How Membrane Properties Shape the Discharge of Motoneurons: A Detailed Analytical Study

2005 ◽  
Vol 17 (11) ◽  
pp. 2383-2420 ◽  
Author(s):  
Claude Meunier ◽  
Karol Borejsza
Keyword(s):  
High Frequency ◽  
Refractory Period ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Maximal Conductance ◽  
Current Frequency ◽  
Voltage Threshold ◽  
Steady State Current ◽  
Input Conductance ◽  
Firing Properties

Electrophysiological experiments and modeling studies have shown that after hyperpolarization regulates the discharge of lumbar motoneurons in anesthetized cats and is an important determinant of their firing properties. However, it is still unclear how firing properties depend on slow after hyperpolarization, input conductance, and the fast currents responsible for spike generation. We study a single-compartment integrate-andfire model with a slow potassium conductance that exponentially decays between spikes. We show that this model is analytically solvable, and we investigate how passive and active membrane properties control the discharge. We show that the model exhibits three distinct firing ranges (primary, secondary, and high frequency), and we explain the origin of these three ranges. Explicit expressions are established for the gain of the steady-state current-frequency (I− f) curve in the primary range and for the gain of the I− f curve for the first interspike interval. They show how the gain is controlled by the maximal conductance and the kinetic parameters of the after hyperpolarization conductance. The gain also depends on the spike voltage threshold, and we compute how it is decreased by threshold accommodation (i.e., the increase of the threshold with the injected current). In contrast, the gain is not very sensitive to the input conductance. This implies that tonic synaptic activity shifts the current-frequency curve in its primary range, in agreement with experiments. Taking into account the absolute refractory period associated with spikes somewhat reduces the gain in the primary range. More importantly, it accounts for the approximately linear and steep secondary range observed in many motoneurons. In the nonphysiological high-frequency range, the behavior of the I− f curve is determined by the fast voltage-dependent currents, via the amplitude of the fast repolarization afterspike, the duration of the refractory period, and voltage threshold accommodation, if present.

Effect of Common Anesthetics on Dendritic Properties in Layer 5 Neocortical Pyramidal Neurons

2008 ◽  
Vol 99 (3) ◽  
pp. 1394-1407 ◽  
Author(s):  
Sarah Potez ◽  
Matthew E. Larkum
Keyword(s):  
High Frequency ◽  
Pyramidal Neurons ◽  
Animal Experiments ◽  
Apical Dendrite ◽  
Network Activity ◽  
Calcium Spikes ◽  
Firing Properties ◽  
The Impact

Understanding the impact of active dendritic properties on network activity in vivo has so far been restricted to studies in anesthetized animals. However, to date no study has been made to determine the direct effect of the anesthetics themselves on dendritic properties. Here, we investigated the effects of three types of anesthetics commonly used for animal experiments (urethane, pentobarbital and ketamine/xylazine). We investigated the generation of calcium spikes, the propagation of action potentials (APs) along the apical dendrite and the somatic firing properties in the presence of anesthetics in vitro using dual somatodendritic whole cell recordings. Calcium spikes were evoked with dendritic current injection and high-frequency trains of APs at the soma. Surprisingly, we found that the direct actions of anesthetics on calcium spikes were very different. Two anesthetics (urethane and pentobarbital) suppressed dendritic calcium spikes in vitro, whereas a mixture of ketamine and xylazine enhanced them. Propagation of spikes along the dendrite was not significantly affected by any of the anesthetics but there were various changes in somatic firing properties that were highly dependent on the anesthetic. Last, we examined the effects of anesthetics on calcium spike initiation and duration in vivo using high-frequency trains of APs generated at the cell body. We found the same anesthetic-dependent direct effects in addition to an overall reduction in dendritic excitability in anesthetized rats with all three anesthetics compared with the slice preparation.

