = − 0.37, p = 0.29). Our prediction of a significant correlation between cross-over frequency and frequency sensitivity was not confirmed (r = 0.26, p = 0.44). However, we did observe a strong positive correlation between the subjective vertical time constant and general motion sickness sensitivity (r = 0.74, p = 0.0006). We conclude that frequency sensitivity is best considered a property unique to the individual. This has important consequences for existing models of motion sickness, which were fitted to group averaged sensitivities. The correlation between the subjective vertical time constant and motion sickness sensitivity supports the importance of verticality perception during exposure to translational sickness stimuli.

Effects of ouabain on background and voltage-dependent currents in canine colonic myocytes

1990 ◽  
Vol 259 (3) ◽  
pp. C402-C408 ◽  
Author(s):  
E. P. Burke ◽  
K. M. Sanders
Keyword(s):  
Membrane Potential ◽  
Potential Gradient ◽  
Circular Muscle ◽  
Input Resistance ◽  
Pump Current ◽  
Muscle Layer ◽  
Membrane Properties ◽  
Resting Potential ◽  
Voltage Dependent ◽  
In Cells

Previous studies have suggested that the membrane potential gradient across the circular muscle layer of the canine proximal colon is due to a gradient in the contribution of the Na(+)-K(+)-ATPase. Cells at the submucosal border generate approximately 35 mV of pump potential, whereas at the myenteric border the pump contributes very little to resting potential. Results from experiments in intact muscles in which the pump is blocked are somewhat difficult to interpret because of possible effects of pump inhibitors on membrane conductances. Therefore, we studied isolated colonic myocytes to test the effects of ouabain on passive membrane properties and voltage-dependent currents. Ouabain (10(-5) M) depolarized cells and decreased input resistance from 0.487 +/- 0.060 to 0.292 +/- 0.040 G omega. The decrease in resistance was attributed to an increase in K+ conductance. Studies were also performed to measure the ouabain-dependent current. At 37 degrees C, in cells dialyzed with 19 mM intracellular Na+ concentration [( Na+]i), ouabain caused an inward current averaging 71.06 +/- 7.49 pA, which was attributed to blockade of pump current. At 24 degrees C or in cells dialyzed with low [Na+]i (11 mM), ouabain caused little change in holding current. With the input resistance of colonic cells, pump current appears capable of generating at least 35 mV. Thus an electrogenic Na+ pump could contribute significantly to membrane potential.

Why is the perceptual octave stretched? An account based on mismatched time constants within the auditory brainstem

2021 ◽  
Author(s):  
Alain de Cheveigné
Keyword(s):  
Time Constant ◽  
Auditory Brainstem ◽  
The Other ◽  
Inhibitory Synapses ◽  
Coincidence Counting ◽  
Time Constants ◽  
Direct Pathway ◽  
Lower Tone ◽  
Excitatory And Inhibitory Synapses

This paper suggests an explanation for listener’s greater tolerance to positive than negative mistuning of the higher tone within an octave pair. It hypothesizes a neu- ral circuit tuned to cancel the lower tone, that also cancels the higher tone if that tone is in tune. Imperfect cancellation is the cue to mistuning of the octave. The circuit involves two pathways, one delayed with respect to the other, that feed a coincidence-counting neuron via excitatory and inhibitory synapses. A mismatch between the time constants of these two synapses results in an asymmetry in sen- sitivity to mismatch. Specifically, if the time constant of the delayed pathway is greater than that of the direct pathway, there is a greater tolerance to positive than to negative mistuning, which can lead to a perceptual“stretch” of the octave. The model is applicable to both harmonic and – with qualification – melodic oc- taves. The paper describes the model and reviews the evidence from auditory psychophysics and physiology in favor – or against – it.

Rapidly Deactivating AMPA Receptors Determine Excitatory Synaptic Transmission to Interneurons in the Nucleus Tractus Solitarius From Rat

1997 ◽  
Vol 78 (1) ◽  
pp. 82-91 ◽  
Author(s):  
Stefan Titz ◽  
Bernhard U. Keller
Keyword(s):  
Synaptic Transmission ◽  
Ampa Receptor ◽  
Decay Time ◽  
Ampa Receptors ◽  
Time Course ◽  
Nucleus Tractus Solitarius ◽  
Synaptic Cleft ◽  
Excitatory Synaptic Transmission ◽  
Membrane Properties ◽  
Time Constants

Titz, Stefan and Bernhard U. Keller. Rapidly deactivating AMPA receptors determine excitatory synaptic transmission to interneurons in the nucleus tractus solitarius from rat. J. Neurophysiol. 78: 82–91, 1997. Excitatory synaptic transmission was investigated in interneurons of the parvocellular nucleus tractus solitarius (pNTS) by performing patch-clamp experiments in thin slice preparations from rat brain stem. Stimulation of single afferent fibers evoked excitatory postsynaptic currents (EPSCs) mediated by glutamate receptors of the dl-α-amino-3-hydroxy-5-methylisoxazole-propionic acid (AMPA) and N-methyl-d-aspartate types. AMPA-receptor-mediated EPSCs displayed decay time constants of 3.5 ± 1.2 (SD) ms (13 cells), which were slow compared with EPSC decay time constants in neurons of the cerebellum or hippocampus. Slow EPSC decay was not explained by dendritic filtering, because the passive membrane properties of pNTS interneurons provided favorable voltage-clamp conditions. Also, the slowness of EPSC decay did not result from slow deactivation of AMPA receptors (0.7 ± 0.2 ms, 5 cells), which was investigated during rapid application of agonist to outside-out patches. Comparison of AMPA receptor kinetics with EPSC decay time constants suggested that the slow time course of EPSCs resulted from the prolonged presence of glutamate in the synaptic cleft.

Voltage behavior along the irregular dendritic structure of morphologically and physiologically characterized vagal motoneurons in the guinea pig

1990 ◽  
Vol 63 (2) ◽  
pp. 333-346 ◽  
Author(s):  
R. Nitzan ◽  
I. Segev ◽  
Y. Yarom
Keyword(s):  
Steady State ◽  
Guinea Pig ◽  
Time Constant ◽  
Dendritic Structure ◽  
Input Resistance ◽  
Membrane Properties ◽  
Small Cells ◽  
Physiological Data ◽  
Motor Nucleus ◽  
Cable Length

1. Intracellular recordings from neurons in the dorsal motor nucleus of the vagus (vagal motoneurons, VMs) obtained in the guinea pig brain stem slice preparation were used for both horseradish peroxidase (HRP) labeling of the neurons and for measurements of their input resistance (RN) and time constant (tau 0). Based on the physiological data and on the morphological reconstruction of the labeled cells, detailed steady-state and compartmental models of VM were built and utilized to estimate the range of membrane resistivity, membrane capacitance, and cytoplasm resistivity values (Rm, Cm, and Ri, respectively) and to explore the integrative properties of these cells. 2. VMs are relatively small cells with a simple dendritic structure. Each cell has an average of 5.3 smooth (nonspiny), short (251 microns) dendrites with a low order (2) of branching. The average soma-dendritic surface area of VMs is 9,876 microns 2. 3. Electrically, VMs show remarkably linear membrane properties in the hyperpolarizing direction; they have an average RN of 67 +/- 23 (SD) M omega and a tau 0 of 9.4 +/- 4.1 ms. Several unfavorable experimental conditions precluded the possibility of faithfully recovering ("peeling") the first equalizing time constant (tau 1) and, thereby, of estimating the electrotonic length (Lpeel) of VMs. 4. Reconciling VM morphology with the measured RN and tau 0 through the models, assuming an Ri of 70 omega.cm and a spatially uniform Rm, yielded an Rm estimate of 5,250 omega.cm2 and a Cm of 1.8 microF/cm2. Peeling theoretical transients produced by these models result in an Lpeel of 1.35. Because of marked differences in the length of dendrites within a single cell, this value is larger than the maximal cable length of the dendrites and is twice as long as their average cable length. 5. The morphological and physiological data could be matched indistinguishably well if a possible soma shunt (i.e., Rm, soma less than Rm, dend) was included in the model. Although there is no unique solution for the exact model Rm, a general conclusion regarding the integrative capabilities of VM could be drawn. As long as the model is consistent with the experimental data, the average input resistance at the dendritic terminals (RT) and the steady-state central (AFT----S) and peripheral (AFS----T) attenuation factors are essentially the same in the different models. With Ri = 70 omega.cm, we calculated RT, AFS----T, and AFT----S to be, on the average, 580 M omega, 1.1, and 13, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

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