The influence of a 5-wk whole body vibration on electrophysiological properties of rat hindlimb spinal motoneurons

2013 ◽  
Vol 109 (11) ◽  
pp. 2705-2711 ◽  
Author(s):  
M. Bączyk ◽  
A. Hałuszka ◽  
W. Mrówczyński ◽  
J. Celichowski ◽  
P. Krutki
Keyword(s):  
Whole Body Vibration ◽  
Motor Units ◽  
Membrane Properties ◽  
Whole Body ◽  
Control Group ◽  
Spinal Motoneurons ◽  
Body Vibration ◽  
Electrophysiological Properties ◽  
Male Wistar Rats ◽  
Firing Properties

The study aimed at determining the influence of a whole body vibration (WBV) on electrophysiological properties of spinal motoneurons. The WBV training was performed on adult male Wistar rats, 5 days a week, for 5 wk, and each daily session consisted of four 30-s runs of vibration at 50 Hz. Motoneuron properties were investigated intracellularly during experiments on deeply anesthetized animals. The experimental group subjected to the WBV consisted of seven rats, and the control group of nine rats. The WBV treatment induced no significant changes in the passive membrane properties of motoneurons. However, the WBV-evoked adaptations in excitability and firing properties were observed, and they were limited to fast-type motoneurons. A significant decrease in rheobase current and a decrease in the minimum and the maximum currents required to evoke steady-state firing in motoneurons were revealed. These changes resulted in a leftward shift of the frequency-current relationship, combined with an increase in slope of this curve. The functional relevance of the described adaptive changes is the ability of fast motoneurons of rats subjected to the WBV to produce series of action potentials at higher frequencies in a response to the same intensity of activation. Previous studies proved that WBV induces changes in the contractile parameters predominantly of fast motor units (MUs). The data obtained in our experiment shed a new light to possible explanation of these results, suggesting that neuronal factors also play a substantial role in MU adaptation.

Altered desensitization produces enhancement of EPSPs in neocortical neurons

1994 ◽  
Vol 72 (2) ◽  
pp. 1032-1036 ◽  
Author(s):  
M. R. Pelletier ◽  
J. J. Hablitz
Keyword(s):  
Nmda Receptors ◽  
Time Course ◽  
Glutamate Release ◽  
Epileptiform Activity ◽  
Brain Slices ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Repetitive Firing ◽  
Resting Membrane Potential ◽  
Bath Application

1. Neocortical brain slices were prepared from rats (35–50 days of age) and maintained in vitro. Intracellular recordings were obtained from neurons in cortical layers II/III. The effect of bath application of cyclothiazide (CYZ), a potent blocker of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor desensitization, on evoked synaptic activity and passive membrane properties was investigated. 2. Bath application of CYZ did not significantly affect resting membrane potential, input resistance, or repetitive firing. CYZ increased both the amplitude and duration of evoked excitatory postsynaptic potentials (EPSPs). Polysynaptic responses were also augumented. These effects persisted after the blockade of N-methyl-D-aspartate (NMDA) receptors with D-2-amino-5-phosphonovaleric acid (D-APV). The magnitude of these effects appeared to vary directly with stimulation intensity and presumably, amount of glutamate release. 3. Epileptiform activity was induced by bath application of bicuculline methiodide. The amplitude and duration of evoked paroxysmal discharges were increased by CYZ. Similar results were seen in presence of D-APV. 4. These results indicate that CYZ has significant effects on synaptic transmission. Desensitization of non-NMDA receptors may be an important mechanism for determining the time course of EPSPs and in curtailing epileptiform responses in the rat neocortex.

Synaptic and intrinsic control of membrane excitability of neostriatal neurons. II. An in vitro analysis

1990 ◽  
Vol 63 (4) ◽  
pp. 663-675 ◽  
Author(s):  
P. Calabresi ◽  
N. B. Mercuri ◽  
G. Bernardi
Keyword(s):  
Membrane Potential ◽  
Tetanus Toxin ◽  
Reversal Potential ◽  
Membrane Potentials ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Membrane Excitability ◽  
Epsp Amplitude ◽  
The Relationship

1. The effects of intrinsic membrane properties on the spontaneous and synaptically evoked activity of neostriatal neurons were studied in an in vitro slice preparation with the use of intracellular recordings. The recorded neurons did not show spontaneous action potentials at rest; depolarizing current pulses triggered a tonic firing pattern. 2. Subthreshold spontaneous depolarizing potentials (SDPs) were observed in 52% of the recorded neurons. The amplitude of these potentials at rest ranged between 2 and 15 mV, and their duration between 4 and 100 ms. The frequency and the amplitude of the SDPs were functions of the membrane potential: membrane depolarization by constant positive current increased the frequency of the SDPs and reduced their amplitude; hyperpolarization of the membrane decreased their frequency and increased their amplitude. Often, at membrane potentials more negative than -90 mV, SDPs were completely suppressed. 3. SDPs were blocked by low calcium-cobalt containing solutions. In the presence of tetrodotoxin (TTX, 1-3 microM), SDPs were completely abolished in 50% of the tested neurons; in the remaining neurons, small (1-4 mV) TTX-resistant SDPs were observed. In most of the neurons, bicuculline (BIC, 10-100 microM) and low concentrations of tetanus toxin (5-10 micrograms/ml) did not clearly affect the SDPs. Higher concentrations of tetanus toxin (100 micrograms/ml) blocked the SDPs as well as the synaptic potentials evoked by intrastriatal stimulation. 4. At resting membrane potential, intrastriatal stimulation produced a fast depolarizing postsynaptic potential (EPSP) that was reduced by BIC (10-100 microM). The relationship between EPSP amplitude and membrane potential was studied either by utilizing K(+)-chloride electrodes or by the use of cesium-chloride electrodes. In both these cases, the reversal potential for the EPSPs was between 0 and -14 mV. In cesium-loaded neurons, the decrease of the EPSP, usually observed at negative membrane potentials (below -85 mV), was clearly reduced. Internal cesium prolonged the duration of the SDPs and the EPSPs evoked by intrastriatal stimulation. 5. The relationship between spontaneous and evoked synaptic activity and membrane potential was studied in the presence of different external potassium blockers. 4-Aminopyridine (4AP, 0.1-1 mM) increased the EPSP amplitude and the frequency of the SDPs, but did not decrease membrane rectification and the shunt of the EPSPs present at negative membrane potentials. On the contrary, rectification of the membrane and the shunt of the EPSPs below -85 mV were clearly reduced by tetraethylammonium (TEA, 10-20 mM).(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Transmitter Regulation of Plateau Properties in Turtle Motoneurons

1998 ◽  
Vol 79 (1) ◽  
pp. 45-50 ◽  
Author(s):  
Gytis Svirskis ◽  
Jørn Hounsgaard
Keyword(s):  
Membrane Potential ◽  
Metabotropic Glutamate Receptors ◽  
Input Resistance ◽  
Pattern Generation ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Resting Membrane Potential ◽  
Type I ◽  
Plateau Potentials ◽  
Inward Current

Svirskis, Gytis and Jørn Hounsgaard. Transmitter regulation of plateau properties in turtle motoneurons. J. Neurophysiol. 79: 45–50, 1998. In motoneurons, generation of plateau potentials is promoted by modulators that block potassium channels. In voltage-clamp experiments with triangular voltage ramp commands, we show that cis-(±)-1-aminocyclopentane-1,3-dicarboxylic acid ( cis-ACPD) and muscarine promote the generation of plateau potentials by increasing the dihydropyridine sensitive inward current, by increasing the input resistance, and by depolarizing the resting membrane potential. Type I metabotropic glutamate receptors (mGluR I) mediate the effects of cis-ACPD. Baclofen suppresses generation of plateau potentials by decreasing the dihydropyridine sensitive inward current, by decreasing the input resistance, and by hyperpolarizing the resting membrane potential. These results suggest that membrane properties of motoneurons are continuously modulated by synaptic activity in ways that may have profound effects on synaptic integration and pattern generation.

Facilitated Glutamatergic Transmission in the Striatum of D2 Dopamine Receptor-Deficient Mice

2001 ◽  
Vol 85 (2) ◽  
pp. 659-670 ◽  
Author(s):  
C. Cepeda ◽  
R. S. Hurst ◽  
K. L. Altemus ◽  
J. Flores-Hernández ◽  
C. R. Calvert ◽  
...  
Keyword(s):  
Voltage Clamp ◽  
Glutamate Receptor ◽  
Excitatory Amino Acid ◽  
Glutamate Release ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Receptor Subtype ◽  
Da Receptors ◽  
Change In Mean ◽  
Deficient Mice

Dopamine (DA) receptors play an important role in the modulation of excitability and the responsiveness of neurons to activation of excitatory amino acid receptors in the striatum. In the present study, we utilized mice with genetic deletion of D2 or D4 DA receptors and their wild-type (WT) controls to examine if the absence of either receptor subtype affects striatal excitatory synaptic activity. Immunocytochemical analysis verified the absence of D2 or D4 protein expression in the striatum of receptor-deficient mutant animals. Sharp electrode current- and whole cell patch voltage-clamp recordings were obtained from slices of receptor-deficient and WT mice. Basic membrane properties were similar in D2 and D4 receptor-deficient mutants and their respective WT controls. In current-clamp recordings in WT animals, very little low-amplitude spontaneous synaptic activity was observed. The frequency of these spontaneous events was increased slightly in D2 receptor-deficient mice. In addition, large-amplitude depolarizations were observed in a subset of neurons from only the D2 receptor-deficient mutants. Bath application of the K+ channel blocker 4-aminopyridine (100 μM) and bicuculline methiodide (10 μM, to block synaptic activity due to activation of GABAA receptors) markedly increased spontaneous synaptic activity in receptor-deficient mutants and WTs. Under these conditions, D2 receptor-deficient mice displayed significantly more excitatory synaptic activity than their WT controls, while there was no difference between D4receptor-deficient mice and their controls. In voltage-clamp recordings, there was an increase in frequency of spontaneous glutamate receptor-mediated inward currents without a change in mean amplitude in D2 receptor-deficient mutants. In WT mice, activation of D2 family receptors with quinpirole decreased spontaneous excitatory events and conversely sulpiride, a D2 receptor antagonist, increased activity. In D2 receptor-deficient mice, sulpiride had very little net effect. Morphologically, a subpopulation of medium-sized spiny neurons from D2 receptor-deficient mice displayed decreased dendritic spines compared with cells from WT mice. These results provide evidence that D2 receptors play an important role in the regulation of glutamate receptor-mediated activity in the corticostriatal or thalamostriatal pathway. These receptors may function as gatekeepers of glutamate release or of its subsequent effects and thus may protect striatal neurons from excessive excitation.

Effects of aging on the intrinsic membrane properties of medial NTS neurons of Fischer-344 rats

1993 ◽  
Vol 70 (5) ◽  
pp. 1975-1987 ◽  
Author(s):  
S. M. Johnson ◽  
R. B. Felder
Keyword(s):  
Action Potential ◽  
Nucleus Tractus Solitarius ◽  
Input Resistance ◽  
Membrane Properties ◽  
Repetitive Firing ◽  
Resting Membrane Potential ◽  
Fischer 344 Rats ◽  
Fischer 344 ◽  
Steady State Current ◽  
Intrinsic Membrane Properties

1. Recent studies have demonstrated that the arterial baroreflex is imparied with aging and have implicated central components of the baroreflex arc in this autonomic dysfunction. Neurons in the medial portion of the nucleus tractus solitarius (mNTS) receive a major input from the arterial baroreceptors. The present study was undertaken to characterize the intrinsic membrane properties of mNTS neurons in young rats and to test the hypothesis that these properties are altered with aging. An in vitro brain stem slice preparation was used to record intracellularly from mNTS neurons; passive membrane properties, action potential characteristics, and repetitive firing properties were examined and compared. 2. Neurons in the mNTS of young (3-5 mo old) Fischer-344 rats (F-344; n = 35) had a resting membrane potential of -57 +/- 6.9 mV (mean +/- SD), a membrane time constant of 18 +/- 9.0 ms, and an input resistance of 110 +/- 60 m omega. Action potential amplitude was 81 +/- 7.5 mV with a duration at half-height of 0.83 +/- 0.15 ms. The spontaneous firing rate in 24 cells was 4.3 +/- 2.9 Hz. The amplitude and duration of the action potential afterhyperpolarization (AHP) were 6.6 +/- 3.0 mV and 64 +/- 34 ms, respectively. All neurons expressed spike frequency adaptation, action potential AHP, and posttetanic hyperpolarization. Delayed excitation and postinhibitory rebound were present in 34 and 14% of neurons tested, respectively. Neurons from adult (10-12 mo old) F-344 rats (n = 34) were similar to the young F-344 rats with respect to all of these variables. 3. Neurons from aged (21-24 mo old) F-344 (n = 32) were similar to those from young and adult rats, but there were two potentially important differences: the mean input resistance of the aged neurons was higher (170 +/- 150 M omega), with a larger proportion (46% of aged neurons vs. 20% of young neurons and 21% of adult neurons) having input resistances > 150 M omega; and there was a tendency for a smaller percentage of aged neurons (16% of aged neurons vs. 34% of young neurons and 29% of adult neurons) to express delayed excitation. 4. The potential significance of a high input resistance was tested by comparing the steady-state current-voltage (I-V) relationships and the frequency-current (f-I) relationships among low-resistance (1-100 M omega), medium-resistance (101-200 M omega).(ABSTRACT TRUNCATED AT 400 WORDS)

Physiological response properties of displaced amacrine cells of the adult ferret retina

2004 ◽  
Vol 21 (2) ◽  
pp. 135-144 ◽  
Author(s):  
SALLY W. ABOELELA ◽  
DAVID W. ROBINSON
Keyword(s):  
Large Population ◽  
Amacrine Cells ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Oscillatory Activity ◽  
Large Field ◽  
Resting Membrane Potential ◽  
Mammalian Retina ◽  
Displaced Amacrine Cells ◽  
Intrinsic Membrane Properties

The ganglion cell layer (GCL) of the mammalian retina contains a large number of neurons called displaced amacrine cells (DACs) that do not project to the optic nerve. However, with the exception of the rabbit starburst amacrine cell little is known regarding the function of this large population due to the difficulty experienced in making physiological recordings from these neurons. We have overcome these difficulties and have used whole-cell patch-clamp techniques to examine the intrinsic membrane properties of DACs in the ferret retina. Our results indicate a large degree of diversity in their intrinsic membrane properties. In response to maintained depolarizing current injection, DACs responded with graded depolarization or by eliciting either transient or sustained bursts of spiking activity. At the resting membrane potential, 10% of the DACs generated spontaneous spikes in either an apparently random manner or at the peak of intrinsic waves of depolarization. The resting membrane activity of the remaining DACs recorded could be classified into three groups that were quiescent (28%), had robust uncorrelated synaptic activity (30%), or underwent slow waves of depolarization (42%). Diversity was also revealed in the membrane currents recorded in voltage-clamp where some DACs were quiescent (19%), or exhibited robust nonrhythmic synaptic events (42%). The remaining DACs exhibited waves of oscillatory activity (39%), characterized by either rhythmic bursts of synaptic events (17%) or slow inward currents (22%). Bath application of 50 μM biccuculine or 150 μM picrotoxin had no effect on the waves of activity, however, the gap junction blocker, carbenoxolone (100 μm), blocked both oscillatory patterns. By including Lucifer yellow and biocytin in the recording pipette, it was possible to determine the morphology of recorded neurons and group them based on dendritic extent as small-, medium-, or large-field DACs. There were few relationships between these morphologically defined groups and their intrinsic membrane properties. The present study provides the first in-depth examination of the intrinsic membrane properties of DACs in the ferret retina and provides new insights into the potential roles these neurons play in the processing of visual information in the mammalian retina.

scholarly journals Pathological high frequency oscillations associate with increased GABA synaptic activity in pediatric epilepsy surgery patients

2020 ◽  
Vol 134 ◽  
pp. 104618 ◽  
Author(s):  
Carlos Cepeda ◽  
Simon Levinson ◽  
Hiroki Nariai ◽  
Vannah-Wila Yazon ◽  
Conny Tran ◽  
...  
Keyword(s):  
Epilepsy Surgery ◽  
High Frequency ◽  
Synaptic Activity ◽  
Pediatric Epilepsy ◽  
High Frequency Oscillations ◽  
Pediatric Epilepsy Surgery

Characteristic Membrane Potential Trajectories in Primate Sensorimotor Cortex Neurons Recorded In Vivo

2005 ◽  
Vol 94 (4) ◽  
pp. 2713-2725 ◽  
Author(s):  
Daofen Chen ◽  
Eberhard E. Fetz
Keyword(s):  
Membrane Potential ◽  
Sensorimotor Cortex ◽  
High Frequency ◽  
Cortical Neurons ◽  
Type I ◽  
Type Ii ◽  
Interspike Intervals ◽  
Cortical Oscillations ◽  
Firing Properties

We examined the membrane potentials and firing properties of motor cortical neurons recorded intracellularly in awake, behaving primates. Three classes of neuron were distinguished by 1) the width of their spikes, 2) the shape of the afterhyperpolarization (AHP), and 3) the distribution of interspike intervals. Type I neurons had wide spikes, exhibited scoop-shaped AHPs, and fired irregularly. Type II neurons had narrower spikes, showed brief postspike afterdepolarizations before the AHP, and sometimes fired high-frequency doublets. Type III neurons had the narrowest spikes, showed a distinct post-AHP depolarization, or “rebound AHP” (rAHP), lasting nearly 30 ms, and tended to fire at 25–35 Hz. The evidence suggests that an intrinsic rAHP may confer on these neurons a tendency to fire at a preferred frequency governed by the duration of the rAHP and may contribute to a “pacemaking” role in generating cortical oscillations.

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